Goldschmidt Abstracts 2009 – H

A484

Goldschmidt Conference Abstracts 2009

Proteomic study of Chlorobium clathratiforme in Lago di Cadagno, Switzerland

Sequestering CO2 in marine sediments – Geochemical insights from a natural case study

K.S. HABICHT1*, M. MILLER2, L.F. NIELSEN2, N.-U. FRIGAARD3 AND J.S. ANDERSEN2

MATTHIAS HAECKEL1, NIKOLAUS BIGALKE1, ANTJE BOETIUS2, DIRK DE BEER2, GREGOR REHDER3 1 AND JEAN PHILIPPE SAVY

1

NordCEE and Institut of Biology, University of Southern Denmark, 5230 Odense M, Denmark (*correspondence: [email protected]) 2 Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark ([email protected], [email protected], [email protected]) 3 Department of Biology, University of Copenhagen, DK-2200 Copenhagen N, Denmark ([email protected]) In the sulfide rich (meromictic) Lago di Cadagno, primary production is dominated by anoxygenic photosynthesis, and hence serves as a model system for an early prokaryotedomiated ocean. Organic matter produced in the anoxic part of the water column by the phototrophic S-bacteria can have large impact on how carbon and sulfur is recycled in the lake. The bacteriochlorophyll e-containing green sulfur bacterium Chlorobium clathratiforme is the most dominant anoxygenic phototrophic organisms in Lago di Cadagno, making up 95% of the anoxygenic phototrophic population. The vertical distribution of bacteriochlorophyll e and cell counts showed that Chl. clathratiforme is found not only in the chemocline where it oxidizes sulfide to elemental sulfur during photosynthesis but also below the photic zone. No green sulfur bacteria are known to fix carbon without light and it is therefore unknown how Chl. clathratiforme survives in the deep dark part of the lake. As the genome of Chl. clathratiforme has been fully sequenced it is potentially possible to identify the proteins of this organisms in an environmental proteomic study. We therefore collected cells from four different water depths in Lago di Cadagno in October 2008 with the aim to study the most important proteins associated the cycling of carbon and sulfur by Chl. clathratiforme. Proteins were extracted from the water samples and the trypsin-digested proteins were analyzed using liquid chormatography (LC) coupled to tandem mass spectrometry (MS/MS). The proteins where identified using Mascot and quantified using MaxQuant. We were able to identify 940 proteins that could be assigned to Chl. clathratiforme. Based on the relative distribution of the identified proteins at the different water depths we will show how the metabolism of Chl. clathratifome is regulated by different natural light conditions.

1

Leibniz Institute of Marine Sciences (IFM-GEOMAR) Kiel, Germany ([email protected], [email protected], [email protected]) 2 Max Planck Institute for Marine Microbiology, Bremen, Germany ([email protected], [email protected]) 3 Baltic Research Institute, Rostock-Warnemünde, Germany ([email protected]) Carbon dioxide capture and storage (CCS) has been recognized as one practical option for mitigating global climate change by stabilizing atmospheric CO2 concentrations (IPCC, 2005). In the marine environment potential storage options arise from the unique pressure and temperature conditions: CO2 can be stored in the sediments either as a dense liquid (>3000 m water depth) or as an ice-like solid (gas hydrate) below water depths of 300 m. However, the technical feasibility needs to be demonstrated and, most importantly, the long-term safety (i.e., >10,000 years) has to be assessed together with acceptable rates of CO2 leakage into the marine environment. Therefore, expedition SO196 with RV SONNE has visited the submarine CO2 seeps in the Okinawa Trough, off Taiwan. Two seep sites in the Yonaguni Knoll area were investigated in detail: (a) Abyss vent, where vigorous emanations of supercritical CO2 and low pH fluids have been observed, and (b) Swallow chimney, where the surface sediments harbour liquid CO2 and CO2 hydrate. First results from porewater and mineralogical analyses indicate intense reactions of the CO2 with the sediments, in particular, complete dissolution of carbonates as well as weathering of plagioclases and pyroxenes. In addition, high-pressure experiments have been conducted to determine the dissolution kinetics of liquid and gaseous CO2 in pure water and seawater as well as the growth rate of CO2 hydrate at the CO2-water interface by means of Raman spectroscopy. This integrated approach combining lab experiments and field studies will be complemented by numerical simulations and finally enable us to predict the processes and timescales involved in CO2 sequestration.

Goldschmidt Conference Abstracts 2009

CO2 evasion in relation to system metabolism and rock weathering on multi-annual time scales. A mass balance approach in rivers of the Australian Victorian Alps BENJAMIN HAGEDORN* AND IAN CARTWRIGHT School of Geosciences, Monash University, Melbourne 3800 Vic, Australia (*correspondence: [email protected]) We examined the CO2 system, mainly the dissolved inorganic carbon (DIC), partial pressure of CO2 (pCO2) and δ13C values of DIC, DOC and POC in Victorian rivers and estuaries sampled during high discharge (winter 2006) and low discharge (summer 2007) conditions. Together with historical (1978-1990) data, this study provides, for the first time, a full multi-annual coverage of the linkage between CO2 release via wetland evasion and CO2 consumption via combined carbonate and aluminosilicate weathering. δ13C values imply that DIC in the freshwater reaches is mainly derived from baseflow/interflow flushing of respired C3 plant detritus (39% in winter; 66% in summer), carbonate weathering (42% in winter, 12% in summer) and evaporation of atmospheric precipitation (25% in winter; 20% in summer). DIC concentrations in Victorian estuaries are higher than the oceanic value and generally decreased with increasing salinity as a result of tidal freshwater and seawater mixing. In each river the fraction of excess CO2 that was not accounted for by oxygen depletion was negatively correlated with the runoff and positively correlated with total organic carbon content and temperature. This suggests that long water-soil contact times coupled with high baseflow/interflow flushing of organic carbon and warm water temperatures favor high excess CO2 concentrations. Victorian rivers evade ~14.6 x 106 mol/km2/yr CO2 to the atmosphere which is about half the global average and probably due to an arid climate, low wind speed and low heterotrophic activity. Respired CO2 efflux in Victorian soils is not balanced by combined in river photosynthesis, CO2 evasion, CO2 advection and rock weathering with ~49% to 94% of CO2 left unaccounted for. This discrepancy implies that chemical weathering does not significantly neutralize respiration derived H2CO3. On a global scale tropical river systems with high water temperatures, thick vegetated soils and therefore high respiration derived H2CO3 concentrations should not be directly connected to high carbonate and silicate weathering rates.

A485

Integrating lunar sample data with Lunar Prospector thorium data: Insights into the thermal and magmatic evolution of the Moon J.J. HAGERTY1*, D.J. LAWRENCE2, C.K. SHEARER3 4 AND B.R. HAWKE 1

United States Geological Survey, Astrogeology Research Program, Flagstaff, AZ (*correspondence: [email protected]) 2 Johns Hopkins University, Applied Physics Laboratory, Laurel, MD 3 University of New Mexico, Institute of Meteoritics, Albuquerque, NM 4 University of Hawai'i, Hawai'i Institute of Geophysics and Planetology, Honolulu, HI Much can be learned about the thermal and magmatic evolution of the Moon by integrating two separate, but complementary data sets: 1) thorium (Th) data derived from analyses of lunar samples; and 2) Th data derived from the Lunar Prospector Gamma Ray Spectrometer (LP-GRS). The  integration  of  the  LP‐GRS  geochemical  data  with  sample  data provides ground‐truth for remotely sensed observations and allows us to extend sample data to regional and global scales. Specifically, we use Th data to investigate the composition, structure, and thermal budget of the lunar crust and mantle by determining the abundance of Th (and other heat-producing elements) in volcanic lunar lithologies. We have compared Th data from lunar pyroclastic glasses, mare basalts, and compositionally evolved lithologies from the lunar sample suite with Th data derived from large expanses of similar lithologies on the lunar surface. These comparisons have led to the following results: new compositional information about unsampled features on the lunar surface, new information about the heterogeneity of the lunar mantle, development of a new model for silicic volcanism, new estimates for the distribution of heat-producing elements in the lunar mantle, revised Th paritition coefficients for the Moon, and new estimates of the heat-production potential within the lunar mantle. In summary, our work has shown that the Moon contains a larger abundance of heat-producing elements than previously thought and that heat-producing elements were once globally distributed within the lunar interior (as opposed to concentrated on the nearside of the Moon). In total, the results derived from the integration of sample and remote sensing data have allowed us to place additional constraints on models for the formation and evolution of the Moon.

Goldschmidt Conference Abstracts 2009

A486

Implications of dynamical stability for the detection of Super-Earths via transit timing variation method N. HAGHIGHIPOUR1*, T. HINSE2, J. STEFFEN3 4 AND E. AGOL 1

Inst. Astronomy & NASA Astrobiology Inst., Univ. Hawaii (*[email protected]) 2 Armagh Observatory, Armagh, BT61 9DG, Northern Ireland 3 Fermilab, Batavia, IL 60510-5011, USA 4 Dept. Physics & Astronomy, Univ. Washington, 3910 15th Avenue NE, Seattle, WA 98105, USA Measurement of variations in the transit timing of a closein giant planet is an efficient way to detect small bodies in transiting systems. Known as Transit Timing Variation method, TTV is particularly efficient in detecting small planets in mean-motion resonant (MMR) orbits. We have carried out an extensive search of the parameter-space for identifying stable MMRs between a transiting giant planet and a Super-Earth object that will produce high TTV signals. We have studied the effects of interior and exterior MMRs on the detectability of Super-Earths, and have shown that for a tidally locked Jovian body, a Super-Earth companion has a greater chance of detection if it has a long-term stable orbit with low eccentricity and low inclination, and in a low-order MMR. Our simulations also indicate that regions may exist in the vicinity of unstable MMRs, where a Super-Earth object can maintain its orbit for a long time and produce strong TTV signals. We present the results of our study, and discuss the capability of TTV method in detecting Super-Earth objects in more detail. 14

1:5

Figure 1: Graph of (e-a) space for a Super-Earth (15ME) in a transiting system with a 3-day orbit giant planet. Dark shades correspond to longer life times. Stable MMRs that produce large TTV signals are also shown. Supports from NASA Astrobiology Inst., and through cooperative agreement NNA04CC08A with the Inst. for Astronomy at the U Hawaii are acknowledged.

Textural features and isotopic ratios of the magmatic and inherited zircons in the mafic migmatites from the Takab core complex, NW Iran ROBAB HAJIALIOGHLI AND MOHSSEN MOAZZEN Department of Geology, University of Tabriz 51664, Tabriz, Iran U-Pb isotopic data from the Takab migmatite suggest two types of inherited and melt grown zircons. We interpret that the young zircon (c. 25 Ma) is newly grown grain whereas the old zircon (2961±72 Ma) is inherited. Zircons in various parts of the investigated migmatites are different in the view of grain size, modal abundance and morphology. We interpret scarce zircon in the mesosome due to mafic composition of the protolith or existence of Zr-bearing phases such as hornblende and ilmenite, hindering zircon crystallization in these parts. Newly crystallized zircon in mesosome may have been crystallized from the melt which was not extracted. Melt grown zircon in melanosome and leucosome occurs as large newly grown unzoned crystals. They are commonly subhedral to rounded, scarcely preserved perfect euhedral shapes. The rounded edges of the prismatic zircon grains suggest in situ recrystallization rather than by precipitation from a melt. The newly formed zircon in the investigated rock has variable Th/U ratios ranging from 0.20-1.10. High Th/U ratio is typical feature of melt grown zircons.

Goldschmidt Conference Abstracts 2009

Behavior of nitrogen and its isotopes during high-pressure fluid-driven metasomatic processes: A case study from the Tian Shan, China

High-resolution analysis of trace elements in encrusting coralline red algae by laser ablation ICP-MS J. HALFAR1*, S. HETZINGER1, T. ZACK2, K. SIMON3, A. KRONZ3, R.S. STENECK4, W. ADEY5, P.A. LEBEDNIK6, B.R. SCHÖNE2 AND J. FIETZKE7

R. HALAMA1*, G. BEBOUT2 AND T. JOHN3 1

SFB 574 and Institut für Geowissenschaften, Universität Kiel, 24098 Kiel, Germany (*[email protected]) 2 Lehigh University, Bethlehem, PA 18015, USA 3 Institut für Mineralogie, Universität Münster, 48149 Münster, Germany The nitrogen (N) isotope system has a great potential as geochemical tracer for crustal and volatile recycling due to the large isotopic differences in the various terrestrial reservoirs, and nitrogen is a sensitive tracer of sediment-derived fluids and metasomatic processes [1]. In this study, we investigate the behavior of N and N isotopes in a major fluid conduit – wall rock system within the high-pressure mélange of the Tian Shan, western China. A massive blueschist is cross-cut by a garnet-omphacitecarbonate-quartz vein, which is surrounded by an eclogitic reaction halo [2]. A profile from the unaltered blueschist via a blueschist alteration zone (BAZ) and the eclogitic selvage towards the vein shows a continuous decrease in N concentrations. The concomitant decrease in Cs, Rb, K and Ba contents provides evidence that N is incorporated as NH4+ into white mica and liberated during fluid-rock interaction. δ15N values of blueschists and the BAZ are overlapping (~2‰), but increase in the eclogitic selvage (+2.6±0.2‰) and the vein (+4.8‰). Three alternative explanations for the N systematics are discussed. Devolatilization leads to a decrease in N contents and an increase in δ15N in the residual rock, i.e. the eclogitic selvage, but for a good fit with the observed data pure batch devolatilization and isotopic fractionation factors slightly lower than those published have to be assumed. Second, the elevated δ15N signature in vein and eclogitic selvage may be externally derived. This explanation is supported by positive correlations of δ15N with Ca, Sr and Pb, the latter elements being enriched by an infiltrating fluid [2]. Finally, N may have been leached together with Cs, Rb, K and Ba from the selvage near the vein involving diffusion. One can speculate that the diffusion caused a preferential removal of the light 14N isotope causing an elevated δ15N in the selvage, whereas the δ15N signal in the vein is dominated by an external source. [1] Bebout (1997) EPSL 151, 77-90. [2] Beinlich et al. (in review) GCA.

A487

1

CPS-Department, University of Toronto, Canada (*correspondence: [email protected]) 2 Institute of Geosciences, University of Mainz, Germany 3 Geowissenschaftliches Zentrum, Göttingen, Germany 4 Darling Marine Center, University of Maine, Maine, USA 5 Smithsonian Institution, Washington, USA 6 LFR Inc., Ecosystems Services Group, California, USA 7 IFM-GEOMAR, Kiel, Germany Coralline red algae are ideal extratropical marine climate recorders owing to their common occurrence not only in the tropics but also in mid- to high latitude oceans. Coralline red algae archive past climate information along fixed annual growth increments in a high Mg-calcite skeleton. Livecollected specimens have yielded radiometrically-determined ages of up to 850 years and recent calibration experiments have demonstrated the value of a number of coralline algal species as paleothermometers. Annually to seasonally resolved stable oxygen isotope and Mg/Ca records have provided up to century-scale climate reconstructions. Here we present high-resolution Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS) elemental ratios (Mg/Ca, Sr/Ca, Ba/Ca, U/Ca, Pb/Ca) from the encrusting coralline red algal genus Clathromorphum. Specimens were live-collected from the North Atlantic and North Pacific Oceans and elemental ratios were measured in sub-monthly resolution to provide centuryscale proxy records. Duplicate transects were analyzed in multiple specimens in order to assess the robustness of the proxy data. The reproducibility is excellent and LA-ICP-MS results were validated by comparison to electron microprobe measured elemental ratios and bulk sample ICP-OES data. In particular, algal Mg/Ca ratios show a high degree of correlation with local seawater temperatures on different timescales, providing further evidence for the temperature dependency of algal Mg/Ca variations and their use as a valuable paleothermometer. Hence, this study demonstrates the feasibility of extracting high-resolution geochemical signals from coralline red algae using LA-ICP-MS. This technique allows rapid sampling of the algal surface with unprecedented resolution and provides a valuable tool for future analysis of algal-derived environmental records.

A488

Goldschmidt Conference Abstracts 2009

Effects of acidic organic molecules on the solvation of biologically relevant divalent cations

Stability of dissolution flutes under turbulent flow

L.M. HAMM*, A.F. WALLACE AND P.M. DOVE

Physics of Geological Processes (PGP) University of Oslo, PO Box 1048 Blindern, 0316 Oslo, Norway ([email protected])

Department of Geosciences, Virginia Tech, Blacksburg, VA 24061 USA (*correspondence: [email protected]) Biomolecules rich in aspartic acid (Asp) are known to play a role in biomineral morphology and polymorph selection, and have been shown to greatly enhance the growth kinetics of calcite. These compounds may favor calcification by partially desolvating cations to lower the energy barrier to mineralization [1]. To test the idea that biomolecular species modulate ion hydration environments, we investigated the influence of acidic amino acids and dipeptides on the solvation of divalent cations using molecular dynamics (MD). For each simulation we monitored the hydration environment of a divalent cation (Mg, Ca, Sr) in the presence of an acidic amino acid or dipeptide (Asp, AspAsp, AspLeu). Calculated radial distribution functions were used to determine the structure of the primary hydration shell at various cation-organic separation distances. Free energy profiles for the complexation of cations in solution by carboxylate moities were generated by umbrella sampling and the weighted histogram analysis method (WHAM). All simulations were carried out with the LAMMPS software employing the TIP3P model of water, CHARMM22 force field, and Åqvist ion-water potentials [2]. We show the hydration environments of Ca and Sr are perturbed as the ions approach the negatively charged amino acid carboxylate groups. Complexation of Ca and Sr by the carboxylate oxygen atoms results in a decreased total first shell coordination number relative to the ions in bulk water. The primary solvation shell of Mg is largely unchanged by organics until the physical replacement of a water molecule with a caboxylate oxygen, which appears to be highly unfavorable energetically. Proximity to organics has no effect upon ion-oxygen distances of waters in the first hydration sphere. The calculated energy barrier for Ca association with the biomolecules is very small (a few kT). For Sr, sterics appear to prevent the larger ion from taking the same path of approach as Ca, resulting in a larger energy cost. The findings suggest origins of biomolecule-specific influences on nucleation and growth of calcium carbonates and phosphates and the roles of matrix organic molecules in biomineral phase selection. [1] Elhadj et al. (2006) Proc. Natl. Acad. Sci. USA 103 19237. [2] Åqvist (1990) J. Phys. Chem. 94 8021.

ØYVIND HAMMER

Dissolution of mineral surfaces such as carbonate, gypsum or ice under turbulent flow can lead to periodic roughness on a centimeter scale, known as scallops. Flutes are ripple-like scallops, normal to flow. Such structures are important paleoflow indicators in caves. It has previously been known that dissolution flutes can become stable in time, except for stiff translation of the whole pattern both normal to and parallel with the surface [1]. This shape stability requires a certain compatibility between flute shape and the resulting dissolution profile. We will present simulation results from 2D hydrodynamics modelling using a k-epsilon turbulence model in a fixed geometry, coupled with gypsum dissolution and the mean-flow advection and eddy diffusion of calcium and sulphate. The numerical simulations reproduce the dissolution profile required for shape stability, except for poor resolution of flow separation at the flute crest. To obtain a reasonable dissolution profile, it was necessary to include the effect of turbulence on the thickness of the diffusion-limiting boundary layer. The study demonstrates the feasibility of modelling surface dissolution and precipitation under complex, turbulent flow. Such modelling may aid the interpretation of natural structures in terms of flow velocity and flow reversal. [1] Blumberg & Curl (1974) J. Fluid Mech. 65 735-751.

Goldschmidt Conference Abstracts 2009

Trace element and δ7Li geochemistry of Tonga arc submarine basalts

Timing of brittle deformation in the Deokpori - Gakdong thrust zone, South Korea

S.J. HAMMOND1*, N.W. ROGERS1, I.J. PARKINSON1 2 AND R.H. JAMES

RAEHEE HAN1,2, JIN-HAN REE1 3 AND HORST ZWINGMANN

1

Department of Earth and Environmental Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK (* Correspondance: [email protected]) 2 National Oceanography Centre Southampton, European Way, Southampton, SO14 3ZH, UK The intra-oceanic Tonga-Kermadec arc is considered to represent the simplest endmember of arc systems. The highly depleted nature of the mantle wedge beneath the Tonga arc means that it is sensitive to the distinct inputs from the subducting slab, while the sediment input is limited but well characterised [1]. The sparce number of aerial volcanoes along the arc is accompanied by more numerous submarine volcanic centres. We present trace element and δ7Li data from submarine samples, collected on the NoToVE cruise (2004), from the northern most portion of the arc, and also samples from the back arc spreading region of the Fonualei rifts. The arc lavas are characterised by sub-chondritic Zr/Hf ratios (27.8-36.7) that reflect mantle wedge depletion. Modelling indicates the mantle source has been depleted by 23% from a MORB mantle source. However, arc samples show no systematic variation along strike of the arc, indicating all samples are derived from a similarly depleted source. Given that the rate of extension in the back arc increases from 8 to 16 cm yr-1 from S to N of the Lau basin [2] our data clearly demonstrate that wedge depletion is not controled by the rate of back arc extension. Zr/Hf is correlated positively with the La/Yb ratio in both arc and back-arc lavas, that results from mixing between depleted mantle wedge and subducted sediment, and implying a greater contribution from sediment in the back-arc lavas (0.7%) compared with the arc (0.3%). Moreover samples from the back arc region only require an input from a sediment melt component whereas those from the arc require both a sediment and fluid input. Li isotope variations for this sample suite indicate that the fluid component from the slab is rich in 7Li, as arc samples have heavier δ7Li (up to 6.4‰) than samples from the back arc(3.0-4.8‰). This observation implies that subducted sediment melts are released into the wedge from the slab, forming the source of back arc magmas, and the subsequent addition of fluids from the slab to this hybridised mantle induces melting above the arc. [1] Turner et al. (1997) GCA 61, 4855-4884. [2] Bevis et al. (1995) Nature 374, 249-251.

A489

1

Department of Earth and Environmental Sciences, Korea University, Seoul 136-701, Korea ([email protected]) 2 Department of Earth and Planetary Systems Science, Hiroshima University, Japan, ([email protected]) 3 CSIRO Petroleum, PO Box 1130, Bentley, WA 6102 Australia ([email protected]) The Deokpori (Gakdong) Thrust is an important structure for the Mesozoic tectonic evolution of Korea. Although the Deokpori Thrust has been interpreted as an Early Triassic intercontinental transform fault or Middle Jurassic intracontinental thrust, there has been no study on the kinematics and absolute age of the thrusting. This study is the first to attempt to directly date geologically young fault movements in the Deokpori (Gakdong) Thrust on the basis of neocrystallization of clay minerals recently applied in other orogens [1]. In the eastern Yeongwol area, the NNE-striking Deokpori Thrust occurs as at least 100 m-wide fault zone between the overlyng Ordovician marble and the underlying Middle Jurassic siliciclastics. The fault core (about 3 m wide) consists of foliated cataclasite, ultracataclasite and foliated gouge. Three samples were taken from the foliated gouge layer (20 to 30 cm thick) of the fault core for this study. One host rock shale was also sampled in the footwall about 40 m away from the fault core. K-Ar dates of illite separates from fault rock samples, and grain sizes < 0.1 to 6-10 micron yield values ranging from 55.4±1.1 to 75.8±1.5 Ma (n=15). All dated sample fractions were extensively characterized by XRD, SEM and TEM. The host rock samples yield ages of 93.8±2.6 and 95.6±2.0 Ma respectively. The internal consistency of the age results from K-Ar dating of fault gouges from both surface samples, as well as their consistency with constraints from field relationships and existing geochronological data demonstrate the potential of this method for providing new data to constraint absolute timing of brittle deformation in the Deokpori (Gakdong) Thrust of South Korea. [1] Zwingmann, H. & Mancktelow, N. 2004. Timing of Alpine fault gouges. EPSL, 223, 415-425.

A490

Goldschmidt Conference Abstracts 2009

Isotope geochemical evidences for sources of ore fluid in carbonatehosted Zn-Pb-(Ag-Ge) metallogenic district, Northeast Yunnan, China

Gold-rich sulfide melt inclusions in xenocrysts from a mid-crustal magma chamber, Mt. Milligan porphyry deposit, B.C., Canada

RUN-SHENG HAN AND BIN HU

JACOB HANLEY1 AND MARCEL GUILLONG2

Kunming University of Science and Technology, Southwest Institute of Geological Survey, Geological Survey Center for Non-ferrous Mineral Resources, Kunming 650093, P.R.C (*correspondence: [email protected])

1

The typical medium-to large-sized carbonate-hosted highgrade Zn-Pb-(Ag-Ge) deposits (exemplified as the Huize deposit, Zhaotong Maoping deposit etc.) in the well-known Sichuan-Yunnan-Guizhou Zn-Pb Polymetallic Metallogenic District are distributed mainly over northeast Yunnan. The deposits were controlled by the NE-extending Structural Zone. The ore fluids containing Pb and Zn belong to the Na+-K+2+ Ca -Cl--F-type in these deposits. The isotope compositions and fluid inclusion features are similar. For the Huize deposit, the ore fluids are characterized by temperature at 164–221°C and salinity in 5–10.8 wt%NaCl [1]. The waters of fluid inclusions have δD values from -43.5‰ to -55.4‰ of calcite. Theδ18OV-SMOW values of the ore fluids range from 17.09‰ to 18.56‰ of calcite and 17.80‰ to 23.14‰ for dolomite. δ13CVPDB values range from -1.94‰ to -3.31‰ for calcite and 3.35‰ to 0.85‰ for ore-hosted dolomite; For the Maoping deposit, the ore fluids are characterized by temperatures of 180–218°C and salinity in 4.1 wt%–9.5wt% NaCl. The waters of fluid inclusions have δD values from -23‰ to -64‰. The δ18OV-SMOW values of the ore fluids range from 0.3‰ to 6.2‰ for galena, -9.0‰ to 3.4‰ for sphalerite, and -6.8‰ to -12.7‰ for pyrite. δ13CV-PDB values range from -1.1‰ to -3.7‰ for calcite and dolomite. These data better demonstrate that the ore-forming fluids were mainly derived from metamorphic water, magmatic hot fluid and hosted formation water, in relation to the metamorphism of the Kunyang Group in the basement, the magmatic hydrothermalism and sedimentation. On basis of field studies, The Zn-Pb-(Ag-Ge) doposits in Northeast Yunnan can be designated as deformed, carbonate-hosted, MVT-type deposits. This paper was financially supported by the NSFC (No.40863002), NCET (NCET-04-917) and the innovation team of ore-forming dynamics and prediction of concealed deposits, KMUST, Kunming, China (2008).

Very coarse-grained amphibole xenocrysts (potassian magnesiohastingsite) hosted in an early monzonite stock at the Mount Milligan Cu-Au porphyry deposit, British Columbia, Canada contain coeval sulfide and silicate melt inclusions of primary origin. The sulfide melt inclusions have a bulk composition comparable to Cu-rich ISS. Late growth zones in the amphibole are devoid of sulfide inclusions and contain only low salinity, chalcopyrite-bearing fluid inclusions (average 7.4 wt% NaCleq.). Thermobarometry constrains the minimum conditions of sulfide entrapment (amphibole crystallization) to ~8 kbar and ~700°C. LA-ICP-MS analyses of 22 sulfide melt inclusions show that it was highly enriched in Au (50 ± 20 ppm, 1σ), Ag (140 ± 70 ppm, 1σ) and Ni (5000 ± 3000 ppm, 1σ). Ratios of Cu/Au (7500 ± 2500, 1σ) and Au/Ag (0.45 ± 0.24, 1σ) are identical to metal ratios in porphyry-stage veins, demonstrating that these metals were not fractionated from one another during suspected volatile exsolution, fluid-melt partitioning, and subsequent transport and precipitation of ore metals. The extremely Au-rich composition of the sulfide melt may reflect fractional crystallization of the sulfide liquid prior to entrapment in the amphibole. Both the xenocrysts and rare, high Mg, alkali basalt xenoliths hosted in the intrusions are depleted in Cr, Co, Ni and Cu, reflecting the sequestering of the base metals into a sulfide liquid in a mid-crustal magma chamber where amphibole and Cr-spinel were cumulus phases. The results of this study show that a Cu-Au-rich sulfide melt coexisted with a amphibole-saturated alkalic basaltic liquid in mid-crustal magma chamber prior to the emplacement of the main intrusions and associated porphyry stage mineralization at Mt. Milligan. This sulfide melt appears to have destabilized with the appearance (exsolution) of a single-phase low salinity aqueous fluid. Identification and analysis of ore metals in sulfide melt inclusions in relatively common xenocryst phases may serve as a useful exploration tool for predicting the metal ratio of undiscovered Cu-Au porphyry deposits in the Canadian Cordillera.

[1] Han R S et al. (2007). Ore Geology Reviews, 31: 360383.

Dept. of Geology, St. Mary’s University, Halifax, Canada, B3H3C3 ([email protected]) 2 Dept. of Earth Sciences, ETH Zurich, Clausiusstrasse 25, Zürich, Switzerland CH-8092

Goldschmidt Conference Abstracts 2009

Re-Os isotopic disturbances at unconformities: Challenges and opportunities 1,2

1

1

A491

Rb-Sr systematics of angrites U. HANS, T. KLEINE AND B. BOURDON 1

J.L. HANNAH , G. YANG , G. XU , A. ZIMMERMAN , H. STEIN1,2, B. BINGEN2 AND S. EGENHOFF1 1

AIRIE Program, Department of Geosciences, Colorado State University, Fort Collins, CO 80523-1482, USA (*correspondence: [email protected]) 2 Geological Survey of Norway, 7491 Trondheim, Norway In the increasingly mature practice of Re-Os geochronology of black shales, we can now begin to predict which sections will provide robust geochronology and how to extract information from problematic sections. We present two case studies. In each case, we analyzed two sample suites, one near the base and one near the top of a shale unit. In each, we acquired precise isochrons for the lower suite, but scattered data for the top suite. In each, the scatter can be explained by oxidation that leaves little trace in the rocks. In the Neoproterozoic Biri Formation, southern Norway, 80 meters of black shale are exposed in a steep bedrock stream channel. Samples from a 4-m stratigraphic interval mid-way through the section yield a robust Model 1 isochron age of 561 Ma (initial 187Os/188Os = 1.10, MSWD = 0.5, n = 6). Data scatter, however, for samples taken within 3 m of the unconformable upper contact with a fluvial conglomerate. The disturbed section is not visibly altered and shares features with the undisturbed section; both contain fine pyrite framboids and total organic carbon (TOC) near 1%. In the Middle Triassic Botneheia Formation, western Spitsbergen, 90 meters of black shale are exposed in sharp cliffs and incised gullies. Samples from a 70-cm stratigraphic interval near the base of the shale member yield a wellconstrained Model 3 age of 241 Ma (initial 187Os/188Os = 0.83, MSWD = 16, n = 8). Data scatter, however, for samples from a 1-m stratigraphic interval 4 m below the upper contact with a red pro-delta siltstone. Like the Biri section, the disturbed samples are not visibly altered. TOC contents of 2-8% are representative of the shale section. In both cases, the tops of shale units were potentially oxidized prior to burial and/or during post-burial exchange of pore fluids across a redox boundary between contrasting sediment types. Oxidizing fluids mobilize Re and Os, decoupling radiogenic 187Os from parent 187Re. Over time, transport of Re and Os may exceed the sample size, resulting in variable 187Os/188Os within the sample suite. This violates a basic tenet of the isochron method. Isotopic disturbance may therefore mark the vertical extent of visually undetectable oxidation of shales underlying fluvio-deltaic systems.

Institute of Isotope Geochemistry and Mineral Resources, ETH Zürich, Clausiusstrasse 25, 8092 Zürich, Switzerland ([email protected]) Volatile depletion in many meteorite parent bodies as well as in the terrestrial planets resulted in a fractionation of volatile Rb from more refractory Sr, such that the initial 87 Sr/86Sr of a volatile-depleted planetesimal can be used to estimate the time at which this planetesimal separated from the solar nebula or any other source reservoir with known Sr isotope evolution. The angrite parent body has the most extreme depletion in volatile elements and the 87Rb-87Sr systematics of angrites LEW 86010 and Angra dos Reis (AdoR) were used previously to determine the timeing of volatile depletion [1,2]. However, these samples formed ~10 Myr after CAIs and thus may not represent the initial 87Sr/86Sr of their parent body. We developed improved techniques for precise Sr isotope measurements (≈5 ppm, 2 σ external reproducibility for NBS 987) and present high-precision Sr isotope data for plagioclase separates from several angrites. These data are used to better determine the timing of volatile loss from the angrite parent body. The 87Sr/86Sr ratio of D’Orbigny plagioclase is among the lowest yet measured for angrites and provides the currently most precise estimate for the initial 87Sr/86Sr of the angrite parent body of 0.698955±0.000004. This value is in excellent agreement with the estimate based on AdoR and LEW 86010 of 0.698967±0.000015 [1,2]. D’Orbigny and LEW 86010/AdoR have crystallization ages of ~4 and ~10 Myr after CAI formation [3] and their initial 87Sr/86Sr ratios thus provide the Sr isotope composition of the angrite parent body at ~4 and ~10 Myr after CAI formation (assuming that both angrites sample the mantle of the their parent body). This allows estimating the Sr isotope evolution of the angrite parent body and calculation of the time at which the solar nebula had reached the initial 87Sr/86Sr of the angrite parent body. In this two-stage model volatile loss occurred within the first ~2 Myr of the solar system, a timescale similar to Hf-W ages for the accretion and differentiation of the angrite parent body [4]. [1] Lugmair and Galer (1992) GCA 56, 1673–1694. [2] Nyquist et al. (1994) Meteoritics 29, 872–885. [3] Amelin (2008) GCA 72, 4874-4885. [4] Kleine et al. (2009) LPSC XL, 2403.

A492

Goldschmidt Conference Abstracts 2009

Microbially mediated geochemical iron and carbon cycling in a cold mineral spring KURT HANSELMANN1,3*, FLORIAN HEGLER1, THOMAS HORATH2, SEBASTIAN BEHRENS1, CAROLINE SCHMIDT1 AND ANDREAS KAPPLER1 1

University of Tübingen, Germany, Centre for Applied Geoscience, 2 University of Zürich, Institute of Plant Biology, 3 swiss | i-research & training, P.O. Box 1206, CH-8032 Zürich (*correspondence [email protected]) We are investigating the highly mineralized, iron-rich, micro-oxic Fuschna spring, which is an excellent model site for studies on coupled carbon and iron cycling in surface environements at near neutral pH. The spring offers oxicanoxic gradients, is accessible at the surface and the carbon cycle is linked to inorganic carbon stemming from subsurface dissolution of rock minerals. The spring emerges from a fractured aquifer consisting of layers of slightly metamorphic, pelagic sediments (Bündner shale). It is located in the Lower Engadin Window, an erosion opening into the penninic layers near Ftan (Swiss Alps). During percolation the water gets enriched with HCO3- and H2CO3. It is characterized as an Fe(II)-rich Ca-Mg-SO4-HCO3 spring (TDS ≈ 4.4 g/l, > 70% HCO3-; pH ≈ 6.3; dissolved Fe2+ ≈ 8.5 mg/l. Bissig, P. 2004, Bull. angew. Geol, 9/2, 39-47). Dissolved CO2 escapes from the spring-water at the surface, thereby creating oversaturation with regard to calcium carbonate. So called “carbonate ice” precipitates as a thin film on water surfaces or forms carbonate terracettes. Once the dissolved oxygen concentration increases in the outflow water, dissolved ferrous iron gets oxidized and precipitates along the flow channels as ferric iron oxides. These oxides contain large numbers of microorganisms. We have isolated an anoxigenic, phototrophic, Fe(II)oxidizing bacterium and characterized the microbial community composition genotypically, employing 16S rRNA phylogeny. Besides clones of filamentous Cyanobateria related to Phormidium spp., Tychonema spp. and Lyngbya spp., and of Synechocystis sp. we also detected clones of alpha and beta-Proteobacteria that are closely related to Rhodoferax spp., Gallionella spp., Iodobacter spp. and Rhodobacter spp. The geochemical conditions of the Fuschna spring and the kind of microorganisms detected indicate that the carbon and iron cycles are coupled via biotic and abiotic redox-reactions and acid-base equilibria. Organic carbon from phototrophic primary production fuels the reductive part of the redox cycle.

Reduction of aqueous hexavalent chromium by steel slag EERO HANSKI1AND ANU KANKAALA2 1

Department of Geosciences, P.O. Box 3000, 90014 University of Oulu, Finland ([email protected]) 2 MTT Agrifood Research Finland, Tutkimusasemantie 15, 92400 Ruukki, Finland ([email protected]) Trivalent chromium, Cr(III), is an essential element for humans, while hexavalent chromium, Cr(VI), is an established human carcinogen. In situ remediation of groundwater contaminated with hexavalent chromium can be achieved by reduction of Cr(VI) to barely soluble Cr(III) with a reducing agent, such as zero-valent iron, and its subsequent precipitation as stable hydroxides. Millions of tons of steel slag is produced annually as a byproduct of steel industry. For this reactive, alkaline material new environmental applications have recently been developed. Due to the presence of Mn(II) and Fe(0,II,III), steel slag is a strong reductant. To test steel slag’s capacity to reduce aqueous hexavalent Cr to a trivalent form and its potential use in treating Cr(VI)-contaminated land, we have performed laboratory batch (24 h) and kinetic experiments using slag samples from the Rautaruukki Co., Finland. Total chromium in water samples was analysed with ICP-OES, and hexavalent chromium was separated using ion exchange columns and determined spectrophotometrically. As a comparative material we employed agricultural soil, which did not show any significant uptake (reduction) of dissolved Cr(VI). Steel slag instead was effective in chromate reduction. The percentage of reduction was dependent on the solid/liquid ratio (L/S) and initial Cr(VI) concentration. Using L/S = 20, more than half of hexavalent chromium was converted to trivalent even with high initial Cr(VI) contents of up to 45 mg/L and the reducted fraction was 90% or more when the initial Cr(VI) concentration was 1.0 mg/L or less. Increasing L/S to 500 did not remove the reduction capacity as the adsorption percentage was still >50% if the initial Cr(VI) was 1.0 mg/L (note that EPA’s max. contaminant level for total Cr in drinking water is 0.1 mg/L). The obtained reduction (adsorption) pattern follows a Langmuir-type isotherm model. The reduction rate in the experiments was fast as a 90% removal of chromate from the solution took place within a shaking time of 2 minutes (L/S 20, initial Cr(VI) 5 mg/L). Our results demonstrate that steel slag can provide a low-cost material for remediation of contaminated land containing hexavalent chromium.

Goldschmidt Conference Abstracts 2009

Stratospheric input of heavy halogens (Br, I) from large explosive volcanic eruptions: Information from melt inclusions THOR H. HANSTEEN, STEFFEN KUTTEROLF, ARMIN FREUNDT, MATTHIAS FRISCHE, HEIDI WEHRMANN, HANS-ULRICH SCHMINCKE AND SUSANNE HORN IFM-GEOMAR, and SFB 574, Kiel, Germany ([email protected]) Large explosive volcanic eruptions inject gases, aerosols and ash into the stratosphere, thus influencing stratospheric chemistry and the Earth´s radiation budget. Halogens responsible for catalytic ozone depletion following large eruptions comprise chlorine (Cl), and the heavy halogens bromine (Br) and iodine (I) occurring in trace amounts in volcanic plumes. Due to the higher catalytic potential for ozone destruction of Br and I compared to Cl, even trace amounts of these elements in volcanic emissions are relevant for stratospheric chemistry. We have analysed halogens in volcanic glasses and in glass inclusions in phenocrysts using electron microprobe and synchrotron-XRF microprobe methods. Halogens from bulk glass samples were extracted using pyrohydrolysis, and analysed by ICP-MS. Eruptions investigated include Baitoushan, China /North Korea (ca. 969 AD), Mt. Hudson, Chile (1991), and several dacitic Quaternary eruptions from Nicaragua. Chlorine concentrations in glass inclusions are typically 2000 to 4000 ppm, which is on average about 50% higher than the concentrations in the matrix glasses. Br concentrations in glass inclusions are typically in the range of 2 to 20 ppm. This gives an average Cl/Br ratios of about 300:1. Using the petrologic method, involving the concentration differences of halogens between the glass inclusion and those retained in the matrix glass, the average Cl/Br ratio of the volcanic emissions were about 200:1. Typical I concentrations of Nicaraguan glass inclusions range between 1 and 3 ppm. The resulting Cl/ I ratio of eruptive emissions is about 1100:1. Depending on eruption size, each large event injected between several kt and several hundred kt Br and I into the atmosphere. As a first approach to estimate global Br and I fluxes from subduction zones, although affected by several sources of uncertainty, we combine these halogen ratios of 200:1 and 1100:1 for Cl/Br and Cl/I, respectively, with the global eruptive Cl flux of 1.5 x 108 kg m-1 Ma-1 (Wallace 2005, JVGR) , leading to fluxes of 7.5 x 105 kg m-1 Ma-1 for Br and 1.4 x 105 kg m-1 Ma-1 for I.

A493

XAFS study of the structural behaviour of monazite M. HARFOUCHE1*AND F. FARGES2 1

Paul Scherrer Institut, Villigen, Switzerland (*correspondence: [email protected]) 2 Museum national d'Histoire Naturelle, Paris, France Natural monazite that have undergone radiation damage over billion years, appear to be good analogues to understand the behavior of such matrix under storage and weathering conditions. To investigate the structural behavior of monazite, several natural samples were collected from different location around the world. The samples were characterized using SEM, XRD and electron microprobe. Analysis of the EXAFS data collected at the LIII edge of Th incorporated in monazite structure show an average interatomic distance Th-O equal to that of Ce-O (2.50(2) Å) in crystalline monazite. Therefore, no expansion or contraction of the local structure around Th substituting REE in monazite was observed. In addition, EXAFS spectra at P-K edge show an average of ~4.5 atoms in the coordination shell in metamict monazites. This over-estimation of the coordination number in metamict monazites is explained by the presence of certain P atoms 3-, 5- and/or 6-fold coordinated: This is due, undoubtedly, to the effects of the radiation damage on the structure of monazite. Moreover, the average interatomic distance of the coordination shell was found to be (~1,61(2) Å) longer than the one in crystalline monazites (~1,56(2) Å). This is explained by the large number of atoms first neighbours and the large distortion of the polyhedron of coordination.

A494

Goldschmidt Conference Abstracts 2009

A mesoscale analysis of the effects of idealized ice nuclei during austral spring in South America

Particulate matter optical properties and emission trends for gasoline and diesel vehicles

M.K. HARKEY* AND M.H. HITCHMAN

ROBERT A. HARLEY1, GEORGE A. BAN-WEISS1, THOMAS W. KIRCHSETTER2, MELISSA M. LUNDEN2 3 AND ANTHONY W. STRAWA

University of Wisconsin-Madison, Madison, WI 53706, USA (*correspondence: [email protected]) Populations of idealized ice nuclei (IN) have been modeled using the University of Wisconsin Non-hydrostatic Modeling System (UWNMS) to investigate the sensitivity of water vapor and ice concentrations and distributions to IN concentration, activation temperature, and location over a 60hour period of time coincident with frontal and mesoscale convective activity in Amazonian springtime. The magnitude of positive and negative changes in both vapor and ice appear to be most dependent on the concentration and altitude of IN. For example, ice and vapor concentrations increase at high altitudes when a relatively small or high-altitude IN concentration is modeled. Vertical velocity and altitude play dominant roles in the spatial distribution of changes to water concentrations—higher altitude environments are more sensitive to the effects of IN and vertical velocity combined, and upward velocities are usually correlated with positive changes to vapor and ice. We will explain the mechanisms that cause these patterns with a view toward expanding the understanding of how the distribution of humidity in the upper troposphere/lower stratosphere may be impacted by aerosol.

1

Department of Civil and Environmental Engineering, University of California, Berkeley, CA 94720-1710 USA ([email protected], [email protected]) 2 Atmospheric Science Department, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA ([email protected], [email protected]) 3 NASA-AMES Research Center, Moffett Field, CA 94035 USA ([email protected]) Gasoline and diesel-powered motor vehicle emissions were measured at the Caldecott tunnel near San Francisco, California, during summer 2006. Measured emission rates for particulate matter (PM2.5), black carbon (BC), and particle number (PN) were compared to previous measurements made at the same site. PM2.5 mass emission factors decreased by 36±17 and 48±12% for gasoline (light-duty) and diesel (heavy-duty) vehicles, respectively, between 1997 and 2006. BC and PN emissions also decreased. In 2006, emission factors for BC and PN were measured from 226 individual heavy diesel trucks as they drove through the tunnel on a 4% uphill grade. BC emission factors were log-normally distributed, and there was minimal overlap between highemitters of BC and PN. The absoprtion and extinction coefficients of tunnel aerosols were measured directly, and mass absorption efficiencies were calculated to be 9.1 and 5.1 m2 per g BC for gasoline and diesel vehicle PM emissions, respectively. Corresponding values of single scattering albedo were 0.31±0.06 and 0.20±0.05.

Goldschmidt Conference Abstracts 2009

Magmatism and metamorphism in the middle-lower crust, SW Sweden DANIEL HARLOV1, ALFONS VAN DEN KERKHOF2, EDWARD HANSEN3 AND LEIF JOHANSSON4 1

GeoForschungsZentrum, D-14473 Potsdam, Germany 2 University of Göttingen, D-37077 Göttingen, Germany 3Hope College, Holland, Michigan 49423 USA 4Lund University, SE-22362 Lund, Sweden The 1.4 Ga Varberg-Torpa charnockite-granite intrusion (Kattegatt coast, Varberg, SW Sweden) consists of the Varberg charnockite (Opx-Cpx-Bt-Amph-Gt-Plg-Kfs-Qtz) and the synmagmatic Torpa granite (Bt-Amph-Gt-Plg-Kfs-Qtz), which contains several charnockite enclaves, and has a similar whole rock chemistry. Granite and charnockite were intruded at 650–700°C and 750 MPa (Gt-Opx, Gt-Cpx thermometry; Gt-Opx-Plg-Qtz barometry). Fluid inclusions from the charnockite are characterized by high partial CO2 densities (40-90 % bulk CO2; no CH4 or N2) and are found in Qtz, Gt, Plg, and FAp. Magmatic fluids in the granite correspond to aqueous-carbonic inclusions with an estimated bulk composition (mol%) of H2O(73), CO2(25), and NaCl(2). Fluid inclusion, petrographic, mineralogic, geochemical, and field evidence suggest that charnockite-granite crystallization was more a function of relative H2O activity than relative depth. The Varberg charnockite is associated with in-situ, highly localized areas of fluid-induced (metamorphic) dehydration in the surrounding regional, amphibolite-facies, migmatised, granitic gneiss. These areas include a 1.4 Ga, Opx-bearing, 3 m wide dehydration zone surrounding a former shear zone 70 km SE of Varberg. They also include numerous Cpx megacryst-bearing veins and patches (5 cm – 2 m wide) in the granitic gneiss, continuing 80 km southwards from the Varberg charnockite in a broad band along the Kattegatt coast. Also found in the same area are Plg-bearing leucosomes (1420-1460 Ma or 970 Ma) of which half contain either Opx or Cpx megacrysts which indicate local, fluid-rich, partial melts with low H2O activities. Each feature described emphasizes the role of low H2O activity fluids during magmatism, partial melting, and metamorphism in the lower crust and suggests a connection between the two.

A495

Structural complexity in pyrrhotites: What are the implications for fluid-mineral interactions? D. HARRIES*, K. POLLOK, K. ETZEL AND F. LANGENHORST Bayerisches Geoinstitut, Universität Bayreuth, D-95440 Bayreuth, Germany (*correspondence: [email protected]) Pyrrhotite (Fe1-xS with x < 0.125) comes a close second after pyrite among the most abundant iron sulfides in ore deposits. At temperatures well below 140°C its various NiAs based superstructures can be described as modulations of vacancy ordering among and within Fe layers along principal crystallographic axes. The many possible modulations are intimately coupled to the deficiency of Fe resulting in large numbers of possible polytypes with distinct Fe/S ratios. Crystallographic models of NC-type modulations – being most common in natural pyrrhotites – suggest the possibility of structural continuity among pyrrhotite polytypes, i.e. widely varying and non-intergral N values of stacking schemes governed by modulation along the c-axis are to be expected and allow for high structural variability on smallest scales. We studied a selection of natural pyrrhotites by analytical transmission electron microscopy (ATEM), atomic force microscopy (AFM), and electron backscatter diffraction (EBSD) techniques which provide the advantage of highly resolved structural analysis. Our results show that structural and compositional heterogeneity of different magnitudes exists on µm to nm scales. Selected area electron diffraction reveals very long range ordering of Fe vacancies being of enigmatic structural (meta?)stability. Slight variations of stacking schemes occur frequently and are accompanied by various defect structures like stacking faults, twin and antiphase boundaries. Exsolution-like lamellae of distinct polytypes within pyrrhotite hosts apparently formed by reordering of vacancies and show more pronounced structural contrasts but still share common crystallographic orientations and coherent displacements by subgrain boundaries. Etching of pyrrhotite surfaces reveals topography contrasts between lamellae and hosts and indicates different solubilities in low temperature aqueous fluids which we attempt to quantify by AFM to realistically resolve reactivity differences between different pyrrhotite polytypes. Batch experimental designs and bulk X-ray diffraction have so far rendered this impossible. Besides this subject our preliminary studies will furthermore address the replacement relationships with secondary phases encountered during low temperature alteration and weathering.

A496

Goldschmidt Conference Abstracts 2009

Biomarker lipid diversity as a function of growth conditions in Rhodospirillum rubrum

Biodegradation of solvent extractable coal-associated organic matter by a methanogenic microbial consortium

KATE HARRIS1*, TANJA BOSAK1, ROBERT NELSON2, CHRISTOPHER REDDY2, LILLIAM CASILLAS3 3 AND JOSE L. LUGO

STEVE H. HARRIS1*, ELIZABETH J. JONES2, WILLIAM OREM3, MARY VOYTEK2, ARTHUR CLARK1, MARGO CORUM3, HARRY LERCH3, PETER WARWICK3, ANNE BATES3 AND RICHARD L. SMITH4

1

Massachusetts Institute of Technology (*correspondence: [email protected], [email protected]) 2 Woods Hole Oceanographic Institution ([email protected] , [email protected]) 3 University of Puerto Rico ([email protected]) Sedimentary rocks of all ages abound with geostable lipids of microbial origin, but many of these biomarkers lack known organismal sources and a clear environmental context. Here we use Rhodospirillum rubrum, a metabolically versatile, genetically tractable alpha-Proteobacterium, to explore the diversity of its polycyclic triterpenoids as a function of growth conditions. By using comprehensive two-dimensional gas chromatography [1], we detect a number of bicyclic, tetracyclic and pentacyclic triterpenoids derived by the enzymatic cyclization of squalene in R. rubrum and produced in amounts comparable to squalene and diploptene. These tentatively identified compounds include bicyclic polypodatetraene, malabaricatriene, euphadiene, adianene, fernene, and scalarane. The greatest abundance and diversity of non-hopanoid polycyles are observed when microbes grow photolithoautotrophically under anaerobic conditions, while the least abundance and diversity occurs during heterotrophic growth in the dark under aerobic conditions. Although certain organisms, such as Arabidopsis thaliana, contain multiple triterpene cyclases that engender a diversity of polycyclic lipids [2], R. rubrum’s genome contains only a single gene encoding a squalene-hopene cyclase. Some of the observed diversity of sedimentary microbial triterpenoids could thus be attributed to a small number of enzymes operating under a range of environmental and physiological conditions. [1] Ventura (2007) PNAS 104, 14260-14265. [2] Lodeiro (2007) J. Am. Chem. Soc. 36, 11213-22.

1

U.S. Geological Survey, Geologic Discipline, Denver, Colorado, 80225 USA 2 U.S. Geological Survey, Water Resources Discipline, 956 National Center, Reston, Virginia 20192, USA 3 U.S. Geological Survey, Geologic Discipline, 956 National Center, Reston, Virginia 20192, USA 4 U.S. Geological Survey, Water Resources Discipline, 3215 Marine Street, Boulder, Colorado, 80303 USA Methane from unconventional natural gas reservoirs represents an increasingly important source of domestic energy in several countries including the United States. The US has considerable reservoirs of this natural gas, some of which is sorbed to subsurface coals and held in place by in situ hydrostatic pressures. For many of the coalbed methane reservoirs, the isotopic composition of the gas and the site’s geologic history implicate a microbial origin for the methane. In light of these factors, we investigated the potential for extant coalbed methanogenesis as well as the ability for solvent extractable coal-associated organic matter to support methane production. Methane production was measured in laboratory incubations containing either crushed coal or chloroform-extracted organic matter inoculated with a methanogenic consortium previously shown to degrade coal. Incubations containing the coal-free organic extracts demonstrated methane production levels well above those observed for the unextracted coal. In contrast to earlier preliminary work, there was not a clear correspondence between methane production and the amount of extractable organic matter for a given coal. Thus, quality and bioavailability, and not quantity of coal-associated organic matter in providing carbon and energy sources supporting methanogenesis are likely critical factors influencing the process of methane production in coalbeds.

Goldschmidt Conference Abstracts 2009

A497

Probing the dark age: Crust-water interactions on Hadean Earth

Continuous thermal histories from muscovite 40Ar/39Ar age spectra

T.M. HARRISON

T.M. HARRISON1, M.T. HEIZLER2, I. HAVIV3 3 AND J.-P. AVOUAC

Institute of Geophysics and Planetary Physics & ESS, UCLA, Los Angeles, CA, 90095 USA ([email protected]) The Hadean Eon (ca. 4.5-4.0 Ga) is the dark age of Earth history; there is no known rock record from this period and as a result our knowledge of the growth history of continental crust is equally consistent with the planet then hosting massive early crust or essentially none at all. Without support from a rock record, our understanding of pre-Archean continental crust largely comes from investigating Hadean detrital zircons. We know that these ancient zircons yield relatively low crystallization temperatures and some are enriched in heavy oxygen, contain inclusions similar to modern crustal processes, and show Hf isotope evidence of silicate differentiation by 4.51 Ga. These observations are interpreted to reflect an early terrestrial hydrosphere, early felsic crust in which granitoids were produced and later weathered under high water activity conditions, and even the possible existence of plate boundary interactions – in profound contrast to the traditional view of an uninhabitable, hellish world. As virtually all researchers agree that life could not have emerged until there was liquid water at or near the Earth’s surface, a significant implication is that our planet may have been habitable as much as 600 million years earlier than previously thought. Possible scenarios are explored with a view to reconciling our growing but fragmentary record with our knowledge of conditions then extant in the inner solar system.

1

Institute of Geophysics & Planetary Physics & ESS, UCLA, Los Angeles CA, 90095 USA, [email protected] 2 NMBGMR, New Mexico Tech, Socorro, NM 87801, USA 3 Division of Geological and Planetary Sciences, Caltech, Pasadena, CA 91125 USA The recent recognition that 40Ar/39Ar age spectra and 39Ar Arrhenius plots derived from vacuum step-heating of white micas correspond to simple diffusion theory [1] leaves open the possibility that continuous thermal histories can be extracted from muscovite via the multi-diffusion domain (MDD) model [2] instead of only a single T-t datum. If so, then terranes not previously accessible to high resolution thermochronometry (e.g., low grade regional metamorphism) could routinely access vastly improved T-t histories leading to refined tectonic interpretations. We followed up our experimental study [1] by applying laboratory heating protocols designed to maximize the extraction of kinetic information to white mica separates from a N-S transect across the Main Central Thrust, Arun Valley, Nepal. Most 40Ar/39Ar spectra reveal internal age gradients that we interpret to reflect 40 Ar* retention during protracted cooling due to tectonic activity. The age and log (r/ro) spectra show clear correlations – remarkable considering that the latter is not calculated from 40 Ar release – confirming that muscovite can retain Ar diffusion boundaries and mechanisms during vacuum stepheating that define the natural retentivity. Using recently published Arrhenius parameters for Ar diffusion in muscovite (E = 64 kcal/mol, Do = 4 cm2/s; [1]), these gradients reflect intragrain closure between ~425 and 280°C. That muscovite is amenable to MDD treatment places additional requirements on mineral separation practices. For example, the decision to reduce grain size in order to eliminate composite grains in the analyzed aliquot needs to be balanced against the requirement that the largest diffusion domain in the sample remain intact. The generality of our conclusion regarding MDD analysis of muscovite to other geologic environments remains to be tested. However, the numerous observations of staircase-type 40 Ar/39Ar age spectra of white micas from accretionary, anchimetamorphic and granitoid terranes suggest that this behavior is intrinsic to the mineral. The MDD approach applied to white micas has tremendous potential to increase the application of continuous, high resolution 40Ar/39Ar thermochronology to virtually all crustal provinces. [1] Harrison et al. (2009) GCA 73, 1039-1051. [2] Lovera et al. (1989) JGR 94, 17917-17935.

Goldschmidt Conference Abstracts 2009

A498

Geochemical availability of dietary Se possible etiological determinant of viral infectious diseases (VIDs)

Colloids in karstic percolation waters: Implications for the interpretation of trace element variations in speleothems

M. HARTHILL

ADAM HARTLAND, IAN J. FAIRCHILD 1 AND JAMIE R. LEAD

PO Box 3523 Frederick Maryland 21701 USA ([email protected]) 1

Se Biogeochemistry May Determine Outbreak of Pandemic Flu and other VIDs Regions of low geologic Se bioavailability [1] overlain with etiological origins of diseases indicates pandemic influenzas (1918 “Spanish” flu, 1957 Asian flu, 1968 Hong Kong flu, Avian H5N1 flu) and SARS originated in east central China “Guangdong” and Hubei Provinces; whereas, HIV and Ebola hemorrhagic fever originated in west central Sub-Saharan Africa, respectively [2]. These diseases are viral and infectious. Sparse data from literature indicate nutritional Se in these regions can fall substantially below dietary 37 mcg Se/d required to achieve metabolic 1µMol Se/L blood for full expression of immunocompetence [3].

Discussion of Results Micronutrient Se contributes to immunocompetence. Sedeficient individuals are susceptible to enterovirus, and benign viral forms mutate to virulence under Se-deficient host conditions [4]. Individuals <1µMol Se/L blood are susceptible to poliovirus, have decreased immune response to poliovirus vaccination, and poliovirus mutates under those host conditions; Se supplementation of the low Se status population raises immune response and decreases viral mutations [5]. Subsequent research confirms viral virulence and infectivity occurs under Se-deficient host conditions. Determinations of geochemical bioavailability of Se to food crops in these geographic regions are needed to help abate probable nutrient Se-deficiencies – and potential subsequent VIDs. [1] Oldfield (2002) Se-Te Assoc , 70p. [2] Harthill (2008) GSA annual mtg, [3] Xia et al. ( 2005) Am J Clin Nutr 81, 829-834. [4] Beck et al. (1994) J Med Virol 43, 166-170. [5] Broome et al. (2004) Am J Clin Nutr 80, 154-166.

School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK

Much of the current understanding relating to colloidal organic matter (COM) in speleothem-forming groundwaters has been obtained from detailed studies of the optical and chemical properties of speleothems. In particular, marked increases in trace elements known to coordinate with oxygencontaining groups of organic ligands (Y, Pb, Cu, Zn, P, Br) have recently been shown to coincide with UV-fluorescent laminae in a stalagmite from Grotta d’Ernesto, NE Italian Alps. Variations in the abundances of trace elements associated with COM in speleothems over time may be linked to the magnitude of infiltration events in the soil-aquifer system, but there have been no specific studies of element binding to organic or other finer colloids in speleothemforming groundwaters. Percolation water samples from three contrasting locations have been size-separated utilising membrane filtration (1 µm, 0.1 µm) and ultrafiltration (1 kD) and analysed for total organic carbon (TOC), UV-fluorescence and trace elements (ICP-MS). One study location (Pooles Cavern) offers high pH (>10) conditions resulting in chargestabilisation of finer colloids. At both high and lower pH drip sites, including Ernesto, enhanced autumnal infiltration coincides with higher TOC concentrations and elevated concentrations of trace metals. Also, observed depletions in trace metal concentrations between size-separated drip water samples reflect the same relationship found in soil leachates from the same site. Hence episodes of high abundances of colloid-associated trace elements measured in speleothems correspond to palaeo-precipitation events.

Goldschmidt Conference Abstracts 2009

The effects of metasomatic sulphide on mantle Re-Os systematics: Unravelling melt depletion and secondary processes

Magmatic evolution of the northwestern edge of Tauride-Anatolide Platform: Geochronological and isotopic implications

JASON HARVEY1*, ABDELMOUHCINE GANNOUN1,2, KEVIN BURTON1,3 AND PIERRE SCHIANO2

A. HASOZBEK1,2*, M. SATIR2, B. ERDOGAN3, E. AKAY3 AND W. SIEBEL2

1

Department of Earth and Environmental Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK (*correspondence: [email protected]) 2 Laboratoire ‘Magmas et Volcans’, Université Blaise Pascal, 5 Rue Kessler, 63000 Clermont-Ferrand, France 3 Department of Earth Sciences, University of Oxford, Parks Road, Oxford, OX1 3PR, UK Spinel lherzolite xenoliths from Mont Briançon, French Massif Central, retain evidence of several metasomatic events. Many individual xenoliths contain interstitial glasses and melt inclusions that are not in equilibrium with the major primary minerals [1-2]. Incompatible trace element mass balance calculations demonstrate that metasomatic components comprise a significant proportion of the bulk rock budget for these elements (e.g. <25% Nd; <40% Sr) [1]. Critically, for Re-Os geochronology, metasomatism within these xenoliths is accompanied by the mobilisation of sulphide. Evidence for prior melt depletion is still preserved in the co-variation of bulk rock, major elements (MgO 38.7–46.1 wt %; CaO 0.9– 3.6 wt %), and many samples yield unradiogenic bulk rock Os isotope ratios (187Os/188Os = 0.11541-0.12626). However, the subsequent metasomatism means that bulk rock isotope measurements, whether using lithophile (e.g. Rb-Sr, Sm-Nd) or siderophile (Re-Os) based isotope systems, will only yield a homogenised average of multiple events. Os mass balance calculations demonstrate that >95% of bulk rock Os in peridotite is hosted within 2 populations of sulphide grain: (i) interstitial, metasomatic sulphide with low [Os] and radiogenic 187Os/188Os, and (ii) primary sulphides with high [Os] and unradiogenic 187Os/188Os, which have been preserved within host silicate grains and shielded from interaction with transient melts and fluid [3]. The latter often preserve geochronological information of the melt that they originally precipitated from as an immiscible liquid [e.g. 4]. TRD ages of individual primary sulphide grains preserve evidence for melt depletion beneath the Massif Central from at least 1.8 Gyr ago [1]. [1] Harvey et al. submitted to Geochim. Cosmochim. Acta [2] Schiano & Clocciatti (1994) Nature 368 622-624 [3] Alard et al. (2002) Earth Plan. Sci. Lett 203 651-633. [4] Harvey et al. (2006) Earth Plan. Sci. Lett 244 606-621.

A499

1

DEU, Marble Programme, Torbalõ-Izmir-Turkey (*correspondence: [email protected]) 2 Institute of Geoscience, University Tübingen, Germany 3 DEU, Geology Engineering, Tõnaztepe-Izmir-Turkey In the study region between Alacam Mountains and Emet, the northwestern edge of the Tauride-Anatolide platform is observed as laterally continuous tectonic zones which were experienced different history of metamorphism. These tectonic zones are; Menderes Massif, Afyon Zone, Tavşanlõ Zone, İzmir-Ankara Zone stacked as nap packages in ascending structural order from the south to the north. These tectonic zones were assembled together by the collision of the Sakarya Continent and the Tauride-Anatolide platform. In this study, we newly mapped various parts of these nap packages to understand their order of evolution. Geochronological and isotopic studies were performed on various magmatic suites of the Menderes and the Afyon Zones. U-Pb zircon and 207Pb/206Pb evaporation ages indicate 550-600 Ma for the gneissic rocks of the Menderes Massif. Carboniferous age is determined for a magmatic suite of the Afyon Zone. From the syntectonic granites, emplaced during the Main Menderes Metamorphism, 30.04 ± 0.56 Ma were determined. Tectonically assembled nap packages of the Menderes Massif, the Afyon Zone and Izmir-Ankara Zone are cut by Early Miocene granitic plutons. Their ages are determined as 21.7 ± 1.0 Ma, 19.3 ± 4.4 Ma, 20.0 ± 3.7 Ma by U-Pb isotopic dilution method. These granitic bodies are post-collisional and shallow seated. They are aligned to form a NE-SW trending magmatic belt. The map patterns, radiogenic ages and petrologic characteristics indicate that these young granites were formed by melting of abnormally thick continental crust. The interpretations of their being related to detachment tectonics as put forward in some recent literatures [1, 2, 3] are not valid. [1] Işõk et al. (2004) J Asian Earth Sci 23/4, 555-566. [2] Ring and Collins (2005) J Geological Soc Lond 162, 289-298. [3] Thomson and Ring (2006) Tectonics 25, 1-20.

Goldschmidt Conference Abstracts 2009

A500

Gochemical studied of the basement rock at Abu Ghalaga area, South Eastern Desert, Egypt

Probing the intrinsically oil-wet surfaces of pores in North Sea chalk at sub-pore resolution

M.H. HASSAN

T. HASSENKAM, L.L. SKOVBJERG AND S.L.S. STIPP

Department of Geology, Faculty of Science, Assiut University, Assiut, Egypt ([email protected])

Nano-Science Center, Department of Chemistry, University of Copenhagen ([email protected])

The analysis of structural and metamorphic events affecting Abu Ghalaga area revealed the presence of two lithostructural unite, viz. infrastructure (Abu Masila gneissose granite), suprastructure (ophiolitic metavolcanics) and arc metavolcanics. These rocks are syn - and late - tectonically intruded by metagabbros, granitoids (subduction-related), followed by younger gabbros. Hammamat sediments unconformably overlie these rocks. The geochemical characteristics of the Abu Masila gneissose granite and granitoids of the study area have calcalkaline, sodic character and peraluminous to peraluminous nature. The different discrimination diagrams indicate that the Abu Masila gneissose granite and granitoids are subductionrelated, crustal origin (C-type), of igneous origin (I-type) and were generated in a volcanic arc environment (VAG). The estimated thickness is 20-30 km which is in accordance with thickness estimated reported for the pan-African crust. The Abu Masila gneissose granite and granitoids display low Σ REE. The Abu Masila gneissose granite displays a positive Eu anomaly whereas the granitoids is negative Eu anomalies.

Pore surface properties control oil recovery. Wettability, the tendency for a surface to cover itself with fluid, is traditionally defined by the angle a droplet makes with a surface, but this macroscopic definition is meaningless when the particles are smaller than even the smallest droplet. Understanding surface wetting, at the pore scale, will provide clues for more effective oil recovery. We used a special mode of atomic force microscopy (AFM) and a hydrophobic tip to collect matrices of 10,000 force curves over chosen areas on internal pore surfaces and constructed maps of topography, adhesion and elasticity. We investigated chalk samples from a water-bearing formation in the Danish North Sea oil fields that had never seen oil. Wettability and elasticity were inhomogeneous over scales of 10’s of nanometers, smaller than individual chalk particles. Some areas were soft and hydrophobic, whereas others showed no correlation between hardness and adhesion.

Figure 1. SEM picture of Chalk from the North Sea. We conclude that the macroscopic parameter, “wetting”, averages the nanoscopic behaviour along fluid pathways and “mixed wet” samples have patches with vastly different properties. Development of reservoir hydrophobicity has been attributed to infiltrating oil, but these new results prove that wettability and elasticity are inherent properties of chalk [1]. [1] Hassenkam et al. (2009), PNAS, in press.

Goldschmidt Conference Abstracts 2009

Molecular characterization of atmospheric particulates using Fourier transform ion cyclotron resonance mass spectrometry 1

1

PATRICK G. HATCHER , RACHEL L. SLEIGHTER , AMANDA S. WILLOUGHBY1, PAULA A. MAZZER1, ANDREW S. WOZNIAK2 AND JAMES E. BAUER2 1

Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, VA 23529 ([email protected]) 2 Virginia Institute of Marine Sciences, College of William and Mary, Gloucester Point, VA 23062 ([email protected]) A significant component of the organic matter in atmospheric particulates is composed of “humic-like substances”. Molecular level charaterization of these has been limited in the past to compounds that are either extracted by organic solvents or chemically and thermally degraded from macromolecular precursors. We have recently introduced a new approach to molecular-level studies of humic substances from soils and natural waters-use of ultrahigh-resolution mass spectrometry available only from Fourier transform ion cyclotron resonance mass spectrometers [1]. This instrumentation allows us to identify unique elemental formulas for the types of organic molecules existing in atmospheric particulates. We also can evaluate the major compound classes to which these molecules belong and essentially provide an avenue for molecular characterization that has not been possible previously. Our studies of aerosols collected in the Eastern USA [2], diesel exhaust, and aerosols from a plume of natural vegetation fires identify molecules of clear combustion origin intermixed with compounds having a clear vegetative or soil origin. Many of these soot or black carbon-derived compounds appear to be sulfur or nitrogen-substituted. Nitric acid oxidation of diesel exhaust and atmospheric particulates tends to enhance the production of these compounds. It is obvious that a new approach for molecular characterization of the humic-like molecules in atmospheric particulates will revolutionize our understanding of the chemistry of these substances and can lead us to better understanding of their chemistry and role in atmospheric processes. [1] Sleighter and Hatcher (2007) J. Mass Spectrom, 42, 559– 574. [2] Wozniak et al. (2008) Atmos. Chem. Phys 8, 50995111.

A501

Isotopic investigation of Hamamayagı hot water spring (Samsun, Turkey) E. HATIPOĞLU1*AND F. GÜLTEKIN2 Karadeniz Technical University, Department of Geological Engineering, 61080, Trabzon Turkey (*[email protected], [email protected]) In this investigation Ladik (Samsun) hot water spring has been studied from the point of geology and environmental õsotopes. The study area is located around middle-north of Turkey. In the studied area, Permian to Pliocene age, sedimentary unites interbedded with volcanic rocks are crop out. δ 18O, δ 2H and δ3H isotope analyses were carried out to determine the origin of waters, recharge altitude, precipitation types, groundwater circulation. In the 18O, δ 2H diagram all of the waters in the study area situated near the Globol Meteoric Water Line (MWL) and indicate meteoric origin. According to the 18O- temperature relation all water samples recharged the same elevation in the plain. Due to the snowfall on the river in the winter a variation is occurred in 18O values of the river water. Low tritium and high electrical conductivity value in the Hamamayağõ Thermal Spring indicate that this spring has deep circulation. High tritium and low EC values in the in the Kocapõnar Spring and Hamamayağõ River show that these spring waters have shallow circulation. Tritium values of the Hamamayağõ Thermal Spring is near the zero indicated that this spring water has deeply circulation. In order to determinate the origin of sulpher (SO4) and carbon in the waters, all waters were analysed for their 13CVPDB (Bee Pee Belemnite) and 34SCDT (Canyon Diablo Triolite). According to the HCO3-13C relation in the thermal spring and cold spring, while HCO3 contend of the cold spring is reduced, δ13C value is increased. This situation in the thermal spring has opposite. Carbon in the Hamamayağõ Thermal Spring has come different origins that are marine carbonates and fresh water carbonates, CO2 gas from mantle origin. Carbon in the Kocapõnar Spring and Hamamayağõ River has controlled by CO2 in the soil and subsurface pores. δ34SCDT values show that the sulphure has come different sources in cold and hot springs. δ34S isotope compositions in Hamamayağõ Thermal Spring come from rocks which are reduced sulphur compounds with respect to δ34SCDT. Source of the sulpher in Kocapõnar Spring and Hamamayağõ River are formed limestone and shale in the study area. [1] Craig, H., 1961. Isotopic Variations in Meteoric Water, Science, 133, 1702-1703. [2] Clark, I. ve Fritz, P., 1997. Environmental Isotopes in Hydrogeology, Lewis publıshers, New York. 328 p.

A502

Goldschmidt Conference Abstracts 2009

Ion kinetic energies’ influence on mass bias in (MC)ICPMS B. HATTENDORF1*, G.H. FONTAINE1, F. OBERLI2, B. BOURDON2 AND D. GÜNTHER1 1

ETH Zurich, Laboratory for Inorganic Chemistry, Wolfgang Pauli Str. 10, 8093 Zurich (*[email protected]) 2 ETH Zurich, Isotope Geochemistry and Mineral Resources, Clausiusstr. 25, 8092 Zurich ([email protected]) The variability of mass bias imposes a severe limitation on the accuracy and precision of isotope ratio measurements achievable by multi collector inductively coupled plasma mass spectrometry (MCICPMS). There are a number of processes that affect not only the magnitude of mass fractionation but also its stability with respect to subtle changes in the operating conditions. Space charge effects and diffusion processes are most likely the dominating sources but cannot fully explain the dependence of mass fractionation changes on subtle variation of the operating conditions within the ICP [1]. This study investigated the dependence of the mass discrimination on the operating conditions of MCICPMS instruments. Variation of the carrier gas flow rates revealed that mass fractionation is not monotonously depending on the temperature in the ion source, which would be expected from changes in the respective ion mobilities and mean kinetic energies. The respective changes are however well explained by energy- and thus mass-dependent changes of ion transmission inside the ion optics of the ICPMS. The mean ion kinetic energies were found to be generally correlated with the gas temperature inside the ion source, which may thus be considered a significant contribution to variation of mass bias with changes in the physical properties of the ICP source. A reduction of mass bias variability can be achieved by adjusting the operating conditions of the ion source in a way that small changes in the respective ion energies have similar instead of opposite effects on the relative trasnmission of different isotopes. For example, this approach reduced the mass bias variation of Nd, in the presence of a 10 fold excess of Ho, by a factor of six. [1] Fontaine G.H. et al. J Anal. At. Spectrom., 2009, DOI: 10.1039/b816948a

Novel tools for in situ detection of biodiversity and function of dechlorinating and uranium-reducing bacteria in contaminated environments K. HAUER1, D.B. MEISINGER1, M. PAVLEKOVIC1, S.H. THOMAS2; A.K. KNIGGENDORF3, J. CHEE-SANFORD4, R. SANFORD5, C.A. LEBRÓN6, W. LIEBL1, F.E. LOEFFLER2 AND N.M. LEE1 1

TUM, Technische Universität München, Freising, Germany ([email protected]) 2 Georgia Institute of Technology, Atlanta, GA, USA ([email protected]) 3 Leibniz Universität Hannover, Hannover, Germany ([email protected]) 4 USDA Agricultural Research Service, Goodwin, Urbana, IL, USA ([email protected]) 5 University of Illinois at Urbana-Champaign, Urbana, IL, USA ([email protected]) 6 NFESC, Port Hueneme, CA, USA ([email protected]) The combination of chlorinated and radioactive compounds impose a serious, long-lasting threat to our environment that demand a holistic approach for successful bioremediation. During the last years, several different species have been discovered that can degrade or transform these compounds to a less hazardous state. However, in order to fully exploit their potential, it is necessary to develop reliable and quick analytical tools for real time in situ detection of target cells and their activities. To achieve this, we developed and compared different types of in situ detection tools: i) a hierarchic set of 16S rRNA oligonucleotide probes to detect highly active species, targeting relevant genera and key species on different taxonomical levels; ii) a 16S rRNA ribosomal based CARD-FISH probe set to detect cells that evade detection with standard FISH procedures; iii) a functional gene FISH approach, to target single copy genes encoding degradative traits; and iv) RAMAN microscopy, to develop a probe-independent and non-invasive alternative to the FISH protocols. All tools were applied to pure cultures, enrichment cultures and samples from contaminated environments, and the results retrieved with these tools were compared with other analytical tools such as PCR and degradation kinetics. Interestingly, we often observed discrepancies between the results produced with the different tools, which most likely reflect the inherent biases of each respective tool. Hence, for a full mapping of microbial ecological parameters, a combined approach is best suited for providing a better understanding of in situ activities and overall systems ecology in environmental systems.

Goldschmidt Conference Abstracts 2009

A503

Accelerated acidification in eastern boundary current systems

Volatile element variability in MORB: origins and consequences

CLAUDINE HAURI1*, NICOLAS GRUBER1, ZOUHAIR LACHKAR1 AND GIAN-KASPER PLATTNER1,2

E.H. HAURI1 AND A.E. SAAL2

1

Institute of Biogeochemistry and Pollutant Dynamics, ETH Zürich, 8092 Zürich, Switzerland (*correspondence: [email protected]) 2 now at University of Bern, Bern, Switzerland Eastern Boundary Upwelling Systems (EBUS), such as the California Current System (CalCS), are particularly sensitive to ocean acidification: the pH of their surface waters is comparatively low and their change in pH for a given uptake of anthropogenic CO2 is particularly high. This effect is particularly strong in the Pacific Ocean, as evidenced by the dramatic shoaling of the aragonite saturation horizon off the U.S. West Coast to depth of less than 100 m (Feely et al., 2008). We investigate this high vulnerability to ocean acidification of Eastern Boundary Current upwelling systems by conducting simulations with the ETH-UCLA Regional Oceanic Modeling System (ROMS) at eddy-resolving resolution for two of the four EBUS, namely the California, and the Canary Current Systems. Our simulations for the CalCS show that between pre-industrial times and present, the mean pH of the surface ocean has decreased by already about 0.1 pH units. As a result, the aragonite saturation horizon has shoaled by ~100 m and now reaches the euphotic zone in a few eddies and in near-shore environments during upwelling, in agreement with recent observations. Projections up to 2050 (IPCC SRES A2-scenario) suggest an additional drop of pH by ~0.2 units and a wide-spread and year-round shoaling of the saturation horizon into the euphotic zone. Transient simulations are currently underway to determine when critical thresholds are passed. We expect that the aragonite saturation horizon will be reaching up into the euphotic zone in nearshore environments throughout the upwelling season already during the next decade. The passing of certain thresholds will not be gradual, however. Due to the high temporal and spatial variability that characterizes EBUS, organisms are exposed to a wide range of pH (variations of up to 0.3 to 0.4 units) and saturation states, an effect that likely will increase in the future due to enhanced upwelling and lowered buffer capcity. As a result, the effect of ocean acidification in EBUS will consist of a simultaneous downward shift and a widening of the probability density function for pH and saturation state. Both effects will cause a rapid increase with time of the frequency, at which given thresholds will be passed. What this means for organisms can only be speculated about at present.

1

DTM, Carnegie Institution of Washington, Washington DC 20015 ([email protected]) 2 Brown University, Providence RI 02912 ([email protected]) The abundances of H2O, CO2 and other volatiles in MORB can provide unique information on depths and extents of melting and lateral variations in mantle viscosity and melting temperature, but this information can also be obscured by degassing, fractionation and assimilation processes within the crust. Degassing begins at depths within the crust that depend on initial enrichment in CO2, and depleted samples often show vapor saturation pressures consistent with the depths of axial magma chambers revealed by seismology. Magma transport times estimated from vapor supersaturation are generally faster on-axis than off-axis, and on-axis magmas generally show less assimilation (excess Cl). Assimilation tends to be stochastic in geographic distribution, such that uncontaminated magmas can be found both on- and off-axis, but contaminated magmas may become more frequent on-axis as magma supply and spreading rate decrease. CO2/Nb ratios decrease systematically with MgO, indicating concurrent degassing and fractional crystallization. An upper bound on CO2/Nb (~400) appears to be a widespread feature of primitive depleted and normal MORB that have erupted quickly through the crust. A CO2/Nb ratio of ~400 is also characteristic of vapor-undersaturated melt inclusions from the northern rift zone of Iceland, and place firm constraints on the flux of CO2 and He from ocean ridges. At Pacific ridges, ratios of H2O/Ce, F/Nd and Cl/K in uncontaminated magmas show systematic co-variations with other trace element indices of enrichment (Th/La, Nb/La) that are correlated with Sr and Nd isotopes, indicating lateral variability in long-lived mantle source compositions in the upper mantle. The data are consistent with the entire spectrum of Pacific MORB (far from hotspots) being generated by melting of variable mixtures of only two sources, one highly depleted (D-MORB) and one enriched (E-MORB). Sparse stable isotope data are available from Pacific ridges and the MAR [1,2]; the data are permissive of enriched sources originating as “contamination” of the upper mantle by plumes, by recirculation of mantle-wedge peridotite from subduction zones, and by melts and residues of subducted oceanic crust, but not all of these origins are compatible with all the isotope, trace element and volatile data. [1] leRoux et al. (2003) Fall AGU #V51A-03. [2] Cooper et al. (2004) EPSL 220:297-316.

A504

Goldschmidt Conference Abstracts 2009

Stable isotope systematics of volatiles in Apollo 15 lunar volcanic glasses E.H. HAURI1, A.E. SAAL2, J.A. VAN ORMAN3 2 AND M.J. RUTHERFORD 1

DTM, Carnegie Institution of Washington, DC 20015 ([email protected]) 2 Brown University, Providence, RI 02192 ([email protected], [email protected]) 3 Case Western Reserve University, Cleveland, OH 44106 ([email protected]) The presence of magmatic water in lunar volcanic glasses (LVGs) [1] requires a re-evaluation of conventional wisdom that the Moon was entirely dehydrated following its formation via giant impact. The LVGs are the most primitive melts erupted on the surface of the Moon, and the presence of water and chlorine in these magmas indicates the presence of a deep volatile-bearing mantle source within the Moon. New volatile abundance data for over 200 individual Apollo 15 lunar glasses [2] show an increase in the highest volatile concentrations by a factor of 2 over previously reported data (up to 70 ppm H2O, ref. 1). D/H ratios range from +700‰ to +5400‰ and are inversely correlated with water contents. The presence of tritium (T) in lunar samples [3] requires the presence of a spallogenic component of volatile isotopes from interactions with solar and galactic cosmic rays, but the distribution (surface vs interior) of this component within LGVs remains poorly defined. At the lowest H2O contents, spallogenic D can potentially account for half of the abundance of D (and less than 0.005 ppm of the H) in the interiors of the glass beads based on estimated T, D and H production rates [3, 4], but the production rates would have to be underestimated by a factor of 100 to account for the D/H ratios of LVGs with high H2O. The D/H ratios of magmatic water in H2O-rich LVGs are thus undisputably fractionated from terrestrial values. The data are consistent with kinetic fractionation of D from H during post-eruptive degassing, from a pre-eruptive H2O-D/H composition similar to terrestrial basalts, provided that H and D diffuse as protons/deuterons. Alternatively, the high D/H ratio of LVG water could be inherited from gas condensed within the Moon from a residual atmosphere surrounding the proto-lunar disk after the giant impact. The stable isotope composition of other volatile elements in LVGs will also be discussed at the meeting. [1] Saal et al. (2008) Nature 454, 192-195. [2] Saal et al., this volume. [3] Bochsler et al. (1971) LPSC 2, 1803-1812. [4] Merlivat et al. (1976) LPSC v. 7, 649-658.

Determining trace metal-nanoparticle associations in contaminated sediment using analytical TEM and FFF coupled to MALLS and HRICPMS K.L. HAUS1*, F. VON DER KAMMER2, M. HASSELLÖV3, J.N. MOORE4, M.F. HOCHELLA, JR.1 1

Department of Geosciences, 4044 Derring Hall, Virginia Tech, Blacksburg, VA 24061 USA (*correspondence: [email protected]) 2 Department for Environmental Geosciences, University of Vienna, Althanstraße 14 UZ AII, 1090 Vienna, Austra ([email protected]) 3 Department of Chemistry, University of Gothenburg, SE-412 96, Gothenburg, Sweden ([email protected]) 4 Department of Geology, University of Montana, Missoula, MT 59812 USA Analytical electron microscopy (AEM) and flow fieldflow fractionation (FlFFF) are being used to study the associations between trace metals and nanoparticulate materials in sediment. Six samples have been taken from the channel of the Clark Fork River system in western Montana, USA. A large dam-removal and channel re-construction project has released reservoir sediment contaminated with toxic trace metals (Pb, Zn, Cu, As) from over 150 years of base-metal mining activities upstream. Digestion and analysis by inductively coupled plasma atomic emission spectroscopy (ICPAES) revealed that all samples contained elevated amounts of the trace metals of interest. Nanoparticles were recovered from the sediment samples by aqueous extraction and analyzed using FlFFF coupled to multi angle laser light scattering (MALLS) and high resolution inductively coupled plasma mass spectroscopy (HR-ICPMS). Aliquots of the extracts were also used to prepare samples for analysis with a FEI Titan high resolution scanning/transmission electron microscopy (S/TEM) equipped with EDS and EELS detectors. Results to date indicate extensive association of these toxic trace metals with the naoparticulate size fraction in the sediments. In addition to the comparably large surface area to mass ratio of nanoparticles, the properties of nanoparticles have been shown in many cases to be dramatically altered from that of similar material at larger sizes. These property changes and potentially increased reactivity may have a large impact on the cycling of trace metals in natural systems. This has major implications for stream health in other dam-removal projects that may release contaminated sediments downstream.

Goldschmidt Conference Abstracts 2009

Merging Geochemical and Metagenomic Data to Predict C and N-fixation Pathways in Hydrothermal Microbial Communities JEFF R. HAVIG1, JASON RAYMOND4, D’ARCY R. MEYER-DOMBARD3, NATALYA ZOLOTOVA1 1,2 AND EVERETT L. SHOCK 1

School of Earth & Space Exploration, Arizona State University, Tempe, AZ 85287, USA ([email protected]) 2 Department of Chemistry & Biochemistry, Arizona State University, Tempe, AZ 85287, USA 3 School of Natural Sciences, University of California, Merced, CA 95344, USA 4 Department of Earth and Environmental Sciences, University of Illinois at Chicago, Chicago, IL 60607 Comparisons among isotopic data from multiple hot spring microbial communities (biofilms) indicate that geochemically similar hot springs can host functionally distinct biofilms, as in the case of Octopus Spring and ‘Bison Pool’ (BP) in Yellowstone National Park. Isotopic variations coupled with metagenomic (MG) data allow prediction of predominant C-fixation pathways in biofilms. Comparison of measured biofilm fractionation with that found in literature predict the reductive tricarboxylic acid cycle and the 3-hydroxyproprionate pathway (TCA and 3HP) to dominate at the high temps. MG data reveal that biofilms found at high temps can perform TCA and the acetyl-coenzyme A pathway (ACP), but not 3HP. Combining these results, we predict biofilms above ~80°C in BP predominately utilize TCA for fixing carbon. Using this methodology, we also predict C-fixation dominance to shift to ACP at ~80°C, and to the pentose phosphate cycle at ~66°C. BP biofilm N isotopic data reveal a shift from N-limitation at high temps to N-fixation at lower temps, born out in MG data. Sharp changes in isotopic signatures over short thermal gradients hint at shifts in limiting factors driving biofilm complexity.

A505

The generation, evolution and preservation of the continental crust CHRIS HAWKESWORTH1*, CRAIG STOREY1, BRUNO DHUIME1, HORST MARSCHALL1, ANNA PIETRANIK2 AND TONY KEMP3 1

Department of Earth Sciences, University of Bristol, Bristol BS8 1RJ, UK (*correspondence: [email protected]) 2 Institute of Geological Sciences, University of Wrocław, 50205 Wrocław, Poland 3 School of Earth and Environmental Sciences, James Cook University, Townsville, QLD 4811, Australia The geology of the continental crust is marked by peaks in the crystallization ages of zircon, and the ages of rocks that represent new continental crust. There is increasing evidence that these may reflect the different preservation potential of rocks generated in different tectonic settings, rather than major changes in the rates at which new crust is generated. The development of dry granulite facies rocks appears to facilitate the stabilization of continental crust, and granulite facies conditions are associated with the generation of new crust behind retreating plate margins. For example, much of the crust of eastern Australia was stabilized in accretionary orogens with dominant granite-turbidite basins from ~520-220 Ma, and the proportion of new crust can be estimated from Hf isotope variations in magmatic zircons. Mafic and granitic rocks have different Lu/Hf ratios, and combined Hf-O isotope data in Archaean zircons indicate that much of the initial crust generated was mafic in composition. The proportions of felsic and mafic crust may therefore have been similar to that predicted by heat production considerations. A number of studies have highlighted that zircons remain poor windows into the upper mantle. We review the constraints of a recent analysis of the evolution of depleted upper mantle from Hf isotopes in near concordant zircons and from Nd isotopes in titanites. Reconciling the sedimentary and igneous records of the evolution of the crust requires better constraints on the erosion factor ‘K’, which relates the model age of the bulk sediments to the average model age of the crustal sources from which they derived. We indicate how this may be evaluated from studies of Hf and Nd isotopes in recent river systems. Present models of crustal evolution are based on records from “stable” areas and they may therefore be biased by the formation of stable supercontinents. One issue is how such records compare with those from settings with poor preservation potential.

A506

Goldschmidt Conference Abstracts 2009

Rutile solubility in supercritical NaAlSi3O8-H2O fluids L.A. HAYDEN* AND C.E. MANNING University of California Los Angeles, Los Angeles CA 90095 USA ( [email protected]) (*correspondence: [email protected]) Subduction zones are important settings for chemical cycling. The transfer of material in subduction zones is often the result of a water-rich fluid; however, the nature of these fluids and their capacity for mobilizing key trace elements, such as Ti, remains uncertain. A central question is: Are these fluids silicate-rich or dilute solutions, or can intermediate fluids act as metasomatizing agents? Previous work on Ti has focused on hydrous melts or water-rich solutions [1-5]. We present new results of an experimental study on rutile (TiO2) solubility in supercritical, intermediate NaAlSi3O8-H2O fluids. Experiments were conducted in a piston-cylinder apparatus at 900°C and pressures between 0.9 and 2.2 GPa for a range of fluid compositions. At pressures within the supercritical regime (1.0-2.0 GPa) rutile solubility was determined by electron probe microanalysis of the quench glass; at <1.0 and >2.0 GPa, solubility was determined both by analysis of quench glass and rutile weight loss. Rutile solubility shows a non-linear increase with increasing Na-Al silicate in the fluid. At l.25-1.5 GPa, rutile solubility shows a strongly sigmoidal dependence on fluid composition, implying that dissolved Na-Al silicates enhance Ti solubility in fluids. Rutile solubility also shows a non-linear decrease with increased pressure at a given composition. This pressure effect is diminished at high water content (~70%), where solubility values begin to converge for supercritical fluids. Overall, relatively high solubility (~1000s ppm) of rutile in the supercritical fluids give insight into the magnitude and mechanism for mobilizing Ti and other HFSEs in subduction zones and other high pressure metasomatic environments. [1] Tropper & Manning (2005) Am. Mineral. 90 502-505. [2] Audétat & Keppler (2005) Earth Planet. Sci. Lett. 232 393-402. [3] Hayden & Watson (2007) Earth Planet. Sci. Lett. 258 561-568. [4] Manning et al. (2008) Earth Planet. Sci. Lett. 272 730-737. [5] Antignano & Manning (2008) Chem. Geol. 255 283-293.

Interactions of metal cations with mineral/water and organiccontaining mineral/water interfaces studied by second harmonic generation P.L. HAYES, J.N. MALIN, C.T. KONEK AND F. GEIGER Dept. of Chemistry, Northwestern Univ., Evanston, IL 60208, USA (*correspondence: [email protected]) The interactions of several metal ions – Ca(II), Sr(II), Ba(II), Zn(II) and Cd(II) – with model environmental interfaces are investigated using the Eisenthal χ(3) method for second harmonic generation (SHG) [1]. SHG is used to evaluate adsorption at silica/water and carboxylic acid functionalized silica/water interfaces [2, 3]. Utilizing a dynamic flow system and the sensitivity of SHG to interfacial potential, we track metal binding in real time. Results show that adsorption reaches steady-state conditions in a few minutes and is fully reversible. Adsorption isotherms are obtained for the metal ions at each interface and fit with the Gouy-Chapman and triple-layer models to obtain adsorption free energies ranging from –18 to –36 kJ/mol. Interfacial potentials, adsorbate number densities, interfacial charge densities are also obtained from the SHG experiments. For the alkaline earth metals, the adsorption free energies and adsorbate number densities for the silica/water interface increase with atomic number. The carboxylic acid functionalized interface displays lower adsorption free energies but higher maximum adsorbate number densities than the bare silica/water interface, which is consistent with acid deprotonation due to metal ion adsorption. Our SHG experiments provide valuable quantitative data that can be used in computational geochemistry for model validation. [1] Salafsky & Eisenthal (2000) J. Phys. Chem. B 104, 77527755. [2] Hayes, Malin, Konek & Geiger (2008) J. Phys. Chem. A 112, 660-668. [3] Malin, Hayes & Geiger (2009) J. Phys. Chem. C 113, 2041-2052.

Goldschmidt Conference Abstracts 2009

Application of the field seismic data in the security assessment of coal mining in Cuijiazhai Area SHIGEN HE AND ERGEN GAO*

A507

Nd isotopic compositions of adakites from Dabieshan: Implications for the subducted mafic lower crust of the South China Block YONGSHENG HE1,2*, SHUGUANG LI1, JOCHEN HOEFS2 2 AND ILKA SCHOENBERG

Institute of Disaster Provention Science Technology,Beijing 101601, China (*correspondence: [email protected]) 1

Introduction The Cuijiazhai area is located in Hebei Province in north China, where plenty of coal resources are mined. In recent years, a large amount of seismic exploration work with the aim at coal recources has been done in the area successively. Based on the foundation of seismic exploration data, this study focuses on the structure of sedimentary basin and the security assessment of coal mining in the Cuijiazhai area.

Experiment and Results A crisscross seismic exploration lines had been measured. the exploration lines are little longer than the field survey profile to cover all the possible coal resources area. Seismic data processing can be summarized concisely into the following steps [1]: (1) carefully checked the positions of field shot-receiver pairs to obtain accurate localities; (2) calculated the static corrections in details; (3) eliminated bad shots, bad courses and abnormal amplitudes; (4) selected appropriate deconvolution parameters; (5) made accurate velocity analysis and got residual static corrections through stacking; (6) carried out the post stack processing and precise migration. The result indicates that there is a buried reverse fault structure in the region, suggesting long-term tectonic push influenced Cuijiazhai area since Jurassic. This crustal deformation was accompanied with rock cracking in both coal sills and their wall rocks, which could lead to the security difficulty and potential danger to the deep exploitation for coal mines.

CAS Key Laboratory of Crust-Mantle Materials and Environments, Department of Earth and Space Sciences, Univ. of Sci. and Tech. of China, Hefei, Anhui 230026, China (*correspondence: [email protected]) 2 Geowissenschaftliches Zentrum der Göttingen Univ., Goldschmidtstrasse 1, D-37077 Göttingen, Germany A thick mafic lower crust (MLC) is necessary for the South China Block (SCB) to promote Triassic deep subduction, indicated by the exposed UHP rocks [1]. A systematic Sm-Nd isotopic study of early Cretaceous adakites from Dabieshan except those from the North Huaiyang zone provides constraints on the subducted MLC. TDM ages of adakites (from 1.56 to 2.56 Ga) can be divided into two main groups: ~1.7 to ~1.9 Ga and ~2.2 Ga (Fig. 1), significantly older than the main Neoproterozoic crustal growth event uniformly recorded in exposed UHP rocks [2,3]. With respect to TDM ages, adakites exhibit a clearly spatial zonation. Samples from South Dabie and one pluton adjacent to it have TDM ages > 2.19 Ga, while others are < 2.15 Ga. TDM ages of adakites imply that Paleoproterozoic (possibly some Archean) components are uniformly distributed in the subducted MLC of SCB. This agrees with U-Pb data of zircons mainly from the upper and the felsic lower crust [4]. These old components participated in the formation of the MLC of SCB either by being incorporated into later underplating magmas (e.g., Neoproterozoic) or as relics of ancient basements. The TDM ages and the spatial heterogeneity imply a multi-stage growth history for the MLC of SCB.

This study is supported by the National Natural Science Foundation of China (Grant No.: 40674071) [1] Zhang Z. J., Qin Y. L., et al. (2004) Chinese J . Geophys. (in Chinese ) 469-474.

Figure 1 Spectrum of TDM ages of adakites from Dabieshan [1] Yamato (2008) EPSL 271, 63-74. [2] Zheng YF (2004) GCA 68, 4145-4165. [3] Liu YC (2007) J. metamorphic Geol. 25, 975-989. [4] Zheng YF (2007) CS Bulletin 52, 1-10.

Goldschmidt Conference Abstracts 2009

A508

Geochemical characteristics of basalts from Shilipo and Heilongfeng native copper mineralized areas, eastern Tianshan, Xinjiang 1

ZHIJUN HE , DI ZHENG

2

2

AND BIN CUI

1

China Non-ferrous Metals Resource Geological Survey, P.R. China ([email protected]) 2 Geoscience and Resource School, China University of Geoscience, P.R. China Shilipo and Heilongfeng native copper mineralized areas are belonging to Xinjiang native copper mineralized belt, which is in the south part of Later Paleozoic Qoltag island arc belt and about 3 to 5 kilometers away from north margin of Aqqikkuduk fault. The outcropped strata in the areas are the first member of Yamansu formation and native copper occurs in altered tuff and basalt. Ore-bearing basalts from Shilipo and Heilongfeng native copper mineralized areas were collected and analysed. In comparison with Iceland basalts, they have relative low content of MgO (3.06% to 3.61%); Na2O ranges from 0.68% to 4.10% and K2O ranges from 0.03% to 2.37%. The basalts all have similar REE patterns showing slightly enrichtment of LREE, indistinct negative Eu anomalies and N-Mull positive anomalies, which is very similar to basalts from Iceland related to mantle plume, reflecting the characteristics of magma from mantle. The ratios of Zr/Nb, Rb/Nb, Th/Nb and Th/La are very close to those of N-MORB type oceanic basalt and HIUM-OIB type oceanic island basalt [1], but the ratios of La/Nb and Ba/La are close to continental crust, which is important geochemical sign of mantle plume. The basalts are depleted in Rb, Ba and Th. Above all, ore-bearing basalts from Shilipo and Heilongfeng native copper mineralized areas, eastern Tianshan, were derived from mantle, with similar geochemical characteristics of mantle hot plume. Combined with close spatial relation between the occuring environment of large scale banding native copper and mantle plume, native copper from eastern Tianshan may be related to metallogenesis of mantle plume. This research was financially supported Technologies R&D Programme, P.R. China

by

Key

[1] Wang et al. (1998) Mantle plume and mineralization, Beijing: SeismicPress, 1-60 (in Chinese with English abstract).

Global budget of organic aerosol from fungal spores COLETTE L. HEALD1* AND DOMINICK V. SPRACKLEN2 1

Department of Atmospheric Science, Colorado State University, Fort Collins, CO, 80524, USA (*correspondence: [email protected]) 2 School of Earth and Environment, University of Leeds, Leeds, UK The contribution of primary biological aerosol particles (PBAP) to the global budget of organic aerosol is poorly understood. Concentrations of mannitol, a biotracer for fungal spores, are used here to constrain the first global model (GEOS-Chem) simulation of PBAP from fungal sources. Emissions are driven by a combination of leaf area index (LAI) and atmospheric water vapor concentrations and are empirically optimized based on the geographical and seasonal variability of observed mannitol concentrations. Optimized global emissions total 28 Tg yr-1, with 25% of that total emitted as fine mode (PM2.5) aerosol. We will discuss here the geographical and temporal variability of this source of organic carbon aerosol, and compare the fungal spore contribution to the organic aerosol budget with other known sources.

Goldschmidt Conference Abstracts 2009

A509

The composition of noble gases in the solar wind as collected by Genesis: A proxy for solar nebula composition.

Structural incorporation of Neptunyl(V) into calcite – Interfacial reactions

V.S. HEBER1, N. VOGEL2, R. WIELER2 3 AND D.S. BURNETT

FRANK HEBERLING1,2*, MELISSA A. DENECKE1, JOHANNES LÜTZENKIRCHEN1 AND DIRK BOSBACH2,3

1

1

Genesis, a NASA sample return mission, collected solar wind (SW) in space for 2.5 years for precise elemental and isotopic analyses. SW matter originates from the photosphere and outer convective zone of the Sun and serves as a proxy of solar nebula composition. One major objective of Genesis was to determine solar abundances and isotopic composition of volatile elements. The solar composition of noble gases is difficult to determine as they are depleted in primitive meteorites and also not detectable in the photospheric spectrum due to their high excitation energies. SW is known to be slightly fractionated relative to photospheric composition, as detected mainly by spacecraft measurements. Ionisation of solar matter enhances elements with low first ionisation potential (FIP). Noble gases are high FIP elements, nevertheless, Kr and Xe enrichments relative to Ar similar as low FIP elements were detected in SW extracted from lunar samples [2]. However, enrichments are expressed relative to solar abundances which recently changed significantly [e.g. 3]. Light elements are also affected by isotopic fractionation presumably upon acceleration of the SW ions. For example Genesis data revealed that 3He/4He is 6% different between two distinct SW velocity regimes and Ne varies by ~1%/amu [1]. The magnitude of isotope fractionation decreases with atomic mass and is probably negligible for elements heavier than Ar (Ar fractionation is ~0.3%/amu). Thus, the isotopic composition of Kr and Xe in the SW are probably equal to photospheric values. Here, we present abundances and isotopic composition for all five stable noble gases in the SW as collected by Genesis [1,4,5] and compare them with estimates of solar abundances (derived otherwise) and other primitive solar system objects (Jupiter atmosphere, comets, etc.). We discuss how our values compare with existing SW fractionation models and how we can extract solar abundances from the SW data obtained from Genesis.

In this experimental study a wide range of methods has been used to investigate processes leading to incorporation of neptunyl(V) (NpO2+) cations into the calcite structure. As part of the investigation calcite surface properties were characterized over a wide range of pH and p(CO2) conditions using zetapotential and in situ crystal truncation rod measurements. A detailed picture of surface charging phenomena and the corresponding molecular surface arrangement under varying solution conditions could be gained. The NpO2+ adsorption species on the calcite surface were investigated by means of room temperature and low temperature (15 K) EXAFS spectroscopy. NpO2+ seems to adsorb at the calcite surface as an innersphere complex. Adsorption kinetic and desorption experiments indicate that even under equilibrium conditions NpO2+ becomes incorporated into the calcite structure. Upon coprecipitation from calcite supersaturated solutions NpO2+ is readily incorporated into the calcite structure. Incorporation species were investigated using room temperature, low temperature (70 K), and polarization dependent EXAFS measurements, together with conventional powder XRD, NIR and Raman spectroscopy. The linear NpO2+ molecule seems to substitute one calcium ion and two adjacent carbonate ions in the calcite structure. It is hence coordinated by four monodentate bound carbonate ions in the equatorial plane. Polarization dependent EXAFS measurements indicate, in agreement with NIR spectroscopic results, that the coordination polyhedron is a distorted tetragonal bipyramid. Powder XRD data indicates that NpO2+ incorporation causes local distortion in the calcite lattice.

Earth and Space Sciences, UCLA, Los Angeles, USA ([email protected]) 2 Isotope Geology and Mineral Resources, ETH Zurich, Switzerland ([email protected]) 3 CalTech, JPL, Pasadena, USA ([email protected])

[1] Heber, V. S. et al. (2008) LPSC 39th. [2] Wieler, R. & Baur, H. (1995) ApJ 453, 987-997. [3] Asplund et al. (2005) ASP Conf. Series,. 336 p.25. [4] Heber, V. S. et al. (2008) AGU Fall meeting. [5] Vogel, N. et al., this volume.

Institute for Nuclear Waste Disposal, Forschungszentrum Karlsruhe, PO Box 3640, 76021 Karlsruhe, Germany (*correspondence: [email protected]) 2 Helmholtz Virtual Institute, Advanced Solid –Aqueous RadioGeochemistry 3 Institut for Energy Research 6, Forschungszentrum Jülich, 52425 Jülich, Germany

Goldschmidt Conference Abstracts 2009

Melt permeability barriers beneath slow and ultraslow mid-ocean ridges LAURA BAKER HEBERT* AND LAURENT G.J. MONTÉSI University of Maryland, College Park, MD 20742 USA (*correspondence: [email protected]) The transition from slow to ultraslow spreading at midocean ridges may be related to a change in the efficiency of vertical melt extraction [1]. As spreading rates decrease, some combination of reduced melt volume and thickened lithosphere results in localization of volcanic centers separated by amagmatic segments, as in the highly oblique Southwest Indian Ridge [2]. Deep, low-F melts seem to be redistributed along the axis of ultraslow spreading ridges, maybe following a permeability barrier in the lithosphere [3]. As this permeability barrier is likely associated with the rapid crystallization of plagioclase ± clinopyroxene [4], Montési & Behn [1] adopted a simple depth-dependent relation to address the efficiency of melt extraction in this environment: Tbarrier = 1240°C + 1.9z,

(Eq.1)

We verify and refine this relation using the thermodynamics software (pH)MELTS [5] in conjunction with 2D numerical models of the mantle flow field and the thermal regime of mid-ocean ridges. We model the evolution of magma batches as they rise through the thermal boundary layer of the ridge and determine at what depth the crystallization rate is maximum as a proxy to the potential permeability barrier. Eq. 1 appears appropriate for near-axis melt trajectories at slow to fast spreading ridges where there are high aggregate melt fractions (> 15 wt. %) and the lithosphere is thin. However, at ultraslow ridges and off-axis at slow ridges, where the lithosphere is thicker and melt fractions are lower, we observe steadily increasing crystallization along melt trajectories over a wider depth interval controlled by the thick conductive lid. The protracted crystallization history may allow melt to be incorporated into the lithospheric mantle instead of being focused toward the axis, explaining the dearth of volcanism at ultraslow ridges [2, 6]. However, the potential absence of a strong permeability barrier calls for a revision of melt focusing scenarios. [1] Montési & Behn (2007) GRL 34, L24307, doi:10.1029/2007GL031067. [2] Dick, Lin, & Schouten (2003) Nature 426, 405-412. [3] Standish et al. (2008) Gcubed 9, Q05004, doi:10.1029/2008GC001959. [4] Korenaga & Kelemen (1997) JGR 102, 27729-27749. [5] Smith & Asimow (2005) G3 6, Q02004, doi:10.1029/2004GC000816. [6] Cannat et al. (2008) G3 9, Q04002, doi: 10.1029/2007GC001676.

Ion chromatography of inositol phosphates with high resolution mass spectrometric detection M.S. HEERBOTH1* AND W.T. COOPER2 1

Department of Chemistry, Gannon University, Erie, PA 16541 (*correspondence: [email protected]) 2 Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306 ([email protected]) Inositol phosphates are a class of organic phosphorus compounds that are found widely in the environment. They are the family of phosphoric monoesters of hexahydroxycyclohexane (inositol) containing 1-6 phosphate groups. Synthesized by plants and strongly complexed by metals (principally iron) in soils, inositol phosphates represent the dominant form of identifiable organic phosphorus in soils. They are also prevalent in aquatic environments, especially aquatic sediments. Inositol hexakisphosphate, commonly referred to as phytic acid, is by far the most prevalent of these compounds. Despite their significant presence in the environment, the role of inositol phosphates in the phosphorus cycle remains poorly understood. The primary reason for this is a lack of methods available for their analysis. Anion exchange chromatography coupled to electrospray ionization-time of flight mass spectrometry with ion suppression has been used to develop a fast analytical method for the determination of phytic acid. Using a strong hydroxide mobile phase, phytic acid could be eluted in less than six minutes. Detection of phytic acid was achieved by monitoring an extracted ion mass chromatogram at m/z =659, the molecular ion peak of the compound (Figure 1). This method has been applied to detect and quantify phytic acid in soil extracts from the Florida Everglades and the United Kingdom. 180000 150000

Intensity (cps)

A510

120000 90000 60000 30000 0 0

2

4

6

8

10

Retention Time (min)

Figure 1: Extracted ion mass chromatogram at m/z = 659 of a United Kingdom pasture soil extract.

Goldschmidt Conference Abstracts 2009

A511

Cenozoic intra-plate volcanism in Northeast Africa: Evidence for African plate motion

Phototrophic Fe(II) oxidizing bacteria – Strategies to avoid encrustation by Fe(III) minerals

HUSEIN A. HEGAZY

F. HEGLER1*, C. SCHMIDT1, H. SCHWARZ2, 1 AND A. KAPPLER

Assiut University, Egypt ([email protected]) Northeast Africa witnessed considerable Cenozoic volcanic activity. Flood basalts, shield volcanoes and trachyte domes are exposed in Libya the tholeiitic to alkaline basaltic rocks of Egypt and Sudan the Afar depression transitional volcanics and the surrounding Ethiopian plateau basalt. These volcanic provinces have been formed over the last 50 Ma. Chronological data reveal an increase in age from SSE toward a NNW.AS an example in Libya the Gharian province in the far NNW has an age of 42±10 Ma. Gabal El Hasawina24±1Ma and the Gabal As Sawda range from 12.3 to 10.9 Ma, whereas at Gabal El Haruj 6.0 to 0.04 Ma and the Tibisti volcanic series in the far SSE extend from Pliocene to Quaternary. Cenozoic intra-plate volcanism in the Northeast Africa is either mantle plume (e.g. Libyan basaltic rocks) or rift-related (e.g. volcanics of the Red Sea region). It is believed that the linear trend of the Tertiary volcanic provinces of Libya (SSENNW) follow one track over a hot spot. This trend reveals the direction in which African plate is moving. The calculated rate of the absolute movement is an approximately 2 to 10 cmy-1 in the NNW direction.

1

Geomicrobiology, Centre for Applied Geoscience, University of Tuebingen, Germany, ([email protected]) 2 Max-Planck-Institut fuer Entwicklungsbiologie, Spemannstr. 35, D-72076 Tuebingen, Germany Bacteria can oxidize Fe(II) to Fe(III) under anoxic conditions either phototrophically or chemotrophically with nitrate as electron acceptor. The Fe(III) is poorly soluble at neutral pH and usually precipitates as Fe(III) (hydr)oxide. Bacteria catalyzing the oxidation of Fe(II) to Fe(III) at neutral pH therefore face the challenge dealing with an almost insoluble product. SEM and TEM show for phototrophic Fe(II) oxidizing cells at circumneutral pH show no precipitation of Fe(III) minerals on the cell surface. Thus, neutrophilic Fe(II)-oxidizing cells accept electrons from Fe(II) without acting as a nucleation site for the Fe(III). It is vital for a cell to avoid mineral precipitates at the cell surface as these would limit the uptake of substrates and therefore metabolic activity of the cell. Several strategies are plausible for the cell to avoid precipitation of minerals: i) modification of the cell surface; ii) acidification of the cell vicinity; iii) production of Fe(III)chelating ligands. In order to test the hypothesis of acidification of the cell microenvironment we determined the pH around cells with confocal laser scanning microscopy in combination with a pHsensitive fluorescent dye. We showed that an acitve cell metabolism was necessary. Biogeochemical modelling confirmed that a low pH-microenvironment is beneficial to the cell as it slows Fe(III) precipitation and reduces the extent of Fe(III) mineral precipitation on the cell surface. We thus demonstrated the benefits of an actively modified pH-microenvironment around a cell dealing with poorly soluble Fe(III) minerals.

A512

Goldschmidt Conference Abstracts 2009

Three methods for the calculation of equilibrium fractionation factors from isotopic exchange experiments.

Traces of a fossil deep biosphere in fracture fillings of the Äspö Diorite (Sweden)

T.C. HEIJBOER*, T.W. VENNEMANN AND L.P. BAUMGARTNER

CHRISTINE HEIM1, JUKKA LAUSMAA2, PETER SJÖVALL2, KLAUS SIMON1, JOACHIM REITNER1 AND VOLKER THIEL1

Institute of Mineralogy and Geochemistry, University of Lausanne, Switzerland (*correspondence: [email protected]) Three methods, based on a newly derived exact massbalance equation for isotopes in a system containing multiple phases, have been used for the calculation of equilibrium fractionation factors (αe) from isotopic exchange experiments. The first method is valid for pseudo first-order rate kinetics, similar to [1,2], the second for isotopic fractionation due to volume diffusion in a mineral phase with a restricted amount of fluid surrounding the mineral [3], and the third for netisotopic fractionation due to dissolution-precipitation of a single phase, similar to [4]. The second and the third method both are forward calculating models, which allow the calculation of a final isotopic composition of the bulk mineral and water phases from their initial isotopic compositions. An algorithm is then used to minimize the difference between the final calculated isotopic compositions and the final measured isotopic compositions. In these methods the αe values (mineral-fluid) and in the case of the second method the average diffusion coefficient of the diffusing element in the mineral, and in the case of the third method, the extent of the dissolution-precipitation reaction are simultaneously determined. All three new methods yield similar αe values from a given experiment, which are in most cases also similar to previously determined values. Different αe values for the same pair of phases calculated from different types of isotope exchange experiments done by different research groups are in most cases not related to the method of calculation. These new derivations and methods also show that 1) The exact mass balance equation for isotopes of an element present in different phases is mathematically the same as for multiple elements substituting on sites in different phases (e.g. Mg-Fe in pyroxene and olivine). 2) During volume diffusion in a mineral, which is in contact with a fluid, only in the final stages towards equilibrium is the reaction of first order, with a constant rate constant. 3) The isotopic composition of phases at equilibrium is independent of the process, when local equilibrium is maintained at one point in the system during the process. [1] Northrop D.A. and Clayton R.N. (1966) J. of Geology 74, 174-196. [2] Criss R.E. (1999) University press, Oxford. 3] Crank J. (1975) University press, Oxford. [4] Dubinina E.O. and Lakshtanov L.Z. (1997) GCA 61, 11, 2265-2273.

1

University of Göttingen, Geoscience Centre ([email protected]) 2 SP Technical research institue of Sweden, Borås ([email protected]) Organic biomarkers are widely used as molecular fingerprints for the characterization of recent and ancient microbially driven ecosystems. We here report on ToF-SIMS experiments aiming on organic remains of a fossil deep biosphere in fracture fillings within the 1.8 Ga old Äspö Diorite, Sweden. The fracture fillings consist of fluorite and calcite formed at low temperature conditions [1]. Samples were taken from a 50mm drill core obtained at 450 m depth in the Tunnel of Äspö (Äspö Hard Rock Laboratory). ToF-SIMS molecular mappings were performed on thick sections along the phase boundaries of fluorite and calcite. The measurements reproducibly revealed numerous organic compounds producing ions at e.g. m/z 44.05 (C2H6N), 55.06 (C4H7), 57.04 (C3H5O), 81.07 (C6H11). In addition, ions of complex organic molecules showing masses as high as 339 Da were observed within the fracture fillings. These substances are considered indigenous as they show a very specific distribution confined to the boundary between calcite and fluorite. Subsequent La-ICP-MS measurements on the same target areas revealed a concomitant, significant accumulation of the light rare earth elements (Lanthanum – Samarium) along mineral phase boundaries, most likely induced by biologically driven element fractionation. Additional investigations are underway to further elucidate these organic biosignatures in the ancient deep biosphere ecosystem. [1] Drake, H., Tullborg, E.-V., (2004). SKB P-04-250.

Goldschmidt Conference Abstracts 2009

The role of microbial processes in Banded Iron Formation (BIF) genesis as constrained by Fe, C, and O isotopes in BIF carbonates A. HEIMANN1,2*, C.M. JOHNSON1,2, B.L. BEARD1,2, J.W. VALLEY1,2 AND M.J. SPICUZZA1,2 1

Univ. of Wisconsin – Madison, USA (*correspondence: [email protected]) 2 NASA Astrobiology Institute Iron-rich carbonates from the ~2.5 Ga Kuruman banded iron formation (BIF), South Africa, were investigated at a submillimeter scale for Fe, C, and O isotope variations. The C isotope contrast between ankerite and siderite (δ13C = -2 to -12 ‰) and platform calcite/dolomite (δ13C ~0 ‰) cannot be explained by compositional effects on C isotope fractionation factors, but instead reflect distinct C pathways. A strong negative correlation between δ13C and Fe contents in BIF and Ca carbonates, along with small-scale isotope heterogeneity, suggest a constant ocean δ13C, which would indicate that no ankerite or siderite were in C isotope equilibrium with seawater, but instead reflect contributions from organic carbon oxidation coupled to dissimilatory Fe(III) reduction (DIR). Stoichiometric relations associated with production of siderite by CH2O oxidation and Fe(III) reduction suggest that δ13C values of ~ -8 ‰ or lower reflect carbonate formation by biogenic processes. δ18OSMOW values vary from +19 to +21 ‰ and do not correlate with δ13C values or Fe contents; this range overlaps that measured in previous studies of ~2.5 Ga Transvaal carbonates, and rules out extensive post-lithification diagenesis. δ56Fe values for BIF carbonates range from +1.0 to -1.0 ‰, and nearly the entire range can be found in low-δ13C samples. BIF carbonates that have positive δ56Fe values tend to have micron-size hematite inclusions, although these inclusions are insufficient to control the Fe isotope compositions. Instead, their occurrence, in combination with their negative δ13C values, suggests near-complete DIR. Lower δ56Fe values in Fe-rich BIF carbonates that have low δ13C values reflect mobilization and transport of low-δ56Fe Fe(II)aq produced by partial Fe(III) reduction in the sediment, followed by siderite precipitation. The combination of C and Fe isotope measurements on the same carbonates is essential for determining the formation pathways of Archean/Proterozoic Fe-rich carbonates, which in turn bears on the use of Fe isotope compositions of carbonates as tracers of ancient seawater compositons or microbial cycling in restricted marine environments or the soft sediment section prior to lithification.

A513

Cosmogenic dating of ‘old’ glacial events in Patagonia A.S. HEIN1*, N.R.J. HULTON1, T.J. DUNAI1, C. SCHNABEL2, M.R. KAPLAN3, S. XU2 1

University of Edinburgh, Edinburgh, UK (*correspondence: [email protected], [email protected], [email protected]) 2 S.U.E.R.C. East Kilbride, UK 3 LDEO, Columbia University, NY, USA In Argentinean Patagonia, outlet valleys of former Patagonian ice sheets commonly preserve three to four distinct groups of moraines and associated outwash terraces that predate the LGM, which are as old as ca. 1.1 Ma. Importantly, few of these deposits are dated. Preservation of clear moraine ridges from the oldest deposits attests to low erosion rates and long-term landform stability in the region, making it ideal for cosmogenic surface exposure dating methods. However, exposure dating of moraine boulders becomes increasingly problematic on older moraines due to the increasing uncertainties in boulder erosion rates and exposure histories with time. In this study, we demonstrate the stability and suitability of outwash terrace sediment to date specifically ‘old’ glacial events in the Lago Pueyrredón valley, 47.5° S, Argentina. 10Be and 26Al exposure ages from cobbles located on the outwash terrace surface are compared to exposure ages from associated moraine boulders. The outwash cobbles consistently yield older exposure ages than the moraine boulders. A 10Be concentration depth-profile in the outwash terrace sediment was measured to further constrain the deposition age, terrace erosion rate, average nuclide inheritance and stability of the outwash sediment. These data yield a well defined exponential profile indicating the longterm stability of the surface. A best-fitting model establishes that 1) nuclide inheritance is negligible 2) the terrace erosion rate is low and 3) the deposition age is consistent with exposure dates from the oldest surface cobbles. Based on these findings we use the oldest surface cobbles to date the deposit. These indicate a major advance of a Patagonian ice sheet occurred at ca. 260 ka (MIS 8). In contrast, the associated moraine boulders underestimate the age of the deposit by a full glacial cycle. If the stability of outwash terraces is a common feature in the region, it should be possible to date older glacial events by this method, and thereby reconstruct the long-term glacial history across Patagonia.

A514

Goldschmidt Conference Abstracts 2009

Sulfate-reducing bacteria as major players in the formation of reefmicrobialites during the last sea-level rise (Tahiti, IODP 310) K. HEINDEL*, D. BIRGEL, J. PECKMANN, H. KUHNERT AND H. WESTPHAL MARUM ‘Center for Marine Environmental Sciences’, University of Bremen, Leobener Strasse, 28359 Bremen, Germany (*correspondence: [email protected]) During IODP Expedition 310, drowned Pleistocene to Holocene barrier reefs seaward of the modern fringing reefs of the volcanic island Tahiti have been drilled. The Tahitian deglacial (last sea-level rise ~15,000-9,000 yr) reef-succession is a coral framework encrusted by coralline algae and microbial carbonates, so-called microbialites. The laminated and partly dendritic reef-microbialites predominate the cores (up to 80 vol. %), which is very uncommon when compared with modern shallow-water coral reefs from Tahiti and other sites. The processes leading to that voluminous formation of microbialites in Tahitian coral reefs during the last sea-level rise are still under discussion. Here we present lipid biomarkers, which were used for the first time to identify organisms, which were involved in the formation of these reef-microbialites. The most abundant compounds preserved in the microbialites are fatty acids. Among those, bacterially-derived terminally-branched fatty acids (iso- and anteiso C15:0 and C17:0) are unusually abundant with an average contribution of around 20% of all fatty acids. Iso- and anteiso C15:0 and C17:0 fatty acids are considered to be typical biomarkers of sulfate-reducing bacteria. Because enzymatic carbon isotope fractionation of heterotrophic sulfate reducers is insignificant, the minor shift between the average δ13C values of the bulk organic matter (−20‰ to -19‰) and the average compound-specific δ13C values of the iso- and anteiso C15:0 and C17:0 fatty acids (−19‰) agrees with sulfate reducers as source of the bacterial fatty acids. Sulfate-reducing bacteria are known to induce carbonate precipitation by increasing alkalinity. Biomarker evidence for the involvement of oxygenic phototrophs (e.g., cyanobacteria) in the microbialite formation was not found. It is suggested, that strong weathering of Tahiti basalt elevated the deglacial nutrient levels. That promoted the growth of algal mats, which provided the organic matter for sulfate reduction. Our results imply that a rather specific community of bacteria, most likely dominated by sulfatereducing bacteria, was responsible for microbialite formation in the coral reefs off Tahiti during the last sea-level rise.

Acidification-sensitivity of M. edulis A. HEINEMANN1*, J. FIETZKE2, C. HIEBENTHAL1, J. THOMSEN1 AND F. MELZNER1 1

IFM-GEOMAR, Leibniz Institute of Marine Sciences, Hohenbergstr. 2, 24105 Kiel, Germany (*correspondence: [email protected]) 2 IFM-GEOMAR, Leibniz Institute of Marine Sciences Wischhofstr. 1-3, 24148 Kiel, Germany

Holistic Approach Baltic Mytilus edulis were kept in a flow through system for 3 month at six different CO2 concentrations ranging from 380 ppm to 4,000 ppm. During the experimental period calcification rates were determined using alkalinity anomaly (δTA) technique after Smith and Key 1975 [1] and shell growth was measured. Calcification rates showed that mussels start to dissolve at values higher than 2,400 ppm. This stands in contrast to Gazeau et al. 2007 [2] who found that mussels dissolved at values higher than ~1800ppm.

Figure 1: Net calcification rates vs. seawater pCO2 At the end of the experiment hemolymph and extrapallial fluid were taken and pH, pCO2 and elemental ratios were measured. Shell composition will be investigated via microprobe and LA-ICP-MS. Further, the dry weight of tissue and lipofuscin accumulation will be determined as an indicator for stress. A second experiment was designed to investigate the combined effects of different CO2 levels (380, 840 and 1,400 ppm) and temperatures (5, 10, 15, 20, 25°C). [1] Smith and Key (1975) Limnol. Oceanogr. 20(3) 493– 495. [2] Gazeau et al. (2007) Geophysical Research Letters 34, L07603

Goldschmidt Conference Abstracts 2009

Gold-rich epithermal liquid by contraction of magmatic vapor C.A. HEINRICH1, C. PUDACK1 AND T. PETTKE1,2 1

ETH Zurich, Department of Earth Sciences, Clausiusstr. 25, 8092 Zurich, Switzerland ([email protected]) 2 Now at University of Bern, Institute of Geological Sciences, Baltzerstrasse 1+3, CH-3012 Bern, Switzerland Vapor inclusions in porphyry-type ore deposits commonly contain very high concentrations of Cu, As and Au [1]. This observation has been taken to suggest that magmatic vapor may be an essential ingredient for the formation of rich epithermal precious-metal deposits, as opposed to thermally convecting meteoric (‚geothermal’) water leaching the oreforming components from solid rocks. Thermodynamic data indicate that magmatic vapor can homogeneously contract to a gold-rich aqueous liquid, if it cools at elevated pressure above the critical curve of the saline fluid system, and if it contains enough sulfur for gold complexation [2]. Preliminary hydrodynamic modeling [3] indicates that magmatic vapor contraction is a plausible process in hydrothermal systems that are driven by cooling of a subjacent hydrous magma chamber. This contribution confirms these predictions with two sets of new data. First, we demonstrate that metal-rich magmatic vapors are indeed sufficiently sulfur-rich to support the required Cu-S and Au-S complexes, based on progress in the quantification of S in fluid inclusions by LA-ICPMS microanalysis [4, 5]. Second, we present the first fluid inclusion analyses of exceptionally metal-rich epithermal liquids from the Famatina system in Argentina [5]. Geological timing relationships indicate that the gold-rich aqueous liquids in quartz – sericite – pyrite veins were formed by contraction of magmatic vapor at the transition, in space and time, from subeconomic porphyry mineralization to rich high-sulfidation epithermal gold – telluride ores. [1] Heinrich et al. (1999) Geology 27, 8, 755-758. [2] Heinrich et al. (2004) Geology 32, 761-764. [3] Driesner & Geiger (2007) Reviews in Mineralogy and Geochemistry 65, 187-212. [4] Seo et al. (2009) GCA this volume, and submitted to EPSL. [5] Guillong et al. (2008) J. Anal. At. Spectrom. 23, 1581-1589 and abstract, this volume. [6] Pudack et al. (2009) Econ. Geol., in press.

A515

Influence of organic matter content on specific surface area of a Eutric Cambisol and its particle size fractions from Ultuna (Sweden) determined by different methods KATJA HEISTER*, GEERTJE PRONK AND INGRID KÖGEL-KNABNER Lehrstuhl für Bodenkunde, Department für Ökologie und Ökosystemmanagement, Technische Universität München, 85350 Freising-Weihenstephan, Germany (*correspondence: [email protected]) The determination of specific surface area (SSA) of soils is important in order to estimate the ability of a soil to retain certain compounds. There are different methods available for measuring SSA. But since the various adsorbates used in these methods exhibit different adsorption affinities for different types of surfaces, the determined SSA can differ significantly depending on the adsorbate used. Normally, N2-physisorption at 77 K according to Brunauer, Emmett and Teller (BET-N2) is done, but it is known that nitrogen has a low affinity to organic surfaces. Ethylene glycol monoethyl ether (EGME) is an organic liquid which is known to additionally enter organic material and interlayer surfaces of clay minerals leading to an increased measured SSA. We investigated SSA by means of BET-N2 and EGME retention of bulk soil and particle size fractions of a Eutric Cambisol from a long-term field experiment in Ultuna, Sweden. For several decades, the soil received either a treatment with Ca(NO3)2 fertiliser or animal manure. Due to the different amount of organic material present (15 g C kg-1 for the Ca(NO3)2 treated soil and 21 g C kg-1 for the manure treated soil), SSA varied between 13.1 and 19.6 m2 g-1 for BET-N2 and 53 to 86 m2 g-1 for EGME. At low organic matter content, a linear relationship between N2- and EGME-surface areas was observed. Calculated C constants from BET-N2 determinations indicated that with higher organic matter content, the binding affinity for nitrogen decreases. However, removal of organic matter by oxidation with H2O2 led to differing results. In the silt fractions, the C constants actually decreased. We assume that iron oxides which contribute significantly to the SSA in these fractions were closely associated with the organic material and were partially modified or dissolved and eluted by this treatment.

Goldschmidt Conference Abstracts 2009

A516

Constraints on outer core compositional stratification and core-mantle reaction from outer core wavespeed profiles G. HELFFRICH Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol BS8 1RJ, UK ([email protected]) Light elements in the nearly pure iron core of the Earth are required in order to match the material properties of the outer and inner core [1,2]. Recent seismological models [3.4] of outer core structure suggest that the outermost outer core could contain velocity gradients that deviate from homogeneous self compression, signalling thermal or chemical changes. Using a thermodynamic megallurgicallybased model of core liquids, I show that in the Fe-O-S system, light element stratification with 1.3-2.2 wt% sulfur enrichment coupled with 0.3-1.0 wt% oxygen depletion, yields feasible wavespeed profiles and is a structurally stable density profile in the outer core. In contrast, stratification by superadiabatic thermal gradients or reactive chemical transport of oxygen between the mantle and the core [5,6] is incompatible with the seismic information. Consequently, if present, anomalous seismic velocity structure in the outer core records the gradual growth of the inner core if sulfur and oxygen are the dominant liquid alloy components. [1] Stevenson (1981) Science, 214, 611-619. [2] Poirier (1994) PEPI 85, 319-337. [3] Tanaka (2007) EPSL 259, 486-499. [4] Kennett et al. (1995) GJI 126, 108-124. [5] Rubie et al. (2004) Nature 429, 58-61. [6] Asahara et al. (2007) EPSL 257, 435-449.

Dissolved carbon in large boreal catchment basins and hydroelectric reservoirs: Isotopic clues JEAN-FRANCOIS HÉLIE*, ÉRIC ROSA, ANNIE LALONDE AND CLAUDE HILLAIRE-MARCEL GEOTOP – Université du Québec à Montréal, C.P. 8888 succursale Centre-ville, Montréal (QC) Canada, H3C 3P8 (*correspondence: [email protected]) Carbon sources and cycling in boreal environments are currently the focus of a growing number of investigations in Eastern Canada, mainly because of the importance of hydropower and its potential in this region. Here, we investigate dissolved inorganic and organic carbon fluxes and sources in 5 impounded (La Grande 3400 m3/s, Eastmain, St. Lawrence 12 100 m3/s, Ottawa 1950 m3/s and Nelson 2370 m3/s) as well as 2 pristine (Great Whales 680 m3/s and Koksoak) river systems. These major rivers were sampled monthly at their outlet for at least one year. The St. Lawrence River has been under investigation since June of 1997 on a biweekly basis. Also, synoptic surveys were undertaken in August 2008 on the La Grande and Great Whales Rivers. At each visit, water temperature, pH, Gran alkalinity and specific conductivity were measured. Samples were also collected for the analysis of i) major ions concentrations; ii) δ13C of dissolved inorganic and organic carbon as well as particulate organic carbon (respectively DIC, DOC and POC); iii) δ18O and δ2H of the water molecule; and iv) radio-isotopes (Uranium series and Strontium - not discussed here). In all the sampled river systems, POC concentrations were at least an order of magnitude smaller than the dissolved forms. As a result, the dissolved forms will be the focus of this investigation. Rivers draining carbonates (St. Lawrence and Nelson Rivers) present higher DIC concentrations and higher 13 C-contents in dissolved inorganic carbon (DIC), in response to the dissolution of soil carbonates. DOC/DIC ratios above 2.4 are observed in rivers draining silicates; their lower 13CDIC content directly reflects the organic matter oxidation in soils. However, the DIC isotopic composition of impounded rivers draining silicates reflects both the organic oxidation origin of DIC and CO2 degassing along the reservoir. The striking feature of this boreal data set is the homogeneity of the isotopic composition of DOC (-27.4±0.2‰ vs V-PDB). Moreover, C:N ratios and 14C activity (A14C) of bulk dissolved organic matter (MOD) measured in the La Grande River reveal that this DOC is relatively fresh and young (A14C higher than 100% MC).

Goldschmidt Conference Abstracts 2009

A517

Composition, distribution and properties of the Ultra-Depleted Mantle component

First results of geo- and biochemical analyses of terrestrial methaneemittingen mud volcanoes in Italy

E. HELLEBRAND1, A. VON DER HANDT1, K. JOHNSON1, J. SNOW2, C. LIU3, H. DICK4 AND A.W. HOFMANN5

C. HELLER1, M. BLUMENBERG1, A. DREIER2, C. WREDE2, T. ZILLA1, S. KOKOSCHKA2, C. HEIM1, M. HOPPERT2, M. TAVIANI3 AND J. REITNER1

1

Dept. of Geology and Geophysics, Univ. Hawaii, Honolulu, USA ([email protected]) 2 Dept. of Geosciences, Univ. Houston, Houston, USA 3 State Key Lab. of Lithospheric Evolution, Beijing,China 4 WHOI, Woods Hole, USA 5 Max-Planck-Institute for Chemistry, Mainz, Germany Many chemo-geodynamical considerations are based on trace element and isotopic variations in erupted basalts. This has led to the concept of a heterogeneous convecting mantle that is composed of a variety of "enriched plums" dispersed in a matrix of Depleted MORB mantle (DMM). Incompatible element isotope systems reveal subtleties in plum composition and distribution, assuming that the DMM matrix is of relatively constant composition. Abyssal peridotite studies have shown recently that old, ultra-depleted harzburgites may be an important component in the convective upper mantle [1]. These residues are too depleted to generate basaltic melt and their -possible extreme- isotopic compositions are thus entirely invisible in erupted basalts. In addition, percolation of plum-derived melts can easily overprint the trace element budget of depleted harzburgites, as observed along the Arctic and Mid-Atlantic ridges. The Ultra-Depleted Mantle (UDM) is a harzburgite melted beyond cpx-out, with an opx mode around 10%, spinel Cr# of 0.65, and bulk Al2O3 of 0.2-0.3 wt%. Not only is UDM invisible in MORB, it will reduce the melt productivity and magmatic crustal thickness by reactive plum-derived melt stagnation. The abundance and distribution of such ultradepleted components in the oceanic mantle cannot be inferred from basalt studies. Evidently, there is a range between DMM and UDM that is a function of extent of depletion prior to recent upwelling. We emphasize that even mid-range (Cr# 0.3) harzburgites are nearly cpx-free and also too depleted for significant melt extraction. Future studies will need to establish criteria other than Os isotopes to distinguish between old inherited depletion from local-scale heterogeneity caused by recent focused melt percolation. On the basis of the extent and distribution of local-scale variation in Gakkel Ridge peridotites, we infer that as much as 25% of the convecting upper mantle consists of old UDM that is not rehomogenized by convective stirring. [1] Liu, et al. (2008) Nature 452, 311-316.

1

Geoscience Centre, University of Goettingen, Goldschmidtstr. 3, 37077 Goettingen, Germany ([email protected], [email protected]) 2 Institute of Microbiology and Genetics, University of Goettingen, Grisebachstr. 8, 37077 Goettingen, Germany ([email protected]) 3 ISMAR-CNR, Via Gobetti 101, 40129 Bologna, Italy ([email protected]) The microbially mediated anaerobic oxidation of methane (AOM) supposedly follows the overall chemical equation CH4 + SO42- → HCO3- + HS- + H2O and is now identified as the major sink of the greenhouse gas in marine systems (Reeburgh 1996; Hinrichs and Boetius 2002 and references therein). In the meantime the AOM is also found in terrestrial fluid venting structures like mud volcanoes [1]. The area of “Salse di Nirano” is located near Bologna (Italy) and was formed by the expulsion of water, mud and gas like methane and higher hydrocarbons. These hydrocarbons could be the substrates for microorganisms that perform the AOM. We studied the gas compostion, lipid biomarkers and stable isotope ratios to identify the unknown microbial community at this site and to obtained insights into this system. Phylogenetic analyses indicated the presence of bacterial and archaeal lineages that are generally associated with the anaerobic oxidation of methane. First results of the lipid biomarkers showed that sulfate reducers, methanogens and methanotrophs were present in this habitat. 13C-depletion of the specific lipid biomarkers indicate that the AOM takes place at this site. Furthermore we have studied ancient seep sites in Italy to compare the results with the active mud volcanoes of Salse di Nirano. Therefor we analysed lipid biomarkers, element contents and the stable istope ratios of ancient seep carbonates. [1] Alain, Holler, Musat, Elvert, Treude & Krüger (2006) Environ Microbiol 8 (4) 574-590. [2] Hinrichs & Boetius (2002) In: Ocean Margin Systems, Wefer, Billett & Hebbeln (eds) Berlin, Germany, Springer Verlag, 457-477. [3] Reeburgh (1996) In: Lidstrom & Tabita (eds) Kluwer Academic Publishers, Boston 334–342.

A518

Goldschmidt Conference Abstracts 2009

Hydration of forsterite at 1 atm PCO2 and 80 to 120°C – Comparisons of numerical simulations and laboratory experiments to understand the factors that govern the overall mineral transformation rate H. HELLEVANG*, E. SOKALSKA AND P. AAGAARD Department of Geosciences, University of Oslo, Pb. 1047, Blindern, Oslo, Norway (*correspondence: [email protected]) We have characterized the coupled mineral reactions following hydration of forsterite at 80 to 120°C and a CO2 pressure of 1 atm in a closed well-mixed system. To do so we compare numerical simulations with laboratory experiments. The numerical simulations use far-from-equilibrium dissolution rate parameters obtained from the literature and a reaction rate equation that govern both dissolution and precipitation through an affinity term. This is a common way of modeling coupled mineral dissolution and precipitation in numerical codes like TOUGHREACT and EQ3/6, and we suspect that errors in factors like the affinity term and the reactive precipitation area lead to deviations between natural reactions and corresponding numerical simulations. To gain some more insight into this we use the simple fast reacting forsterite hydration system and tune parameters like the reactive surface area in order to fit the simulated data to the experimental datapoints. Some preliminary numerical simulations have been done to predict the outcome of the laboratory experiments. The simulations show that hydration of a pure forsterite at 1 atm CO2 leads to formation of magnesite and talc and at some conditions quartz gets supersaturated. The reactions are suggested to be rapid at 120°C with a large fraction of the forsterite hydrated after one week and with an almost complete conversion after 21 days. By using rate data from the literature and change the reactive surface area by ± 1 order of magnitude we see that the formation rate of magnesite is independent of the talc and magnesite precipitation rates and only dependent on the slower dissolution rate of forsterite. Moreover, eventhough the mineral fractions can not be used to trace the sensitivity of the reactive surface areas, the aqueous Mg/Si ratio is suggested to be a strong carrier of information regarding the precipitation rate parameters. A slow talc precipitation rate relative to magnesite leads for instance to a low Mg/Si ratio.

Transformation of iron(oxyhydr)oxides in the presence of dissolved sulphide KATRIN HELLIGE1, PHIL LARESE-CASANOVA2, KILIAN POLLOK3 AND STEFAN PEIFFER1 1

Dept. of Hydrology, University of Bayreuth, Germany ([email protected]) 2 Institute for Geoscience, University of Tübingen, Germany 3 Bayrisches Geoinstitut, University of Bayreuth, Germany The transformation of iron (oxyhydr)oxides by Fe(II) has been the subject of a number of studies and is reasonably well understood with respect to the end products goethite and magnetite. The mechanism of the electron transfer and the process of transformation especially the modification of crystal lattice remain to be clarified. Poulton et al. (2004, Geochim. et Cosmo) found out, that ferrous iron which is formed by the reaction of iron oxides with dissolved sulphide strongly interacted with the mineral surface. In our experiments we intended to study the fate of the bounded Fe(II) and the potential recrystallisation of new solid phases. In particular, the reaction over time and the competition between iron sulphide formation and ferric oxide mineral transformation was studied. Therefore anoxic and abiotic batch experiments with an excess of synthetic lepidocrocite and dissolved sulphide were performed at circumneutral pH. The water phase was sampled over time and analyzed with respect to the concentrations of S°, S(-II)aq, Fe(II)aq, Fe(II)HCl.and FeTOT. The solid phase was investigated by XRD, TEM and Mössbauer spectroscopy. Dissolved sulphide was consumed in the first minutes of the reaction leading to high Fe(II) release and the solution turned black. 25% of the total dissolved sulphide reacted to S° and 75% to FeS. 24 % of the lepidocrocite-Fe was extractable Fe(II) with HCl and only 0.8% was found as Fe(II)aq. TEM measurements demonstrated that Fe(II) interacted with the surface of lepidocrocite which lead to the formation of magnetite. The presence of sulphur species (S° or S(-II)) furthermore caused the precepitation of mackinawite (FeS) at the magnetite surface. After 2 weeks reaction mackinawite had transformed into the more stable FeS2 species marcasite and the black colour disappeared. Our results indicate, that the reaction between dissolved sulphide and iron oxides is a fast surface-controlled process with magnetite as an important intermediate.

Goldschmidt Conference Abstracts 2009

A519

Dissolution kinetics of diopside as a function of the Gibbs free energy of reaction

Time-resolved oxalate speciation at the surface of gibbsite (α-Al(OH)3) using infrared spectroscopy

R. HELLMANN1, D. DAVAL1,2,3, D. TISSERAND1, I. MARTINEZ2, J. CORVISIER3 AND F. GUYOT2

A. HELLSTRÖM*, J.S. LORING AND P. PERSSON

1

LGIT-CNRS, Grenoble, France (*correspondence: [email protected]) 2 IPGP, Paris, France ([email protected]) 3 Laboratoire de Géologie, ENS, CNRS, Paris, France In natural environments, the dissolution of silicates occurs over a wide range of saturation states. The effect of how far from equilibrium the reaction takes place (i.e. f(∆Gr)) on the dissolution rate of silicates is thus a crucial parameter that needs to be determined in order to accurately model mass transfer due to fluid-rock interactions. The present study aims at investigating the relation between the dissolution rate of diopside, a common pyroxene in (ultra)basic rocks, and the Gibbs free energy of reaction, ∆Gr. The experiments were carried out in a continuously stirred flow-through reactor at 90°C and pH(90°C) 5.0 (± 0.1). The overall relation between ∆Gr and the rate R was determined over an extended free energy range of –130 < ∆Gr < -45 kJ mol-1. The data define a highly non-linear relation between R and ∆Gr. At far from equilibrium conditions (∆Gr < -72 kJ mol-1), a rate plateau is observed. A sharp decrease of the dissolution rate (~ 1 order of magnitude) occurs over the range -72 ≤ ∆Gr ≤ -60 kJ mol-1. Dissolution closer to equilibrium (-60 ≤ ∆Gr ≤ -45 kJ mol-1, and ongoing measurements) is characterized by a much weaker dependence of the rates on ∆Gr. A comparison of the experimental R-∆Gr data with a theoretical R-∆Gr curve based on transition state theory (TST) reveals complete incompatibility, in particular at near-equilibrium conditions. Instead, we fit our data with a an overall rate law based on two parallel dissolution mechanisms, adapted from Burch et al. [1] and originally based on BCF theory (e.g., see similar modeling in Hellmann and Tisserand [2]). To highlight the danger of using geochemical codes that use TST-rate laws, we have developed a kinetic module implementing both types of f(∆Gr) functions to model diopside carbonation reactions. Our results show that the use of TST-rate laws can result in a significant overestimation of the carbonation rate, an important effect if accurate amounts of conversion of CO2 into carbonates in (ultra)basic rocks have to be estimated. [1] Burch T.E., Nagy K.L. and Lasaga A.C. (1993) Chem. Geol. 105, 137-162. [2] Hellmann, R. and Tisserand, D. (2006) GCA 70, 364-383.

Department of Chemistry, Umeå University, 901 87 Umeå, Sweden (*correspondence: [email protected]) Numerous studies have investigated the interactions between carboxylate ligands and mineral surfaces. Carboxylate ligands form both inner- and outer-sphere complexes and play a role in the dissolution of minerals [1]. Spectroscopic information about the surface complexes is useful for determining the coordination geometries of the adsorbed ligands, and this can lead to a better understanding of how the ligands cause dissolution. It is known that oxalate, as an example of a ligand forming bidentate mononuclear structures, has a significant effect on the dissolution of certain minerals [2]. The aim of this project was to gain further information regarding the interactions of oxalate at the water-gibbsite (αAl(OH)3) interface using a combination of potentiometric titrations and IR spectroscopy [3]. For the experiments, an overlayer of gibbsite was evaporated onto a ZnSe ATR crystal. A gibbsite suspension was flowed over this overlayer, and its pH was maintained at 6 by additions of dilute hydrochloric acid or sodium hydroxide. Oxalate was added to the suspension, and spectra were recorded as a function of time. Initially, both inner- and outersphere complexes were observed in the spectra, but within the first hour the outer-sphere complexes were replaced by innersphere complexes. The subsequent addition of the siderophore desferrioxamine-B to the mineral suspension resulted in a decrease in surface concentration of inner-sphere complexes and an increase in outer-sphere complexes. These results indicate that the oxalate-gibbsite system might exhibit similarities with a dissolution-readsorption process previously observed in the corresponding oxalate-goethite (α-FeOOH) system [3]. The relative concentrations of the inner- and outersphere complexes do however differ, probably as a consequence of the different stabilities of their respective surface- and solution species. [1] Axe & Persson (2001) Geochimica et Cosmochimica acta 65 4481-4492 [2] Zutic & Stumm (1984) Geochimica et Cosmochimica acta 48 1493-1503 [3] Loring et al. (2008) Langmuir 24 7054-7057

A520

Goldschmidt Conference Abstracts 2009

Review of large low shear velocity provinces in the lower mantle

Clay interaction with organic ligands and siderophores in a CO2 atmosphere

DON HELMBERGER*, DAOYUAN SUN, LIJUN LIU, EH TAN AND MIKE GURNIS Seismological Laboratory, California Institute of Technology, Pasadena, CA 91125, USA (*correspondence: [email protected]) The CMB is one of the most significant boundaries in the Earth which is forced to maintain uniform temperature. This means that the two LLSVP’s in the mid-Pacific and Africa with apparent heavy distinct chemistry play particularly important roles since they are forced to convect by overheating. Meta-stable dynamic models have been proposed to solve this issue by internal circulation with cold material returning to the CMB to reheat. Here we review detailed 2D seismic sections through these two structures to investigate their differences and compatibility with the meta-stable models. The African LLSVP is better known since part of the anomaly is beneath land where a large array is available. Our best model here from waveform modeling has a superdome shape, 1000 km high with sloping walls (roughly 70°). The average shear velocity reduction is 3%. There is a ULVZ at the edge and a narrow plume-like feature emitting from the top, in excellent agreement with the meta-stable model. The mid-Pacific LLSVP is more difficult to study because of obvious data coverage. We can overcome some of this by refining a Trans-Pacific corridor of upper mantle structure so that multiple ScS bounces can be used effectively to validate and modify existing tomographic models. We find that an enhanced lower mantle model (SQ20RT, Ritsema) does quite well, with a -3% slow structure but about half as high as the African structure. It again has relatively sharp edges with a ULVZ along its western edge. Thus, the meta-stable dynamic model is quite compatible with our preliminary results. However, a more complete collaboration with other disciplines involving mineral physics and geochemistry is needed in resolving the fundamental issues, especially with respect to the mixture of minerals and melts, perovskite to post-perovskite, etc.

C. HEM1, A.C. MITCHELL1, N. BOVET1, S.L.S. STIPP1 2 AND E. MAKOVICKY 1

Nano-Science Center, Department of Chemistry, University of Copenhagen, Denmark. 2 GEO Center, Department of Geology, University of Copenhagen, Denmark Understanding the reactivity of common clays is central to the study of weathering and is of vital importance for many environmental engineering and contaminant containment strategies. Organic ligands and siderophores have been shown to enhance rates of clay dissolution and alteration through acidic dissolution, as well as ionic complexation at the mineral surface. Complexation of ions decreases ionic activity, promoting further dissolution. The purpose of our study was to investigate clay interaction in a CO2 atmosphere, to determine how dissolution proceeds in the presence of organic ligands and siderophores. Closed system experiments were performed with pure samples of the common clays, Ca-montmorillonite, Namontmorillonite and kaolinite, in a 99-100% CO2 atmosphere (log pCO2 = 0). Unbuffered and TRIS buffered (0.1 M) experiments were performed with solutions containing oxalic acid (0.01 M) or the siderophore, deferroxamine mesylate (DFOM) (0.05 M). Control experiments contained only TRIS buffer or water. The initial pH of the TRIS buffered experiments was 7 ± 0.5, while unbuffered experiments were titrated to pH 7 ± 0.5 with NaOH after equilibration with the CO2 atmosphere. The rate of clay dissolution was determined from the temporal variation in clay reaction products (Al, Si, Ca, Mg, Na and Fe). Clay surface composition before and after was determined by X-ray photoelectron spectroscopy (XPS) and end products were identified using X-ray diffraction (XRD). Atomic force microscopy (AFM) offered nano-scale observation of surface modification, allowing monitoring of very small changes, after only a few days. Oxalate and DFOM enhanced the release of mainly Al and Fe ions from the clay compared to controls experiments. XRD showed that the clay structure has collapsed and stabilized again with a lower distance between layers. The difference is 2.8 Å in the case of Ca-montmorillonite. A second phase, whewellite, has formed in all cases except for kaolinite. XPS revealed distinct changes in the Al:Si and Na:Al rations at the clay surfaces. AFM showed clear modification of the surface after 4 days.

Goldschmidt Conference Abstracts 2009

Oxygen uptake during marine diagenesis of fresh volcanic material

Indian ridges, hotspots, interaction: Réunion central Indian ridge and Amstersdam St Paul Southeast Indian ridge cases

DEBBIE HEMBURY1, MARTIN PALMER1, GARY FONES2 1 AND MORGAN JONES 1

National Oceanography Centre, Southampton, UK (*correspondence: [email protected]) ([email protected], [email protected]) 2 University of Portsmouth, Portsmouth, UK ([email protected]) Arc volcanism generally occurs in close proximity to the oceans. In such cases, >90% of erupted volcanic material may be deposited in the ocean by various means. Biogeochemical effects of volcanic ash in surface seawater have previously been addressed, but the majority of submarine volcanic deposits are delivered directly to the sea floor. These rapidly emplaced deposits of fresh volcanic material can blanket many km2 of seafloor. Little is known of the early diagenesis of this material, but it is likely to have a significant regional biogeochemical effect. The ongoing eruption of Montserrat, Lesser Antilles, provides an excellent case study for these processes. Microelectrode profiles taken in cores from close to the island show dissolved oxygen penetration depths ranging from <0.3cm in freshly deposited volcanic sediments to 5.6cm in background carbonate pelagic sediment (figure, below). We present these and other geochemical data from sediments and pore waters and demonstrate that oxygen consumption is not due to organic carbon oxidation, but most likely occurs by oxidation of Fe(II). The magnitude of oxygen consumption by volcanic material may be significant for atmosphere-ocean oxygen cycling, during susceptible periods in Earth’s history and in enclosed basins.

A521

C. HÉMOND1*, M. JANIN1, M. MAIA1, E. FÜRI2, D. HILTON2, B. MURTON3 AND J. DYMENT4 1

UMR CNRS-UB-Domaines Océaniques,IUEM, Place Copernic, 29280 Plouzané, France (*correspondence: [email protected] 2 Geosciences Research Division, Scripps Institution of Oceanography, La Jolla,CA-92093,USA 3 National Oceanography Centre, Southampton SO14 3ZH-UK 4 Laboratoire de geosciences marines, IPGP, 4 Place Jussieu, 75252 Paris cedex 05, France Recent samples from the R. Revelle RR11Knox (2007) have allowed us to complete the study by Nauret et al. (2006) based on the GIMNAUT cruise samples (2000) of the interaction area between the Reunion plume and the Central Indian Ridge. New Helium data support the suggestion of Nauret et al. of a flux of 3He enriched material through the off axis ridges Three Magi and Gasitao toward the southern end of the concerned segment of the CIR. Pb, Sr and Nd isotopes establish that this material derives from the Reunion plume and which must travel from the present position of it until the spreading axis. Witnesses of this transfer are the off axis ridges produced by melting of the underlying mantle through tension cracks in the lithosphere. The cruise Pluriel (2006) on the St Paul-Amsterdam plateau has completed the cruise Boomerang 6 (1996) in investigating the off axis volcanism of the eponym plateau whereas the spreading axis was investigated by Nicolaysen et al. 2008. New radiogenic isotope data establish a link between the seamount chain, the plateau and the islands. Subtle changes in composition are due to the two stages construction process of the plateau and seamounts. Some of them, highly alkaline, derive from lithospheric melting during a late phase of off axis magmatism on the Australian plate.

A522

Goldschmidt Conference Abstracts 2009

Pa/230Th as a paleocirculation proxy outside the North Atlantic

Sponge spicules as recorders of deep-water silicic acid

G.M. HENDERSON1, B.J. HICKEY1, J.W. RAE1, A.L. THOMAS1, S.A. MUELLER2 AND N. EDWARDS2

KATHARINE R HENDRY1, R. BASTIAN GEORG1, ROSALIND E.M. RICKABY1, LAURA F. ROBINSON2 1 AND ALEX N. HALLIDAY

231

1

University of Oxford, Department of Earth Sciences, UK ([email protected]) 2 The Open University, Milton Keynes, UK ([email protected]) Since its first application as a proxy for the rate of past ocean circulation more than a decade ago [1], 231Pa/230Th has been applied predominantly to cores in the North Atlantic. In this setting, the advection of surface waters to depth resets the 231 Pa/230Th “clock”, and the uniform southward movement of water masses make interpretation of sediment values relatively straightforward. The applicability of 231Pa/230Th in other settings, where water-masses may not be clearly reset, or where several water masses with different flow paths overlie one another remains unclear. We will present an overview of the potential for 231Pa/ 230 Th in the Southern Hemisphere. Data from the southern Indian Ocean [2] demonstrate that scavenging of 231Pa at the opal belt resets the 231Pa/230Th clock providing potential for application of the proxy to northward flowing water masses in the southern hemisphere. We will present new modelling that also indicates the sensitivity of southern hemisphere sediment 231 Pa/230Th to changes in ocean circulation, and will focus particularly on the Argentine Basin. We have investigated the use of the 231Pa/230Th proxy in four cores spanning all deepwater masses in that basin. Modern-day conditions are similar to those expected in the North Atlantic during the last glacial maximum with overlying southward and northward flowing water masses. Down-core 231Pa/230Th results reflect changes in ocean circulation, but these are compounded with other effects, probably due to changing boundary scavenging. Approaches to deconvolve these effects and to use 231Pa/230Th as a proxy for southern hemisphere deep-water flow will be presented. [1] E.F. Yu, et al., Nature 379, 689 (1996); [2] A. L. Thomas, et al., Paleoceanogr. 22 (4) (2007)

1

Department of Earth Sciences, University of Oxford, Parks Road, Oxford, OX1 3PR, UK ([email protected]) 2 Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02553, USA The distribution of silicon (Si) in the global oceans significantly influences ocean productivity and atmospheric CO2. Understanding changes in Si distribution, ocean circulation and the resulting influence on biological productivity and carbon drawdown, requires quantitative constraints on intermediate and deep-water silicic acid concentration. Previously, only records of surface waters have been available. Here, we have used the silica spicules formed by sponges to provide a record of deep ocean chemistry giving a unique insight into past marine Si cycling. We present here a calibration of the Si isotope composition of modern sponges from the Southern Ocean, which shows a linear inverse relationship with silicic acid concentration, such that sponges that grow under high Si are isotopically light. We apply our new method to deep-water sediment cores from the southern Scotia Sea in order to assess whether there have been changes in the silicic acid concentration of deep Southern Ocean waters since the Last Glacial Maximum (LGM). Our results show there is no significant difference in deep-water silicic acid concentration (<20 µM) between the LGM and modern deep water. This new result implies that Southern Ocean surface nutrient conditions, reconstructed by diatom opal, are controlled by changes in biological utilization rather than modification of upwelling nutrients. These changes in Southern Ocean productivity have the potential to impact directly the drawdown of atmospheric CO2 on glacialinterglacial timescales.

Goldschmidt Conference Abstracts 2009

Energetics of catabolic reactions in diffuse hydrothermal fluids – Clues to subseafloor microbial metabolism M. HENTSCHER1*, W. BACH1, M. PERNER2, A. KOSCHINSKY3, D. GARBE-SCHÖNBERG4 5 AND J.P. AMEND 1

University of Bremen, D-28359 Bremen, Germany (*correspondence: [email protected]) 2 University of Hamburg, D-22609 Hamburg, Germany 3 Jacobs University Bremen, D-28753 Bremen, Germany 4 University of Kiel, D-24098 Kiel, Germany 5 Washington University, St. Louis, MO 63130, USA The hot spots of life in the deep sea are associated with hydrothermal vent systems, where reduced, metal- und sulfide-rich fluids are generated by water-rock-reactions. When these fluids mix with oxygenated seawater, large redox disequilibria develop that can support chemolithoautotrophic microorganisms. Besides hydrothermal plumes and sulfide chimney walls, a likely habitat for microorganisms is the subseafloor, where upwelling vent fluids and cold seawater mix and form low-temperature hydrothermal fluids that slowly seep out of the seafloor (diffuse fluids). Indeed, microbiological [1,2] and geochemical [3,4] investigations provide strong support for microbial activity within this subseafloor mixing zone. Here we use geochemical mixing models and free energy calculations to identify which catabolic pathways are energetically feasible. The approach mixes high temperature vent fluid with seawater until either enthalpy or silica concentrations match the values of diffuse fluids. The difference between predicted and observed concentrations of non-conservative species in the diffuse fluids reveal which chemical species were consumed or produced by microbial metabolism. Further, discrepancies between free energies predicted from the mixing model and those calculated for the diffuse fluid compositions provide insights into the kinds of redox (i.e., potential catabolic) reactions taking place in the system. From 1991 to 2000, the diffuse fluids at 9°N on the East Pacific Rise [3] evolved from supporting predominantly sulfide and hydrogen oxidation, shifting to iron oxidation, and then back to hydrogen oxidation Diffuse fluids from the MidAtlantic Ridge at 5°S [2] indicate that methanogenesis and sulfate reduction are efficiently utilized such that the free energies are lowered to -10 to -20 kJ/mol electron acceptor. [1] Huber et al. (2003) FEMS Microbiol. Ecol. 43, 393-409. [2] Perner et al. Environ. Microbiol., submitted. [3] von Damm & Lilley (2004) Geophys. Monogr. 133, 245-268. [4] Proskurowski et al. (2008) GCA 72, 2005-2023.

A523

Volatility in BABB: Implications for Nb/Ta in the mantle source region J.M. HERGT1*, J.D. WOODHEAD1, A. GREIG1, R.J. WYSOCZANSKI2, M.I. LEYBOURNE3, E. TODD4 5 AND I.C. WRIGHT 1

School of Earth Sciences, The University of Melbourne, VIC, 3010, Australia (*correspondence: [email protected]) 2 NIWA, Private Bag 14901, Wellington, 6021, New Zealand 3 Ocean Exploration, GNS Science, Box 30-368, Lower Hutt, New Zealand 4 Department of Earth and Planetary Sciences, University of California, Santa Cruz, 1156 High St., Santa Cruz, CA 95064-1077, USA 5 National Oceanography Centre, Southampton, Empress Dock, European Way, Southampton SO14, 3ZH, UK New trace element data have been acquired for glass rinds and corresponding whole-rock samples of back-arc basin basalts from the Havre Trough in the SW Pacific. For most elements the match in compositions between glass and wholerock pairs is very close, if not identical. In other cases, small variations exist that can be explained by the lack of olivine (for example) phenocrysts in digests of the handpicked glass. Another suite of more volatile elements also show marked differences that we attribute to outgassing of the magmas during vesiculation and eruption. The levels of W and Mo, for example, are invariably enriched in the data for glass samples relative to the corresponding fine-grained rocks. Closer investigation, employing laser ablation techniques, reveals that there is no element enrichment in the glass per se; rather, the elevated volatile element contents can be attributed to the occurrence of trace minerals lining some of the vesicle walls. One entirely unexpected outcome of this work is the observation that enrichment in W in the bulk-glass digests correlates positively with Nb/Ta indicating that the exotic minerals in vesicles have highly fractionated Nb/Ta ratios. In contrast, the crystalline whole-rock data for each sample suite cluster in both W content and Nb/Ta value. Nevertheless, this observation has a number of important implications 1) we may not have been measuring what we thought when analysing apparently pristine handpicked glass, requiring a re-think of possible correction and/or sample preparation protocols 2) it is less clear that Nb/Ta determinations of BABB (and other vesicular rocks?) genuinely reflect those of the magma and may simply be recording the extent to which the magma has been outgassed prior to or during eruption and 3) petrogenetic models in which the (apparent?) Nb/Ta of the magma is employed to constrain the composition of the underlying mantle source may need to be revisited in the light of this work.

A524

Goldschmidt Conference Abstracts 2009

Water uptake of clay and desert dust aerosol particles at sub- and supersaturated water vapor conditions

Experimental constraints on carbonate and silicate melts, and CO2 release during subduction of sediments

HANNA HERICH1, TORSTEN TRITSCHER2, ALDONA WIACEK1,3, MARTIN GYSEL2, ERNEST WEINGARTNER2, ULRIKE LOHMANN1, URS BALTENSPERGER2 AND DANIEL J. CZICZO1,4

JÖRG HERMANN

1

Institute for Atmospheric and Climate Science, ETH Zurich, CH-8092 Zurich, Switzerland. [email protected] 2 Laboratory of Atmospheric Chemistry, Paul Scherrer Institut, CH-5232 Villigen, Switzerland 3 Now at: Dept of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada 4 Now at: Pacific Northwest National Laboratory, Richland, WA, United States Airborne mineral dust particles serve as cloud condensation nuclei (CCN). Hence, it is of particular interest how dust aerosols with different mineralogy behave when exposed to high relative humidity or supersaturation with respect to liquid water similar to atmospheric conditions. In this study the sub-saturated hygroscopic growth and the supersaturated cloud condensation nucleus activity of pure clays and real desert dust aerosols was determined using a hygroscopicity tandem differential mobility analyzer and a CCN counter (CCNC), respectively. Five different illite, montmorillonite and kaolinite clay samples as well as three desert dust samples (Saharan dust (SD), Chinese dust and Arizona test dust) were used. Aerosols were generated both with a wet and a dry disperser. The water uptake was parameterized via the hygroscopicity parameter, κ. The hygroscopicity of dry generated dust aerosols was found to be negligible as compared to processed atmospheric aerosols, with CCNC derived κ values between 0.00 and 0.02 (the latter corresponds to a particle consisting of 96.7% (by volume) insoluble material and ~3.3% ammonium sulfate). Pure clay aerosols were found to be generally less hygroscopic than real desert dust particles. All illite and montmorillonite samples had κ~0.003, kaolinites were least hygroscopic and had κ=0.001. SD (κ=0.023) was found to be the most hygroscopic dry-generated desert dust. Wet-generated dust showed an increased water uptake as compared to dry-generated samples. This is considered to be an artifact introduced by redistribution of soluble material between the particles. Any atmospheric processing of a fresh mineral dust particle which leads to the addition of more than ~3% soluble material will significantly enhance its hygroscopicity and CCN activity.

Research School of Earth Sciences, The Australian National University ([email protected]) An experimental study was conducted to constrain the phase and melting relations in carbonate bearing sediments from 700-1050°C, 2.5-5 GPa, i.e. under conditions relevant for subducted slabs. 10% of a dolomite-calcite mix was added to a pelite mix containing 2-7 wt% H2O. In all runs, quartz/coesite, clinopyroxene and garnet occur. Residual carbonate is a ternary Fe-Mg-calcite and is only disappearing at temperatures ≥ 900°C, when high amounts of melting occur. At low degrees of melting, residual carbonate coexists with phengite up to 950°C, 3.5 GPa and 1000°C, 4.5 GPa. Hence the presence of carbonate does not significantly reduce the stability of phengite in subducted sediments. While the solid phases remain constant over the investigated P-T range, there are drastic changes in the composition of the fluid phases. At 700°C, 2.5 and 3.5 GPa a non quenchable aqueous fluid was present, likely containing a low CO2 content. The elevated water content induced fluid fluxed melting in experiments at higher temperature. At 3.5 GPa, 800-1000°C a volatile-rich granitic melt is present that shows an incrasing CO2/H2O from ~0.1 (800°C) to 1.5 (1000°C). At 3.5 GPa, 1000°C, all the added 10% carbonate reacted away leading to 4.5 wt% H2O and 6.5 wt% CO2 dissolved in the granitic melt. Similarly at 4.0 GPa, 900°C there was 50% of melt in the experiment containing 12 wt% H2O and 9 wt% CO2. At 4.5 GPa another fundamental change in the fluid compositions has been observed. Within the silicate melt, there are globules of Fe-Ca-rich carbonatequench indicating that at 850-1050°C immiscible silicate and carbonate melts coexists. These carbonate melts contain SiO2, Al2O3 and surprisingly P2O5 and TiO2 at a wt% level and high amounts of U and Th. Moreover, silicate melts with high amounts of dissolved CO2, display significant enrichments of trace elements when compared to CO2-free melts at the same conditions. The experimental study provides evidence that external influx of aqueous fluids is needed to liberate CO2 from subducted sediments and that the extraction of CO2 strongly increases in efficiency with increasing temperature. Additionally at P > 4 GPa, T≥ 850°C immiscible carbonate melts occur, which could be important carriers for trace elements and CO2 in hot subduction zones.

Goldschmidt Conference Abstracts 2009

Impact of aeolian deposition on Mn cycling in soils

Norway’s first exploitation of oil? The processing of marine mammal blubber in slab-lined pits

ELIZABETH M. HERNDON1, LIXIN JIN2 3 AND SUSAN L. BRANTLEY

C. HERON1, G. NILSEN2, B. STERN1, O.E. CRAIG3 4 AND C. NORDBY

1

Dept of Geosciences, Penn State University, University Park, PA, USA, 16801 (*correspondence: [email protected]) 2 Earth and Environmental Systems Institute, Penn State University, University Park, PA, USA, 16801 ([email protected]) 3 Earth and Environmental Systems Institute, Penn State University, University Park, PA, USA, 16801 ([email protected]) Aeolian mass transport is a potentially critical, yet largely unrecognized, component of the manganese cycle. Mn is an essential micronutrient for plants and animals; however, high Mn exposure can lead to neurological disease in humans and forest decline in sensitive ecosystems. Furthermore, reactive Mn-compounds can affect organic matter breakdown, nutrient cycles, and heavy metal mobility. High Mn levels are observed in soils at the Susquehanna Shale Hills Observatory (SSHO), a forested watershed in central Pennsylvania, USA. The SSHO is a Critical Zone Observatory established to examine regolith evolution on shale. Using the mass transfer coefficient, τTi,Mn, to evaluate Mn mobility in the regolith, we find that surface soils are enriched relative to the parent shale (τTi,Mn = 5.18 ± 4.9). Here, we present findings that Mn addition to SSHO soils is best explained by industrial-aged aeolian inputs and propose a mass balance model to quantify atmospheric deposition. Elevated Mn concentrations in foliage (4,600 ± 1,500 ppm), leaf litter (8,500 ± 1,000 ppm) and the organic horizon (16,400 ± 13,800 ppm) indicate active cycling by vegetation; therefore, biotic mixing is incorporated into the model in order to evaluate the role of biota in creating the observed addition profile. Additionally, x-ray absorption spectroscopy is used to characterize structural and redox changes in Mn-compounds through biogeochemical cycling. Analysis of soils data from throughout the United States and Europe suggests patterns of Mn enrichment in surface soils coincident with industrial or population centers. The SSHO field study can provide a comprehensive analysis of biogeochemical Mn cycling and may have international relevance concerning the long-term effect of industrial Mn emissions on ecosystems.

A525

1

Division of Archaeological, Geographical and Environmental Sciences, University of Bradford, Richmond Road, Bradford, West Yorkshire BD7 1DP, UK (*correspondence: [email protected], [email protected]) 2 Institutt for Arkeologi, University of Tromsø, NO-9037 Tromsø, Norway ([email protected]) 3 Department of Archaeology, University of York, The King’s Manor, York YO1 7EP, UK ([email protected]) 4 Cultural Historical Laboratory, Tromsø University Museum, University of Tromsø, NO-9037 Tromsø, Norway ([email protected]) Analysis of lipids of archaeological interest from soils and sediments has focussed largely on anthropogenic markers of manuring and cess deposition. This presentation targets a specific archaeological feature known as the slab-lined pit. Some 700 of these pits have been recorded in northern Norway. Lipid analysis and bulk carbon and nitrogen isotope determinations have been performed on samples (‘cemented organic residues’, charcoal, sediment and fire-cracked rock) excavated from twelve slab-lined pits to test the premise that these features were used for the extraction of oil from the blubber of marine mammals, such as seal, porpoise and whale. A wide range of lipid compound classes was detected especially in the ‘cemented organic residues’. The presence of long-chain mono- and diunsaturated fatty acids together with a wide range of oxidation and thermal alteration products of diagnostic unsaturated acids suggests that these features were used for oil extraction from marine tissues. Further information was provided by the presence of long-chain fatty acids associated with surviving triacylglycerols and the presence of cholesterol. A probable biomarker of microbiological activity impacting on the organic matter deposited in the pits was also identified. Bulk isotope analysis conducted on the ‘cemented organic residues’ is consistent with modern reference samples of blubber and oil from seal and whale. These data provide the first analytical evidence for the function of slab-lined pits in the archaeological record and confirm widespread exploitation of marine mammals for producing oil for heating, lighting and myriad other uses in the past.

A526

Goldschmidt Conference Abstracts 2009

Potential of visualisation methods to further our understanding of soil organic matter dynamics A.M. HERRMANN1*, N. NUNAN2 AND K. RITZ3 1

Uppsala BioCentre, Swedish University of Agricultural Sciences, Sweden (*[email protected]) 2 CNRS, Laboratoire BioEMCo, Thiverval-Grignon, France 3 School of Applied Sciences, Cranfield University, U.K In the light of the expected future climate change, soil organic matter decomposition and its possible feedback to CO2 concentrations into the atmosphere has recently received considerable interest. The magnitude of this effect and differences among soils are uncertain due to the inherent complexity of soils that are structurally heterogeneous across a wide range of spatio-temporal scales. In terms of understanding of CO2 feedback mechanisms, fundamental approaches which explicitly recognise the complexity of soils and the spatial organisation of their constituents are necessary in order to further our understanding of soil organic matter dynamics. A major obstacle to progress is the lack of techniques of adequate sensitivity and resolution for data collection needed to further our understanding of soil organic matter dynamics at relevant scales. Contemporary visualisation methods are providing new insights into the spatial organisation of pore networks and location of micro-organisms within the fabric of the soil [1]. Recently, secondary ion mass spectrometry (SIMS) has received much interest from soil scientists to explore the biophysical interface in soils. This innovative approach [2] provides a hitherto unavailable means to evaluate links between the heterogeneous architecture of the soil matrix and the location of microbial activity at scales at which soil processes are mediated (nano- and micro-scale, i.e. molecular and microbial) [3]. We will present our recent findings illustrating the capacity of the latest technology available in microscopy and isotope detection, including optical fluorescent microscopy and SIMS, to improve our fundamental understanding of soil organic matter turnover. Particularly, practical considerations in the use of these techniques with respect to experimental design and sample preparation will be emphasized. [1] Nunan et al. (2003) FEMS Microbiol. Ecol. 44, 203-215. [2] Herrmann et al. (2007) Rapid Comm. Mass Spec. 21, 2934. [3] Herrmann et al. (2007) Soil Biol. & Biochem. 39, 1835-1850.

Natural organic matter and the event horizon of mass spectrometry N. HERTKORN1*, PH. SCHMITT-KOPPLIN1 2 AND E.M. PERDUE 1

Institute of Ecological Chemistry, Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Ingolstaedter Landstrasse 1, D-85764 Neuherberg, Germany. 2 School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, 30332, USA Soils, sediments, freshwaters and marine waters contain natural organic matter (NOM) - an exceedingly complex mixture of organic compounds that collectively exhibit a nearly continuous range of properties (size-reactivity continuum). Ultrahigh resolution Fourier transform ion cyclotron (FTICR) mass spectra of NOM reveal several thousand molecular formulae, corresponding in turn to several hundred thousand distinct chemical environments of carbon even without accountancy of isomers. The degree of complexity of NOM can be brought into sharp focus through comparison with the theoretical limits of chemical complexity, as constrained and quantized by the fundamentals of chemical binding [1]. Throughout a sizable range of mass, H/C and O/C elemental ratios, the molecular formulae within NOM attain one-hundred percent of the theoretical C,H,O-compositional space which denotes the isomer-filtered complement of the entire, very vast space of molecular structures composed solely of carbon, hydrogen and oxygen. The method-dependent selectivity of the ionization process suggests that the observed mass spectra represent simplified projections of still more complex mixtures. [1] Hertkorn et al. (2008) Anal. Chem., 80, 8908-8919.

Goldschmidt Conference Abstracts 2009

MC3: Mass conservation, metamorphic changes and modelling consequences

Lu-Hf dating of biogenic phosphates – Prospects and pitfalls D. HERWARTZ*, T. TÜTKEN, C. MÜNKER, AND P.M. SANDER Steinmann Institut, University of Bonn, 53115 Bonn, Germany (*correspondence: [email protected]) Lutetium-Hf geochronology has been successfully applied to date high Lu/Hf phases such as garnet or apatite. The Lu-Hf system also appears to be a promising tool for direct radiometric dating of fossil biogenic apatite [1]. However, this chronometer will only yield meaningful ages, if the skeletal apatite behaved as a closed system with respect to Lu and Hf after a rapid early diagenetic REE-uptake. To closely assess the potential of the Lu-Hf chronometer in biogenic phosphates, we performed Lu-Hf measurements on well characterized fossil bones and teeth from many different taphonomic settings and fossil sites of Mesozoic to Cenozoic age. Measurements were perfomed using a mixed 176Lu-180Hf tracer and the Neptune MC-ICP-MS at Bonn. An evaluation of different digestion strategies on a fossil bone standard [2] resulted in significantly different Hf contents and 176Lu/177Hf. Measured Hf contents where highest employing bomb digestion in 10:1:1 HCl:HF:HClO4. The measured contents become successively lower for the same acid mixture employing tabletop digestion and for dissolution in conc. HNO3 only. Rare Earth Element profiles through fossil bones in combination with our Lu-Hf measurements indicate late diagenetic REE uptake and open system behaviour for many specimens. In these cases, Lu-Hf isochrons yield significantly younger ages than the known chronostratigraphic age. For LuHf dating of phosphatic fossils it is thus crucial to ensure a closed system behaviour for each fossil site. Lutetium-Hf systematics of phosphatic vertebrate fossils from the world famous 47 Ma old Messel pit, Germany, were analyzed as a potential example for a closed system site, including bones and teeth of terrestrial mammals, fish scales, turtle carapaces and coprolites as well as diagenetic siderite and the sourrounding oil shale. The samples exhibit remarkably low 176 Lu/177Hf (<0.035), hence only defining an isochron with a large error (48±28 Ma, MSWD = 1.4). However, the low 176 Lu/177Hf appear to be a site specific feature of Messel fossils, controlled by bedrock properties. [1] Barfod et al. (2003) Chem. Geol. 200, 241-251. [2] Chavagnac et al. (2007) Analytica Chimica Acta 599, 177190.

A527

G. HETÉNYI1*, J.A.D. CONNOLLY1, V. GODARD2 3 AND R. CATTIN 1

ETH Zürich, Department of Earth Sciences, Zürich, Switzerland (*correspondence: [email protected]) 2 Université Aix-Marseille 3, Aix-en-Provence, France 3 Géosciences Montpellier, Montpellier, France Geodynamic models [e.g. 1] simulating subduction zone or mountain building processes have evolved rapidly with the increasing availability of phase equilibrium data. Typically these data are used to compute the physical properties, and in particular, to account for density effects in the conservation of momentum equation; but few, if any, attempts have been made to account for the volumetric effects of phase transformations in the continuity governing equation of geodynamic models. We explore the consequences of this simplification by developing an approach that allows us to obtain rigourously correct solutions for continuity. Density data are used to control volumetric changes due to phase transformations through the modification of the regional stress-field. The approach is implemented in the finite element modelling tool Cast3M [2] and has been tested using elastic and visco-elastic rheologies, in the presence of erosion. Preliminary applications focusing on the deformation of an orogen show that the neglect of densification in the continuity equation has major consequences: the effects on the evolution of topography are of the same order of magnitude as effects resulting from the action of erosion. The two processes compete in shaping the orogen and in localizing deformation; the domination of either process over the others depends on defintion of the boundary conditions. In models where metamorphic reactions are not correctly implemented, not only are the resultant errors with regard to mass conservation significant, but the importance of different physical processes governing crustal deformation and topographic evolution of the orogen are also misrepresented. [1] Burov and Yamato (2008) Lithos 103, 178–204. [2] Verpeaux et al. (ed.)(1988) Castem2000: une approche moderne du calcul des structures. Calcul des Structures et Intelligence Artificielle, Pluralis, 261–271.

A528

Goldschmidt Conference Abstracts 2009

Thallium-mineralization during late magmatic activity in the peralkaline complex Ilimaussaq, Greenland KAI HETTMANN1*, MICHAEL MARKS1, THOMAS WENZEL1, THOMAS ZACK2 1 AND GREGOR MARKL 1

Institut für Geowissenschaften, Univ. of Tübingen, D-72074 Tübingen, Germany (*correspondence [email protected]) 2 Institut für Geowissenschaften, Univ. of Mainz The layered peralkaline igenous Ilimaussaq complex (Gardar failed-rift province in southwest Greenland) has attracted exploration activities in past and present. The intrusion was emplaced in three magmatic phases, evolving in an essentially closed-system. The composition of the rocks covers a broad range of alkaline rocks, ranging from alkaline to peralkaline granites and syenites to highly evolved nepheline syenites. The latest magmatic rocks are among the most differentiated, known on earth [1]. During late-stage magmatic activity hydrothermal fluids released by the magma formed veins cutting earlier rocks of the complex. The rare mineralization of the Tl-Cu-Fe-minerals thalcusite, chalcothallite and djerfisherite-thalfenisite solid-solutions occurs associated with veins containing aegirine-feldsparsodalite-ussingite assemblages [2]. These assemblages were formed by CH4- and H2O-rich fluids at temperatures ranging from 200 to 400°C and anomalous high pH (7 to 9) [3, 4]. The unusual enrichment of Tl in these late magmatic fluids was most likely triggered by fluid-wall rock interaction. During magma crystallization, Tl shows an incompatible lithophile behavior and is incorporated into silicate minerals exchanging for K [5]. During vein formation, K-bearing minerals were partly replaced by K-poor minerals. The resulting K-excess causes astrophyllite to crystallize at the expense of primary mafic minerals (aegirine+aenigmatite±Na-amphibole). The Tl released by these reactions is enriched in the Cu-bearing fluids and lead to the formation of Tl-Cu-Fe-sulfides, which are thermodynamically stable at high pH-conditions. This process is an example for the decoupling of elements with coherent magmatic behavior under hydrothermal conditions. [1] Sørensen (2001) Geology of Greenland Survey Bulletin 190, 7-24. [2] Karup-Møller & Makovicky (2001) Geology of Greenland Survey Bulletin 190, 127-130. [3] Graser & Markl (2008) J Petrol 49, 239-265. [4] Markl & Baumgartner (2002) Contrib Mineral Petrol 144, 331-346. [5] Kyono & Kimata (2001) Eur J Mineral 13, 849-856.

Calcium isotope systematics of dinosaur teeth A. HEUSER1*, T. TÜTKEN1 AND S.J.G. GALER2 1

Steinmann Institut, Universität Bonn, Poppelsdorfer Schloss, 53115 Bonn, Germany (*[email protected]) 2 Max-Planck Institut für Chemie, Abteilung Geochemie, Postfach 3060, 55020 Mainz, Germany We present new data on the Ca isotopic compositions of Late Cretaceous to Early Triassic dinosaur teeth (enamel and dentin) from different sympatric herbivorous and carnivorous dinosaurs. To investigate potential diagenetic alteration we analyzed teeth of various extant reptiles for comparison. Diagenetic alteration of the dinosaur teeth seems negligible as they have a similar δ44/40Ca difference of ~0.4‰ between enamel and dentin compared to extant reptiles. Furthermore, no systematic relationship between δ44/40Ca of fossil teeth and the embedding sediment is observed. Preservation of original δ44/40Ca in Mesozoic fossil bones and teeth thus seems likely. Extant mammalian bones display a trophic level effect with δ44/40Ca values from carnivores being ~1‰ lighter compared to herbivores [1]. However, δ44/40Ca values of skeletal apatite of sympatric herbivorous and carnivorous dinosaurs do not show any systematic difference. Since no Ca isotope fractionation between diet and soft tissue occurs [2] the lack of a trophic level offset between herbivores and carnivores can be explained if the investigated carnivorous dinosaurs only fed on soft tissue from herbivores. This would result in very similar δ44/40Ca of the diet of herbivores and non-bone-ingesting carnivores and thus in very similar δ44/40Ca ratios of the mineralized tissues. In contrast, a Tyrannosaurus rex tooth yields an enamel δ44/40Ca value ~1‰ lower than those of all other herbivorous and carnivorous dinosaurs analyzed. T-Rex was capable to crush and ingest bone [3]. Thus we hypothesize that T-Rex ingested significant amounts of bone tissue with low δ44/40Ca. This would explain the lower δ44/40Ca values than for presumably non-bone-ingesting carnivorous dinosaurs. This hypothesis will be further tested by analyzing teeth of sympatric smaller theropods as well as extant hyenas and lions. [1] DePaolo (2004) Reviews in Mineralogy & Geochemistry 55, 255-288. [2] Skulan & DePaolo (1999) PNAS 46, 1370913713. [3] Chin, Tokaryk, Erickson & Calk (1999) Nature 393, 680-682.

Goldschmidt Conference Abstracts 2009

A529

Applications of neutron diffraction studies at LANSCE to environmental and energy problems

Incomplete mixing of nucleosynthetic components in Ba isotopes of primitive chondrites

D.D. HICKMOTT1*, H. XU1, Y. ZHAO1, J.LUO1, K. LOKSHIN1 AND W. MAO2

HIROSHI HIDAKA1* AND SHIGEKAZU YONEDA2

1

EES/LANSCE, LANL, Los Alamos, NM 87545, USA (*correspondence: [email protected], [email protected], [email protected], [email protected], [email protected]) 2 School of Earth Sciences, Stanford U., Stanford, CA 94305, USA ([email protected]) Time-of-flight (TOF) neutron diffraction (ND) with Rietveld refinement is a powerful tool for investigating materials of interest in environmental and energy science. The high-pressure preferred orientation (HIPPO) beamline coupled with a torroidal anvil press or high-P low-T gas/liquid cells allow determination of EOS and D positions of D-bearing phases as f(P,T). Recent investigations at Los Alamos Neutron Science Center (LANSCE) have focused on a range of energy/ environmentally relevant materials. Jarosite (KFe3(SO4)2(OD)6) structure was investigated using TOF ND from room T to its dehydroxylation T. With increasing T its c axis expands 10 times more rapidly than its a axis. Fitting of cell volumes yields α = αo + α1T with αo = 1.01 x 10-4 K-1 and α1= -1.15 x 10-7 K -2. H bonds holding the (001) octahedral-tetrahedral sheets together are weakened with increasing T. Near the dehyroxylation T, jarosite decomposes into yavapaiite and hematite (+ vapor). H clathrate has potential as a H storage material. TOF ND at low T (10-300 K) and high P (1-2000 bar ) show: 1) large cages of the SII clathrate structure reversibly varies from 2 to 4 D2 molecules with decreasing T while the small cage contains a single D2 molecule over the full T range; 2) D2 are localized in both cages of the SII clathrate structure at low T and become delocalized in both cages at higher T; 3) there is shortening of D-D bonds in the clathrate cages, with bond lengths shorter than in metallic H. Studies of molecular organic framework (MOF) compounds potentially useful for H2 storage or gas separation reveal D2 positions and crystal structures. We studied H adsorption in Cu3[Co(CN)6]2, a Prussian blue analogue, at 10 MPa of D2 from 40 to 200 K. Cell volume increases from 990.5(4) Å3 under vacuum to 993.5(3) Å3 at 10 MPa, implying incorporation of significant amounts of D2 into the nanoporous framework. In addition, we synthesized a highly stable porous lanthanide MOF, Y(BTC)(H2O)·4.3H2O, and ND of the dehydrated phase revealed four distinct D2 sites that are progressively filled within the framework.

1

Dept. of Earth Planet. Sys. Sci., Hiroshima Univ., HigashiHiroshima 739-8526, Japan (*correspondence: [email protected]) 2 Dept. of Science and Engineering, National Museum of Nature and Science, Tokyo 169-0073, Japan ([email protected]) Heterogeneous isotopic compositions observed in several elements of carbonaceous chondrites support the incomplete mixing model of some nucleosynthetic components in the early solar system. Barium is one of promising elements to address the details of nucleothentesis and presolar grain formation of the solar system [1-3]. Barium has seven stable isotopes with the mass numbers 130, 132, 134, 135, 136, 137 and 138. 130Ba and 132Ba are p-process isotopes produced by photodisintegration, 134Ba and 136Ba are s-only process isotopes, and 135Ba, 137Ba and 138Ba are s- and r-process isotopes. In addition, 135Ba isotopic abundance may be affected by decay from presently extinct 135Cs isotope (t1/2=2.3 Ma), which can be used for Cs-Ba geochronological application [3,4]. Ba isotopic compositions of chemical leachates from eleven carbonaceous chondrites, Orgueil (CI) Mighei (CM2) Murray (CM2) Murchison (CM2) Sayama (CM2) Allende (CV3) Efremovka (CV3) Isuna (CO3) Kainsaz (CO3) Maralinga (CK4) and Karoonda (CK4) were determined by thermal ionization mass spectrometry to assess the chemical evolution in the early solar system. The barium isotopic data in most of the leachates show variable 135Ba excesses correlated with 137 Ba excesses, suggesting the presence and heterogeneity of additional nucleosynthetic components for s- and r-processes in the solar system. The isotopic deviation treated in this study are generally small (-3<ε<+3). As exceptional cases, large deviations of 135Ba (ε=-13.5 to -5.0) and 137Ba (ε=-6.2~-1.2) observed in the acid residues from one CI and four CM meteorites show significant evidence for enrichments of sprocess isotopes derived from presolar grains. Subtraction of s- and r-isotopic components from the total Ba isotopes of CM meteorites allows us to consider the possible existence of presently extinct 135Cs isotope in the early solar system. [1] Ranen and Jacobsen (2006) Science 314, 809-812. [2] Carlson et al. (2007) Science 316, 1175-1178. [3] McCulloch and Wasserburg (1978) Ap.J. 220, L15-L19. [4] Hidaka et al. (2003) EPSL 214, 455-466.

A530

Goldschmidt Conference Abstracts 2009

A dynamic magnesium cycle during the Cenozoic? Insights from the magnesium isotopic composition of pelagic carbonates JOHN A. HIGGINS* AND DANIEL P. SCHRAG Department of Earth and Planetary Science, Harvard Univ., Cambridge, MA 02138 (*correspondence: [email protected]) Evidence from fluid inclusions in evaporites and systematic changes in the mineralogy of CaCO3 (‘aragonite seas’ vs. ‘calcite seas’) suggest that the chemical composition of seawater has changed during the Cenozoic. In particular, magnesium in seawater is thought to have increased by as much as 20 mM since the early Cenozoic [1]. However, the mechanisms responsible for the observed chagnes in magnesium in seawater are not well understood. Proposed mechanisms include changes in the rate of high-temperature hydrothermal reactions at mid-ocean ridges as well as changes in the rate of dolomite precipitation [2-3]. Recent work on magnesium isotopes in deep-sea pore fluids shows that magnesium isotopes are fractionated very differently during the preciptiation of Mg-clays and dolomite [4]. A consequence of this is that the magnesium isotopic composition of seawater has likely changed with time. To reconstruct the magensium isotopic composition of seawater, we measured the magnesium isotopic composition of pelagic carbonates from two ODP sites (807 and 1265). Measured δ26Mg values range from -4 to -5.5‰ and vary systematically with time. Similar changes in δ26Mg are observed at both sites, though there appears to be a small offset (0.2-0.3‰) between sites. Although we cannot exclude changes magnesium isotope fractionation as the source of the observed variability, we tentatively interpret our data as reflecting changes in the δ26Mg of seawater. Our results suggest a dynamic global magnesium cycle in the Cenozoic driven either by changes in the isotopic composition of the weathering flux [5] or the rate of dolomite precipitation. [1] Horita, J. et al. (2001) GCA 66, 3733-3756. [2] Holland & Zimmermann (2000) Int. Geo. Rev. 42, 481-490. [3] Spencer & Hardie (1990) Spec. Pub. Geochem. Soc. 2, 409-419. [4] Higgins & Schrag (2008) GCA 72, A375. [5] Tipper et al. (2006) EPSL 250, 241-253.

Revisiting Mediterranean sapropel formation: New insights from chlorin nitrogen isotope measurements M.B. HIGGINS1*, R.S. ROBINSON2 AND A. PEARSON1 1

Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138, USA (*correspondence: [email protected]) 2 Graduate School of Oceanography, University of Rhode Island, Narragansett, RI 02882, USA Sedimentary nitrogen isotopic ratios are a useful tool for reconstructing past water column nutrient dynamics and budgets. However, isotopic values of bulk sediments may be prone to diagenetic alteration, especially in oxic environments. One way to circumvent potential isotopic alterations is to measure the isotopic composition of intact fossil chlorophyll molecules, which represent a primary signal from surface waters. The sedimentary record of the Mediterranean Sea contains several sapropel horizons during the late Pleistocene, which are characterized by high total organic carbon contents. Previous work utilizing a compound-specific nitrogen isotope approach suggested that in the Eastern Mediterranean, bulk nitrogen isotope measurements are enriched due to diagenetic processes in non-sapropel horizons [1]. However, past analytical limitations prevented the direct comparison of chlorins from non-sapropel and sapropel horizons, due to the low concentrations of nitrogen in non-sapropel samples, and this interpretation was based on an assumed isotopic composition for non-sapropel chlorins. The recent development of a new method for chlorin nitrogen isotopic analysis [2] allows for measurements of samples containing ~30 nmol N, enabling the measurement of chlorins from nonsapropel horizons. We have obtained chlorin fractions from sapropels S2-S5, and from the surrounding non-sapropel layers, from two sites in the Eastern Mediterranean. We will report on the nitrogen isotopic values obtained from these fractions, and compare the isotopic composition of sapropel and non-sapropel horizons to determine whether the difference in their bulk isotopic composition reflects different sources of nitrogen to surface waters, or is an artifact of sedimentary diagenesis. [1] Sachs and Repeta (1999) Science 286, 2485-2488. [2] Higgins et al. (2009) Anal. Chem. 81, 184-192.

Goldschmidt Conference Abstracts 2009

Geothermobarometric and fluid inclusion data of historic lavas of Fogo Volcano, Cape Verde islands E. HILDNER* AND A. KLÜGEL University of Bremen, 28334 Bremen, Germany (*correspondence: [email protected]) ([email protected]) Fogo is one of the most active oceanic volcanoes and the only island of the Cape Verde archipelago with historic volcanic activity. The 1995 eruption has been preceded and accompanied by seismic activity beneath the submarine FogoBrava-platform and also on the adjacent island of Brava. We have carried out a geobarometric study of basantic to tephriphonolitic volcanic rocks from several historic eruptions of Fogo in order to reconstruct the depths of magma reservoirs and magma pathways prior to eruption. Our investigations focused on the most recent eruptions of 1995 and 1951. The eruption of 1995 was mineralogically and chemically zoned; the early ejecta were phonotephritic, the later main volume was tephritic in composition. Clinopyroxene-melt thermobarometry of 75 clinopyroxene phenocrysts in nine samples of 1995 yields a dominant pressure range of 400-690 MPa (average 510 MPa). There is no systematic pressure difference between the tephrites and the phonotephrites. For the 1951 eruption 87 clinopyroxene phenocrysts in eight samples yield a range of 380-710 MPa (average 500 MPa). Six clinopyroxene phenocrysts of a lava flow from 1694 yield a pressure range of 450-500 MPa. These pressures are interpreted to reflect different fractionation levels at ca. 15-24 km depth, within the uppermost mantle, where melt and phenocrysts last equilibrated. Microthermometry of CO2–rich fluid inclusions in clinopyroxene and olivine phenocrysts of the 1995 eruption yields a slightly different pressure range. Inferred pressures range from 260-580 MPa with a maximum between 360 and 420 MPa. There is thus considerable overlap with the cpx-melt data and a spread to lower pressures, which indicates limited reequilibration of fluid inclusions during magma transit to the surface. Our data suggest that the 1995 magmas ascended from mantle depth to the surface with only short residence times at crustal levels, probably on the order of one day. This conclusion is in accordance with the absence of plagioclase phenocrysts and microphenocrysts in the vast majority of Recent Fogo lavas.

A531

Ab initio studies of Fe isotope fractionation in Fe sulfides P.S. HILL AND E.A. SCHAUBLE UCLA, Los Angeles, CA 90095-1567 ([email protected]) Iron sulfide compounds form in many natural and microbial processes involving the reduction of iron and/or sulfur. 56Fe/54Fe ratios in sedimentary pyrites deposited before the rise of atmospheric oxygen were much lighter those of today[1]. The Fe isotope signatures of such minerals as pyrite depend on the fractionation between their dissolved precursors and upon the reservoirs from which the iron is taken. Understanding of redox and non-redox effects on equilibrium iron isotope fractionation in Fe sulfides will help us decipher modern and ancient Fe-isotopic signatures. Here we predict 56Fe/54Fe fractionations in Fe-S and II Fe -Cl complexes with 3 sets of ab initio models, extending our previous studies of aqueous ferric chloride complexes [2]. In B3LYP/6-31G(d) models, 1000 ln β56-54 (reduced partition FeIIICl2+(H2O)5, function ratios) of FeIII(H2O)6, III III III + – Fe Cl2 (H2O)4, Fe Cl3(H2O)3, Fe Cl4 , FeIIICl52-(H2O)2, FeIIICl63- show roughly linear decreases of ~0.9‰/Cl. The FeII-S series and the FeII-Cl series show slightly smaller decreases of ~0.6‰/S and ~0.6‰/Cl repsectively. 1000 ln β for the tetrahedral complex FeIIICl4– is slightly larger than FeIIICl3(H2O)3, most likely due to the smaller coordination number. Surprisingly, tetrahedral ferrous species such as FeIICl42– will not have the abnormally high 56Fe/54Fe, demonstrating that in this case, the change of bond partners is more significant than the change in coordination number. Redox fractionations between equivalent species (e.g., FeIIICl2+(H2O)5 vs. FeIICl+(H2O)5 ) range from 2.7 to 3.9‰, the oxidized member being heavier. Fractionation between ferric and ferrous Fe modeled with an inner hydration sphere of 6 waters, is 3.2‰ when calculated with the same basis set and method. A model of the tetrahedral iron sulfide site in the iron protein rubredoxin (Fe-(SH-R)4) shows a 2.6‰ difference between the ferric and ferrous versions. We also compare the effects of coordination number and bond length in sulfide species. FeII(SH)4 is predicted to have higher 56Fe/54Fe than FeII(SH)6 suggesting that the mineral mackinawite (tetrahedral coordination of Fe) will have higher 56 Fe/54Fe than triolite or pyrrhotite (octahedral coordination of Fe). Trends in equilibrium iron isotope fractionation among the ferric chloride complexes appear as reasonable predictors of trends in other sequences of Fe-ligand complexes. [1] Rouxel, Bekker, Edwards, (2005) Science 307 1088-1091 [2] Hill & Schauble (2008) Geochim, Cosmochim. Acta 72 1939-1958.

A532

Goldschmidt Conference Abstracts 2009

Isotopic clues (U-series, 14C, 13C, 18O) on growth process and age of Arctic fissure calcretes (endostromatolites) from Northern Canada CLAUDE HILLAIRE-MARCEL1, BASSAM GHALEB1, PIERRE DESCHAMPS1,2 AND BERNARD LAURIOL3 1

GEOTOP-UQAM, CP 8888 Montreal (Qc) H3C 3P8 Canada (*correspondence: [email protected]) 2 CEREGE, BP 80, 13545 Aix-en-Provence cedex 04, France 3 Dept of Geography, University of Ottawa, Ottawa (ont.) K1N 6N5, Canada Fissure calcretes could represent early continental forms of life in the Earth’s history and are of interest for exploration purposes on other planets. They are observed filling diaclases in permafrosted karsts from Arctic environments and consist of secondary carbonates with layered and/or dendritic submillimetric microstructures, suggesting sub-aerial bacterial activity under relatively extreme climatic conditions. We report here on 238U, 234U, 230Th, 226Ra, 14C, 13C & 18O analyses of a few specimens from Bear Cave (Yukon). A first sample yielded inconsistent 14C- and 230Th-ages (ranging from bottom to top of the concretion10-4 ka and 260-55 ka, respectively). Higher resolution measurements in a second sample better illustrate trends from the layer immediately attached to the host rock (here Paleozoic limestones) and the outer, columnar surface of the concretion: i) 230Th/238U activity ratio decrease from near secular equilibrium values to appr. 0.2; ii) 238Uconcentrations increase from ~ 2 to ~ 6 ppm, and iii) 226 Ra/230Th activity ratios increase from near secular equilibrium values to 1.2. This pattern suggest a pseudoRayleigh fractionation process with redistribution of U-series isotopes from the host-rock into the calcrete growth layers, more or less in function of their relative solubility. Some addition of more soluble elements relating to water fluxes cannot be ruled out. Stable carbon isotopes suggest a similar process with a progressive enrichment in 13C (up to +8.5 ‰ vs. VPDB) attributed to kinetic fractionation with freezing of water inducing outgazing of an isotopically light CO2 with precipitation of a 13C-enriched calcite. The trend for a progressive enrichment in 14C suggests partial exchanges with the atmospheric CO2 circulating in bedrock fissures. Thus, if 14 C and U-series methods cannot be used to set the age of such calcretes, they provide information on their accretion process. In view of the excess 226Ra observed throughout most of the concretion, the overall age of the study specimen cannot exceed a few thousand years (i.e., mid- to late-Holocene), but one cannot estimate any precise duration for the growth phase within this interval.

He-CO2 characteristics of submarine and subaerial fluids of the Costa Rica forearc D.R. HILTON1, E. FÜRI1, T.P. FISCHER2, C. RAMÍREZ3, M. TRYON1, P.H. BARRY1, K. BROWN1, G. ALVARADO3, W. MONTERO3 AND P. DENYER3 1

Scripps Inst. Oceanography, La Jolla, CA 92093, USA ([email protected]) 2 Univ. of New Mexico, Albuquerque NM, 87131 USA 3 Escuela Centroamericana de Geología, Univ. Costa Rica, San José, Costa Rica. We report He-CO2 isotopic and relative abundance results for groundwater and cold seep fluids from subaerial (Nicoya Peninsula/Pacific Coast) and submarine segments of the Costa Rica (CR) forearc, respectively. Our aim is to assess and characterize shallow outputs from the subducting slab – in terms of chemistry and fluxes - for comparison with deep(er) slab outputs sampled via arc magmatism at the volcanic front. All samples indicate a strong and variable contribution of mantle-derived He to the CR forearc. Groundwaters on Nicoya and the adjacent coast have 3He/4He ratios significantly above crustal production values – from 0.45 to 3RA (RA = air 3 He/4He), which equates to a mantle contribution up to ~38 % of the total He. CO2/3He ratios span 3 orders of magnitude (0.3-300 x 109) with δ13C values mostly low (-15 to -20 ‰). The maximum 3He/4He ratio off-shore is 1.4 RA, at Jaco Scar, the δ13C values span a much greater range (-11 to -60 ‰) and the fluids show greater super-saturation in CO2, up to 0.34 ccSTP/gH2O. In contrast, arc front volatiles have 3He/4He ratios between 6-8 RA, a narrow range of CO2/3He ratios (~ 1010) and mostly high δ13C values (-6 to -3 ‰). There is a clear contribution of mantle volatiles to both the forearc and arc front. At the forearc, this contribution occurs from the mantle wedge and/or the lithospheric mantle of the subducting plate via the plate interface and upper plate faults. It is dominated, however, by CO2 – partially modified by the effects of methane oxidation - from the shallow slab and/or over-riding plate. Volatiles at the arc front reflect an enhanced mantle contribution superimposed upon a strong slab flux. Significantly, CO2 fluxes at the forearc are extremely low compared to the arc front reflecting effective retention of slabderived CO2 through the shallow subduction cycle. Recycling of CO2 to the atmosphere is dominated by arc front emissions.

Goldschmidt Conference Abstracts 2009

Seasonal stream water chemistry at the Damma Glacier, Switzerland

Short and long-term denudation rates at the Altiplano margin, La Paz region, Bolivia

R.S. HINDSHAW1,2*, B.C. REYNOLDS1, J.G. WIEDERHOLD1,2, R. KRETZSCHMAR2 1 AND B. BOURDON 1

Institute of Isotope Geochemistry and Mineral Resources, ETH Zurich, Switzerland (*correspondence: [email protected]) 2 Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Switzerland In the past few years a number of catchment-based studies have focused on the role of glaciers and have come to conflicting conclusions regarding the effect of the glacier on chemical weathering rates and resulting CO2 consumption. Gaining a clear picture of weathering processes in glacial regions is difficult due to dilute meltwaters, the truncated field sampling season and the influence of daily melt cycles. This work forms part of the multi-disciplinary BigLink Project which is investigating the 10.7 km2 granitic Damma catchment (Switzerland). The glacier has retreated rapidly, exposing fresh mineral surfaces, allowing the initial stages of granite weathering to be studied. Stream waters were sampled for six months in five different locations, in conjunction with high-resolution hydrological and meteorological measurements. Selected isotope ratios were analysed in addition to the overall chemical composition to characterise spatial and temporal variations in stream water chemistry. After correction for atmospheric inputs, daily and seasonal cycles were clearly observed in the cation concentrations. These trends were independent of dilution and indicated the mixing of at least two distinct water sources whose relative proportions changed over seasonal and daily timescales. These sources reflected differing water-rock interaction times as evinced by variable elemental ratios (e.g. Na/Ca) which were offset from bulk rock ratios. The δ44/42Ca isotope ratios (measured by TIMS using a 43 Ca-46Ca double spike) were uniform and indistinguishable from bedrock samples. Thus, the dissolved Ca isotopic signature of the catchment output is that of the granitic bedrock and this indicates that Ca isotopes are not fractionated during the initial stages of granite weathering. The calculated cationic and silica fluxes are among the lowest reported from alpine glaciers and are at the low end of the range reported for non-glaciated granitic catchments. Further analyses will help to provide better constraints and improve our understanding of the chemical weathering and mixing processes that occur in glacial, granitic catchments.

A533

K. HIPPE1*, F. KOBER2, G. ZEILINGER3, S. IVY-OCHS4, P.W. KUBIK4, R. WIELER1 1

Isotope Geology and Mineral Resources, ETH Zürich, 8092 Zürich, Switzerland (*correspondence: [email protected]) 2 Institute of Geology, ETH Zürich, 8092 Zürich, Switzerland 3 Institute of Geology, Univ. Potsdam, D-14476 Golm, Germany 4 Laboratory of Ion Beam Physics, ETH Zürich, 8093 Zürich, Switzerland Erosional unloading by focused incision causing flexural rebound has been proposed for the Rio La Paz drainage system, Bolivia [1]. However, relief, landscape morphologies and processes, as well as tectonics and precipitation rates contrast sharply across the drainage divide. This results in high denudation rates towards the east where precipitation rates are highest, landsliding processes dominate [2,3] and flexural rebound is focused down-valley [1]. Denudation rates in the Rio La Paz drainage realm are temporally variable with present day rates of 0.6-6 mm/yr (sediment yield data [4]), millennial rates of 0.1-0.6 mm/yr (cosmogenic nuclides [2]) and long-term (my) sediment budget rates of ~ 0.23 mm/yr [2]. Assuming rebound to be constant since the initiation of the Rio La Paz system (~ 2.8 My [1]), the denudation rates would be several times higher than the modelled rebound, but could also point towards rebound rates increasing with time. Here we quantify denudation rates and the effects of a suggested flexural rebound due to erosional unloading by the Rio La Paz drainage system on the Altiplano side. Precipitation rates are relatively low and the landscape exhibits smooth hillslopes and diffusive hillslope processes. For catchments bordering the Rio La Paz drainage divide but draining towards the Altiplano we have determined catchment wide denudation rates based on cosmogenic 10Be in river sediments. Preliminary denudation rates vary between 0.005 to 0.025 mm/yr, with higher rates in catchments affected by partial glacial modifications. Modern sediment yield rates [5] are similar to the cosmogenic nuclide-derived values, although the latter integrate over >30-200 ky. Therefore, on the Altiplano side, the proposed rebound appears to be in steady state with denudation. Nevertheless, ongoing headward capture of the Rio La Paz into the Altiplano seems yet to be the dominant process at the eastern margin of the Altiplano. [1] Zeilinger & Schlunegger (2007), Terra Nova 19, 373-380. [2] Zeilinger et al. (2009), EGU. [3] Safran et al. (2005), ESPL 30, 1007-1024. [4] Bourges et al. (1990), IHAS 193, 351-356. [5] Guyot et al. (1992), Lake Titicaca 113-119.

A534

Goldschmidt Conference Abstracts 2009

Variation of salinity and gas composition of fluid inclusions in the Culebra granitic rocks of the Pallca mining area in Peru T. HIROTAKA* AND K.HOSHINO Hiroshima University, Higashi-Hiroshima, 739-8526, Japan (*correspondence: [email protected]) The Raman microprobe can analyze vapor-rich and other inclusions of low liquid water content which are difficult to analyze by microthermometry [1]. In order to apply Raman spectroscopic analysis to salinity measurements of natural fluid inclusions, synthetic brines were analyzed to obtain calibration curves by the reflex Raman microscope (Renishaw) with a LD laser as the source of 532 nm radiation. Dubessy et al. [2] mentioned the dependency of the crystal orientation of host quartz on the Raman spectra of water inclusions. Therefore, the dependency was also investigated by analyzing the synthetic brines covered with doubly polished thin sections of natural quartz cutting in parallel to and perpendicular to its C axis. The results show systematic variations in the spectra due to the orientation of the covered thin sections. A number of fluid inclusions were observed in quartz phenocryst of the Culebra granodiorite and quartz porphyry of the Pallca mining area in Peru. Most fluid inclusions distribute within several trails probably formed by microfracturing and healing. Raman spectroscopic analyses of the trailed inclusions revealed four types of trails with different salinities and gas compositions of the CO2-CH4-N2 (-H2O-salt) systems. It is also worth to note that CH4 is a major gas component in fluid inclusions of the trail in which sphalerite was observed, implying CH4 dominant fluids as a source of ore dissemination in the rocks. [1] Mernagh and Wilde (1989) GCA 53, 765-771. [2] Dubbesy (2002) Appl spectrosc 56, 99-106.

Partial melts in the seismic low velocity zone MARC M. HIRSCHMANN Dept. Geology and Geophysics University of Minnesota, Minneapolis, MN 55455 USA ([email protected]) More than 30 years ago, Peter Wyllie and the other pioneers of high pressure experimental petrology explored the possibility that small amounts of CO2±H2O rich magma could plausibly be stable in the seismic low veloxity zone (LVZ). Today, the hypothesis is still debated, with some arguing that the LVZ arises from the properties of solid peridotite close to its solidus and others advocating hydrous silicate or carbonatitic partial melts as the responsible agents . Experiments defining the partitioning of H2O between peridotitic minerals and silicate melts demonstrate that H2O is modestly incompatible during partial melting of the mantle. Consequently, near-solidus partial melts of mantle with normal sub-oceanic H2O concentrations (100 ppm) are not particularly H2O-rich, ranging from ~1.25 wt.% at 100 km to ~2.5 wt% at 200 km. These small concentrations are insufficient to incite partial melting in the LVZ beneath mature oceanic lithosphere without a significant influence of CO2. On the other hand, carbonate is effectively incompatible in peridotite once the stability of magnesite is exceeded at ~300 km, and therefore carbon-rich melts may be stable throughout the LVZ. However, these melts may be carbonatitic only in the deepest (>150 km) and oldest (>60 Ma for a cooling half-space model, older for a plate model) portions of the LVZ. In the younger shallower portions of the LVZ, carbonatite will react with peridotite to form hydrous carbonated silicate melts with compositions ranging from melilitite to alkali basalt as the volatiles become diluted in the shallowest and youngest parts of the LVZ. Thus, partial melts are thermodynamically stable throughout the LVZ and their composition varies spatially. However, this does not resolve the debate as to whether the LVZ is caused by small amounts of retained partial melt. First, the fractions of partial melt generated from normal suboceanic mantle are very small (<0.02% carbonatite and <0.1% carbonated silicate, except at depths >80 km and lithospheric ages <20 Ma) and may not be sufficient to account for the seismic properties of the LVZ. Second, thermodynamic stability is not the same as dynamic stability, as the buoyant melts may be extracted rapidly from the LVZ by compaction.

Goldschmidt Conference Abstracts 2009

The trace metal cycling in the water column of the South China Sea T.-Y. HO1*, B.-N. WANG1 AND W.-C. CHOU2 1

Research Center for Environmental Changes, Academia Sinica, Taipei, Taiwan (*correspondence: [email protected], [email protected]) 2 Institute of Marine Environmental Chemistry and Ecology, National Taiwan Ocean University, Keelung, Taiwan ([email protected])

Introduction Our previous study found that the trace metal composition in the phytoplankton collected in an offshore time series station of the South China Sea (SEATS) was mainly dominated by extracellular portion [1]. The trace metals were mostly anthropogenic, most likely originally derived from the aerosols emitted from fossil fuel burning which contained highly soluble trace metals [1]. Here, we studied the elemental composition and fluxes of the elements in the water column of the South China Sea, including Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, and Cd) through the sinking particles collected at the SEATS site. The sinking particles were collected by floating traps at 30, 100, and 160 m at four occasions in 2007, and were also collected by moored sediment traps deployed at the depths of 200, 600, and 3500 m for one year to examine their composition features and to study the roles of the biotic and abiotic particles on their vertical cycling processes.

Results and Discussions Overallall, strong vertical and seasonal elemental fluxes were observed. Most of the metal fluxes increased with increasing depths, indicating that lateral lithogenic particle input was the dominant particulate metal source in the deep water. However, the metal composition in the surface water was consistent with the previous finding on phytoplankton [1], proving that the trace metals were mainly anthropogenic. The East Asia has been the largest consumer of coal in the world. With the sharp increase of coals consumed in the East Asia during the past several decades, it is expected that the metals introduced to the marginal seas and the western Pacific due to fossil fuel burning may leave significant signatures spatially and temporally in the environment, which should be able to be quantitatively traced by their elemental and isotopic composition recorded in environmental recorders such as corals and sediments. [1] Ho et al. (2007) Limnol. Oceanogr. 52, 1776.

A535

A study of sulfate mineral stability in marine sediments using the whole ODP/IODP porewater composition data base G. HOAREAU1,2,3*, C. MONNIN1,2,3 AND F. ODONNE1,2,3 1

Université de Toulouse, UPS (OMP) LMTG, 14, Av. Edouard Belin, F-31400 Toulouse, France (*correspondence: [email protected]) 2 CNRS, LMTG, F-31400 Toulouse, France 3 IRD, LMTG, F-31400 Toulouse, France The whole ODP and IODP porewater data base (14416 samples from 95 Legs) was used to investigate the stability of celestite, barite, and gypsum in marine sediments, through the calculation of the mineral saturation indices at the in situ sediment temperatures and pressures using a model for the NaK-Ca-Mg-Sr-Ba-Cl-SO4-H2O system [1]. The in situ temperatures were calculated from a compilation of the geothermal gradient for all the boreholes while pressure is simply calculated from depth. Molarities have been converted to molalities through the calculation of the porewater densities [2]. We also calculated the calcite and aragonite saturation indices using a seawater model for the carbonate system, in an attempt to provide some insight into the relationship between carbonate and sulfate minerals in marine sediments. Although rarely reported, celestite saturation is reached in 83 boreholes drilled at 60 different sites during 22 ODP/IODP Legs. This is due either to the Sr increase linked to the dissolution of Sr-rich aragonite and precipitation of Sr-poor calcite, or to a salinity increase due to presence of brines that may increase all porewater concentrations, including Sr2+ and SO42-. Porewater at equilibrium with gypsum (22 sites from 12 Legs) have a Ca content at least 5 times higher than the seawater value, in relation with CaCO3 undersaturation. Barium concentration profiles are more erratic and often lead to large barite supersaturation. Our results show that equilibrium with sulfate minerals as celestite or gypsum can be easily reached during early burial diagenesis. We also illustrate cases where precipitation of a mineral destabilizes another one sharing a common ion (e.g. gypsum and celestite, or gypsum and aragonite or calcite). [1] Monnin (1999) Chem. Geol. 153, 187-209. [2] Monnin (1994) Comput. Geosci. 20, 1435-1445.

Goldschmidt Conference Abstracts 2009

A536

Primary hematite formation in an oxygenated deep sea 3.46 billion years ago 1

2

2

M. HOASHI , D.C. BEVACQUA , T. OTAKE , Y. WATANABE2, A.H. HICKMAN3, S. UTSUNOMIYA4 2 AND H. OHMOTO * 1

FSRC, Kagoshima Univ., Kagoshima 890-0065 Japan NASA Astrobiology Inst. & Dept, of Geosciences, Penn State Univ., University Park, PA 16803 USA (*correspondence: [email protected]) 3 GSWA, Perth, WA 6400 Australia 4 Dept. of Chemistry, Kyushu Univ., Fukuoka 810-8560 Japan 2

The 3.46 Ga Marble Bar Chert/Jasper unit (MBC) in the Pilbara Craton, Western Australia is a 50-200 m-thick and ~30 km-long body, precipitated at depths >200m in a submarine caldera. Using a variety of techniques (SEM, TEM, EPMA, XRD, etc), we have investigated the mineralogical characteristics of the principal Fe-bearing minerals in more than 100 jasper samples from a MBC core, which was recovered by the Archean Biosphere Drilling Project. We have found that each hematite particle in the MBC is a nano-sized (100–600 nm), single, clean, euhdedral crystal, whereas both magnetite and siderite crystals are much larger and often contain inclusions of nano-sized hematite crystals. These features indicate the hematite particles are primary. They directly nucleated as single hematite crystals at T >~60°C during rapid mixing of Fe2+-rich (~1 mM) hydrothermal fluids (T = 100-200°C) with O2-rich (>10 µM) local seawater at depths >200 m; the hematite did not form through transformation of ferrihydrite and/or goethite that formed by UV photolysis of Fe2+-rich solution in the photic zone. In contrast, the magnetite and siderite crystals most likely formed during the early diagenesis of the MBC where an anoxic environment was created by the decay of organic matter. Our findings imply that oxygenic photoautotrophs had evolved, resulting in the oxygenation of at least some intermediate and deep ocean regions ~3.46 Ga ago.

Adsorption of HCl onto volcanic ash LAURA HOBBS* AND HANS KEPPLER Bayerisches Geoinstitut, Universität Bayreuth (*correspondence: [email protected]) HCl molecules emitted from volcanoes breakdown to form chlorine free radicals via heterogeneous chemical reactions and photolysis, which act as catalysts to the breakdown of ozone in the stratosphere. Ozone depletion of up to 2-7% was estimated following the Pinatubo 1991 eruption [1]. However, only stratospheric HCl is dangerous to ozone, and the amount of HCl that reaches these levels is often lower than expected [2]. This suggests that HCl is removed from the eruption column at tropospheric levels. Previously suggested mechanisms include inclusion of HCl into supercooled droplets or ice crystals [3]. In order to investigate the removal of HCl from the atmosphere by adsorption onto ash in volcanic plumes, glass with the composition of the Pinatubo 1991 dacite [4] was synthesised and ground to ash-sized particles using a planetary mill. The ash was then placed in a simple volumetric vacuum device, which was purged with HCl gas to a desired pressure. The ash was connected to the system and the adsorption of HCl onto the ash surface recorded by the resulting pressure drop until an equilibrium pressure was reached. Preliminary results from experimental runs beginning with an HCl gas pressure of 31 mbar, 100 mbar, 250 mbar, 504 mbar and 975 mbar indicate that adsorption on the order of 0.5 mgm-2 occurs even at low partial pressures of HCl. [1] Robock (2000) Rev. Geophys. 38, 191-219. [2] Oppenheimer (2003) In Treatise on Geochemistry. [3] Textor et al. (2003) Geol Soc Lon Spec Pub 213, 307-328. [4] Scaillet & Evans (1999) J. Petr. 40, 381-411.

Goldschmidt Conference Abstracts 2009

A537

Microbial life in alkaline environments on Earth and the potential for life on other planets

Modeling organic aerosols during MILAGRO: importance of biogenic secondary organic aerosols

C.E. HOBDAY1*, I.A. CRAWFORD1, A.P. JONES1, G.A. SHIELDS1 AND J.D. WARD2

ALMA HODZIC1, J.L. JIMENEZ2, S. MADRONICH1, A.C. AIKEN2, B. BESSAGNET3, G. CURCI4, J. FAST5, T.B. ONASCH6, G. ROUX1 AND I.M. ULBRICH2

1

UCL/BBK Centre for Planetary Sciences, Department of Earth Sciences, University College London, WC1E 6BT, UK (*correspondence: [email protected]*) 2 UCL Research Department of Strucutral and Molecular Biology, University College London, WC1E6BT, UK The concept of life on the Earth and the potential for life on other planets is an exciting field of research and growing steadily. The conditions on the early Earth are continually debated. Particularly regarding which environments early life thrived in, on this planet, and in addition what potential there is for life on other planets, such as Mars. The model of an alkaline, “Soda Ocean”, containing NaCO3 and a high pH, having been present on the early Earth is one theory for the oceans at this time [1]. With this in mind, modern alkaline lakes and springs can be considered analogues of these past milieu, and therefore excellent places to characterise the microbial biota. In addition the discovery of carbonate deposits and smectite clays on the surface of Mars may indicate that alkaline conditions were present during a period in the planets history [2]. Lakes Natron and Magadi of East Africa are bodies of water with high pH and salinity, fed by warm alkaline springs which vary in their temperature from 32°C to 52°C [3]. Samples from the springs and the lakes themselves will provide information on the biota. Characterisation of the microbes living in these conditions can be done with 16s rDNA analysis and microbial culturing techniques. Sediment cores to ~1m depth will provide samples of organisms that occupy depths in the shore muds. Questions such as how they preserved and what biosignatures they leave behind will be explored. This will assist with identifying organisms which were present in other similar sediments, when living material has decayed. It is also important to ensure that if there are sediments similar to those present on Mars, then rovers looking for evidence of life are capable of identifying deposits from alkaline environments. [1] Kempe and Dagens (1985) Chemical Geology 53 95-108. [2] Bibring et al. (2006) Science 312 400-404. [3] Warren, J. K. (2006) Evaporites sediments, resources and hydrocarbons. Springer.

1

National Center for Atmospheric Research, Boulder, USA University of Colorado, Boulder, USA 3 INERIS, France 4 Universita' degli Studi dell'Aquila, Italy 5 Pacific Northwest National Laboratory, Richland, USA 6 Aerodyne Research, MA, USA 2

The meso-scale chemistry-transport model CHIMERE is used to investigate major sources and formation processes leading to a fairly large amount of organic aerosols (OA, including primary OA (POA) and secondary OA (SOA)) observed in Mexico City during the MILAGRO field project (March 2006). Comparison of near-surface model predictions with aerosol mass spectrometer data shows that predicted OA correlates reasonably well with measurements during the campaign, however it remains a factor of 2 lower than the measured total OA. Very good agreement is found between observed and predicted POA within the city indicating that primary anthropogenic and biomass burning emissions are reasonably captured. Consistent with previous studies in Mexico City, large discrepancies are encountered for SOA species, with a factor of 5-10 model underestimate. When only anthropogenic SOA precursors were considered, the model was able to reproduce within a factor of two the sharp increase in SOA concentrations during the late morning at both urban and near-urban locations. However, predicted SOA concentrations were unrealistically low when photochemistry was not active, especially overnight. These discrepancies were not significantly reduced when greatly enhanced partitioning to the aerosol phase was assumed. Model sensitivity results suggest that observed night-time SOA concentrations are dominated by the regional background (~2µg/m3) from biogenic origin which is transported from the coastal regions into the Mexico City basin. The relative contribution of biogenic SOA to monthly mean SOA levels was estimated to over 20% within the city and up to 65-90% at the regional scale which is consistent with measurements of modern carbon during low biomass burning periods. Our results confirm the large underestimation of the SOA mass by traditional models in polluted regions, and emphasize for the first time the key role of biogenics in this region. Significance of newly proposed SOA formation pathways (i.e. night-time oxidation of isoprene, POA volaitilty) is also investigated in this study.

A538

Goldschmidt Conference Abstracts 2009

Controls on isotope fractionation during sulfate reduction

The origin of EM1 alkaline magmas during Cenozoic reorganization of subduction zone of Kamchatka

J. HOEK AND D.E. CANFIELD University of Southern Denmark, Nordic Center for Earth Evolution (NordCEE) and Dept. of Biology, 5230 Odense M, Denmark (*correspondence: [email protected]) Sulfur isotopes are fractionated during dissimilatory sulfate reduction. The magnitude of fractionation is controlled by the flow of sulfur through the reaction network: SO42-↔ adenosine-5’-phosphosulphate (APS) ↔ SO32- → H2S, where individual enzymes operate at different efficiencies and with distinct fractionation factors. While the influence of this flow on fractionation has been modelled [1-4], the factors controlling the fractionation during the individual enzymatic steps are still poorly understood. Using cell free extracts of Desulfovibrio vulgaris, we measured the fractionation during the reduction of sulfite to sulphide by the dissimilatory sulfite reductase (dsr) under different temperatures and with organic and inorganic substrates. Temperature had a greater influence on the magnitude of fractionation than substrate type. At 37°C, H2 and formate produced fractionations of 18 and 15 ‰ respectively. At 25°C the magnitude of fractionation increased to 25 ‰. This was coupled to a reduction in the rate of sulfite reduction. The fractionation during sulfite reduction by sulphate reducers who produce distinct fractionations and have different types of dsr’s will be evaluated. [1] Brunner & Bernasconi (2005) GCA 69, 4759-4771. [2] Canfield et al. (2006) GCA 70, 548-561. [3] Farquhar et al. (2003) Geobiol 1, 27-36 [4] Hoek et al. (2006) GCA 70, 58315841.

K. HOERNLE1*, M.V. PORTNYAGIN1, F. HAUFF1, P. VAN DEN BOGAARD1 AND G. AVDEIKO2 1

Leibniz Institute of Marine Sciences, IFM-GEOMAR, Wischhofstr.1-3, 24148, Kiel, Germany (*correspondence: [email protected]) 2 Institute of Volcanology and Seismology, Blvd Piip 9, 683006, Petropavlovsk-Kamchatsky, Russia We report new Ar/Ar age and geochemical data on the oldest magmatic rocks from the central segment of the Eastern Volcanic Belt of Kamchatka, a neovolcanic zone formed during the Late Miocene due to migration of frontal arc volcanism in Kamchatka from the Sredinny Range to its present eastern position [1,2]. Volcanic rocks from the upper Left Zhupanova River (N54.1° E158.9°) range from older (7-12 my) LREE- and HFSE-rich alkaline and transitional basalts (La/Yb=7-38, Nb/La=0.8-1.3, Ba/Th=40-140) to younger (3-8 my) strongly calc-alkaline andesites and dacites with adakitic affinity (La/Yb=7-17, Sr/Y=53-68, Nb/La=0.400.65, Ba/Th=300-600). The younger calc-alkaline rocks have isotope compositions similar to the recent island-arc rocks in Kamchatka (87Sr/86Sr = 0.7032 - 0.7034, εNd = +7.0 - +8.8, 206Pb/204Pb = 18.2-18.3, 207Pb/204Pb = 15.45 - 15.46, 208Pb/204Pb =37.7-37.9). These compositions indicate derivation from subduction-modified depleted Pacific mantle and/or through melting of the subducting Pacific oceanic plate. The older alkaline to transitional basalts range from moderately to strongly enriched OIB-like compositions with EM-1 isotope characteristics (87Sr/86Sr = 0.7033 - 0.7044, εNd = +2.1 - +7.3, 206Pb/204Pb = 17.9 - 18.1, 207Pb/204Pb = 15.44 15.53, 208Pb/204Pb = 37.8 - 38.2). The EM-1 alkaline basalts are unique among the Cenozoic rocks of Kamchatka and thus are unlikely to originate from a long-lived anomalous mantle region beneath Kamchatka. The geochemically anomalous mantle region, however, could be correlated to the lowvelocity mantle plume-like anomaly under Meiji Seamount mapped by seismic tomography studies [3]. Therefore, we propose that the enriched mantle flowed westward through a slab window beneath Kamchatka at the initiation of the modern subduction zone. [1] Avdeiko et al. (2002) Geotectonics 4, 64-80. [2] Lander & Shapiro (2007) AGU Monograph 172, 57-64. [3] Gorbatov et al. (2001) Geophys. J. Int. 146, 282-288.

Goldschmidt Conference Abstracts 2009

A539

Guidelines for experiments on CO2 sequestration in peridotites based on a natural example

Temperature-dependent formation of biogenic Cu(0) and metal sulfide colloids in flooded soil

J. HÖVELMANN* AND H. AUSTRHEIM

A.F. HOFACKER1*, F.-A. WEBER1, A. VOEGELIN1, R. KAEGI2 AND R. KRETZSCHMAR1

Physics of Geological Processes (PGP) University of Oslo, 0316 Oslo, Norway (*correspondence: [email protected]) Although natural examples show that olivine rich rocks react extensively with CO2 to form ophicarbonates, it has proven to be difficult to develop practical CO2 sequestration technologies based on olivine. The Solund and Fensfjorden Devonian basins of SW Norway contain numerous peridotite clasts that record natural CO2 sequestration. This situation provides a natural laboratory for studying the storage of CO2 in basins as suggested by the IPCC [1] and determining how CO2 reacts with peridotite in nature. A detailed petrographic and geochemical study [2] reveals that the peridotite clasts were affected by a multi-stage alteration process. During the early stage peridotite was partly serpentinised forming the typical mesh texture with veins of serpentine surrounding compartments of relict olivine (Fo90). The olivine in the compartments is partly or completely replaced by a clay-like alteration product with a composition close to that of sepiolite (Mg4Si6O15(OH)2·6H2O). Chemical analyses and mass balance calculations show that Mg was extensively removed, whereas Si remained virtually immobile. The continuous serpentine framework that persists in this alteration stage suggests that the replacement took place at constant volume. In the most evolved stage the mineralogy is dominated by calcite and silica. Dissolution of calcite after treatment with 0.1 M HCl reveals that the silica builds up a 3-dimensional network suggesting that it was formed from the breakdown of the Mg-phases. The bulk MgO content in the overall process decreased from 40 to 2 wt%, whereas the CaO concentration increased from 1 to 35 wt%. The findings reported here (that a clay-like mineral phase is involved in the reaction, that dominantly calcite rather than magnesite forms and that Mg is almost completely removed from the peridotite) are interpreted to be important for the storage of CO2 in peridotites. We suggest that the most appropriate reactant for successful CO2 sequestration is weathered peridotite (Ca-source) rather than pure olivine. Furthermore, the process must allow the removal of Mg. [1] Metz et al. (2005) Cambridge Univ. Press, 442 pp. [2] Beinlich et al. (2009) GCA, this volume.

1

Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Switzerland (*[email protected]) 2 Particle Laboratory, Eawag, Zurich, Switzerland We recently observed that the formation of biogenic Cu(0) and metal sulfide colloids mobilized Cu, Cd and Pb in a contaminated riparian floodplain soil [1]. At the onset of soil reduction, Cu was mobilized as metallic Cu(0) crystals associated with bacteria. During sulfate reduction, two types of Cu-rich sulfide colloids formed also incorporating Cd and Pb: i) hollow particles of ~100 nm associated with bacteria likely formed by reaction of sulfide with Cu(0) and ii) dispersed nanoparticles of <50 nm likely formed by reaction of sulfide with dissolved metals. Because temperature strongly influences the kinetics of biotic and abiotic processes, we extended our earlier microcosm experiments (done at 23°C) to 14°C and 5°C to study colloid dynamics over temperatures common for the field site (Muldenstein, Germany). Colloids isolated from the soil porewater over periods of up to 5 weeks of flooding were analyzed by transmission electron microscopy (TEM) and X-ray absorption spectroscopy (XAS). Porewater dynamics indicated that lower temperatures increasingly delayed microbial Mn(IV), Fe(III), and especially sulfate reduction. Colloid formation was accordingly delayed, but involved the same colloid types (Cu(0), metal sulfide hollow particles and nanoparticles) as at 23°C. In contrast to 23°C, metallic Cu was not completely transformed into metal sulfide colloids. Furthermore, at 14°C and 5°C, a longer gap between the onset of Mn(IV)/Fe(III)-reduction and sulfatereduction resulted in higher dissolved Cd levels (displaced from sorption sites by Fe2+ and Mn2+) and subsequently larger sulfide nanoparticles with higher Cd contents. Our new results demonstrate that temperature affects metal sulfide colloid generation in a flooded wetland soil mainly via its influence on microbial reduction of terminal electron acceptors. At all studied temperatures, however, sulfate reduction led to the formation of metal sulfide colloids that have the potential to greatly enhance the release of chalcophile metal contaminants from contaminated floodplain soils into ground and surface waters. [1] Weber et al. (2007) GCA 71, A1094.

A540

Goldschmidt Conference Abstracts 2009

The origin of TTGs inferred from high-precision HFSE measurements

Messinian gypsum stromatolites – A molecular approach

J.E. HOFFMANN1*, C. MÜNKER1,2, M.T. ROSING3, T. NÆRAA4, A.A. GARDE4 AND D. GARBE-SCHÖNBERG5

L. HOFFMANN1*, D. BIRGEL1, J.-M. ROUCHY2, S. ZIEGENBALG1 AND J. PECKMANN1

1

Universität Bonn, Steinmann Institut, Poppelsdorfer Schloss, 53115 Bonn, Germany (*[email protected]) 2 Universität zu Köln, Institut für Geologie und Mineralogie, Germany 3 Nordic Center of Earth Evolution, Natural History Museum of Denmark, Copenhagen, Denmark 4 Geological Survey of Denmark and Greenland, Copenhagen, Denmark 5 Universität Kiel, Institut für Mineralogie, Germany There is an ongoing debate as to whether Archean TTGs have formed by melting of mafic subducted crust in the garnet-amphibolite or in the (rutile-bearing) eclogite stability field (e.g. [1],[2]). High-field-strength element ratios of TTGs can potentially help to settle this debate, as they mirror the residual mineralogy of these TTG sources. We have carried out high-precision Nb/Ta, Zr/Hf, and Lu/Hf measurements by isotope dilution on 3.85 to 2.8 Ga TTGs from SW-Greenland and India using the Neptune MC-ICP-MS at Bonn. In combination, major and trace element data have been obtained by XRF and quadrupole ICP-MS. Migmatitic gneisses display exceptionally high Nb/Ta (23-42), reflecting secondary intracrustal melting processes. Excluding these samples, pristine early Archean (3.85-3.6 Ga) TTGs exhibit Nb/Ta from 10 to 24, meso- to late Archean (3.3-2.8 Ga) TTGs from 11 to 32. Ratios of Zr/Hf and Lu/Hf overlap between the two groups, ranging from 31 to 46 and 0.006 to 0.051, respectively. In both groups, Nb/Ta increases with Gd/Yb, La/Yb, Zr/Sm, and decreases with Lu/Hf. There is no correlation of Nb/Ta with Zr/Hf or Zr/Sm (31–151). These compositional systematics are best explained by melting of typical Archean tholeiites in both the garnet-amphibolite (10-15 kbar) and rutile-bearing eclogite stability field (>15 kbar), with subsequent mixing of melts generated from both sources. Notably, the early Archean and meso- to late Archean TTGs all display both low Ni (<20 ppm) and Cr contents (<14 ppm), indicating no significant interaction with mantle wedge peridotite. Hence, these systematics would be consistent with alternative models for TTG generation arguing for thickened mafic crust as being a likely source for the TTGs. However, as one mixing end-member originates from the eclogite stability field, the minimum thickness of such mafic crust would need to be at least ca. 30 km. [1] Foley et al. (2002) Nature 417, 837-840. [2] Rapp et al. (2003) Nature 425, 605-609.

1

MARUM – Center for Marine Environmental Sciences, University of Bremen, 28334 Bremen, Germany (*correspondence: [email protected]) 2 CNRS UMR 5143, Dept. Earth History, Muséum National d'Histoire Naturelle, CP48, 75005 Paris, France ([email protected]) The Messinian Salinity Crisis (5.96 – 5.33 Ma) resulted in deposition of massive evaporitic sequences throughout the Mediterranean area. Stromatolitic fabrics in Messinian gypsum deposits have been reported from different locations including Crete, Cyprus, and the Northern Appenines (Italy) [1, 2]. These stromatolites are characterized by abundant filamentous textures, which have been interpreted either as remains of cyanobacteria [1] or algal mats [2]. Similar textures were identified in Messinian limestones and were interpreted as faecal pellets of brine shrimps [3, 4]. In this study we apply lipid biomarker analyses and compound-specific stable carbon isotope ratio measurements to elucidate the origin of these filamentous textures. We extracted Messinian gypsum samples from different locations containing filaments. The extracted gypsum samples were subsequently dissolved and extracted once more to recover lipids preserved in the crystalline lattices. Comparison of extracts prior and subsequent to gypsum dissolution enabels us to determine whether the lipid biomarker patterns reflect the conditions during gypsum formation, comprising molecular fossils derived from organisms that represent or produced the filaments. [1] Rouchy & Monty (2000) in Riding & Awramik (Eds.) Microbial Sediments, Berlin, Springer, pp. 209-216. [2] Vai & Ricci-Lucchi (1977) Sedimentology 24, 211-244. [3] Decima et al. (1988) J. Sed. Petrol. 58, 256-272. [4] Guido et al. (2007) Palaeogeogr. Palaeoclimatol. Palaeoecol. 255, 265283.

Goldschmidt Conference Abstracts 2009

Photochemical formation of large molecular weight oligomers from low-molecular weight keto-carbonyls in haze aerosol MICHAEL R. HOFFMANN*, ANGELA RINCON AND A.J. COLUSSI W. M. Keck Laboratories, California Institute of Technology, Pasadena, California 91125 USA, (*correspondence: [email protected], [email protected], [email protected]) The optical properties of the atmospheric aerosol play a fundamental role in the Earth’s radiative balance. Since ~60% of the aerosol mass consists of complex natural and anthropogenic organic matter that absorbs in the ultraviolet and, particularly, in the visible regions of the solar spectrum, it is important to establish the chemical identity of the organic chromophores and the mechanism by which they contribute to aerosol color. Here we report studies on the chemical composition versus chromism of photolyzed (λ > 305 nm) solutions of PA, under a variety of experimental conditions that include substrate concentration, temperature and the presence of relevant spectator solutes, such ammonium sulfate. We use high resolution mass and 1H, 13C NMR spectrometries to track chemical speciation in photolyzed solutions as they go through thermochromic and photobleaching cycles. The chemical identity of the components of these mixtures does not change in these cycles, in which photobleached solutions gradually recover their yellow color in the dark with non-conventional kinetics typical of aggregation processes, we infer that visible absorptions involve the intermolecular coupling of carbonyl chromophores in supramolecular assemblies.

A541

Advanced analytical methods for understanding the chemistry of iodine in the marine boundary layer T. HOFFMANN Institute of Inorganic and Analytical Chemistry, Johannes Gutenberg-University, 55128 Mainz, Germany ([email protected]) Measurements of trace compounds in the gas and particle phase are essential for understanding the chemistry of the troposphere. Within the last few years the impact of iodine on the chemistry of the marine boundary layer (MBL) received increasing attention. One reason is that gaseous iodine precursors have been proposed to be involved in the enrichment of iodine in marine aerosols, the formation of new particles in the MBL and their evolution to form cloud condensation nuclei [1,2]. Although progress has been made, a number of uncertainties about the sources, sinks, kinetic parameters and the recycling of iodine remain and the identification and quantification of reactive key species are still challenging analytical problems [3]. Interest in iodine atmospheric chemistry has been greatly stimulated in the last few years by the suggestion that molecular iodine (I2) rather than biogenic iodocarbons (e.g., CH3I, CH2I2) is the most important precursor for new particle formation and also the dominant source of coastal reactive iodine in the MBL. Other key iodine compounds can also be formed within tropospheric reaction cycles, such as hypoiodous acid (HOI). Uptake of HOI on sea-salt aerosol has been proposed to enhance chlorine and bromine activation by the reaction of HOI with Cl- and Br-. The subsequent products, ICl and IBr, can again be released from the sea salt particles. However, the exact underlying chemical mechanisms leading to the different iodine species are still not understood, mostly due to the lack of analytical techniques to accurately measure certain key species, such as I2, HOI or ICl [4]. This contribution focusses on advanced analytical methods used for iodine speciation in the gas and particle phase, including some recent developments using an Aerodyne TOF aerosol mass spectrometer. [1] O’Dowd et al. (2002) Nature 417, 632–636. [2] O’Dowd & Hoffmann (2005) Environ. Chem. 2, 245–255. [3] von Glasow & Crutzen (2007) Treatise on Geochemistry Update 1, 1 – 67. [4] Huang & Hoffmann (2009) Anal. Chem., in press.

Goldschmidt Conference Abstracts 2009

A542

Displaced helium in mantle plumes 1,2

3

A.W. HOFMANN * AND C.G. FARNETANI 1

Max-Planck-Institut für Chemie, 55020 Mainz, Germany (*correspondence: [email protected]) 2 Lamont-Doherty Earth Observatory, Palisades NY 10964, USA ([email protected]) 3 Institut de Physique du Globe de Paris, 4 Place Jussieu, 75252 Paris, France ([email protected]) The distribution of primordial He and Ne in the mantle is the subject of lively debate. Here we assume that these primordial gases enter the source regions of some mantle plumes from an external reservoir such as the D’’ layer at the base of the mantle [1]. Support for (though not proof of) this is derived from geochemical mapping of He and Ne at hotspot locations ascribed to plumes. On Iceland and the adjacent MAR, high 3He/4He is centered on the hotspot. At Amsterdam-St. Paul on the SEIR, high 3He/4He is also centered on the hotspot, but also appears on the normal ridge segment N of the Amsterdam fracture zone. On the Hawaiian and the Galapagos hotspots, the high-3He/4He signal is asymmetrically distributed toward the “edge” of the plume on Loihi and Fernandina, respectively. In all three cases, the He signal is offset from the plume center in the “upstream” direction of asthenospheric flow driven by local plate motions. We propose that this asthenospheric flow tilts the plume. Primordial He, initially located in the plume center, is strongly partitioned into a small amount of carbonatite liquid [2], which forms in the plume at depths of 400 km or more, migrates vertically through the tilted plume, and displaces the helium maximum from the plume core toward its margin. We model this process for the Hawaiian plume to explain the 3He/4He maximum located in Loihi melts, which sample the front edge of this plume rather than its center. Relative ascent velocities of this (low-ρ, low-µ) carbonatite liquid are on the order of tens of centimeters/year. The model predicts significant displacements of the He signal derived from plume cores and decoupling of He from Sr, Nd, Pb isotope signatures in tilted plumes, if helium is similarly incompatible in the mantle as carbon. This is consistent with the similar 3He/C ratios found in OIB as in MORB and experimental data [3]. The high rates of migration are consistent with permeabilities inferred from [4, 5]. [1] Tolstikhin & Hofmann (2005) Phys. Earth Planet. Int. 148, 109-130. [2] Dasgupta & Hirschmann (2006) Nature 440, 659-662. [3] Heber et al. (2007) GCA 71, 1041-1061. [4] Minarik & Watson (1995) Earth Planet. Sci. Lett. 143, 423-437. [5] Wark et al. (2003) J. Geophys. Res. 108, 10.1029/ 2001JB001575.

Sub-micron scale Ti variations in zircons of known provenance AMY E. HOFMANN, MICHAEL B. BAKER, AND JOHN M. EILER California Institute of Technology, Pasadena, CA 91125, USA ([email protected]) The Ti-in-zircon geothermometer has been applied to zircons from rocks of both known (e.g., [1]) and unknown (e.g., [2]) provenance. Hofmann et al. [3] have recently shown that Ti concentrations ([Ti]) in Hadean zircons from the Jack Hills, Australia, are positively correlated with other trace elements and cathodoluminescent (CL) banding at the submicron scale; these correlations suggest that Ti partitioning in zircon is dependent upon non-equilibrium effects in addition to temperature and/or that the incorporation of co-varying trace elements (e.g., Y, P, Ce) affects Ti partitioning. Here we consider whether younger zircons of known provenance show similarly correlated trace-element distributions. Zircons from volcanic and plutonic rocks (i.e., Toba and Bishop Tuffs, Quottoon quartz diorite and Sierra Nevada batholith) and metamorphic zircons from an Adirondack migmatite were analyzed down to length scales of ca. 300 nm using a CAMECA NanoSIMS 50L ion microprobe with an Oprimary beam. All data were calibrated by comparison to primary and secondary standards previously characterized by other laboratories. The external precision of our measurements on 2-µm raster images is typically < 10%. Most volcanic and plutonic zircons we analyzed display positively correlated [Ti], [P], [Ce], and [Y] conformable to oscillatory µm- to sub-µm CL zonations. In these cases, high trace-element concentrations correspond to CL-dark regions, and [Ti] varies by a factor of ~2-3 between adjacent oscillatory CL bands. These variations resemble those observed in Jack Hills zircons [3]. One Toba zircon exhibits a different zoning pattern in which [Y], [P], and [Ce] are positively correlated with one another and negatively correlated with [Ti] (all concordant with CL bands); average trace-element concentrations in this zircon are a factor of 3-5 times higher than those we have observed in other samples. We are synthesizing zircons from granitic melt compositions in order to deconvolve Ti temperature-dependent equilibrium partitioning from potential kinetic effects and/or Ti partitioning as a function of [Y], [P], or [Ce]. [1] Lowery Claiborne, L. et al. (2006) Mineral Mag 70, 517543. [2] Watson, E.B. & Harrison, T.M. (2005) Science 308, 841-844. [3] Hofmann, A.E. et al. (2009) Contrib Mineral Petrol in press, doi: 10.1007/s00410-009-0385-6.

Goldschmidt Conference Abstracts 2009

Hydrous ferric oxide nanoparticles – Structural reordering in response to surface sorption of Al-hydroxy species 1

2

A. HOFMANN , D. VANTELON , F. VILLAIN 3 AND E. MONTARGES-PELLETIER

2

1

Géosystèmes, Univ. Lille, 59655 Villeneuve d’Ascq, France 2 Synchrotron Soleil, 91192 Gif sur Yvette, France 3 LEM/CNRS 54500 Vandoeuvre les Nancy, France To explore the influence of a sorbate on the structural evolution of freshly precipitated ferrihydrite in the aqueous environment, experiments were conducted in a Fe/Al oxyhydroxy system. Al-hydroxyde coated ferrihydrite nuclei were prepared by forced hydrolysis of acid solutions containing varying ratios of Fe- and Al- nitrates. Equivalence points of the titration curves showed that pure Fe- respectively Al-(oxy)hydroxides formed, indicating that no significant Fe by Al substitution had taken place initially. The dried products, analysed by Raman spectroscopy showed indeed the presence of Fe- and Al-oxyhydroxides in all samples, but they also showed that the Fe phase evolves from a 2-line ferrihydrite in the absence of Al to a disordered akaganetite when Al increases in the synthesis system. These observations were confirmed by EXAFS spectra at the Fe K-edge. The change in structure seems to be caused by increasing amounts of Al substituting for Fe, as is suggested by a concomittant decrease of Fe atoms in the local environment around Fe. The XANES spectra at the Al K-edge also varied with Al concentrations, and supported the substitution hypothesis. To reconcile the results from titration experiments with those of the spectroscopic analyses, it must be concluded that Al substitution occured after precipitation of ferrihydrite, most probably during a 15 hours period of equilibration at neutral pH allowed after hydrolysis. The results high light the dynamic interactions that may occur between sorbates and weakly ordered nano-size particles.

A543

Nanoparticle facilitated transport of organic contaminants THILO HOFMANN AND FRANK V.D. KAMMER University of Vienna, Althanstrasse 14, 1090 Vienna, Austria ([email protected], [email protected]) Naturally occurring nanoparticles (NP) are capable to enhance the transport of hydrophobic organic contaminants (HOCs) in porous media. Since HOC bind strongly to carbonaceous ENP the recent debate on the environmental impact of engineered nanoparticles (ENP) has become increasingly important. Carbonaceous ENP may act as carriers for contaminant transport and might be important when compared to existing transport processes. ENP bound transport is strongly linked to the sorption behavior, and other carbonaceous ENP-specific properties. In our analysis the HOC-ENP sorption mechanism, as well as ENP size and ENP residence time, were of major importance. Our results show that depending on ENP size, sorption kinetics and residence time in the system, the ENP bound transport can be estimated either as (1) negligible, (2) enhancing contaminant transport, or (3) should be assessed by reactive transport modeling. The obtained results allow us to conclude that the importance of ENP mobility for contaminant transport in soils and aquifers is scaled according to two parameters, the affinity of the HOC to the ENP and the desorption kinetics of the HOC from the ENP. These parameters can be determined by standardized laboratory experiments and should be included in risk assessment frameworks. To obtain a realistic estimate of ENP carrier properties for HOC it is important to know if the system reacts under equilibrium conditions or if the desorption is extremely slow due to high affinity sites or trapping into aggregates. The model results show that under equilibrium conditions the contribution of ENP to the transport process is negligible. It is also shown that in instances where desorption is very slow or inexistent the ENP mobility and apparent concentration becomes increasingly important. A worst-case scenario, using an unrestricted ENP mobility and high ENP concentrations, may produce too high estimates for the ENP contribution to the HOC transport. In these cases, ENP mobility in the porous media should be investigated under the local hydrochemical conditions on a case-by-case basis.

A544

Goldschmidt Conference Abstracts 2009

Fractionation of stable isotopes in organic contaminants by volatilization and sorption PATRICK HÖHENER1, DANIEL BOUCHARD2 2 AND DANIEL HUNKELER 1

Université de Provence-CNRS UMR 6264: Laboratoire Chimie Provence, Marseille, F. ([email protected]) 2 Centre for Hydrogeology, University of Neuchâtel, CH The assessment of degradation of organic contaminants in groundwater plumes by measuring compound-specific ratios of stable carbon and hydrogen isotopes is increasingly used in practice, but relies on the assumption that phase transfer processes do not create any significant isotope fractionation. The aims of our studies were to find quantitative arguments for or against the validity of this assumption. Volatilization experiments with artificial kerosene were performed at a field site and in a laboratory column and yielded both significant enrichment of 13C in hydrocarbon vapors [1]. A quantitative explanation was given based on the faster diffusion of isotopic light contaminants through soil to the atmosphere. The isotopic evolution of a volatilizing source can be modelled analytically or numerically. Previous studies on the fractionation of stable isotopes by equilibrium sorption by other authors have shown that the effects are very close to detection limits by actual mass spectrometers, but may nevertheless be significant at the field scale. We propose thus an indirect method to quantify fractionation by sorption. Linear free energy relationships (LFERs) were established which relate stable carbon and hydrogen isotope enrichment factors for equilibrium sorption to equilibrium vapor-liquid enrichment factors for alkanes, monoaromatic hydrocarbons, and chloroethenes. These LFERs predict that isotopic light compounds sorb more strongly than their heavy counterparts. The effect is very small for 13C, and larger for 2H. Some values predicted by LFER agree well to values measured experimentally in sorption experiments with perdeuterated compounds on soils. It is concluded that 1) volatilization creates isotopic enrichment in remaining contaminant pools, and 2) sorption can create isotopic enrichment at plume fronts, but only for hydrogen isotopes and for compounds that sorb strongly. [1] Höhener, P.. Bouchard, D.. Hunkeler, D. In Advances in Subsurface Pollution of Porous Media. Indicators, Processes and Modelling. Candela, L.. Vadillo, I.. Elorza, F. J., eds.. CRC Press, Taylor and Francis Group: Boca Raton, 2008, pp 123-135.

Primordial krypton in the terrestrial mantle is not solar GREG HOLLAND1*, CHRIS J. BALLENTINE1 2 AND MARTIN CASSIDY 1

SEAES, University of Manchester, Manchester M13 9PL, U.K (*correspondence: [email protected]) 2 Department of Geosciences, University of Houston, Houston, TX 77204-5503, U.S ([email protected]) Noble gases are key tracers for the origin of volatiles in the terrestrial planets and of interaction between mantle reservoirs and the atmosphere. The general consensus is that material accreting in the solar nebula and nebula gases from the Sun itself were incorporated into the Earth, providing a starting point for models of planetary evolution. Recent noble gas data from magmatic CO2 natural gases have proved to be an additional and invaluable resource when investigating noble gases from the mantle. Of particular note is the Bravo Dome natural CO2 gas field which shows clear Xe isotopic anomalies over air and very similar values to those observed in MORB [1,2], although the specific source of this primitive component was not resolvable due to the limited precision of the single collector instrument employed. We have returned to the Bravo Dome suite to measure Kr and Xe isotopes with a multicollector instrument which permits much improved precision. Kr isotope data show a clear non-air signature which trends towards average carbonaceous chondrite (AVCC) Kr, compatible with Xe isotope data. These results require that there is no solar heavy noble gases in the mantle and the most likely source of Earth’s primitive Kr and Xe is the same as that which contributed noble gases to the primitive meteorites. Further implications of an AVCC rather than solar mantle include the need for a hidden Xe reservoir and the prohibition of mantle outgassing of Kr to form the atmosphere. [1] Caffee et al. (1999) Science 285, 2115-2118. [2] Holland and Ballentine (2006) Nature, 441, 186-191.

Goldschmidt Conference Abstracts 2009

A545

Nitrogen dynamics in oceanic basement and its implications for HCN and abiotic organic synthesis

A new trend for the Cape Verde hotspot magmas: Isotopic evidence from Boa Vista

NILS G. HOLM1* AND ANNA NEUBECK2

P.M. HOLM1, D.W. PEATE2, C.T. DYHR1 1 AND SCHMITH

1

Dep. of Geology and Geochemistry, Stockholm Univ., Stockholm, Sweden (*correspondence: [email protected]) 2 Dep. of Geology and Geochemistry, Stockholm Univ., Stockholm, Sweden ([email protected])

Seawater is constantly circulating through oceanic basement as a low-temperature fluid (<150°C). Passive offaxis hydrothermal convection of seawater in older crust is in general a Rayleigh-Benard type circulation driven by the heat flow from the underlying, cooling crust. Convection even in quite old crust is, however, in most cases still related to the original convection at the spreading ridge axis, although offaxis hydrothermal systems driven by exothermic hydration processes do exist in ultramafic rocks. One example is the Lost City hydrothermal system near the Mid-Atlantic Ridge. Results from the ODP Leg 201 reveal that fresh seawater is channeled upwards into deep-sea sediments from the rocks underneath. This happens still 40 Ma or more after formation of the basement and can be seen in concentration profiles of dissolved nitrate in sediment porewater from ODP Sites 1225 and 1231. This means that nitrogen that has been oxidized at the Earth’s surface may be continuously transported by ocean water down into reducing environments of mafic or ultramafic rocks in oceanic basement. On the early Earth, oxidized nitrogen compounds (NO2- and NO3-) may have been formed from N2 in a redox neutral atmosphere by lightning, corona discharge and impacts and subsequently transported by fluid circulation into reducing environments of the lithosphere. Among aqueous environments, hydrothermal systems represent regions of the highest NH3 conversion rates and stability on the Earth. Layer silicates, like smectites, and zeolites have high cation exchange capacity (CEC). The CEC of minerals is generally determined in the laboratory by the uptake and release of ammonium ions (NH4+) of a 1 M ammonium acetate solution. The adsorption properties of zeolites are very powerful, and particularly molecules with dipolar moments such as H2O, NH3, CO and HCN are strongly adsorbed. In experiments at temperatures of about 250-325°C, CO+ NH3 adsorbed on zeolites react to give HCN. In the same experiments, several amino acids and the puric substance adenine have been found [1]. [1] Fripiat et al. (1972) Clays Clay Min. 20, 331-339.

1

Department of Geography and Geology, University of Copenhagen. Øster Voldgade 10, 1350, Copenhagen, Denmark ([email protected]) 2 Department of Geoscience, University of Iowa, Iowa City, IA 52242, USA Cape Verde hotspot volcanism has lasted for >20 Ma, shows great isotopic diversity (EM1, HIMU) and is therefore well suited for studies of mantle plume dynamics. Third largest in the archipelago, the eastern island Boa Vista was formed relatively early, mainly 16-5 Ma, from nepheliniticbasanitic-basaltic magmas and derivatitve phonolites and trachytes. We present isotopic data showing that the early hotspot magmas of Boa Vista are distinct from both the HIMU-trend of the northern islands and the EM1-trend of the southern, constituting a third trend for Cape Verde hotspot. With time the Boa Vista compositions evolved away from the other Cape Verde compositions. The oldest Boa Vista rocks have radiogenic Pb comparable to early Santo Antão (206Pb/204Pb = 19.7) but with lower 143Nd/144Nd. Pb trends towards less radiogenic compositions with 208Pb/204Pb intermediate between the northern and southern islands. A new end member for Cape Verde is defined with Sr and Nd isotope compositions intermediate between northern and southern islands and 208Pb/204Pb lower than in southern islands (i.e. ∆8/4 ≈ 0) at 206Pb/204Pb = 19.0. Most of the melts defining this end member suffered little modification prior to eruption (10-15 wt% MgO). The Boa Vista data demonstrate that Cape Verde magmas had contributions from at least three distinct mantle compounds. Boa Vista magmas with relatively unradiogenic Pb tend to have melted at shallower level by less degree of melting of a more depleted source (lower L/HREE, SiO2 and Zr) but with relatively lower 143Nd/144Nd, and the source is likely part of plume mantle. The possible mantle setup under Cape Verde to explain the lateral and temporal distribution of components for the magmas of the archipelago will be discussed.

A546

Goldschmidt Conference Abstracts 2009

Contribution of ectomycorrhizal fungi to biogeochemical processes during iron and calcium limitation S.J.M. HOLMSTRÖM1,2*, A. ROSLING3, R.D. FINLAY3, P.A.W. VAN HEES4 AND U.S. LUNDSTRÖM1 1

Department of Natural Sciences, Engineering and Mathematics , Mid Sweden University, S-851 70, Sundsvall, Sweden 2 Current Address: Department of Geology and Geochemistry, Stockholm University, S-106 91, Stockholm, Sweden (*[email protected]) 3 Department of Forest Mycology and Pathology , Swedish University of Agricultural Sciences, S-750 07, Uppsala, Sweden 4 Man-Technology-Environment Research Centre, Department of Natural Sciences, Örebro University, S-701 82 Örebro, Sweden The symbiotic ectomycorrhizal fungi mediate nutrient uptake to boreal forest trees. Fungi are known to produce low molecular mass organic acids (LMMOAs), which are important weathering agents. Through weathering Al, Si and Fe, as well as nutrients important for plant growth i.e. P, Ca, K, Mg, and Na are released from solid minerals. The impacts of biogeochemical weathering caused by microbial exudates have been discussed but there is still a lack of knowledge regarding the production of important ligands from boreal forest tree-ectomycorrhiza interactions, as well as the effect of this symbiosis on mineral dissolution and nutrient cycling in forest soils. Here we examine how mineral nutrient mobilization was affected by fungal exudates in a closed mineral column experiment with pine seedlings with and without symbiotic ectomycorrhizal fungi (Hebeloma crustuliniforme or Suillus variegatus) with biotite and oligoclase as the only source for iron and calcium, respectively. The experiment was conducted for 20 months. We monitored the solution chemistry continually through out the experiment. At harvest the mineral chemistry and morphology, as well as size and element composition of the plant tissue was determined. We conclude that both the investigated ectomycorrhiza species, especially H. crustuliniforme, had a significant impact on the production of LMMOAs, mobilization of important mineral nutrients for plant growth, accumulation of elements in the plant shoot and root tissue, the exchangeble pool of elements, and plant growth during nutrient deficiency.

Cosmogenic neon exposure dating of young basalt lavas in Australia M. HONDA1*, A.R. CHIVAS2 AND D. PHILLIPS3 1

Research School of Earth Sciences, The Australian National University, Canberra, ACT 0200, Australia (*correspondence: [email protected]) 2 GeoQuEST Research Centre, School of Earth and Environmental Sciences, University of Wollongong, NSW 2522, Australia ([email protected]) 3 School of Earth Sciences, The University of Melbourne, Melbourne, VIC 3010, Australia ([email protected]) Cosmogenic 21Ne was utilised to determine exposure ages of young subaerial basaltic lava flows from the Newer Volcanic Province, western Victoria, Australia. The ages (36 – 53 ka) determined from co-existing cosmogenic 21Ne and 3He in olivines separated from basalts collected from four locations, the Tyrendarra flow, the Harman Valley flow, Hopkins Falls; and Mount Porndon, are consistent within analytical uncertainties with ages previously determined by cosmogenic 36Cl exposure dating. Thus, the cosmogenic 21Ne method can provide reasonable exposure age estimates for young basalts, and it could prove complementary to established techniques such as conventional 14C dating (which is generally considered unreliable above ~60 ka) and K-Ar and Ar-Ar dating (which is problematic for samples < 100 ka old). More research, however, is needed before cosmogenic neon exposure dating becomes accepted as an accurate and reliable method. In particular, the uncertainty in cosmogenic neon production rates could be as high as 25%. In order to obtain an improved calibration of the cosmogenic 21Ne (and 3 He) production rate, we are currently assessing various additional sample sites in Australia that have been well characterized by previous geochronology and geomorphology studies. The expected improvement in analytical performance of a new generation multi-collector noble gas mass spectrometer should enhance our capabilities for neon isotope analyses, and it may be possible in a near future to measure cosmogenic 21 Ne ages as young as 1 ka.

Goldschmidt Conference Abstracts 2009

A547

Anoxic and oxic phototrophic primary production during the Precambrian

Smectite and zeolite formation from the pyroclastic deposits of the Aksitero Formation, Philippines

C.M.E. HONEYCUTT1*, C.J. BJERRUM2 3 AND D.E. CANFIELD

M.L.L. HONRADO1*, CHELO S. PASCUA1, EDMUNDO VARGAS1, CARLO A. ARCILLA1, W. RUSSELL ALEXANDER2, KAZUTO NAMIKI3, N. FUJII4, MINORU YAMAKAWA4, TSUTOMU SATO5 6 AND IAN G. MCKINLEY

1

Nordic Center for Earth Evolution and Statens Naturhistoriske Museum, University of Copenhagen, Denmark (*correspondence: [email protected]) 2 Nordic Center for Earth Evolution and Dept. of Geography and Geology, Univ. of Copenhagen, Denmark 3 Nordic Center for Earth Evolution and Biology Institute, Univ. of Southern Denmark, Denmark Large areas of the oceans were reducing during much of the Precambiran (4.5 to 0.5 Ga). The Great Oxidation Event (GOE; 2.45-2.2 Ga) most likely was associated with the establishment of a redox-cline at the base of the surface mixed layer of the ocean. In the modern ocean, the bottom of the mixed layer often lies above the base of the photic zone . Thus, an ecosystem model for the Precambrian should reflect the net primary production (NPP) of oxygenic phototrophs in the mixed layer and anoxygenic phototrophs below (NPPox and NPPred, respectively). Satelite data and a vertically generalized production model (VGPM) can be used to calculate the mixed layer NPP relative to the NPP below. We use this to estimate the potential role of NPPred below the mixed layer. The model implies that ~34% of the Precambrian total NPP would have been NPPred if factors such as climate were comperable to today. High rates of exported NPPred are consistent with the Precambrian sulfur isotope record which suggests that high rates of sulfate reduction proceeded the GOE.

Figure 1: Results of the model of anoxigenic photosynthesis. Percent is relative to total production.

1

National Institute of Geological Sciences, University of the Philippines, Diliman, Quezon City 1101 Philippines (*correspondence: [email protected]) 2 Bedrock Geoscience, Auenstein, Switzerland 3 Obayashi Corporation , Tokyo, Japan 4 RWMC, Tokyo, Japan 5 Graduate School of Engineering, Hokkaido University, Sapporo, Japan 6 McKinley Consulting, Baden-Dattwil, Switzerland The smectites and zeolites dominantly comprising the tuffaceous siltstone and sandstones of the Aksitero formation have been found to form from the interaction of hyperalkaline ground water (pH10-11). These deposits are in proximity to the main hyperalkaline spring emanation called the Manleluag Hot Springs of Mangatarem Town, Pangasinan, Philippines. Geochemical reaction modelling (i.e. Geochemist’s Workbench) suggests that zeolites are formed from the reaction of the smectites with the hyperalkaline groundwater. A very good evidence for this was also found during trenching conducted on the site, basalt rocks directly underlying the Aksitero Formation show reaction pathways in the form of mixed zeolite and smectite veins. This study highlights a natural analogue site in the Philippines for the bentonite – hyperalkaline pore water interaction that is foreseen to occur in underground nuclear waste disposal.

A548

Goldschmidt Conference Abstracts 2009

The noble gas budget of the Kamchatkan mantle wedge

SiC grains from supernovae and the solar Si-isotopic ratios

J. HOPP1* AND D.A. IONOV2

P. HOPPE1*, J. LEITNER1, B.S. MEYER2, L.-S. THE2, M. LUGARO3 AND S. AMARI4

1

Institut fuer Geowissenschaften, Univ. Heidelberg, Im Neuenheimer Feld 236, D-69120 Heidelberg (*correspondence: [email protected]) 2 Université Jean Monnet & LTL-UMR 6524-CNRS, 23 rue P. Michelon, 42023 St. Etienne, France ([email protected]) The Kamchatka peninsula in far-eastern Russia is the site of the most active arc volcanoes worldwide. We performed a stepwise crushing noble gas study on a suite of mantle xenoliths (spinel harzburgites) from the andesitic Avacha volcano in southern Kamchatka to investigate the impact of slab devolatilization on the noble gas budget of the mantle wedge. Only very fresh mantle xenoliths were selected for analysis to ensure negligible late-stage contamination with atmospheric gases. Furthermore, olivine separates had been prepared only from cores of the xenoliths to further prevent contamination by alteration processes during surface exposure. 3 He/4He ratios range from 6 to 8 RA, indistinguishable from most lithospheric mantle samples and at the lower end of typical MORB compositions. There is no evidence for a significant radiogenic 4He* contribution, i.e. the ca. 80 Ma-old Pacific crust currently subducting under Kamchatka appears to have lost most of its radiogenic 4He* before the onset of the main dehydration events within the slab. All other noble gases show an atmospheric isotopic composition (Ne, Xe indistinguishable from air values, 40Ar/36Ar ratios <400) and high concentrations in Ar, Kr, Xe when compared with xenolith data from non-arc settings (e.g. 36Ar: 1-6·10-9 cm³ STP/g). Again, there is no evidence for a significant radiogenic contribution of the subducted oceanic crust. Accepting a slab origin of the sampled atmospheric noble gases these must have entered the oceanic crust lately, shortly before or during the subduction process. 36 Ar/22Ne ratios (up to 100) are strongly fractionated, with higher values than those in seawater. 84Kr/36Ar and 132Xe/36Ar ratios show a linear correlation and are slightly fractionated relative to air composition. The latter two ratios appear to be also correlated with the relative proportion of mantle Ar (i.e. 40 Ar/36Ar ratios). In general, explaining the complex elemental pattern may require multi-stage fractionation and mixing processes e.g. during ocean floor alteration, during the subduction process itself and in the course of magmatic processes within the mantle wedge.

1

Max-Planck-Institute for Chemistry, 55020 Mainz, Germany (*correspondence: [email protected]) 2 Clemson University, Clemson, SC 29364, USA 3 Monash University, Clayton 3800, Victoria, Australia 4 Washington University, St. Louis, MO 63130, USA

Introduction GCE models fail to account for the solar Si isotope abundances; specifically 29Si is too low [1]. SNeII are the most important suppliers of 29Si to the ISM. By con-sidering 1.5x enhanced SNII 29Si yields, [2] achieved a good match between Si-isotopic ratios of SiC mainstream grains and predictions from incomplete mixing of SN ejecta in the ISM. To account for the Si-isotopic ratios of low-density graphite and SiC X grains in SNII mixing calculations, an 2x enhanced 29Si yield in the C- and Ne-burning shells was proposed [3]. Recently, we identified a SN grain with unusual Si-isotopic ratios in a NanoSIMS survey of >1000 presolar SiC grains [4] which strongly supports the suggestion by [3]. Here, we discuss the implications for the production of 29Si in SNeII and for GCE models of Si.

Results and Discussion

SiC grain KJB2-11-17-1 has 29Si/28Si = 1.63x solar, Si/28Si = 0.82x solar, 12C/13C = 265, and evidence for the initial presence of radioactive 44Ti [4]. With an 2x enhanced 29 Si yield in the O/Ne and O/Si shells of a 15 M! SNII [5] we find a perfect match between the grain data and predictions from SN mixing calculations. We have explored the impact of various reaction rates on the 29Si abundance in these shells using a computer code built on the nuclear reaction toolkit libnucnet. The 29Si yield is most sensitive to changes in the 26 Mg(α,n)29Si and, to a lesser extent, 29Si(n,γ)30Si rates. To increase the 29Si yield by a factor of ~2, the currently used 26 Mg(α,n)29Si rate must be increased by 3x, which is compatible with experimental uncertainties. Since the O/Ne and O/Si zones contribute ~90% of 29Si in SNII ejecta, the twofold increase in the 29Si yield will heavily influence GCE predictions. Considering IMF-weighted ejecta from 15, 19, and 25 M! SNeII [5] gives δ29Si = -475‰ (unmodified 29Si yield) and +5‰ (2x enhanced 29Si yield in O/Ne and O/Si zones). The latter value appears a promising starting point for improved GCE models. 30

[1] Timmes & Clayton (1996) ApJ 472, 723. [2] Lugaro et al. (1999) ApJ 527, 369. [3] Travaglio et al. (1998) Nuclei in the Cosmos V, 567. [4] Hoppe et al. (2009) ApJ 691, L20. [5] Rauscher et al. (2002) ApJ 576, 323.

Goldschmidt Conference Abstracts 2009

A549

Highly siderophile element evidence for early Solar System processes in ordinary chondrite components

Rapid progression of kyanitesillimanite type metamorphism in the Unazuki area, southwest Japan

M.F. HORAN1*, C.M.O’D. ALEXANDER1 2 AND R.J. WALKER

K. HORIE1*, Y. TSUTSUMI2, M. CHO3, H. HIDAKA4 5 AND Y. MORISHITA

1

Carnegie Institution of Washington, Dept. of Terrestrial Magnetism, Washington D.C. 20015 (*correspondence: [email protected], [email protected]) 2 Dept. of Geology, University of Maryland, College Park, MD 20742 ([email protected]) The highly siderophile elements (HSE=Re, Os, Ir, Ru, Pt and Pd) are all strongly partitioned into metal relative to silicate during melting, but may be fractionated from each other during melting of Fe-Ni metal. The volatilities of the HSE encompass the condensation temperatures of the earliest solids that formed in the Solar System (i.e., Al, Ti and Ca oxides, magnesian silicates and metal). Our objective is to use high precision and high sensitivity isotope dilution mass spectrometric analyses of the HSE to constrain the origins of some of the diverse components in two ordinary chondrites, Dhajala (H3.8) and Ochansk (H4). Metal from both Dhajala and Ochansk contains about 80% of the HSE present in the bulk samples, with unfractionated HSE abundances, but wide variations in contents. These features likely resulted from the presence of HSE-rich carrier phases that may dominate the HSE budget in the metal. These suggested carrier phases formed in a reducing environment in which Pd was more refractory than Fe, and were incorporated into early-formed metal grains. Nonmagnetic components from Dhajala and Ochansk consist of chondrules and matrix from which metal had been removed in the lab. The metal-free fractions have uniform but fractionated HSE whose abundances are >40 times those expected from metal-silicate equilibrium, with large depletions in Pd and lesser depetions in Re, Ru and Pt, relative to Os and Ir. Their compositions are consistent with microphases of either highly refractory condensates (similar to those in CAIs) or residues of high degrees of metal melting (as during chondrule formation) that were well-dispersed throughout the chondrules and matrix. The low Re/Os ratios suggest these microphases formed in a more oxidizing environment than the unfractionated HSE carriers in the metal. These ordinary chondries thus contain two distinct HSEbearing components that formed separately and out of equilibrium with each other. Early sorting of these HSE carriers prior to chondrite accretion may provide an explanation for the disparate HSE ratios and 187Os/188Os ratios measured among the chondrite classes.

1

Geological Survey of Japan (JSPS fellow) (*correspondence: [email protected]) 2 National Museum of Nature and Science, Tokyo, Japan ([email protected]) 3 Seoul National University, Seoul, Korea ([email protected]) 4 Hiroshima University, Japan ([email protected]) 5 Geological Survey of Japan ([email protected]) Geochronological constraints from metamorphic rocks provide important information for understanding crustal evolution as well as metamorphic processes. The Unazuki region, southwest Japan, which is one of crucial sites for deciphering the Permo-Triassic orogeny in East Asia, has experienced the kyanite-sillimanite type metamorphism characterized by a clockwise P–T path. Radiometric ages of the Unazuki schists, previously determined by Rb–Sr and K– Ar methods, are scattered from 248 Ma to 175 Ma primarily because of multi-phase metamorphism and deformation. In this study, in situ zircon U–Pb geochronology was applied to the schist and granite samples to discuss the timing and the duration of kyanite-sillimanite type, regional metamorphism. Protoliths of the Unazuki schists are sedimentary and felsic volcanic rocks of late Carboniferous to early Permian age, based on the fossil evidence [1]. U–Pb data of quartzofeldspathic schist derived from felsic volcanics yield an eruption age of 258 ± 2 Ma, indicating that regional metamorphism occurred after 258 Ma. On the other hand, U– Pb age of a granite intruding the schist is 253 ± 1 Ma. The granite contains some xenoliths of the Unazuki schist, in which staurolite is replaced by andalusite and cordierite due to thermal flux from granitic magma [2]. Therefore, regional metamorphism occurred between 258 and 253 Ma, suggesting a rapid metamorphic progression. Further work is needed to confirm this rapidity of crustal-thickening process.

Figure: Age constraints from the Unazuki region. [1] Hiroi (1978) J. Geol. Soc. Japan 84, 521-530. [2] Kitamura & Hiroi (1982) Contrib. Mineral. Petrol. 80, 110-116.

A550

Goldschmidt Conference Abstracts 2009

The 3He/4He ratios in hot spring gases after the Iwate-Miyagi Nairiku earthquake in 2008 KEIKA HORIGUCHI*, YOSHIHIRO SHIMO AND JUN-ICHI MATSUDA Department of Earth and Space Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan (*correspondence: [email protected]) On the basis of high density and sensitivity seismograph network progressed in recent years, geophysical studies indicates that aqueous fluids supplied by the slab reach shallow level effecting local contractive deformation and increasing the local crustal contraction rate in NE (northeastern) Japan (e.g. Hasegawa et al., 2005). However, the presence of aqueous liquid is estimated only by the seismic velocity anomalies and it seems difficult to detect a kind of upwelling aqueous liquid simply by geophysical studies. The Iwate–Miyagi Nairiku Earthquake in 2008 occurred on 14 June 2008. The epicenter was 39°1.7’N 140°52.8’E with the magnitude M7.2 (outlined information released from JMA). A 3He/4He ratios could be a good tracer to identify the origin of the aqueous fluid, as the helium isotopic ratios in the mantle and crust are quite different each other. A 39–39.5°N area in NE Japan have ratios as low as 1 Ra, indicating the presence of crustal material under this region, which is also supported from the seismological underground structure (Horiguchi, 2008). In a week and half a year after the earthquake, some water/gases samples were collected from hot springs near the epicenter, with the intention of studying the change of 3He/4He ratios after the event. We measured a 3He/4He ratio with He and Ne concentrations of the dissolved gases by using the noble gas mass spectrometer (VG 5400) installed at Osaka University. The obtained results show that 3He/4He ratios increased in many hot springs in this region by 10-85% after a week. After half a year, 3He/4He ratios decreased at the nearest point of the main shock region. Meanwhile, the isotopic ratios further increased in the northwestern part of the main shock region. These results suggest that there was an uplift of the mantle material containing the primordial 3He-containing fluid and this could be the cause of the earthquake. We plan to compare these geochemical results with the geophysical data in this region.

Isotope fractionation of fluids under geologic conditions J. HORITA1*, V.B. POLYAKOV2 AND A.A. CHIALVO1 1

Chemical Sciences Division, Oak Ridge National Laboratory, TN 37831-6110 (*correspondence: [email protected] and [email protected]) 2 Institute of Experimental Mineralogy, RAS, Russia ([email protected]) Isotopic properties of molecular fluids such as the reduced partition function ratios (RPFR) have traditionally been calculated by means of the well-established statistical mechanical approach, which implicitly assumes no significant intermolecular and solute-solvent interactions. However, recent several laboratory experimental studies [1, 2] clearly demonstrated that isotopic fractionation involving fluids changes measurably as a function of, not only temperature, but also pressure and fluid compositions. These results showed that the above assumption for molecular fluids is not valid under geologic conditions, underscoring the need of better understanding of the isotopic properties of ‘real’ geologic fluids. Along with laboratory experiments, we have been developing theoretical and molecular-based simulation methods for investigating the isotopic properties of fluids (i.e., water, N2, O2, CO2, CH4) to high-pressures and temperatures. Our first method utilizes thermodynamic relationship to calcualte the effect of pressure (density) on the RPFR, using the equation-of-state of isotopologues, which is available from the literature or can be obtained from our novel corresponding-states priciple approach [3, 4]. A second approach is based on statistical-mechanical, molecular-based simulations, using the perturbation method [5, 6]. We present an overview of our efforts, along with literature data, on experimental, theoretical, and simulation results on the isotopic properties of fluids. Sponsored by the Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences, U.S. Department of Energy under contract DEAC05-00OR22725, Oak Ridge National Laboratory, managed by UT-Battle, LLC. [1] Horita et al. (2002) GCA 66, 3769-3788 [2] Hu and Clayton (2003) GCA 67, 3227-3246 [3] Polyakov et al. (2006) GCA 70, 1904-1913 [4] Polyakov et al. (2007) JPC 111, 393401 [5] Chialvo and Horita (2006) JCP 125, 034510 [6] Chialvo and Horita (2009) JCP (in press).

Goldschmidt Conference Abstracts 2009

A551

Deciphering the phase shift of tropical δ18Oforam and Mg/Caforam signals: A salinity effect?

Validation of line scan methods for quantitative analysis of banded iron formations by LA-ICP-MS

C. HORN*, A. EISENHAUER, D. NÜRNBERG AND J. SCHÖNFELD

M.D. HORTON1*, A. BASU2 AND R. HANNIGAN3

IFM-GEOMAR, Leibniz Institute of Marine Sciences, Wischhofstr. 1-3, 24148 Kiel, Germany (*correspondence: [email protected], [email protected], [email protected], [email protected]) Previous studies of coupled δ18Oforam and Mg/Ca across glacial terminations have shown that the planktonic Mg/Ca signal leads the δ18Oforam signal by several thousand years [1,2]. This implies that the tropical ocean warmed before the melting of Northern Hemisphere ice sheets during glacial terminations. Latter observation challenges the role of the North Atlantic as the pacemaker of glacial/interglacial transitions emphasising the tropical ocean as an important area triggering global climate change. In order to test this hypothesis we apply a multi-proxy approach of coupled δ18O, Mg/Ca and δ44/40Ca measurement on G. sacculifer in order to decouple the influence of sea surface temperatures (SST) and sea surface salinity (SSS). The sediment core (SO164-03-4) selected for this study is located in the Central Caribbean Sea providing sufficient foraminferal species for a variety of measurements of different proxies. Our results show that there is a phaseshift in the timing of the glacial/interglacial temperature transition between Mg/Ca and δ18O signals, showing that the former leads the δ18O signal by about 3-4 kyears. However, latter observation is not in support of an earlier warming of the tropical ocean. Rather, the phaseshift correspond to a local Caribbean SSS increase which most likely reflects temporal variations of the ITCZ causing relative changes of the precipitation/evaporation ratio at the site of sediment core SO164-03-4. [1] Lea et al. (2000) Science 289, 1719-1724. [2] Nürnberg et al. (2000) Paleoceanography 15 (1), 124-134

1

CETAC Technologies, 14306 Industrial Rd., Omaha, NE 68144 (*correspondence: [email protected]) 2 University of Rochester, Earth and Environmental Sciences, Rochester, NY 14627 ([email protected]) 3 University of Massachsetts at Boston, Department of Environmental, Earth and Ocean Sciences, Boston, MA 02125 ([email protected]) Laser ablation inductively coupled mass spectrometry (LA-ICP-MS) is a generally accepted technique for high precision analyses of trace elements in solid matrices. With the high lateral resolution possible with this technique, LAICP-MS data can be used to construct trace element maps with minimal destruction of the sample. While multiple ablation points are typically used for this purpose, the positioning of the locations is very time consuming. Accuracy and precision of analytical results using multiple ablation locations are also affected by changes in ablation yield and elemental fractionation associated with increasing pit depth. Our previous work evaluated the use of multiple line scans to construct elemental maps of various geological samples, including a banded iron formation (BIF) that formed 3.4 Ga before present. Because all analyses can be conducted locally on the sample surface with micro scale resolution we were able to “visualize” trace element variations between the dominant silica and iron phases. The data provide unique insight into the partitioning of trace elements on a micron scale. Small-scale chemostratigraphic patterns within the elemental maps reveal interactions between the silica and iron phases which tracks shifts in silica and iron saturation of the water column from which the minerals precipitated. We are currently mapping additional samples from the same location and other locations to assess the consistency in trace element fractionation during BIF formation between the alternate silica and iron-rich layers.

A552

Goldschmidt Conference Abstracts 2009

Apparent dielectric constants of brines estimated from quartz solubilities K. HOSHINO*, Y. UEDA AND T. HIROTAKA Hiroshima University, Higashi-Hiroshima, 739-8526, Japan (*correspondence: [email protected]) The dielectric constant is a key parameter characterizing chemical properties of solvents. Geofluids are coceived commonly as mixutes of water, salt and gas species. The constant of a mixture of water and gas can be calculated by following Akinfiev and Zotov [1], while there may be no reliable equation to obtain that of water and salt. We have reinvestigated about 300 data for quartz solubilities in brines of various salinities in previous experiments at a wide range of P-T conditions to estimate “apparent” dielectric constants of brines. The obtained constants were inter- or extrapolated for 1 molal NaCl solutions. The resultant constants for 0.5, 1 and 2 kb show slightly higher than those of pure water at high temperatures, while they abruptly change at around 350, 400 and 420°C, respectively (Figure 1). It is quite interesting that NaCl changes its major dissolved species from NaCl(aq) to Na+ + Clalmost at around the above temperatures, implying a large effect of ionization of salts on the dielectric constants.

Figure 1: Dielectric constants of pure water (solid lines) and the “apparent” ones of 1 molal NaCl solutions (broken lines). Experimental data of talc-quartz equilibria in brines [2] were used for consistency check by MIX99 [3] in which SUPCRT92 [4] and the Debye-Huckel equation for activity coefficients of aqueous species are included. The calculated solubilities of talc and quartz in brines were well consistent with the experimental results. Therefore, it can be said that the estimated dielectric constants are adequate as “apparent” ones to apply thermodynamic data of solutes in water solvents provided by SUPCRT92 to reactions in brines. [1] Akinfiev and Zotov (1999) GCA 63, 2025-2041. [2] Saccocia and Seyfried Jr. (1990) GCA 54, 3283-3294. [3] Hoshino et al. (2000) Res. Geol. 50, 185-190. [4] Johnson et al. (1992) GCA 18, 899-947.

In situ U-Pb zircon dating using laser ablation-multi ion counting-ICP-MS KEJUN HOU1,2, YOURONG TIAN3 AND YANHE LI1,2 1

MLR Key Laboratory of Metallogeny and Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Bejing, 100037 China 2 MLR Key Laboratory of Isotope Geology, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Bejing, 100037 China([email protected]) 3 Thermo Fisher Scientific (Shanghai) Co., Ltd, Beijing 10037, China Precision and accuracy of laser ablation-inducctively coupled plasma mass spectrometry (LA-ICP-MS) U-Pb dating of accessory minerals is highly developed these years. Moreover the coupling of laser ablation systems to multicollector magnetic sector ICP instruments (MC-ICP-MS) has resulted in the ability to acquire accurate and prcise isotope ratios for many elements at high spatial resolution for its high ionization efficiency of the ICP source and simultaneous acquisition of ion beams having flat topped peak shapes.LA-MC-ICP-MS U-Pb dating has certain advantages when employed for large zircon population, expecially for ditrital zircon. We report results of U-Pb dating of different zircon reference samples (91500, GJ-1, Plesovice, TEM) by laser ablation (Newwave UP 213nm Nd:YAG)-multi ion couting ICP-MS (Thermo Finnigan Neptune) under 25μm diameter. The array of four channeltrons and three faraday cup allows for simultaneous detection of 202Hg(on IC5), 204Hg, 204Pb(on IC4), 206Pb(on IC3), 207Pb(on IC2), 208Pb(on L4), 232Th(on H2), 238U(on H4) ion signals. The linerity and stability of the ion counters are better than 0.2% during any one analytical session, and ion signals were kept below 1×106 cps in almost all of the laser ablation analyses of zircon so as to prolong the longevity of the detectors. It was assumed that mass bias and U-Pb fractionation during the ablation process were similar for both the zircon standard and the samples. Data were evaluated by ICPMSDataCal 3.4 (Liu, 2008) using a type of standardsample bracketing method. Precision of measured Pb/U ratios in zircon after 20s of ablation is better than 5%(2SD), resulting in routinely achieved precision of U-Pb ages obtained by external calibration of ~1% or better. The resulting present U-Pb age for four zircon reference samples and two geological samples show an excellent agreement with the previously reported ID-TIMS or SHRIMP data. This work was supported by funds from Program(K20072-3) from Insitute of Mineral Resources, Chinese Academy of Geological Sciences

Goldschmidt Conference Abstracts 2009

Eco-geochemical Assessment of Agroecosystems — Cadmium in Chengdu Economical Region, Sichuan, China Q.Y. HOU, Z.F. YANG*, T. YU AND X.Q. XIA School of Earth Science and Resources, China University of Geosciences, Beijing 100083, China (*correspondence: [email protected], [email protected]) The cadmium (Cd) in Chengdu economic region was studied as an example of eco-geochemical assessment on agroecosystems. Dry and wet atmospheric deposition, chemical fertilizers, irrigation water, and plants were collected. The concentration of Cd and other elements in these samples were analyzed and the fluxes of input and output of the agroecosystem were calculated. The results indicated that the Cd was more concentrated in the surface soil than in the deep soil, and Cd concentration in some rice samples exceeded the upper limit of the pollution free agricultural products. The input of Cd into the agroecosystem was 17.8 g/hm2·a on average, which accounted for 85.2% of the total input. Infiltration (2.34 g/hm2·a) and harvest (1.87 g/hm2·a) were the two most important Cd outputs. The average increase of Cd content in soil was a result of sources outside the agroecosystem was 0.006 mg/kg·a. In next 20 years, the area of the grade III soil will increase 2-3 times under the current input and output condition of Cd, which lead to significant decrease of the arable land. The decrease of the pH in study area was 0.106/a because of fertilization and acid rain, of which 89.6% was from the contribution of chemical fertilizers. The present study indicates that, even though 95% of rice production is safe, after 20 years, 70% of the safe soil will degrade, and the area of alarming soil will increase rapidly from 4% to 27% of the total cultivated area in the region.

A553

Speciation of 129I in the environment and its application X.L. HOU1,2, G. POSSNERT3 AND A. ALDAHAN4,5 1

SKLLQG, Institute of Earth Environment, CAS, Xi’an, P.R. China 2 Risø National Laboratory for Sustainable Energy, Technical University of Denmark, DK-4000 Roskilde, Denmark 3 Tandem Laboratory, Uppsala University, SE-751 21 Uppsala, Sweden 4 Department of Earth Sciences, Uppsala University, SE-758 36 Uppsala, Sweden 5 Department of Geogology, United Arab Emirates University, Al-Ain, UAE Despite the huge amount of 129I (15.7 Myr) releases from human nuclear activities, data on speciation of the isotope in the environment are still scarce. About 90% of the present day isotope inventory in the Earth’s surface environments relate to liquid and gaseous discharges from the nuclear reprocessing facilities at Sellafield (UK) and La Hague (France). Emissions from these sources provide a unique opportunity for investigation temporal and spatial exchange and movement of water in the North Sea and the Baltic Sea and subsequently understanding part of the pollution transport within the region. Speciation analysis methods of 129I and 127I in environmental samples, such as seawater, and precipaition have been established by our group. The speciation of 129I and 127I (iodide and iodate) were analysed in seawater samples collected in Kattegat and Baltic Sea at different water depth as well as in monthly precipitation collected in Denmark. A relatively high concentration of 129I (3-20×1010 atom/L) is observed in the Kattegat, compared with that in the Baltic Sea (<2×1010 atom/L). There is a positive correlation between the total 129I concentration and salinity in seawater. In Kattegat, the ratio of 129Iiodide/129Iiodate is 1-2, while in the Baltic Sea, most of 129I exists as iodide with a ratio of 2-100. In the precipaition, iodide is the major species of 129I, accounting for 50-99% of total 129I, while iodate represents the major species of 127I, accounting for 43-93% of total 127I. The results indicate that although total 129I may give gross information about the sources, transport pathways and sinks, speciation analysis is indispensible for accurate utilization of the isotope as an environmental tracer. Speciation may also be a vital tool for using the ratio (129Iiodide/129Iiodate)source to (129Iiodide/129Iiodate)sink as an age indicator of the transport from the sources to the sinks.

Goldschmidt Conference Abstracts 2009

A554

Erosion and weathering in Taiwan 1

1

1

1

N. HOVIUS *, A. GALY , D. CALMELS , P. MEUNIER , R.H. HILTON2, M.J. BICKLE1, A.J. WEST3, H. CHEN4 1 AND R.B. SPARKES 1

Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK (*correspondence: [email protected]) 2 Laboratoire de Géochimie et Cosmochimie, IPGP, 4 Place Jusieu, 75252 Paris, France. 3 Department of Earth Sciences, University of Oxford, Parks Road, Oxford OX1 3PR, UK 4 Department of Geosciences, National Taiwan University, Taipei 106, Taiwan ROC Systematic monitoring of river loads helps refine and extend the map of internal dynamics and external feedbacks in Earth’s critical zone. Our focus is on Taiwan where hillslope mass wasting and fluvial sediment transport are driven by earthquakes and cyclonic storms. The biggest trigger events cause instantaneous erosion and seed a weakness in the landscape that is removed over time in predictable fashion. This gives rise to patterns of erosion that can not be understood in terms of bulk characteristics of climate, such as average annual precipitation, a result that is repeated elsewhere. Erosion harvests particulate organic carbon from rock outcrop, soil, and biomass. In Taiwan, most non-fossil POC is carried in hyperpycnal storm floods. This may promote rapid burial and preservation of POC in turbidites. Abundant POC in ancient turbidites has a distinct terrestrial signature, confirming the removal of carbon from short-term circulation by this mechanism. Silicate weathering too is facilitated by rapid erosion. However, weathering within the shallow subsurface, where the effects of erosion are most direct, only yields a part of the dissolved load of rivers. During and after heavy precipitation contributions from surface and shallow sources dominate, but the fraction of dissolved load derived from silicate weathering is relatively low in these conditions. At all other times the dissolved load of Taiwan’s rivers is dominated by a weathering flux from deep within the rock mass. Erosion may facilitate this by perpetuating pervasive brittle deformation, opening pathways for deep groundwater.

Compound-specific stable isotope reconstruction of the paleoelevation of the Western U.S. M.T. HREN*, M. PAGANI AND M. BRANDON Dept. Geology and Geophysics, Yale University (*correspondence: [email protected]) Hydrogen and carbon isotope analyses of individual plantderived organic compounds provides a novel means of reconstructing the isotopic composition of ancient precipitation and biologically-related factors such as water use efficency. We analyzed the H and C isotope compositions of long carbon-chain normal alkanes preserved in Eocene and younger fluvial and lake sediments from the Sierra Nevada and Western U.S. to reconstruct the isotopic composition of ancient precipitation. Hydrogen isotopes of individual leafwaxes extracted from early Eocene sediments decrease by 30‰ across the ancient Sierra Nevada range, a magnitude similar to that observed in the hydrogen isotope composition of authigenic minerals of similar age. In combination, these data provide evidence for large isotopic gradients in precipitation related to high-standing Eocene Sierra Nevada topography. In contrast, long-term changes in the hydrogen isotope composition of leaf-waxes from sediments in the rainshadow of the Sierra exceed 50‰, however the timing and magnitude of change differs markedly from that observed in the isotope composition of coexisting authigenic minerals. Coupled organic molecular and authigenic mineral isotope proxies are used to distinguish between regional changes in paleoelevation and local hydrology of the Western U.S.

Goldschmidt Conference Abstracts 2009

The geochemical characteristics of natural gas and its origin in Tazhong Uplift of Tarim Basin, China GUO YI HU 1*, JIN LI 2 AND ZHISHENG LI2 1

Research Institute of Petroleum Exploration and Development, PetroChina, Beijing, 100083, China (*correspondence: [email protected]) 2 RIPED-Langfang, Hebei, 065007, China The Tazhong Uplift is a favorable zone for natural gas exploration in Tarim basin and Tazhong gas field with proven reserves of 36.6 BCM was discovered in the carbonate reservoir of Ordovician in 2005. Based on the geochemical data of natural gases from 36 gas wells in Tazhong Uplift, the geochemical characteristics of natural gas and its origin have been studied. The carbon isotope of methane is very lighter with δ13C1 from -54.4‰ to -38.0‰ and The carbon isotope of ethane varies widely withδ13C2 from -43.0‰ to -30.7‰. The δ13C values of benzene, toluene and methylcyclohexane of natural gas are less than -24.0‰. According to the genetic classification scheme by the carbon isotope of ethane [1,2] and the above three compounds [3], gases in Tazhong Uplift origined from source rock with organic matter type I-II. Based on the carbon isotope value of methane and ethane, there are three groups of gases in Tazhong Uplift. Group one with δ13C1 less than -50.0‰, δ13C2 ranged from -39.0‰ to -35.0‰ is oil-cracking gas. All of them locate in the west of Tazhong Uplift. Group two with δ13C1 more than -43.0‰, δ13C2 more than -38.0‰ sourced from source rock in Middle to Upper Ordovician with the organic matter type II.All of them locate in the east of Tazhong Uplift. Group three with δ13C1 from -42.0‰ to 47.0‰, δ13C2 less than -39.0‰ and the values of δ13C2 minus δ13C1 less than 5‰ locates in the center of Tazhong Uplift. The geochemical characteristics of these gases are similar to the gas produced from Cambrian reservoir in Tarim basin. So authors deduced that gases in group three came from source rock with organic matter type I-II in Cambrian. [1] Dai J.X. (1992) Science in China (Series B) 35(10) 12461257. [2] Dai J.X. et al. (2003) Giant gas fields and its origin of gas, Science Press, 1-199 (in Chinese). [3] Hu Guoyi, et al. (2008) Science in China Series D,51 Supp. :131-139.

A555

Partitions of Sn, Cu, W, Au between liquid and vapor phases at sub-critical states of metal bearing fluids SHUMIN HU, RONGHUA ZHANG AND XUETONG ZHANG Institute of Mineral resources, Chinese Academy of Geol.Sci., Lab. Geochemical Kinetics.Baiwanzhuang road 26, Beijing 100037 ([email protected]) In order to understand metal transportation by vapor, which was found by detecting volcanic gases, authors performed vapor-liquid separation experiments at sub-critical states. The experiments indicate that metal transportation by vapor of hydrothermal systems is derived from the liquid and vapor separation occurred in the transitions of hydrothermal fluids of NaCl-H2O- CO2 from a supercritical state to vaporliquid immiscibility field at a sub-critical state. Authors designed and assembled a liquid and vapor separator for supercritical fluids, which is a multi-channel reaction device and includes liquid reservoir, pump, main pressure vessel, V-L phase separator, cooling system, back pressure regulators, tubing etc. The main pressure vessel with a Zr metal liner tube mounted vertically. The V-L separation could be controlled and operated at temperatures (T) from 450 to 250°C and at pressures (P) from 40 to 22MPa. We performed vapor-liquid immiscibility field experiments at subcritical states of a metal (Sn, Cu, Au, W and Zn) bearing NaHCO3-HCl-H2O (or NaCl-H2O) as decreasing T or P, and collected L and V samples separately. The results indicated that samples of liquid phase have higher concentrations of Na and Cl than those of vapor samples. For instance, liquid-vapor partition coefficients for Na and Cl, DNa (V/L) (or DCl(V/L)) (<1) vary with temperatures or pressure. And the liquid-vapor partition coefficients for Sn, DSn (V/L) varies from 0.5 to 2.9. DSn (V/L) is correlated to DNa (V/L) (or DCl(V/L)). The experiments suggest that Sn, Cu, W, Au could be transported by vapor phase of NaCl-H2O. But zinc would be transported by a vapor phase of CO2-rich solution of NaCl-H2O-CO2 system.

Goldschmidt Conference Abstracts 2009

A556

Deeper geochemical control to the distribution of W and Sn deposits in Nanling Range, South China

Effect of land use conversion from rice paddies to vegetable plots on phosphorus fractionations in soil

RENMIN HUA

BIAO HUANG AND JEREMY L. DARILEK

State Key Laboratory for Mineral Deposit Research, Department of Earth Science, Nanjing University, Nanjing 210093, China South China, especially the Nanling Range and vicinity areas, is the largest and most important W and Sn mining district in the world. Mineralizations of W and Sn are so closely accompanied each other in this area, that many deposits contain both metals as major products [1]. However, present study shows distinctive difference on the spatial distribution between W and Sn deposits. Generally, the east sector of Nanling, i.e. the southern Jiangxi Province, is characterized by high concentration of W deposits, but very few Sn deposits are found. In the central sector of Nanling, i.e. the southern Hunan and northeastern Guangxi Provinces, W and Sn deposits are of same importance. In the western sector of Nanling, i.e. the northern Guangxi and southeastern Yunnan Provinces, Sn mineralization is predominant, represented by super-large Dachang and Gejiu tin deposits, whereas tungsten deposits are almost not found. It is revealed that the geochemistry of basal formations might play an important role to control the distribution of W and Sn deposits. The E-W striking Nanling Range crosses the two main old landmass of South China, i.e. Yangtse in the west and Cathysia in the east, which are seperated by a major regional deep fault. The Yangtse block is a craton while the Cathysia block a Sinian-Caledonian fold belt. Granitoids related to W and Sn mineralizations in both blocks are mostly crust-remelting type and hence W and Sn concentrations in ore-forming granites are controled by the basal formations. The abundance of Sn is the highest in Yangtse block while that of W is the highest in Cathysia block [2]. This may explain the difference of spatial distribution between W and Sn mineralizations in this area. Studies also reveals that basalts in the two blocks have different sources, EM1 under the Yangtse block while EM2 under the Cathysia block, which may also effect the shallow geological processes. This study is supported by the State Key Fundamental Research Project (Grant No. 2007BC144104). [1] Hua et al. (2008) Geol. J. China Univ. 14 527-538. [2] Chi & Yan (2007) Handbook of Elemental Abundance for Applied Geochemistry. Geol. Publishing House, 148p

Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China ([email protected], [email protected]) Worldwide, excess phosphorus (P) from agricultural soils causes and exacerbates eutrophication in water bodies (Huang et al., 2006). This study investigates the effect of land use conversion and intensification over time on organic P (Po) and inorganic P (Pi) fractions in a pre-urban area of China. Samples (n=60) with a chronological sequence of land use conversion were taken from sites where rice paddies have been converted to vegetable plots for 0, <10, 10-20, and >20 years and analyzed for five Pi fractions, three Po fractions. A large increase took place with regards to both Olsen P and TP, which increased from 3.2 to 58.5 mg kg-1 and from 522 to 1578 mg kg-1, respectively, over >20-year vegetable cultivation. With the exception of reductant soluble Pi, Pi fractions significantly increased by 33.3, 281.1, 292.8, and 437.9 mg kg-1 for soluble and loosely bound Pi, Al-Pi, Ca-Pi, and Fe-Pi, respectively, over the time. Most of the percentage increase in Pi is in the form of Fe-Pi, which increased from 8% of TP on paddy soil to 31% on the soil with >20-year vegetable cultivation, followed by Al-Pi, which increased from 2% of TP to 19%. For Po fractions, there was no significant change in P concentrations, however, the percentage of each fraction decreased as TP increased. The conversion of land use from paddy fields to high intensity vegetable plots is causing significant changes in soil P fractions. Heavy fertilizer application [1] is causing a buildup of soil P, primarily in the Fe-Pi fraction, followed by Ca-Pi and Al-Pi fractions. Farmers in the area should use strategies to maximize P uptake, such as application of gypsum or conversion back to rice paddies. [1] Wang, H.J., Huang, B., Shi, X.Z., Darilek, J.L., Yu, D.S., Sun, W.X., Zhao, Y.C., Chang, Q., Öborn, I. (2008). Nutr. Cycl. Agroecosyst. 81, 203-218. [2] Huang, B., Shi, X.Z., Yu, D.S., Öborn, I., Blombäck, K., Pagella, T.F., Wang, H.J., Sun, W.X., Sinclair, F.L. (2006) Agric. Ecosys. Environ. 112, 391402.

Goldschmidt Conference Abstracts 2009

Constraints on deep crustal magma differentiation by U-series disequilibria of rocks from Southern Peru, Central Volcanic Zone 1

2

3

F. HUANG *, E.V. SØRENSEN , P.M. HOLM , Z.-F. ZHANG1, C.C. LUNDSTROM1 AND J. GLESSNER1 1

Dept. of Geology, UIUC, Urbana, IL 61801, USA (*correspondence: [email protected]) 2 Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen, Denmark 3 Department of Geography and Geology, Geocenter Copenhagen, University of Copenhagen, Øster Voldgade 10, Dk-1350 Copenhagen, Denmark The Central Volcanic Zone (CVZ) in the Andes is characterized by having the thickest continental crust (up to 70 km) of all convergent margin arcs. The historic trachyandesites and trachytes from the Andagua Valley, Southern Peru, have high Sr content and Sr/Y, but low Y and HREE contents [1], similar to the typical “adakite”. Geologic and geochemical evidence do not support their production by 1) melting of a young, hot or flat subducted slab; or 2) garnet fractionation from mantle-derived basaltic melt; or 3) anatectic melting of mafic lower continental crust or underplated basaltic magma. Instead, these signatures more likely form by crustal contamination and deep differentiation of mantlederived magma in high pressure MASH zone [2]. We present U-series disequilibrium data for 20 Andagua lavas with SiO2 ranging from 55.5 to 63.9 wt% to constrain the magma differentiation process at depth in the thickened continental crust. Except for three highly evolved samples with large variations in (230Th/238U) and U/Th, and low (231Pa235 U) (due to ageing effect and crystallization of accessaroy minerals, e.g. zircon and apatite), the Andagua samples have significant 230Th and 231Pa excesses. (230Th/238U) varies from 1.04 to 1.29 and (231Pa/235U) from 1.39 to 1.62, and positively correlate with SiO2 content. This indicates that the crustal assimilant may be a melt from the mafic lower continental crust or underplated basalt, and it should have slightly greater 230 Th and 231Pa excesses than the mantle-derived mafic melt. The 230Th excess in this crustal melt is consistent with garnetcontrolling partial melting, while 231Pa excess cannot be explained by simple batch melting. Instead, it requires a lowporosity in-growth melting process during magma differentiation. [1] Sørensen & Holm (2008) J. Volcanology and Geothermal Res., 177, 378-396. [2] Hildreth & Moobath (1988) CMP, 98, 455-489.,

A557

Influence of competitive adsorption on kinetics of microbial arsenate reduction J.-H. HUANG*, E.D. MELTON, A. LAZZARO, A. VOEGELIN, J. ZEYER AND R. KRETZSCHMAR Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Switzerland (*[email protected]) Microbial reduction of arsenate (As(V)) to arsenite (As(III)) is known to increase the mobility and toxicity of arsenic in the environment [1]. In the presence of mineral surfaces, substantially slower As(V) reduction was observed, and reduction kinetics seemed to be controlled by the desorption of As(V) into the solution phase [2]. In natural systems, As(V) competes with other anions for adsorption to mineral surfaces. Up to date, the effect of competitive adsorption on As(V) reduction kinetics has not been specifically addressed. We therefore investigated As(V) reduction kinetics by Shewanella putrefaciens CN-32 in goethite suspensions in the presence of competitively adsorbing phosphate (P) and exopolysaccharide (EPS). Incubation experiments were carried out at pH 7.0 in solutions initially containing 10 µM As(V) and 25 µM lactate in the presence of 2 g goethite L−1. In the absence of P and EPS, Shewanella putrefaciens CN32 (1.0×109 cells mL−1) reduced As(V) with a half-life of 19 days (pseudo-first-order kinetics). Addition of up to 10 µM P increased initial dissolved As(V) concentrations but not reduction rates. However, increased As(V) reduction rates were observed in the presence of 50 and 100 µM P (half-life of 7 days). On the other hand, the half-life of As(V) also decreased to 10 days if the concentration of bacterial EPS was increased by 20% (spiking EPS isolated from bacterial cultures), indicating that EPS release by bacteria may also promote As(V) release from mineral surfaces [2]. Thus, both oxyanion competition and bacterial EPS production may enhance As(V) reduction in the presence of mineral surfaces. However, whereas increased As(V) reduction kinetics in the presence of 50 and 100 µM P were likely due to higher dissolved As(V) at the early stage of the incubation, spiking EPS appeared to enhance the As(V) reduction rate by steadily increasing the dissolved As(V) concentration during the entire incubation period. [1] Smedley & Kinniburgh (2002) Appl. Geochem. 17, 517568. [2] Huang et al. (2008) Geochim. Cosmochim. Acta 72, A399.

A558

Goldschmidt Conference Abstracts 2009

Geochemical evidence for tectonic setting of the Langjiexue Group in Langxian County, Tibet, China

Analysis and evaluation of the available rock and soil mass in underground space in ChangChun,China

JIAN-GUO HUANG, RUN-SHENG HAN AND BO LI Kunming University of Science and Technology, Southwest Institute of Geological Survey, Geological Survey Center for Non-ferrous Mineral Resources, Kunming 650093, P.R.C ([email protected] ) The research area is located in the southeast Tibet, which is the middle east region of Himalayan-Tethys orogenic belt. The Langjiexue Group in upper Triassic system is a flysch formation which can be divided into three formations: Songre formation, Jiangxiong formation and Zhangcun formation from bottom to top. The regional geological background and the geochemical composition of sandstones in Langjiexue Group are discussed in this paper. In diagrams of SiO2/Al2O3K2O/Na2O, K2O/( Na2O+CaO )-SiO2/Al2O3 and K2O/Na2Ow(SiO2), the data of rocks in Langjiexue Group are mostly plotted in the field of active epicontinental region. While the picture of La-Th-Sc, Th-Sc-Zr/10 and Th-Co-Zr/10 denote the rocks has tectonic background of continental island arc and active continental margin, and the characteristics of rare earth elements is close to the active epicontinental region. The petrochemical and REE geochemical characteristics of the rock indicate that the Langjiexue Group might have been formed in the tectonic environment from the active epicontinental region to the continental island arc. This paper was financially supported by the innovation team of ore-forming dynamics and prediction of concealed deposits, KMUST, Kunming, China (2008).

JING-LI HUANG1,2 YAN ZHOU3 AND LI LIU4 1

Changchun Institute of Technology Changchun China 130021 2 Construction Engineering College Jilin University Changchun China 130026 3 Center of Test Science and Experiment, Jilin University Changchun China 130026 4 JiLin University Museum of Geology Changchun China 130026 Since 20th centry, as the industrialization and the urbanization developing rapidly, the demand of city geology resources is gradually increasing. At the same time, excessive exploiture made the geology entironment frail day by day, such as the city slope geology disaster, land subsidence, groudwater pollution and depletion, city waste meterial geology problem, and etc. How to use the city underground space reasonable, to assure the city’s sustainable development is becoming a more and more important problem. The ChangChun City site in the northeast area in China. The city is mainly confronted with landslip, debris flow, land subsidence, land fracture, groud destabilization and sand liquation because of earthquake, frost heave and thaw collapse on seasonally frozen ground, solid waste meterial’s discharge problem, groundwater resource amount survey and the waterquality pollution problem, or other city environment geology problems. The paper choosed more than 10000 representative bore datas, and used GMS to build a tridimensional visual underground space model for ChangChun City. Analysised above factor’s influence, and evaluated the available rock and soil mass in underground space with the extension synthesis theory. The evaluation contains 0~3m, 3~15m, 15~30m rock and soil mass’s ground availability. This result has the guiding sense for the ChangChun City’s planning and construction, and has the model significance for other citys. [1] Cano-Hurtado, J.J. and J. Canto-Perello, Sustainable development of urban underground space for utilities. Tunnelling and Underground Space Technology, 1999. 14(3). [2] Kaliampakos, D. and A. Benardos. Underground space development: setting modern strategies. Design, Engineering and Environmental Aspects. 2008. New Forest, England.

Goldschmidt Conference Abstracts 2009

A559

Riverine lithium isotope systematic during continental weathering from an active orogenic belt, Taiwan

Composing and analysis of geosciences-social economy GIS of Jiangxi Province

KUO-FANG HUANG1,2*, C.-F. YOU1,2, R.-M. WANG2 2 AND C.-H. CHUNG

MEIHUA HUANG, ZIYU LIN AND TAIYANG GUAN

1

Earth Dynamic System Research Center (EDSRC) National Cheng Kung Univ., Tainan, 70101, Taiwan (*correspndence: [email protected]) 2 Department of Earth Sciences, National Cheng Kung Univ., Tainan, 70101, Taiwan Riverine lithium (Li) isotope potentially offers a unique perspective for continental weathering processes [1, 2]. Based on the investigations of the world’s large rivers [3], Li isotopic composition in dissolved load is mainly depended on the intenisty of silicate weathering and the drained lithologies. This is attributed to the high Li content in silicate minerals relative to carbonates and the preferential uptaken of 6Li by secondary clay minerals [4, 5]. However, little is known about whether and to what extent, the Li isotope ratio in river waters was affected by weathering intensity or drained lithology under different climate conditions. Taiwan is located in an active orogenic belt and its high physcial erosion and chemical weathering rates are mainly due to the tectonic uplift, active earthquake and high runoff discharge. Here we report the systematic survey of Li and its isotopes in the dissolved load along two major tributaries (Laonong and Cishan rivers) of the Kao-Ping River, Southwestern Taiwan, at both wet and dry seasons. Riverine Li contents at dry and wet seasons range from 0.91 to 18.18 µM with δ7Li of +8.2 to +20.3‰, and 0.62 to 2.45 µM with δ7Li of +13.1 to +18.2‰, respectively. Of special interest is that δ7Li in the Laonong river display higher δ7Li values at warm season. This differs significantly from the previous studies [2, 5], which shows low dissolved δ7Li when weathering is more intense because of high runoff and elvated temperature. Combining with Sr isotope and major element data for the dissolved load, our data suggests that in a highrelief, tectonically active terrain the dissolved δ7Li could be significantly influenced by drained lithologies rather than weathering intensity. [1] Huh et al. (2001) EPSL 194, 189-199. [2] Pogge von Strandmann et al. (2006) EPSL 251, 134-147. [3] Huh et al. (1998) GCA 62, 2039-2051. [4] Pistiner and Henderson (2003) EPSL 214, 327-339. [5] Kisakurek et al. (2005) EPSL 237, 387-401.

Department of Earth Science, East China Institute of Technology, Fuzhou, 344000, Jiangxi Province, China ([email protected]) Based on the massive space and attribute data of the Jiangxi special GIS, as well as powerful GIS spatial analysis function, carried through such as earth science background superimposed multi-element analysis, buffer analysis, crosslist of statistics for the administrative center of the city of Jiangxi Province, population, industrial and total agricultural output value, GDP and per capita GDP, the development of an integrated socio-economic indicators, the geological structure units, stratigraphy, lithology and ground elevation, revealed that the socioeconomic development of Jiangxi Geo-related patterns and their inherent laws. City and county administrative center in Jiangxi Province is mainly distributed in the Cenozoic sedimentary areas, hilly areas and along the geological tectonic units on both sides of the distribution of geographical boundaries, the main city and county administrative center located in geographical boundaries of tectonic units 10-kilometer buffer zone. Based on the characteristics of the control of tectonic units, in Jiangxi Province, divided into eight major tectonic belt. The space-time patterns of geoscience background of Jiangxi Province,such as Geological structure units, lithostratigraphic, topography, have different characteristics of the internal differentiation between the South and the North. The geoscience pattern restricted the resources and the environment space allocation, and further profound and lasting impact the socio-economic development of Jiangxi Province.

A560

Goldschmidt Conference Abstracts 2009

Sampling of geochemical heterogeneities within the Hawaiian Plume: A case study of 143Nd/144Nd SHICHUN HUANG AND STEIN B JACOBSEN Department of Earth and Planetary Sciences, Harvard University ([email protected], [email protected])

X.H. HILDA HUANG1, H.S. SIMON IP2 1,2 AND JIAN ZHEN YU *

The observed large isotopic variations in Oceanic Island Basalts (OIB) provide important informations and constraints on the origin, size and sampling of mantle heterogenities. As one of the best defined and studied examples of hotspot volcanism, Hawaiian volcanism plays an important role in our understanding of mantle plumes. There are large isotopic variations in the Hawaiian shield stage tholeiitic lavas. For example, the εNd variation in Hawaiian shield lavas covers over 70% of the global OIB εNd variation, e.g., Fig. 15 of [1]. In detail, each Hawaiian shield is characterized by a different distribution of εNd. The volume-weighted εNd distrubution of modern Hawaiian shield lavas is a near-Gaussian distribution, with a peak at 7.0 and an elongated tail towards low εNd (-1.5). Except for some details, this observed εNd distribution of Hawaiian shield lavas can be reproduced using the simple three-box model discussed in [2]. This model involves a continuously created and recycled crust reservoir, a depleted mantle reservoir and a primitive mantle reservoir, and subreservoirs are generated by returning melting residues, and recycling crusts into the depleted mantle. In this model, the mantle geochemical heterogeneities are randomly sampled. Further, we note that the average isotopic compositions of Hawaiian shield lavas are similar to the “matrix” composition in the model of [3], which is an enhanced version of the model of [2]. The matrix in the model of [3] is made up of subreservoirs with sizes less than 15 km. Consequently, we conclude that the isotopic variations in Hawaiian shield lavas may be the result of random sampling of a geochemically heterogeneous mantle at a smaller scale than it is sampled by the MORB volcanism. Table. Compositions of FOZO, C, Matrix and Average Hawaii 206 207 eSr Pb/204Pb Pb/204Pb eNd FOZO 9 -28 19.5 15.6 C 5 -14 19.5 15.6 Matrix 7 -21 18.7 15.55 6 -10~-14 18.2~18.6 15.43~15.50 Average Hawaii

Secondary organic aerosol formation from ethylene in the urban atmosphere of Hong Kong: A multi-phase chemical modeling study

208

Pb/204Pb 39 39 38.5 37.9~38.2

[1] Hofmann (2003) In The Mantle and Core (ed. R.W. Carlson) Vol. 2, Treatise on Geochemistry, pp. 61-101. [2] Kellogg, Jacobsen & O'Connell (2002) EPSL 204, 183202. [3] Kellogg, Jacobsen & O'Connell. (2007) EPSL 262, 328-342.

1

Atmospheric, Marine and Coastal Environment Program, Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong 2 Department of Chemistry, Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong (*correspondence: [email protected]) Ethylene is one of the most abundant anthropogenic volatile organic compounds (VOCs) in urban atmospheres. The potential of forming secondary organic aerosol (SOA) by this smallest alkene was not previously considered due to the overlook of SOA formation through in-cloud processing of soluble oxidation products. Ethylene reacts with OH radicals to form glycolaldehyde as one of its major products. Glycolaldehyde can partition into cloud water where it is oxidized to glyoxylic acid and oxalic acid and thereby contributing to SOA formation. A chemistry box model incorporating explicit multiphase reactions of relevant C2 oxygenated species is used to evaluate the SOA mass that can be formed from ethylene under the typical conditions of Hong Kong ambient atmosphere. In an idealized scenario involving five cloud cycles, SOA products in the range of 65-290 ng m-3 are predicted when assuming a cloud water content of 0.170.50 g m-3, corresponding to an SOA yield of 0.4-1.8%. The major SOA species derived from in-cloud processing of the ethylene oxidation products are oxalic acid (28 ~ 180 ng m-3) and glyoxylic acid (10 ~ 58 ng m-3). Sensitivity tests show that the SOA mass formed in the model depends strongly on the cloud liquid water content; it increases with increasing cloud period length and is less affected by the pH value of cloud droplet. The modeling results indicate that in-cloud processing is a viable pathway for SOA formation from ethylene. A more general implication is that in-cloud processing is a potentially important pathway to generate SOA, especially for places such as Hong Kong, where the annual cloud coverage is over 50%.

Goldschmidt Conference Abstracts 2009

The importance of melting of a crystalline mush on the volatile transport from an underlying intrusion 1

CHRISTIAN HUBER , OLIVIER BACHMANN 1 AND MICHAEL MANGA

2

1

Department of Earth and Planetary Science, University of California, Berkeley, USA ([email protected], [email protected]) 2 Department of Earth and Space Sciences, University of Washington, USA ([email protected]) The interaction between magmas with different compositions is an important process in the cycle of magmatic systems. Latent heat buffering of magmas cooling to near solidus temperatures prolongs the life of magma batches as crystalline mushes. We study the role of the crystallinitytemperature relationship in the overlying mush on the cooling, crystallization and volatile exsolution of an underplating intrusion. We solve numerically for the enthalpy coupling between the two magmas, the partial melting of the crystal mush and the volatile transfer from the intrusion into the overlying mush in one dimension. We find that the exsolution of volatiles from the intrusion rather than the permeability and melting of the mush is the limiting process for their transport. We also show that partial melting of the mush does not favor volatile transport but, rather, inhibits it by decreasing the local volatile volume fraction. We also show that one dimension models for volatile transport through a mush saturated with a wetting phase (silicate melt) do not take into account a channelization instability of the non-wetting phase (volatiles) due to capillary effects. This channelization instability localizes the volatiles and increases the mass and enthalpy transport through the mush.

A561

First results of a new time-of-flight noble gas mass spectrometer L. HUBER*, I. LEYA, P. WURZ AND D. ABPLANALP Physikalisches Institut, Space Reserach & Planetary Sciences, University of Bern, Switzerland (*correspondence [email protected]) Recent advances in noble gas sector field instruments comprise the development of a compressor ion source for increasing the sensitivity for light noble gases, especially He and Ne [1], and the introduction of multi-detector systems, either with multiple Faraday-Cups or Channeltrons, for simultaneous ion detection. The latter set-up has been developed to reduce analysis times and thereby increasing the accuracy of the measurements. However, compressor ion sources are technically very challenging and multi-detector systems usually suffer from alteration of the various channeltrons, which compromise precise measurements of isotope ratios and require regular calibrations. The latter usually compromises precise measurements, especially those for low gas calibrations, by producing memory in the spectrometer. In contrast, Time-of-Flight (ToF) systems enable the measurement of the total mass spectra with high transmission (there are essentially no slits) and, depending on the length of the flight tube and the dimension of the ion source, also high mass resolution. In addition, in ToF systems background gases, which are not primary objects of the analysis but which often compromise detailed noble gas studies, are measured routinely together with the isotopes of interest. We therefore developed a new type of noble gas mass spectrometer, the first Time-of-Flight machine able to measure He, Ne, Ar, Kr, and Xe isotopes with high precision and high sensitivity in static operational mode, the EGT. The ion source of the EGT is an ion trap with a variable pulse frequency (up to a few kHz) and the detector is a self-made multi-channel plate (MCP). The overall volume of the spectrometer is less than 1000 cm3 and the (calculated) overall transmission is about 80%. At the conference we will present some of the impressive facts of the EGT, i.e., the huge dynamic range of more than 106, the relatively high mass resolution of ∆m/m ~700 (at Kr), the relatively high sensitivity, and its robustness. Besides the performance in the laboratory we will also present some data from the ballon experiment P-Bace, where an identical spectrometer has been used to measure atmospheric gases in about 40 km height [2]. [1] H. Baur, EOS Transactions, AGU Volume 80 (46) [2] D.Abplanalp et al. A neutral gas Mass spectrometer to measure the chemical composition of the stratosphere, Advances in space Research, submitted

A562

Goldschmidt Conference Abstracts 2009

Crystal orientation effects on bias of δ18Ο in magnetite by SIMS

Arsenic uptake by a natural vivianite material

JASON M. HUBERTY*, NORIKO T. KITA, PHILIPP R. HECK, REINHARD KOZDON, JOHN H. FOURNELLE, HUIFANG XU AND JOHN W. VALLEY

K.A. HUDSON-EDWARDS1, S. HOUGHTON1 2 AND K.G. TAYLOR

NASA Astrobiology Institute and Wisc-SIMS, Department of Geology and Geophysics, 1215 W. Dayton St, University of Wisconsin, Madison, WI, 53706, USA (*correspondence: [email protected]) High precision in situ analyses by SIMS reveals fractionation of oxygen isotopes in magnetite due to crystallographic orientation effects. Multiple magnetite samples were analyzed conventionally (2 mg, BrF5) and found to be homogeneous in δ18O, but showed variability of 4 to 5‰ during analysis by a Cameca IMS-1280 ion microprobe (10µm spot ~ 2ng). Magnetite standard #5830 has a δ18O of 3.96 ± 0.2‰ (2SD) VSMOW by laser fluorination. δ18O values by SIMS are within bracketed 2SD errors (0.4‰) within individual grains but vary by 4 to 5‰ between grains. Tests were made to rule out possible effects due to magnetism and thickness of the sample. Crystal orientation effects in magnetite by SIMS were suggested previously and attibuted to ion channeling along <110> (Lyon et al., 1998, Int. J. Mass Spec. Ion Proc.). We used EBSD to determine the crystallographic orientation of randomly oriented magnetite grains cast in epoxy and polished. We plotted the orientation of the Cs+ beam for each grain on a stereonet centered on [111]. Raw δ18O values measured by SIMS were assigned to each beam orientation and the resulting equal area projection was contoured for measured δ18O. The results show that the highest (least fractionated) δ18O values are obtained with the Cs+ beam parallel to . corresponds to parallel planes of atoms along which the Cs+ ions are channeled. Intermediate δ18O values are obtained along . Lower δ18O values are obtained along where the incident beam is not parallel to a channeling direction. SEM images of the ionprobe pits show enhanced development of sub-micron secondary pits when the Cs+ beam is parallel to <100>, <110> or <111>. SIMS precision for δ18O in silicate minerals has improved from ±2‰ twenty years ago to ±0.3‰ 2SD today while at the same time analyses of magnetite have remained at ±2‰. The correlation between δ18O in magnetite by SIMS and crystal orientation may provide the basis for accurate correction in conjunction with EBSD, and may significantly improve SIMS magnetite data allowing in situ quartz-magnetite thermometry among other potential applications.

1

Research School of Earth Sciences at UCL-Birkeck, University of London, Malet St., London WC1E 7HX, UK ([email protected], [email protected]) 2 Department of Environmental & Geographical Sciences, Manchester Metropolitan University, Chester Street, Manchester M1 5GD, UK ([email protected]) The mineral vivianite [Fe3(PO4)2·8H2O] forms and is stable in a variety of anoxic environments such as lakes and urban water bodies [1, 2]. It has been suggested that vivianite may be an efficient sink of arsenic (As) in natural environments [3, 4]. We tested the efficiency of As(III) and As(V) uptake by a low-temperature natural vivianite material at acid, near-neutral and alkaline pH at T = 4°C, which is representative of Lake Baikal-type environments where natural vivianite is reported to occur, and 25°C, which is representative of As-polluted aquifer systems in southeast Asia. Uptake of As(III) and As(V) is pH-dependent, with higher percentage uptake occurring at pHs above 7.5, as previously reported [3, 4]. The uptake of As(III) and As(V) is also temperature-dependent. Detectable amounts of Fe, Mg, Mn and P were released during some of the acid sorption experiments, suggesting that some dissolution of the vivianite material took place. These data, together with characterization of the pre- and post-sorption solids, will yield information on the efficiencies of As uptake by natural vivianite. [1] Fagel (2005) Glob. Planet. Change 46, 315-336. [2] Taylor et al. (2003) Hydrol. Process. 17, 2049-2061. [3] Islam et al. (2007) Geochim. Cosmochim. Acta 71, A432. [4] Thinnappan et al. (2008) Appl. Geochem. 23, 3187-3204.

Goldschmidt Conference Abstracts 2009

Structure and reactivity at mineral surfaces: Kinetic, microscopic and spectroscopic investigations STEPHAN J. HUG Eawag, Swiss Federal Institute of Aquatic Science and Technology, CH-8600 Dübendorf, Switzerland Sorption of dissolved species to mineral surfaces leads to increased concentrations of reactants in a thin layer near the surface with properties which are different from those of the bulk solution. More importantly, strong and specific interactions with surface sites can lead to large changes in the structure and reactivity of adsorbed species. Surface mediated transformations on solid phases are of crucial importance for metal and nutrient cycling in the environment, and surface catalyzed reactions on synthetic solids with specially designed properties find wide application in industrial processes. This presentation will focus on the investigation of reactions on the surfaces of aqueous metal(hydr)oxides with kinetic, spectroscopic and microscopic methods. The combination of different methods is crucial, as metal(hydr)oxides can undergo photoinduced and thermal dissolution, with cycling between dissolved species and newly precipitated phases and generation of reactive species in solution and on the surface. Examples of mechanisms deduced from batch experiments and kinetic modeling of thermal and photo-induced reactions will be shown. A special focus will be on the investigation of surface complexes and reactions with spectroscopic methods and the distinction between inner- and outer-sphere surface complexes. in situ Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) is a powerful method to obtain structural information on surface complexes of small organic compounds. However, the interpretation of spectral data is often challenging and the distinction between different coordination modes is not straightforward, for example when strong hydrogen bonding is involved. in situ ATR-FTIR studies under UV-irradiation can potentially help to distinguish between surface structures. Inner-sphere complexation of organic ligands on the surface of iron(hydr)oxides appears to be an important factor for the efficient photo-transformation of adsorbed compounds. In contrast, most organic ligands are indiscriminately and completely oxidized and degraded on the surface of rutile and anatase particles under UV-A irradiation. Progress in various research groups is rapidly advancing our understanding of reactions on aqueous surfaces.

A563

The CO2 sink potential of the Indo-Tibetan collision zone YOUNGSOOK HUH School of Earth and Environmental Sciences, Seoul National University, Seoul 151-747, Republic of Korea ([email protected]) The fluvial geochemical data of major rivers draining the Himalayas and the Tibetan Plateau are compiled from literature and supplemented with data from the author’s group to explore the spatial variability in the major element and strontium isotopic compositions and in the silicate weathering rates and concomitant drawdown of atmospheric CO2. The results indicate that carbonate weathering dominates the major element compositions of these rivers, and when the silicate contributions are carefully separated, these are highest in the rivers draining the Himalayan front. The eastern Tibetan Plateau rivers are not very radiogenic in their 87Sr/86Sr ratios, their silicate contributions are low, and the CO2 consumption rates are on the order of ~100×103 mol·km-2·y-1. The two syntaxes of the Himalayas, the Indus and the Brahmaputra, have variable 87Sr/86Sr, the silicate contributions are higher than the eastern Tibetan Plateau rivers, but the total CO2 uptake rates are low because of lower runoff in the headwaters. The Ganges tributaries draining the Himalayan front can be extremely radiogenic, have higher median silicate contributions than the eastern Tibetan Plateau rivers, and the CO2 consumption rates are about twice as high. Exposure of silicate lithologies with radiogenic Sr and high runoff seems to be responsible. However, even the high CO2 consumption rates of the Himalayan front are not anomalous globally, considering the uncertainties with spot sampling and calculation of silicate fractions. The rate of CO2 draw-down by silicate weathering in the Himalayan front rivers are on the same order of magnitude as other orogenic rivers of the world, although fluxes of 87Sr are higher. The 87Sr/86Sr ratios do not necessarily correlate with the relative input from silicate weathering, indicating that 87Sr/86Sr cannot be used as a general proxy for silicate weathering. Sources of uncertainty in the analyses presented here and areas of future development will be suggested.

A564

Goldschmidt Conference Abstracts 2009

Carbonate inclusions in mantle olivines: Mantle carbonatite

Uranium precipitation and fluid composition at Maureen U-Mo-F deposit, Australia

E.R. HUMPHREYS1,2*, K. BAILEY1, C.J. HAWKESWORTH1 AND F. WALL3.

N.C. HURTIG1,2, C.A. HEINRICH1, T. DRIESNER1, V. WALL3, I. MATHISON3 AND W. HERRMANN3

1

Department of Earth Sciences, University of Bristol, BS8 1RJ (*correspondence: [email protected]) 2 The Natural History Museum, London, SW7 5BD 3 Camborne School of Mines, University of Exeter, TR10 9EZ Primary igneous carbonate occurs as inclusions within xenocrystic olivines in a leucitite lava from the Calatrava Volcanic Province, Spain. All olivines in the lava show xenocrystic textures including embayments and reaction rims; olivine is not a cognate phase in the lava. Xenoliths of spinel lherzolite are also present, ranging up to several centimetres in diameter. They show pervasive reaction textures against the lava and along grain boundaries within the xenoliths. Xenocrystic olivines have Mg rich cores Fo86-88 with iron enriched rims Fo72-80. Conversly olivines from the spinel lherzolites at Calatrava have Fo90.4-90.5, which are typical of off-craton peridotite xenoliths [1]. Carbonate compositions typically are calcite, but minor element contents vary between inclusions; notably iron, magnesium and strontium (1-5wt%). Carbonate is never seen in isolation and is often associated with other mineral phases such as Cr-spinel, apatite, phlogopite, clinopyroxene and glass. Texturally, carbonate inclusions are fresh, with occasional examples of recrystallised carbonate. The inclusions have globular profiles and range from 700-10µm in diameter, whereas host olivines on average measure 5mm in diameter. The inclusions are not the result of the cross sectioning of embayments as they do not show the iron enrichment typical of contact with the lava seen in the embayments. Inclusions also contain euhedral Cr-spinel whereas all groundmass spinel is titano-magnetite. Finally, carbonate is not present as a groundmass phase. Carbonate inclusions were enclosed in olivines during their growth and as such represent fresh examples of carbonate and associated mineral phases crystallising under mantle conditions. [1] Pearson, D.G. et al. (2005) Mantle sample included in volcanic rocks: Xenoliths and diamonds. Carlson, R. (ed) Treatise on Geochemistry. Elseiver.

1

ETH Zurich, Department of Earth Sciences, Clausiusstr. 25, 8092 Zurich, Switzerland 2 Faculty of Science, University of Iceland, 101 Reykjavik, Iceland (*correspondence: [email protected]) 3 Mega Uranium, c/- Taylor Wall & Associates, Brisbane, QLD 4000, Australia The expected shortage of petroleum and the growing demand for energy has refuelled the interest in uranium resources and exploitation. Unconformity-related U deposits include the largest high grade U ore bodies world wide. They provide a major and poorly explored low-cost uranium resource. Most deposits are of Proterozoic age. The general formation model comprises mixing of oxidized U bearing fluids with reduced basement-derived fluids at the intersection of the unconformity with deep-rooted faults. Maureen deposit is the largest of a series of U occurences along the unconformity between the Proterozoic Georgetown Inlier and the Late Palaeozoic Newcastle Range Volcanic Suite in Queensland, Australia. Insights into U transport and precipitation at Maureen are obtained by combining field observation, mineral geochemistry and LA-ICP-MS analysis of fluid inclusions from this young and well-preserved deposit. The ore forms lenticular bodies preferably along east-west striking steep faults and spreads horizontally on top of basement highs. Devonian quartz conglomerates directly overlying the unconformity are preferentially mineralized. A halo of fluorite, chamosite and dickite surrounds the high grade U and Mo mineralized zones. The ore mineral assemblage comprises an Fe-bearing molybdenum sulfide, arsenian pyrite, arsenopyrite, anatase, goyazite, fluorite, and a sub-µm scale intergrowths of U and Ti oxides. Reduced mineral assemblages and coexistence trails of intermediate-salinity two-phase fluid inclusions and carbonic vapors indicate interaction of two coeval fluids. Fluid inclusions in fluorite and quartz homogenize at 260 ± 40°C. LA-ICP-MS results from quartz-hosted inclusions show a covariation of U and Mo in the fluid at a 1:10 ratio, indicating U and Mo co-precipitation. Primary low-salinity fluid inclusions hosted by fluorite show U-Mo ratios close to 1, corresponding most closely to the U/Mo ratio in high grade ore and probably representing the parental ore fluid.

Goldschmidt Conference Abstracts 2009

On the emanation of thoron (220Rn) from precipitates STEPHAN HUXOL1*, EDUARD HÖHN1, HEINZ SURBECK2 1,3 AND ROLF KIPFER 1

Eawag, Swiss Federal Institute of Water Science and Technology, CH-8600 Dübendorf, Switzerland (*correspondence: [email protected]) 2 Nucfilm Ltd., CH-1792 Cordast, Switzerland 3 Institute of Isotope Geology and Mineral Resources, Swiss Federal Institute of Technology Zurich (ETH) Thoron (220Rn, half-life 55.6 s) is a shorter-lived isotope of the radioactive noble gas radon (the longer-lived isotope is 222 Rn; half-life 3.6 d). These isotopes are found in soil-near air and soil-gas, and, in case of radon, its occurrence in groundwater is well known. We expected to find also thoron in groundwater. But, due to their presence in different decay chains (232Th and 238U-series, respectively), the geophysical and geochemical behaviour (e.g. species, number of precursors, half-life, solubility etc.) of their precursors differs, too. While radon has been a subject to research for a long time, the emanation of thoron from solid material containing the precursor 224Ra and its occurrence in aquatic systems is not well known. To elucidate, two working hypotheses for the emanation of thoron into aquatic systems were devised: Because of their low solubility of in oxic groundwater, the thoron precursors, 232 Th and its daughter nuclides, will remain located at almost the same positions in the crystal lattice. Due to its short halflife, thoron has also a restricted mobility. Therefore, occurrence and concentration of thoron in groundwater are function of the distribution of the precursors in aquifer material (“primary emanation”). The second hypothesis is based on the somewhat enhanced solubility of the radon and thoron precursor radium (224, 226, 228Ra) in anoxic groundwater. Upon subsequent contact with oxygen, radium tends to coprecipitate with Mn and Fe oxide/hydroxides. Thus, the emanation of thoron to the water phase could be intensified by locally accumulated radium, which is attached to surface coatings of the precipitates (“secondary emanation”). Preliminary field measurements with a RAD7 solid-state detector coupled to a RadAQUA unit (closed gas loop, in contact with continuous flowing, sprayed water) in different environments (oxic/anoxic groundwater, anoxic spring water) showed that thoron can be detected in anoxic spring water. This supports the second hypothesis. To get a better insight into thoron emanation processes under anoxic conditions, we will accomplish column experiments with ferric and manganese sand.

A565

An in vivo and in vitro evaluation of mineral-induced formation of reactive oxygen species S.N. HYLTON*, M.A. SCHOONEN AND S.E. TSIRKA Stony Brook University, Stony Brook, NY 11790, USA (*correspondence: [email protected])

Background Given the occurrence of several recent major natural disasters and increasing environmental alarm, the link between the environment and human health is of no doubt important concern. And while the links between specific environmental factors and specific diseases might be clear, such as asbestos and coal, there still remains debatable links between many other earth materials and the effects they have on the human body.

Discussion of Results The role of environmentally-induced reactive oxygen species (ROS) as important bio-markers of toxicity is investigated. ROS are generated by macrophages and neutrophils as a first line of defense in response to foreign substances that have been phagocytosed. However, while ROS can be very helpful in destroying foreigners in the body, they can also damage the environment (tissues, cells, etc) in which they were produced. Here, we present different assays to measure the production of ROS. We aim to draw a parallel connection of the generation of ROS to potential health risks of environmental particulates acellularly utilizing a novel probe 3’-(p-Aminophenyl) Fluorescein (APF), in vitro using lung epithelial cells and in vivo.