Goldschmidt Abstracts 2010 – W

Goldschmidt Conference Abstracts 2010

Quantifying Ag uptake and storage in marine diatoms MEGHAN E. WAGNER* AND INGRID L. HENDY Dept. of Geological Sciences, University of Michigan, Ann Arbor, MI 48109, USA (*correspondence: [email protected]) The biological pump has been identified as a potential mechanism for controlling atmospheric CO2 between glacialinterglacial cycles, with diatoms playing a central role in this process. However, dissolution of the remains of siliceous organisms in the water column and sediments can make reconstructing their past productivity a difficult task. A new proxy is therefore required to overcome this limitation: silver shows promise as this new proxy, in part because similarities between Ag and silica in water column profiles have suggested a link with diatoms. Enrichment of Ag is therefore predicted to occur in sediments underlying regions of high diatom productivity. However, studies have yet to establish an unequivocal route for the delivery of Ag to sediments. This study aims to answer the question of whether diatoms are the main source of Ag to marine sediments. We cultured the marine diatom Thalassiosira pseudonana and added AgNO3 to the growth medium at varying concentrations. Diatoms were collected approximately 24 hours after reaching exponential growth phase and washed with diethylenetriaminepentaacetic acid (DTPA) to remove surface adsorbed Ag. Samples of the growth medium were also taken to determine actual Ag concentration during growth. The diatoms were digested first in HNO3 to isolate the organic material, and then in NaOH to dissolve the silica frustules. Each fraction was subsequently analyzed by ICP-MS for Ag concentration. Our results will aid in quantifying the amount of Ag that diatoms take up from their surroundings, and determine whether Ag is stored in the body or in the diatom frustule.

A1091

Reactive oxygen species generation by elemental iron and silver nanoparticulates T. DAVID WAITE*, ADELE M. JONES AND SHIKHA GARG School of Civil & Environmental Engineering, The University of New South Wales, Sydney, NSW 2052, Australia (*correspondence: [email protected]) Zero-valent iron nanoparticles (nZVI) are recognized to produce hydrogen peroxide on reaction with oxygen with the subsequent production of strongly oxidizing hydroxyl radicals as a result of the reaction of the so-produced H2O2 with ferrous iron concomitantly produced on oxidation of Fe° [1]. While the extent of hydroxyl radical production via this Fenton process is limited because most of the reducing capacity of the elemental iron is utilized in the reduction of oxygen to water rather than hydrogen peroxide, catalysts such as polyoxometallates have been shown to increase the proportion of oxygen reduced to H2O2 thereby increasing the rate of hydroxyl radical production [2]. The hydroxyl radicals so produced are effective in degrading organic contaminants and in reducing bacterial viability [1, 3] Other zero valent nanoparticulates, particularly those of silver and gold, are more effective in producing H2O2 than nZVI with the extent of production strongly dependent upon pH and solution composition as well as the nature of the nanoparticulates. The processes leading to the production of H2O2 on reaction of nanoparticulate silver with oxygen are described here and the implications of this production of H2O2 to the bactericidal properties of nanosilver are discussed. [1] Joo, Feitz & Waite (2004) Environmental Science & Technology 38, 2242–2247. [2] Lee, Kim & Choi (2007) Environmental Science & Technology 41, 3335–3340. [3] Auffan, Achouak, Rose, Chanéac, Waite, Masion, Woicik, Wiesner & Bottero (2008) Environmental Science & Technology 42, 6730–6735.

A1092

Goldschmidt Conference Abstracts 2010

Bosea sp. WAO oxidizes metal sulfides at neutral pH

Collaboration of EarthChem and EARTHTIME to develop a geochronology and thermochronology database

A.B. WALCZAK*, N. YEE AND L.Y. YOUNG Rutgers University, New Brunswick, NJ 08901 USA (*correspondence [email protected], [email protected], [email protected]) Trace heavy metals such as lead and cadmium are typically toxic to humans at even low levels in the environment. The geochemical cycling of trace metals is closely associated with the sulfur cycle due to the reactions between the metals and reduced sulfur compounds in anoxic sediments and pore water [1]. When present in anoxic sediments the metals are bound as monosulfides. However, due to microbial activity or events where oxygen is introduced, the metal sulfides can be oxidized to release a soluble metal ion and sulfate [1]. If microorganisms have a role in oxidizing these metal-sulfides at circumneutral pH then the metals could be more readily bio-available, resulting in a higher risk of human exposure. Bosea sp. WAO was previously isolated in our laboratory from an arsenic containing shale in the Newark Basin of New Jersey, based on its ability to autotrophicly oxidize arsenite to arsenate [2]. Strain WAO is shown here to autotrophically grow on several reduced sulfur sources. The growth yield per electron transferred based on protein analysis was determined for sodium sulfide, sulfur, and sodium thiosulfate. Its ability to oxidize these reduced sulfur sources at circumeutral pH suggests that microorganisms can have an important role in the oxidation reactions of the sulfur cycle. This isolate was used to examine the role of microorganisms in the mobilization of heavy metals from galena (PbS) and greenockite (CdS) at neutral pH. The microbially mediated oxidation of PbS and CdS was compared to the oxidation rate of background and sterile controls. Active cultures containing either PbS or CdS were shown to completely oxidize the 1mM of metal-sulfide to sulfate measured by ion chromotography (IC) within 25 days of incubation. No release of sulfate was measured in the background and sterile controls during the incubation period. This suggests that microorganisms can play a role in oxidizing metal sulfides and releasing hazardouse metals into solution at circumneutral pH. [1] Canavan et al. (2007) Science of the Total Environment 381, 263–279. [2] Rhine et al. (2008) Environmental Sci. Technol. 42, 1423–1439.

J.D. WALKER1*, J.M. ASH1, J. BOWRING2, S.A. BOWING3, A.L DEINO4, R. KISLITSYN1, A.A. KOPPERS5 AND K. LEHNERT6 1

Geology, University of Kansas, Lawrence, KS, USA (*correspondence: [email protected]) 2 Computer Science, College of Charleston, Charleston, SC, USA 3 EAPS, MIT, Cambridge, MA, USA 4 Berkeley Geochronology Center, Berkeley, CA, USA 5 Marine Geology and Geophysics, Oregon State University, Corvallis, OR, USA 6 Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY, USA One of the most difficult aspects of developing data reporting and databases for geochronological and thermochronological studies is to capture all of the metadata needed to completely document both the analytical work as well as the interpretations of the analyst. Such information is available in the data reduction programs used by researchers, but has proven difficult to harvest into either publications or databases. For this reason, the EarthChem and EARTHTIME efforts are collaborating to foster the next generation of data management and discovery for age information by integrating data reporting with data reduction. EarthChem workers have met with groups working on the Ar-Ar, U-Pb, and (U-Th)/He systems to establish data reporting requirements as well as XML schemas to be used for transferring data from reduction programs to database. At present, we have prototype systems working for the UPb_Redux, ArArCalc, MassSpec, and Helios programs. In each program, the user can select to upload data and metadata to the Geochron system hosted at EarthChem (http://geochronportal. org). There are two additional requirements for upload. The first is having a unique identifier (IGSN) obtained either manually or via web services contained within the reduction program from the SESAR system (http://geosamples. org). The second is that the user selects whether the sample is to be available for discovery (public) or remain hidden (private). Search for data at the Geochron portal can be done using age, method, mineral, or location parameters. Data can be downloaded in the full XML format for ingestion back into the reduction program or as abbreviated tables.

Goldschmidt Conference Abstracts 2010

Clues to the formation of the terrestrial planets from highly siderophile elements R.J. WALKER1, I.S. PUCHTEL1, J.M.D. DAY1, M.G. GALENAS1 AND A.D. BRANDON2 1

Dept. of Geology, Univ. of Maryland, College Park, MD, 20742 USA ([email protected]) 2 Dept. of Earth & Atmos. Sciences., Univ. of Houston, Houston, TX 77204 USA The highly siderophile elements (HSE) are normally strongly partitioned into metal relative to silicate. Yet the abundances of these elements estimated for Earth’s primitive upper mantle (PUM) and the martian mantle are only about 200 times lower than those of chondrites. These abundances are considerably higher than would be expected from low P-T metal-silicate partitioning. In contrast, lunar basalts, volcanic glasses and highlands crust suggest that abundances in the lunar mantle may be more than twenty times lower than in the terrestrial PUM. The dominantly chondritic 187Os/188Os estimated for the terrestrial, lunar and martian mantles require that their time integrated Re/Os were also within the range of chondritic meteorites. Most HSE in the projected terrestrial PUM appear to be present in chondritic relative abundances, although Ru/Ir and Pd/Ir are slightly suprachondritic. Similarly suprachondritic Ru/Ir and Pd/Ir have also been reported for some lunar impact melt breccias that were created via large basin forming events. This could reflect a nebular signature outside of the range of known chondrites in the sources of the HSE. Hypotheses to account for the absolute and relative abundances of HSE present in Earth’s mantle include inefficient core formation, lowered metal-silicate D values resulting from metal segregation at elevated temperatures and pressures, and late accretion of materials with broadly chondritic bulk compositions after the cessation of core segregation. Synthesis of the large database now available for HSE in the terrestrial mantle, lunar samples, martian meteorites, and possible mantle samples from the HED parent body reveals that each of the main hypotheses has flaws. Although we favour continued accretion subsequent to the cessation of core segregation as the dominant process, other processes must also have had strong influences. Timing of the dominant contributions from late accretion remains poorly constrained. Whether genetic affinities for late accreted materials can be extracted from available rocks also remains to be seen.

A1093

Cu isotope systematics of the Butte Mining District, Montana A.J. WALL1*, P.J. HEANEY1, R. MATHUR2, C.H. GAMMONS3 AND S.L. BRANTLEY1 1

Center for Environmental Kinetics Analysis, Dept. of Geosciences, Penn State Univ., University Park, PA, 16802, USA (*correspondence: [email protected]) 2 Dept. of Geology, Juniata College, Huntingdon, PA, 16652, USA 3 Dept. of Geological Engineering, Montana Tech of The University of Montana, Butte, MT, 59701, USA We present for the first time Cu isotope values of waters and mineral specimens from the Butte Mining District, Butte, Montana. Our goal is to demonstrate the usefulness of Cu isotopes to determine sources of Cu in stream and ground waters and to assess the degree of Cu-sulfide weathering throughout the mining district. We collected waters from the Berkeley Pit lake, monitoring wells near the lake, and stream samples from Silver Bow Creek and the Upper Clark Fork River downstream of the Butte mine. In addition, we collected Cusulfate salts from within the mine and on the flood plain 30 to 60 km downstream from Butte. Cu-bearing sulfide minerals were collected from within the active mine and from an archived collection of hand samples from the underground workings. The !65Cu values were measured using a Finnigan Neptune MC-ICP-MS. Isotope values have a 2" error of 0.14‰. Primary chalcocite (Cu2S), chalcopyrite (CuFeS2), and bornite (Cu5FeS4) samples from 700 to 1500 meters depth have !65Cu values that range from -0.30 to 0.37‰, whereas supergene chalcocite closer to the surface has values between 5.07 and 5.64‰. !65Cu values of Berkeley Pit waters and groundwater samples surrounding the pit lake range from 1.56 to 2.32‰. A stream water sample approximately 5 km downstream from the Berkeley Pit has a value of 1.22‰ and surficial Cu-salt samples from weathered mine tailings deposited along the stream approximately 30 km and 60 km below Butte have values of 0.40‰ and 0.32‰ respectively. Applying published fractionation factors from previous studies to our isotope results, we conclude that the dominant source of aqueous Cu in the immediate mine district is from rapid oxidative weathering of primary sulfide minerals. The isotopic value of the water sample 5 km downstream from Butte may indicate Cu scavenging by sorption to Fe oxides. The source for Cu-rich salts in the flood plain is likely the highly weathered mine tailings deposits from which most of the isotopically heavy Cu (65Cu) has been leached away.

A1094

Goldschmidt Conference Abstracts 2010

Atomistic simulation of metalcarbonate cluster formation

Thermobarometery of Hawaiian spinel peridotite xenoliths

A.F. WALLACE1*, P. RAITERI2, J.D. GALE2, J.J. DEYOREO3 AND J.F. BANFIELD1,4

S.W. WALLACE1*, M. BIZIMIS1 AND N.J. TIBBETTS2

1

Earth Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA (*correspondence: [email protected]) 2 Nanochemistry Research Institute, Department of Chemistry, Curtin University of Technology, Perth, WA, Australia ([email protected], [email protected]) 3 Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA ([email protected]) 4 Department of Earth and Planetary Sciences, University of California-Berkeley, Berkeley, CA 94720, USA ([email protected]) It is now widely recognized that the carbonate mineral constituents of many biomineralized tissues form by a twostage crystallization process that involves the nucleation and structural reorganization of transient amorphous phases. The extent to which similar crystal growth processes occur ex vivo is not yet fully realized; however, they may be prevalent in both natural and engineered environments where fluids can become highly-supersaturated with respect to M (II)CO3 phases (e.g. soil pore waters, CO2 sequestration reservoirs etc.). The nature of the amorphous to crystalline transition remains controversial, as both solid state and dissolution / reprecipitation mechanisms have been proposed. Yet, an understanding of the underlying processes driving the structural reorganization is essential to interpretation of compositional signatures that are frequently used as indicators of Earth's climate history. This study uses molecular dynamics simulations to investigate the nucleation and structural evolution of metalcarbonate clusters in aqueous solution. We examine both CaCO3, which exhibits extensive polymorphism, and FeCO3, which does not. Comparison of these two end-member systems provides an opportunity to identify common processes related to the amorphous to crystalline transition, and perhaps discern those that are involved in polymorph selection. Clusters are grown from unbiased simulations of highly concentrated solutions, and in an ion-by-ion fashion using umbrella sampling. We report changes in the cluster hydration state and distribution of ion-pair bonding environments as a function of cluster size and simulation time.

1

Dept. Of Earth and Ocean Sciences, Univ. of S. Carolina, Columbia, SC 29208, USA (*correspondence: [email protected]) 2 NHMFL and Florida State Univ., Tallahassee, Fl 32310, USA ([email protected]) Mantle peridotite xenoliths found within the rejuvenated stage lavas on the island of O’ahu, Hawaii provide a unique window into the oceanic mantle. These peridotites are thought to represent variably metasomatized fragments of the Pacific lithosphere, while some samples with highly unradiogenic 187 Os/188Os may be fragments of an ancient recycled oceanic lithosphere that is brought up by the plume [1]. Here we present high precision Ca concentration data on high purity olivine separates from Hawaiian peridotites obtained by standard addition HR-ICP-MS. Together with clinopyroxene (cpx) and orthropyroxene major and trace element data, we attempt to reconstruct the P-T range of the Hawaiian spinel peridotites in order to better constrain the compositional variability of the Hawaiian lithosphere with depth. We use the Ca-in-olivine barometer [2] and the cpx-opx thermometer (TBKN)[3]. The Ca distribution between olivine and cpx (DCaol/cpx) shows no correlation with calculated equilibration temperatures. It also shows no correlation with other highly incompatible elements (e.g. Sr, Ba, Ce) while the DCeol/cpx approaches 0.0005, close to experimental values [4]. These data argues against any disturbance of the olivine Ca contents by post-melting processes and are taken to reflect equilibration at mantle P-T. Pressures calculated for the SLC peridotites show a deeper origin, (up to 32kbar) than the Pali vent peridotites (7 to 15kbar). This is consistent with the presence of deeper garnet pyroxenites found at SLC. Interestingly, the Cr-in-CPX barometer [5], shows an overall similar pressure range as the Ca-in-olivine barometer, even in spite of the Crin-CPX barometer not having been calibrated in the spinel stability field. Further work will constrain the relationship between P-T, depletion and isotope systematics in the Hawaiian lithosphere and the processes that lead to its present compositional heterogeneity. [1] Bizimis et al. (2007) EPSL 257, 259–273. [2] Kohler & Brey, (1990) GCA 54, 2375–2388. [3] Brey & Kohler (1990) J. Petrol. 31, 1353–1378). [4] McDade et al. (2003) Phys. Earth Planet. Init. 139, 129–147. [5] Nimis & Taylor (1998) Contributions to Mineralogy & Petrology 139, 541–554.

Goldschmidt Conference Abstracts 2010

Modelling DIC and DOC transport from the Baltic Sea catchment

A1095

New evidence for a Cambrian suture associated with the North Qaidam UHPM belt

TERESIA W€ LLSTEDT1, CARL-MAGNUS M… RTH1,2, GUY SCHURGERS3, BENJAMIN SMITH3 1,4 AND CHRISTOPH HUMBORG

E.O. WALSH1 AND C.A. MENOLD2 1

1

Dep of Geological Sciences, Stockholm Univ., Sweden (*correspondence: [email protected]) 2 Baltic Nest Institute, Stockholm Resilience Centre, Sweden 3 Dep of Earth and Ecosystem Science, Lund Univ., Sweden 4 Dep of Applied Environmental Sciences, Stockholm Univ., Sweden The aim of this study is to develop a model, simulating the stream concentrations of dissolved inorganic and organic carbon (DIC and DOC) in all major watersheds draining into the Baltic Sea. Available data on general water chemistry are applied in the CSIM model [1] to simulate DIC concentrations. A DOC model [2] is implemented in the LPJ-GUESS dynamic global vegetation model [3, 4] to simulate production of DOC as well as sorbed organic carbon in the soil. The fluxes of DOC are then applied in the CSIM model for integration over the watersheds in the Baltic Sea catchment area. Modelled concentrations of DIC show reasonable agreement with observed concentrations (Fig. 1). These results will be presented along with results for DOC in selected catchments. Further, temporal and spatial variability will be discussed.

Figure 1: Modelled (x-axis) versus observed (y-axis) DIC concentrations (mmol L-1), RŒ ne river (Sweden) [1] Mšr th et al. (2007) Ambio 36, 124Ð133. [2] Yurova et al. (2008) Water Res Res 44, W07411 [3] Smith et al. (2001) Global Ecol. Biogeogr. 10, 621Ð 637 [4] Sitch S et al. (2003) Global Change Biol. 9, 161Ð 185.

Cornell College, Mount Vernon, IA 52314 (*correspondence: [email protected]) 2 Albion College, Albion, MI 49224 Although recent progress has been made in understanding the Paleozoic tectonic formation of northern Tibet, uncertainty remains regarding the pre-Devonian history of the area. We present here new evidence for a Cambrian suture in the Qaidam-Qilian terrane, ~400 km southwest of the early Paleozoic North Qilian, Franciscan-type ophiolite. Of particular significance is the juxtaposition of this Cambrian ophiolite complex with the North Qaidam ultrahigh-pressure (UHP) metamorphic belt across the Luliang Shan detachment, which is the structure believed to have emplaced the UHP rocks into the lower crust. The ophiolite complex, which has been metamorphosed to epidote-amphibolite facies, consists of four mappable units: (1) serpentinized ultramafic rocks including quartz-phlogopite veins; (2) meta-gabbro containing rare plagiogranite; (3) a sheeted dike complex, and (4) a thin, discontinuous sequence of vesicular basalt interlayered with metasediments and marble. Whole-rock geochemistry of the meta-basalts suggests formation in a supra-subduction zone (SSZ) setting; for example, Ti concentrations are lower than typical mid-ocean ridge basalt (MORB), and V and Th are higher [1, 2]. Plagiogranite samples from the meta-gabbro unit were collected at two localities ~20 km apart, and zircons from these samples were dated by SHRIMP at Stanford. Zircons were generally fragmented, oscillatory-zoned, prismatic grains ~100 µm wide by up to ~200 µm long. Low U content produced large errors on individual spot ages, but the samples yielded weighted mean ages of 514 ± 9 Ma (MSWD = 1.8) and 519 ± 8 Ma (MWSD = 1.06). Zircon trace element geochemistry plots in the oceanic crust field of Grimes et al. 2007 [3]. [1] Pearce (2003) GSA Special Paper 373, 269Ð 293. [2] Metcalf & Shervais (2008) GSA Special Paper 438, 191Ð 222. [3] Grimes et al. (2007) Geology 35, 643Ð 646.

A1096

Goldschmidt Conference Abstracts 2010

Distribution of K, Rb, and Cs within Savannah River Site soils inferred from acid-leaching, K-Ar, and isotope-exchange studies

Sedimentary facies analysis and evolution of Permian in Ziqiu Section Changyang County, Hubei Province

J.M. WAMPLER*, EIRIK KROGSTAD, TOM NAUMANN, LAURA K. ZAUNBRECHER AND W. CRAWFORD ELLIOTT

School of Resources and Environment Engineering, Hefei University of Technology, P.R. China (*correspondence: [email protected])

Department of Geosciences, Georgia State University, Atlanta, GA 30303, USA (*correspondence: [email protected]) Most (>80%) of the K in five samples from upland soils of the Savannah River Site in South Carolina is in unaltered remnants of primary minerals, as shown 1) by resistance of the K to strong-acid leaching at elevated temperature and 2) by KAr age values for the clay fractions near 300 million years, close to the mean of K-Ar age values for muscovite concentrates from the Georgia kaolin belt [1, 2]. We infer that much of the K in the soil samples is in hydroxy-interlayered vermiculite (HIV) formed by chemical weathering of detrital mica from the Appalachian Piedmont, a provenance closely similar in time and space to that of the kaolin-belt muscovite. Removal of most of the Cs and Rb from the soils by acid leaching under conditions insufficient for removal of most of the K and radiogenic Ar indicates that Cs and Rb are largely not in unaltered remnants of primary minerals. This and very high Cs/K and Rb/K ratios, relative to crustal abundances, in the leachates indicate that Cs and Rb were selectively held by the soils as K was removed during weathering. Acid leaching at lower temperatures and a Rb isotope exchange study show that very little of the Cs and Rb in the soils is in ordinary cation-exchange sites. Little (<10%) of the K, Rb, and Cs in the soils was released by leaching with HNO3 (0.55 mol/L) at temperatures from 23°C to 70°C. The patterns of release with increasing time and temperature were similar for the three alkali metals. Under conditions similar to those of the natural soil environment, exchange of added 85Rb with a small fraction (<5%) of the soil Rb was found to have occurred in the first two hours after addition. Thereafter, the degree of exchange slowly increased until after two months the added 85Rb had exchanged with a little over 10% of the soil Rb. These experiments indicate that most of the Cs and Rb cations are located in sites where both chemical exchange with hydronium ions and exchange of Rb isotopes is very slow at natural soil temperature. Such sites may be near the apices of interlayer wedges within HIV. [1] A.A. Hassanipak (1980) Ph.D. thesis, Georgia Institute of Technology, Atlanta [2] A.M. Elser (2004) Ph.D. thesis, Georgia State University, Atlanta

Q. WAN*, L.J. ZHANG AND W.L. KONG

The Permian of Ziqiu section at Changyang County, Hubei Province is composed of the Qixia, Maokou, Wujiaping and Changxing Formations. By use of strata study on the field outcrops and microfacies analysis, Permian in Ziqiu section of Hubei Province, lithofacies can be recognized as bioclastic grainstone, micrite calcisiltite, bcalcirud, silica and calcareous shale. According to the sedimentary environment analysis, three kinds of sedimentary environments were identified, which include carbonate slope, platform and basin, the Middle Permian have mainly deposited on the carbonate slope and basin, Upper Permian have mainly deposited on the carbonate slope and basin. Sedimentary evolution of Lower-Middle Permian and Middle-Upper Permian indicates that two sedimentary cycles of transgression and regression occurred in the Permian. This research was supported by the National Natural Science Foundation of China (40572076) and the Natural Science Foundation of Anhui Province, China (9075507).

Goldschmidt Conference Abstracts 2010

A1097

Isolation and characterisation of a bioflocculant M-2 produced by Galactomyces sp

Interfacial properties of alkali halide brines in confined nanopores

YINGXIN WAN

Department of Chemistry, Drexel University, Philadelphia, PA 19104

College of Arts and Science of Beijing Union University, Beijing, 100083, China ([email protected]) Microbial flocculants are biodegradable and their degradation products are harmless to the ecosystem. Some of the microbial flocculants have advantages over other types of flocculants and can be produced economically in large scale culture. A bioflocculant, M-2, was produced from a strain of bioflocculant-producing microoganism isolated from activated sludge and identified as Galactomyces sp.. M-2 had a good flocculating capability and could achieve a flocculating rate of 95% for kaolin suspension at a dosage of only 0.3 ml/l. Bioflocculation microorganism also had high turbidity and color removal ratio when treating in wastewater and soil suspension. The flocculating activity was observed most highly at pH 6.0 and markedly enhanced by the addition of Ca2+. The production of bioflocculant by Galactomyces sp. was approximately parallel to the cell growth. The isolate produced the polysaccharide during the late logarithmic growth phase. The bioflocculant was purified to homogeneity by ethanol precipitation. The major component of M-2 was found to be polysaccharide Infrared spectrum analysis showed the presence of carboxyl and hydroxyl groups in the bioflocculant, and the S.E.M. studies showed that the polymer has a porous structure with small pore-size distribution indicating the compactness of the polymer. The bioflocculant is thermo-stable and 90% of its activity remains after heating at 100°C for 20 min. M-2 is nontoxic and can be used in food industries for suspended solids (SS) recovery. This study was supported by the Natural Science Foundation of Beijing Municipal Commission of Education (KM201011417005).

MATTHEW C.F. WANDER AND KEVIN L. SHUFORD

Bridging aqueous geochemistry and battery science, we are studying the properties of aqueous alkali halide brines in contact with a family of carbon electrode geometries using classical molecular dynamics simulations. These simulations will focus on issues of capacitance and transport within these different environments. The selection of electrolytes from within two atomic groups of elements, allows us to look at size specific trends within those specific geometric environments. The advantage of using carbon, despite its poor geochemical relevance, is its importance in battery chemistry, as well as its ability to control the shape of the interfacial region without loosing topological realism or site-specific atomic information. We intend to study planar graphite sheets, carbon nanotubes of various sizes, and a variety of schwarzite forms to represent the variety of surfaces that may be encountered with a real porous-graphite electrode. By controlling the geometry, we hope to be able to determine fundamental properties of electric double layer behavior at an atomic scale and be able to compare those results with continuum physics models of interfacial properties.

A1098

Goldschmidt Conference Abstracts 2010

Application of primary geochemical halo to gold exploration at Xincheng gold deposit, China

Multistage metamorphic evolution of garnet peridotite from Altyn Tagh UHP terrane, NW China: Records related to slab subduction and exhumation history

C. WANG*, J. DENG AND L. YANG State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, PRC (*correspondence: [email protected])

C. WANG1,2, L. LIU1* AND D.L. CHEN1 1

Primary geochemical halo is one of the most important development directions of metallogeny to explore more new mineral resources lying deep within the crust, especially to the hidden deposit [1-3]. It is being routinely applied to gold exploration programmes at Xincheng gold deposit with 87 t Au metals, Jiaodong gold province, China. Sampling of fresh rock for multi-element analysis is undertaken in all finished and ongoing exploration engineering, including drilling and galleries. Samples are analyzed by ICP-MS for 18 elements. The primary geochemical halo zoning sequence suitable for the mining area above -800m level is Au–Ag–Cu–Sb–Bi– Te!As–Pb–Mo!Ba–Se!Mn–Co–Zn–Ni at Xincheng gold deposit. In addition, the primary halo superimposed model from a typical ore body shows that there appear two circumstances between two ore bodies, one is superimposition of the trail halos and the front halos, and the other is the superimposition of the front, trail and near-ore halos. The former might indicate the existence of other ore bodies underneath, whereas the latter might indicate the existence of not only blind ore bodies below the known ore body but also small ore bodies between two large ore bodies. There are coexisting strong anomalies of typical front halo As element and strong anomalies of typical tail halo Mo elements in the primary geochemical halo zoning sequence at Xincheng gold deposit, which can be interpreted as a sign that there is a large extension of gold ore at depth. Some metallogenic prognostic targets delineated on the basis of such consideration were successfully verified. This research is jointly supported by the National Basic Research Program (No. 2009CB421008), the 111 Project (No. B07011), and China Postdoctoral Science Foundation funded project (No. 20090460400). [1] Li et al. (2006) Beijing: Geological Publishing House, pp.1–146. [2] Schmid & Taylor (2009) Journal of Geochemical Exploration 101, 91–92. [3] Deng et al. (2009) Journal of Geochemical Exploration 102, 95–102.

State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi’an 710069, P R China (*correspondence: [email protected]) 2 Xi’an Center of Geological Survey, China Geological Survey, Xi’an 710054, P R China

Garnet peridotite associated with garnet pyroxenite, and garnet-bearing felsic gneiss, crops out as lenses in the Proterozoic gneiss from South Altyn Tagh HP-UHP metamorphic belt [1, 2, 3, 4, 5]. Parageneses of minerals from garnet peridotite indicate that the rock has experienced the prograde and retrograde reactions during metamorphism. The pre-subducation stage is represented by relict spinel peridotite assemblage of Ol+Cpx+Opx+Spl as inclusions in garnet, and suggests that the rock was formed at the upper mantle at temperatures as high as about 1100#. The peak stage is garnet peridotite with a coarse-grained assemblage of Grt+Ol+Opx+Cpx±Mgs. Some exsolution rods of rutile occurred in the Grt. Magnesite is rimmed by dolomite and orthopyroxene and suggesting the peak stage at 3.8-5.1GPa and 880-970# by P-T estimates. The post-subduction stage is a fine-grained neoblast assemblage of Grt+Ol+Opx+ Cpx±Spl±Amp±Prg which indicate the peridotite continued to uplift gradually to the crust and was emplaced in a shallow level of the upper crust. Mineral parageneses and P-T estimates suggest that previous ultramafic intrusion from the mantle invaded the continental basement and was subducted together with the upper crust to depths over 100 km and experienced ultra-high pressure metamorphic, and then followed by exhumation to the Earth’s surface. The multistage metamorphic history indicates that the garnet peridotite preserved a unique subduction and exhumation process at South Altyn Tagh. [1] Liu et al. (2002) CSB 47, 881–886. [2] Liu et al. (2004) Sci. in China 47, 338–346. [3] Liu et al. (2005) Sci. in China 48, 1000–1010. [4] Liu et al. (2007) EPSl, 263, 180–191. [5] Zhang et al. (2002) CSB 47, 751–755.

Goldschmidt Conference Abstracts 2010

Biomarker evidence for an unique prokaryotic microbial mat ecosystem in a epicontinental sea on the Mesoproterozoic (1.45~1.30Gyr) North China Craton C. WANG Lab. of Geochem. and Environ., Facul. of Geosci., China Univ. of Petroleum, Beijing, 102249, China ([email protected]) Mesoproterozoic marine paleoenvironment has drawn much more attention [1, 2]. Microbial mats may be very important for Proterozoic marine ecosystem [3]. The Mesoproterozoic Hongshuizhuang Formation (HSZF; ca. 1.45Myr) and the Xiamaling Formation (XMLF; ca. 1.4~1.3Myr), predominantly composed of organic-rich shale with TOC content up to 12% and 19%, and with biggest thickness up to 80m and 500m, respectively, developed in a north epicontinental sea on the North China Craton (NCC). The medium-maturated (H/C atomic ratio = 0.9 ~ 1.2) HSZF and XMLF shales present excellent preservation of biomarkers. The results show: 1) Steranes diagnostic for eukaryotes are below the detection limit. 2) The saturates are predominately composed of mono- and bi-methyl substituted mid-chain methyl groups. 3) Aryl-isoprenoid hydrocarbons derived from green and purple sulfur bacteria were not detectable in the HSZF and XMLF shales. Thus, the biomarker assembly of HSZF and XMLF suggests that organic-rich shales were deposited in a unique ecosystem where benthic microbial mats well developed, in which cyanobacteria were the primary production, while eukaryotes and phototrophic green and purple sulfur bacteria were all biogeochemically restricted. It is suggested that this kind of ecosystem might have been developed worldwide and maintained for an extended period during Mesoproterozoic. [1] Anbar & Knoll (2002) Science 297, 1137–1142. [2] Johnston et al. (2009) PNAS 106, 16925–16929. [3] Pierson et al. (1992) in The Proterozoic Biosphere, pp.245–347.

A1099

Investigating an amorphous precursor pathway to calcification: Implications for high magnesium carbonates D. WANG, T. ECHIGO AND P.M. DOVE* Dept. of Geosciences, Virginia Tech, Blacksburg, VA 24061 (*correspondence: [email protected]) With the realization that many calcified skeletons form by processes involving a precursor phase of amorphous calcium carbonate (ACC), a new paradigm for mineralization is emerging. There is evidence the Mg content in biogenic ACC is regulated by carboxylated (acidic) proteins and other macromolecules, but the physical basis for such a process is not well understood. In vitro experiments recently found that ACC compositions express a systematic relationship to the chemistry of carboxyl-rich biomolecules [1]. Molecules with a strong affinity for binding Ca compared to Mg promote the formation of Mg-enriched ACC products that are compositionally equivalent to high Mg-calcites and dolomite. Insights from this study raise the question of whether mineralization by a pathway involving this reactive intermediate could explain why some carbonates often contain higher Mg contents than are possible by classical crystal growth processes in the laboratory. Because this process is well documented in calcifiying organisms, we hypothesize that high Mg carbonates in sedimentary environments can also be formed by non-classical pathways involving the transformation of ACC to the final crystalline products. In new work, we are investigating the fates of high Mg ACC through asking two vital questions: (1) What are the process(es) by which some calcites can form with Mg contents that approximate a dolomitic composition? (2) How is the cation ordering to form a true dolomite structure obtained? To answer these questions we are conducting in vitro precipitation experiments, with a range of solution Mg/Ca ratios, small molecules and environmentally relevant particles at 20-40°C. Preliminary findings show the resulting precipitates are similar to the products reported in laboratory studies of microbially induced dolomites, which also form poorly crystalline aggregates. Structural analysis by XRD show precipitates are calcites of MgCa(CO3) composition, and not dolomites because they lack characteristic cation ordering. These results support the model of an alternative pathway for obtaining high Mg carbonates of dolomite composition, not possible in conditions where classical crystal growth processes dominate. [1] Wang et al. (2009) PNAS 106, 21511–21516.

A1100

Goldschmidt Conference Abstracts 2010

Potassium cycling in soil-plant: Implications for land utilization

Role of water availability in source partitioning for desert nitrate: New evidence from mass-independent oxygen isotopic compositions

D.Y. WANG1, Y.F. LI1, Q. XU1, R.J. BAI2 AND X. SHI1 1

College of Earth Sciences, Jilin University, Changchun 130061, China ([email protected], [email protected], [email protected], [email protected]) 2 Jilin Institute of Geological Survey, Changchun 130061, China ([email protected]) Potassium, as a major nutrition element in land utilization, is of an important indicating implication for reasonable utilization of land. This paper presents potassium contents and variation from different utilizing types of lands and plants located in Jilin province, northeastern China to reveal potassium cycling law between land and plant and further to efficiently utilize lands. The studied soils are chernozem, alkali soil and aeolian sand soil in western part and are mainly brown soil in eastern part. The former chiefly crops sunflower, the latter crops apple-pines. The analytical results of soils indicate that total potassium (Qk) and available potassium (Sk) concentrations from western soils vary from 1.21 wt.% to 3.23 wt.% (averaging 2.26 wt.%) and from 44 to 405 ppm (averaging 136 ppm), respectively, and whereas those from eastern soils range from 2.25 wt.% to 3.53 wt.% (averaging 2.83 wt.%), and from 37.2 to 564 ppm (averaging 160 ppm), respectively. The analytical results for fruits suggest that the average potassium contents from sunflower seeds (Gk) located in western part and from apple-pines located in the eastern part are 0.75 wt.% and 0.78 wt.%, respectively. Although obvious differences exist in soil types, land utilizing types, and potassium concentrations between eastern and western parts, absorption coefficient (Gk/Sk-y) and conversion coefficient (Sk/Qk-x) for potassium between soil and fruit exhibit an obviously negative correlation in two studied areas, yielding a regression equation of y=34.662x-0.8463 (r=0.9376, n=235). Taken together, it is suggested that although potassium absorption and utilization for plants could be affected by potassium abundance in soil, it will decrease as available potassium concentration increases in soil, which is of important implications for revealling potassium cycling law between soil and plant and evaluating soil quality as well as reasonable utilization of potassium fertilizer.

FAN WANG1, WENSHENG GE2 AND GREG MICHALSKI1* 1

Department of Earth and Atmospheric Sciences, Purdue University, West Lafayette IN., USA ([email protected]) (*correspondence: [email protected]) 2 China University of Geosciences, Beijing 100083, China ([email protected]) Mass-independent oxygen isotopic signatures are powerful tracers for delineating the two sources of nitrate in desert soils: nitrification and atmospheric deposition. We have performed isotopic measurements to detect !17O anomalies in NO3- salts from the Atacama (Chile), Kumtag (China), Rajasthan and Mojave (US) Deserts, which indicated the relative importance of these two nitrate sources has been linked to water availability. The most significant !17O anomalies (14-21‰) were observed in the NO3- salts from the Atacama Desert (a few mm precipitation on decadal time scales), close to atmospheric nitrate !17O value (~23‰), suggesting the Atacama well-known nitrate deposits are due to long term atmospheric deposition of photochemically produced nitric acid and biology is severely limited by hyperaridity. Surficial nitrate mineral samples from the Kumtag Desert which is similarly hyperarid (precipitation<25mm annually), also have large !17O values (12-18‰), indicating the accumulation of atmospheric nitrate is the primary source of these nitrate ores while minor, but detectable, biotic sources of nitrate are expected. However, the Rajasthan and Mojave Deserts (mean annual precipitation: 50-100mm) caliche NO3- samples with somewhat lower !17O values (7-13‰) appear to be partially derived from atmospherically deposited N, but also contain substantial amounts of N from terrestrial nitrification. This shift in nitrate source from Atacama to Mojave reflected a function of the availability of water. This suggests oxygen isotopes in pedogenic nitrate may be used as a proxy for past precipitation and as a marker of the intensity of biologic N cycling.

Goldschmidt Conference Abstracts 2010

A1101

Geochemical characterization of the heterogeneous source rocks in petroleum system modeling

Fluid-rock interaction in the deepburial overpressured system of the central Junggar Basin

FEIYU WANG1, CHEN JINYI BO WANG1, TAO JING1, HUASEN ZHEN2 AND XUE WANG2

F.R. WANG AND S. HE

1

China Petroleum University, Beijing, 102200, China 2 Petro China Daqing Oilfield Company, Daqing, Helongjiang 163453, China Kinetic organifacies concept and classification by Pepper & Corvit (1995) were widely applied in petroleum system modeling, and individual kinetic organiface are broadly related to sedimentary face, but sedimentary organifacies geochemical characterization is impeded by vertical significant variation of quantity and quality of organic matter. Simple statistic of geochemical screen analysis data or more complicated chemical kinetical model cannot solve the characterization problem of heterogeneity of source rocks. We have revealed that universal covariant relationship of HI and TOC exist for lacustrine and marine mudstone source rocks, to the less degree for terrestrial source rock. Therefore, characterization of type or hydrocarbon potentials of source rocks can be simplied to their counterparts TOC description. HI appears to increase with increasing TOC, asymptotic to 650-700mg/gTOC for above 3 wt% TOC lacustrine mudstones in immature phase, HI distribution and activation energy are peculiar for different TOC interval (0.5-1%, 1-2%, 2-3%, more than 3%) mudstone, Four TOC interval kinetic organofacies, each characterized by HI, TI, GOGI and bulk petroleum generation kinetics, have been established for lacustrine source rocks, which can be related to evaluation of source rock on wireline logs. Kinetic calibration to observed HI, TI and PI trend for different TOC interval source rocks can constrain hydrocarbon generation kinetics model and restore the initial HI and TOC. Two case studies will be presented to illustrate how to describe heterogeneous lacustrine source rocks, the first case is the upper Cretaceous lacustrine source rocks in Songliao Basin, where the thickness of four source rock members (K2qn1, K2qn2+3, K2n1 and K2n2) with different TOC intervals were calibrated with $logR algorithms for about 800+ wells, The second case is Paleocene lacustrine source rocks in Baihai Bay basin, where the thickness of four source rock members (Ed3, Es1, Es3 and Es4) with different TOC intervals were calibrated for more than 1000+ wells. The high-resolution distribution model of lacustrine source rocks were established integrated with stratigraphic architecture and sedimentological facies..

Key Laboratory of Tectonics and Petroleum Resources of Ministry of Education, China University of Geosciences, Wuhan 430074, China (*correspondence: [email protected]) In the central Junggar Basin, the secondary porosity zones develop in the sandstones between the depths of about 44006000m near the top seals of overpressure with the thicknesses of about 300-350m (Figure 1), the secondary pores were formed due to the dissolving of intergranular calcite cements and feldspar, and the formation of megapores were mostly caused by the dissolution of plagioclase, rather than Kfeldspar.

Figure 1: Relationships of carbonate cements, porosities and distances from the top of overpressure in the studied area. Though the carbonate cements and dissolved porosity was negative correlation, the analyses of thin sections and fluid inclusions demonstrated that most carbonate cements precipitated during the early diagenesis and were dissolved with the secondary pores formation in the deep-burial conditions. Owing to intensive decarboxylation at the temperatures of 105-145#[1], increasing of PCO2 (P = partial pressure) and decreasing of pH in the overpressured system resulted in more early carbonate cements dissolving and formed of 5-10% secondary porosity, and dissolution of feldspar further improved porosity. With the periodical releases of overpressured fluids, the zones of high secondary porosity and carbonate cements were superimposed in the depths near the top of overpressured system [2, 3]. [1] Surdam (1989) AAPG Bulletin, 73(1), 1Ð 23. [2] Huang (2007) Lithologic Reservoirs, 19(3), 7Ð 13. [3] HE (2009) Science-Journal of China University of Geosciences, 34(3), 457Ð 470.

A1102

Goldschmidt Conference Abstracts 2010

Geochronology and significance of the oldest intrusive in Qinling Mountains, China

Chemical compositions of rainwaters from Chengdu city, Sichuan Province, China

HONG-LIANG WANG1,2, XUE-YI XU1, XIN ZHANG1 1 AND TAO ZHU

HUA WANG1 AND GUILIN HAN2

1

Xi’an Center of Geological Survey (Xi’an Institute of Geology and Mineral Resource), CGS, Xi’an, Shaanxi 710054, China 2 State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi’an, Shaanxi 710069, China)

Yudongzi complex is the oldest geological mass in the Qinling area, it consists of two parts: one is deterioration that is called Yudongzi group. This part is composed dominantly of Plagioclase amphibolite, Greenschist, Granulite, Quartzite and Magnet Quartzite. It is High-greenschist facies to amphibolite facies metamorphism; another part is Deformation intrusion of different size of Granitoid. The geological body contact each other in Tectonic foliation. Predecessors Determination of age of Yudongzi group in many ways, but the results are quite different, and low in Accuracy. Based on image features of Zircon, combined Genetic Analysis of Zircon and Microdomains U-Pb isotope LA-ICP-MS (Laser ablation ICP-MS) Determination, separately get the Magma crystallization age 2661±17Ma and 2703±26Ma of Mylonite of fine-grained biotite granite and Strong schistosity biotite granite in Yudongzi complex, and get the Metamorphic zircon age 2647 ± 65 Ma in the Mylonite of fine-grained biotite granite. The age 2703±26Ma (Fig. 1) is the oldest Intrusive that had been detected in the Qinling Orogenic Belt from now on, it provide a new data for research Precambrian tectonic-magmatic events and the evolution of early Earth in Qinling Orogenic Belt. This study was supported by the National Natural Science Foundation of China (Grant No.
40773044
and 40872061).

1

School of Energy and Environment, Xihua University, Chengdu 610039, China ([email protected]) 2 The State Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China ([email protected])

Over the last few decades, China has undergone rapid and extensive industrial growth particularly in the more densely populated. This has inevitable led to dramatic increase in pollutant emissions to the atmosphere and consequently the increases in deposition of these pollutants over wide areas. With a fast economic development, energy consumption has increased significantly in the last two decades in Sichuan Province, China. Acid rain, therefore, has been an atmospheric environment problem especially of several big cities in Sichuan Province. In order to identify and quantify contaminant sources and their fluxes, we have conducted a study on chemistry of the rainwater over Chengdu city, a capital city of Sichuan Province. Forty-four bulk rainwater samples were collected in 2008, and analyzed for their chemical compositions. NH4+, Ca2+, NO3- and SO42- are the principal ions in the rainwater samples. The sum of NH4+ and Ca2+ accounts for more than 90% of the total cations, while SO42- was the most abundant anions and accounts for 38%-90% of the total anions. The second abundant anion is NO3- which account for 22%-56% of the total anions measured. Compared with some sites in China, the ion concentrations of Chengdu rainwater, especially SO42-, NO3-, consumedly exceed those of big cities in China. However, compared with those acid rain areas in China, the problem of acid rain is not serious in Chengdu. This is because the existence of acid rain depends not only on the presence of acidic ions in the precipitation, but also upon other factors such as the amount of alkaline material available as a neutralizing agent. It is noteworthy that the increase of NOx emission from the automobile exhaust is becoming another important cause of the acid ions in Chengdu city. It should be kept in mind that the contribution of nitrate to acid deposition will be more significant. This work was funded jointly by the Innovation Program of Chinese Academy of Sciences (No.KZCX2-YW-QN109) and the National Natural Science Foundation of China (No.40973088).

Figure 1: U-Pb concordia diagram of zircons from strong schistosity biotite granite

Goldschmidt Conference Abstracts 2010

The Low Velocity High Conductivity layer and abyssal geological process for abiogenetic gas in Songliao basin WANG JIANMIN1*, LIU HONGLIN2, ZHUO SHENGGUANG3, WANG XIANBIN4 AND TUO JINCAI4

A1103

Structure and energetics of the orientational ordering of carbonate in vaterite calcium carbonate by molecular modeling J.W. WANG* AND U. BECKER

1

Daqing Drilling & Exploration Engineering Co., Daqing, China (*correspondence: [email protected]) 2 Daqing Petroleum Institute, Daqing, Hei Longjiang, 163318, China ( [email protected] ) 3 North East University at Qinhuangdao, Qinhuangdao, Hebei, 066004, China ([email protected]) 4 Key Lab of Petrol Resources Research, CAS, Lanzhou ([email protected])

The Low Velocity High Conductivity (LVHC) layer nature and abyssal geological process A commercial abiogenetic gas field [1,2] was found around Xujia fault depression, which has a volume of about 500%108m3, in Songliao basin. The LVHC layer underneath and the relevant abyssal geological processes may be related to the formation of abiogenetic gas. In this paper, we discuss the nature of the LVHC layer and abyssal geological processes in relation to the formation mechanics of abiogenetic gas. In Songliao basin, mantle uplift [3] and many Moho boundary breaks were observed in deep reflection seismic profiles. More thermal diapirs developed under the fault depression. Magmatic activities were intense. Deep major faults cut even to Moho forming upwelling mantle fluid a channel and a material interchange geological space. Lithosphere horizontal motion made high heat mantle fluid form flat LVHC layers at weak geological space in upper and bottom of midcrust. We inferred its fluid nature by comparing deep reflection seismic polyspectrum characteristics in combination with seismic wave propagation theories with reflected amplitude analysis. Widespread high heat geothermal value and high conductivity indicate that it may be abundant in metal elements. All are the results of intricate abyssal geological processes [4] which are very favorable for Fischer-Tropsch synthesis.

Conclusion The LVHC layer is metal-rich high heat mantle fluid which is closely related to the formation of abiogenetic gas. The complicated abyssal geological process provided necessary conditions for Fischer-Tropsch synthesis to happen. [1] Wang Xianbin et al. (2009) Science China Earth Science (Series D) 39(5), 602–614. [2] Wang Xianbin et al. (2006) Natural Gas Geoscience 17(1), 7–13. [3] Yang Guang et al. (2001) Oil & Gas Geology 22(4), 326–330. [4] Yang Yufeng et al. (2000) Earth Science Frontiers 7(4), 523–533.

Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan, 48109, USA (*correspondence: [email protected], [email protected]) Vaterite is the least stable phase of anhydrous crystalline calcium carbonates, a rare mineral in geological setting. But it may be an important precursor in several carbonate-forming processes and plays an important role in biological processes. However, issues such as vaterite crystal nucleation, transformation, and stabilization in host materials remain largely unresolved. Understanding these issues may lead to answers to some of fundamental questions including carbonate formation in geological systems and occurrence of vaterite in biogenic systems. All of the above require a basic knowledge of the crystal structure of vaterite and its order-disorder transition. Molecular modeling is employed to understand the crystal structure and orientational order of CO3 in vaterite. By applying a temperature-annealing to the molecular dynamics simulations, a more stable structure with fully ordered CO3 is found. The space group of this newly-derived vaterite structure [1] is P6522 (#179) with z=18 and cell dimensions of "3 times in a, and 3 times in c of the previous well-accepted suggested disordered structure [2]. This structural ordering has been confirmed by new miscroscopic observations. Additional molecular dynamics simulations are employed to understand the thermodynamics and kinetics of the orientational ordering of CO3 in vaterite. Along the [001] direction, the simulation results suggest possible stacking disorder in vaterite. Cyclic high-temperature simulated-annealing MD simulations show that the CO3 orientational disorder-order transition is thermally activated. The potential energy change from disordered to ordered vaterite is -10.6 kJ/mol. The kinetic barrier for the transition is 93.9±9.6 kJ/mol with a preexponential factor of ~1.6"1013 s-1. The heat capacityis estimated to be 102.1±0.4 J/K/mol, comparable to an experimental result 91.5±3.8 J/K/mol. A good linear fit of logarithm transition rate to inverse temperature indicates that the transition is controlled by a single activation process that is related to the librational motion of CO3 in vaterite. [1] Wang & Becker (2009) American Mineralogist 94, 380– 386. [2] Kamhi (1963) Acta Crystallographica 16, 770–772.

A1104

Goldschmidt Conference Abstracts 2010

The geochemistry identifier of ore-type and non-ore-type diapir in Yimen Fengshan copper deposit

The paleosalinity for lacustrine massive source rocks deposition during the Upper Cretaceous in Songliao Basin China

LEI WANG1, RUN-SHENG HAN1, BO LI AND LIPIN DIAO2

LI WANG1,2, ZHIGUANG SONG1 AND JIANGTAO GUO1,2

1

Kunming University of Science and Technology, Southwest Institute of Geological Survey, Geological Survey Center for Non-ferrous Mineral Resources, Kunming 650093, China ([email protected]) 2 Guizhou Institute of Geology and Mineral Resources Exploration for Nonferrous Metals, Guiyang 550005 Yimen Fengshan copper deposit is a typical example of copper deposit which controlled by diapir structure in Yimen rifted-basin of the Kunyang rift valley, Yunnan Province, China. Ore bodys are located in cataclastic dolomite of Lvzhijiang formation. Studies suggest that not all diapir are controlling ore bodies, and diapir are divided into ore-type and non-ore-type. By contrasting the petrography and geochemistry characteristics, the paper established the identification marks of the two type diapir which play an important role in the depth ore-finding prognosis. There are four identification marks: (1) the ore-type diapir rock composition and pretectonic recrystallization are complexity than the non-ore-type diapir, the ore-type diapir rock is cryptoexplosion which mainly made up of intermediate-acid crystal tuff breccias and dacite breccias. But the non-ore-type diapir rock are tuffite and sericite slate. There is a more bigger alteration zone (100-200m) around ore-type diapir than non-ore-type diapir’s (5-10m). The alteration mainly composed of silicification and pyritization, ore-type diapir fluid temperature are 180-320°C [1]. (3) The ore-type diapir with the geochemistry characteristics of that variation in MgO content (3.18!"15.64!), FeO/Fe2O3 value range is big#0.43"28.50!), Na2O content#0.10"7.13!)high, K2O content is low (0.11"2.98!), instead of the non-oretype diapir MgO content is low#1.90!"3.77!), FeO/Fe2O3 value is also low #0.14"0.56$, Na2O content is low (0.07"2.83!), K2O content is high (1.84 "5.11!). (4) The zoning characteristic of metal mineral association and structure of ores from ore-type diapir to adjacent rock is that massive and veined chalcopyrite (a small amount of bornite)!veined and disseminated chalcopyrite, bornite (a small amount of chalcocite)!Scattered punctuate and small vein chalcopyrite, bornite and chalcocite, but the non-ore-type diapir have lowly mineralization. ! Granted by the project of the State Crisis Mine (20089 943) and the Distinguishing Discipline of KUST (2008). [1] Han R S, Liu C Q & Sun K X et al. (2000) Geotectonica et Metallogenia 2, 146–154.

1

SKLOG, Guangzhou Institute of Geochemistry, Chinese Academy of Science, Guangzhou 510640, China (*correspondence: [email protected]) 2 Graduate University of Chinese Academy of Science, Beijing 100049, China Methylated-2-methyltrimethyltride-cylchromans (MTTCs) is a salinity indicating biomarkers that are widely detected in modern and ancient sediments and crude oil. The composition and distribution of methyled-MTTCs identified in Late Cretaceous core samples of Nenjiang Formation (K2n1and K2n2) of SK-1 drilling from Songliao Basin are suggestive of the paleosalinity of depositional environments and redox state, while bearing no relation with organic matter types, burial depth and maturity. Among these MTTCs, !-MTTC is abundant in high salinity reducing environment but absent in the low salinity aerobic environment; while &-MTTC shows a relative higher abundance in the high salinity environment than that of lower saline environment; furthermore, relative abundance of two dimethyl-MTTCs display a relation of &>' in higher-salinity environment, but &<' in lower salinity environment; after all (-MTTC is a non-salinity dependent compound and rich in all environments. This study also suggests that (-MTTC/&-MTTC (( / &) ratio is also indicative of paleosalinity as a ( / & ratio of less than 2 indicates a mesosalinity environment, while a ratio of greater than 15 is indicative of a semi-saline to brackish lacustrine environments, a ratio between 2 and 15 is indicative of normal marine-like salinity. The combination of all related molecular marker index suggest that K2n1and K2n2 were formed under significantly different salinity, as the organic rich source rocks of K2n1 section were deposited under a normal marine-like salinity prevail occurred at the top section; while K2n2 were likely developed under a semi-saline to brackish lacustrine environments under a relative stable salinity. This study is (2006CB701404).

supported

by

State

‘973’

Project

Goldschmidt Conference Abstracts 2010

Early crustal evolution in the western Yangtze Block: Evidence from U-Pb and Lu-Hf isotopes on detrital zircons L.J. WANG1,2, S.Y. O’REILLY2, W.L. GRIFFIN2 1,2 AND J.H. YU 1

State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210093, P.R. China 2 GEMOC ARC National Key Centre, Department of Earth and Planetary Sciences, Macquarie University, Sydney, NSW 2109, Australia ([email protected])

In situ U-Pb and Lu-Hf isotopic data on detrital zircons from Paleoproterozoic-Neoproterozoic sequences in the western Yangtze Block have provided a clearer picture of regional tectonic background and crustal evolution history. The youngest concordant zircon ages for sedimentary units suggest a maximum depositional age of 1014 Ma for the Kunyang Group, 750~649 Ma for the Sinian sequences, and 525 Ma for the Cambrian sediments. The Yinmin Formation, which has been assigned to the middle part of the Kunyang Group, was actually deposited at 1667 Ma and contains zircons whose ages are dominantly from late Archean to Paleoproterozoic (2.7~2.8 Ga, 2.5~2.3 Ga and ~1.85 Ga). The Heishantou Formation in the lower part of the Kunyang Group has two major age populations of ~1.0 Ga and 1.6~1.8 Ga. The younger Sinian and Cambrian sedimentary rocks are dominated by Neoproterozoic zircons with age peaks at ~760 Ma and ~825 Ma, consistent with widespread coeval igneous rocks around the Yangtze Block. The Lu-Hf isotope data suggest that significant juvenile input took place during Archean and Neoproterozoic times, while crustal reworking was dominant during the Paleoproterozoic. The absence of exposed basement rocks that could have been the source of the Archean-Paleoproterozoic detritus suggests an unexposed or now-covered source within the Yangtze Block, probably with minor exotic contributions. These ancient materials are distinct from the exposed Archean-Paleoproterozoic basements in the northern Yangtze block, suggesting that a subarea of old crust exists beneath the young sediments covering the craton. The presence of abundant ~1.85 Ga zircons suggests that the Yangtze Block was probably part of the Columbia supercontinent during Paleoproterozoic time. Comparisons to the other parts of Columbia suggest that South China could have been adjacent to the North China Craton and/or Australia.

A1105

Petrogeochemical characteristics and constraints on the tectonic setting of Guiling Monzogranite pluton of South China RUI WANG, ZUOHAI FENG*, ZHIQIANG KANG, QIANKUN YANG AND RUI LUO Guilin University of Technology, Guilin 541004, China (*correspondence: [email protected]) Guiling monzogranite pluton is located in the western Nanling region of south China.SHRIMP zircon dating of the monzogranite and its widely-spread microdioritic enclaves yielded U-Pb ages of 424.4±5.6 Ma and 428±4Ma [1], confirming a Caledonian emplacement of the pluton. The monzogranite shows relatively high contents of SiO2, K2O, Rb, Sr, and Ba, low contents of CaO, P2O5, and )LREE, and )REE = 108.51-161.56 ppm. Its A/CNK ratio ranges between 0.94 and 1.03 with K2O>Na2O, suggesting that it is a metaluminous to weakly peraluminous granite. The monzogranite also demonstrates strongly negative Eu anomaly. Isotopic analyses of its Sr-Nd-Pb system show that the monzogranite has high 87 Sr/86Sr, 2°8Pb/2°4Pb, 2°7Pb/2°4Pb, and 2°6Pb/2°4Pb and low 143 Nd/144Nd. The petrogeochemistry of the monzogranite suggests that the Guiling magmas were dominantly derived from partial melting of the upper crust with addition of a certain amount of deeply subducted material. In contrast, the microdioritic enclaves have higher CaO, MgO, Fe2O3, TiO2, P2O5, )REE, Cr, Ni, and 143Nd/144Nd, and lower K2O, Rb, Th, 87 Sr/86Sr, 2°8Pb/2°4Pb, 2°7Pb/2°4Pb, and 2°6Pb/2°4Pb, indicating a different source from its host monzogranite. It is suggested that they were derived from the enriched mantle with partial melting. Application of the tectonic discrimination diagrams in this study shows that the Guiling monzogranite dominantly falls in the syn-collision and within-plate fields; it is suggested that it was emplaced during the collision between Cathaysian block and Yangtze block during Caledonian orogeny. The oreforming molybdenite contained within the monzogranite has an age of 424.6±5.7Ma [1], indicating that the quartzmolybdenite vein-type molybdenium deposit hosted by the pluton was produced during the Caledonian orogeny and in the Silurian time. This project was financially supported by the National Natural Science Foundation of China (No. 40772126) and the Guangxi Graduate Innovative Project (No.2009105960818M01). [1] Li et al. (2009) Mineral Deposits 28(4), 403–412.

A1106

Goldschmidt Conference Abstracts 2010

Determination of rare elements in rock samples by Inductively Coupled Plasma Mass Spectrometry

Identification of intrusions by fusion of geo-information from geochemical and geophysical datasets

TIE-FU WANG1 PEI-XI ZHENG2 AND YAN ZHOU1

W. WANG1* AND Q. CHENG1,2,3

1

Center of Analysis and Testing Jilin University Changchun China 130026 2 College of Earth Sciences Jilin University Changchun China 130061

Rare elments are important elments in rocks, it can indicate the diagenesis environment and tectonic settings. so it is important to exactly determining. In the past, it only deteminate buy ICP-AES or AAS. but this instrmnents detection limit are hight comparatively content in sedimentary. Iductively Coupled Plasma Mass Spectrometry (ICP-MS) have low comparatively, it is the right detemination instrument. A method for the determination of Rare elements in rocks was proposed by Iductively Coupled Plasma Mass Spectrometry (ICP-MS). The ICP-MS (Agilent 7500a) running conditions: RF power 1350W; Carrier gas flow rate 1.2L/min; Spray chamber temp 2#; Sample flow rate 0.1ml/min; Sample depth 7mm. In the determination of the method, we analyse elements. The sample was dissolved in mixed acids with pressurized sample digestion and an appropriate amount of mannnitol was added to prevent boron from volatilization. Analytical mass number were carefully selected and the instrumental operating conditionswere optimized. The detection limits of the method for the elements were 0.0001-0.003mg/L. The method has been applied to the determination of these elements in National Standard Reference Materials including GBW and BCR. The results obtained were in agreement with the certified values with recovery of 90.3%-110% and precision of less than 5% RSD (n=3). So this technique has a lot of advantages, such as high accuracy and precision, low limit, and high analytic speed etc. We draw a conclusion that using ICP-MS, we can get satisfactory results. [1] Zheng PX, Zhou Y, Wang TF et al. (2008) Determination of trace elements in sedimentary rock samples by Inductively Coupled Plasma mass spectrometry [J]. Geochimica et Cosmochimica Acta. 72(12) A1097-A1097.

1

Department of Earth and Space Science and Engineering, York University, 4700 Keele St., Toronto, Ontario, Canada M3J1P3 (*correspondence: [email protected]) 2 Department of Geography, York University, 4700 Keele St., Toronto, Ontario, Canada M3J1P3 ([email protected]) 3 State Key Laboratory of Geological Processes and Mineral Resource, China University of Geosciences, Wuhan, Beijing, China

Based on existing literature [1], granite intrusions are believed to be important controlling factors of mineralization in the Gejiu Sn-Cu polymetallic ore district. This knowledge about intrusions benefits future exploration. From stream sediments geochemical data, elements associated with intrusions can be recognized through principal components analysis (PCA). Calculated scores of element association describe the surface chemical properties of areas influenced by intrusions. Singularity index can identify the material enrichment and depletion produced by the various geological activities [2]. From the viewpoint of singularity, intrusions present low gravity and high magnetism in regional scale geophysical data and are currently interpreted, respectively, as depletion of high density materials and enrichment of magnetic materials. This paper applies singularity index mapping technique for gravity data and aeromagnetic data to analyze the physical properties of subsurface intrusions. In order to comprehensively describe the distribution of intrusions, PCA is used further to integrate surface signatures of intrusions from geochemical data with subsurface signatures of intrusions from geophysical data. Contributions of gravity, aeromagnetic and geochemical associations assist to select a principal component representing the intrusions, the patterns of which indicate presence of surface to subsurface intrusions as supported by both physical and chemical properties. [1] Zhuang et al. (1996) Geology of Gejiu Tin-Copper Polymetallic Deposit, Earthquake Publishing House. [2] Cheng (2007) Ore Geology Reviews 32, 314–324.

Goldschmidt Conference Abstracts 2010

Geochemical characteristics of abiogenic hydrocarbons from Songliao Basin, China WANG XIANBIN1*, TUO JINCAI1, ZHUO SHENGGUANG2, WANG JIANMIN3 AND LIU HONGLIN4 1

Key Lab of Petrol Resources Research, CAS, Lanzhou, China (*correspondence: [email protected], [email protected]) 2 Zhuo Shengguang, Northeast University at Qinhuangdao, Qinhuangdao, China ([email protected]) 3 Wang Jianmin, Daqing Exploration Drilling Engineering Co., Daqing, China ([email protected]) 4 Liu Honglin, Daqing Petroleum Institute, Daqing, China ([email protected]) We discuss the formation of abiogenic hydrocarbons by polymerization of simple carbon-bearing molecules (CH4, CO and CO2), and the kinetic fractionation effect on carbon and hydrogen isotope composition and distribution in this process. The !13C values of methane from 26 commercial wells from Songliao Basin vary from -30.5‰ to -16.7‰. The !D values vary from -203‰ to -196‰. The alkane gases from these wells are characterized by a reverse distribution of !13C values and a normal trend of !D values, namely !13C CH4 > !13C C2H6 > !13C C3H8 > !13C C4H10 and !DCH4 < !DC2H6 < !DC3H8. The !13C value and !D value distributions are negatively correlated, showing the characteristics of abiogenic isotope composition controlled by kinetic isotope fractionation. The R/RA values of helium isotope composition of samples are between 1.05 and 2.36, shows significant contribution of helium from mantle. These samples have 21Ne/22Ne-20Ne/22Ne values between Loihi line and MORB line, and have enriched 129Xe with respect to the atmosphere (0.15%-2.16%). The existence of mantle origin noble gases provides isotope evidence of mantle degassing in Songliao Basin. It supports the deep origin of the abiogenic hydrocarbons in Songliao basin. Our early studies [3, 4, 5] show the thermo-stability of hydrocarbons under high pressure condition in deep earth. The present study has revealed that abiogenic hydrocarbons not only exist in nature but also can make significant contribution to commercial gas reservoirs. It is estimated that the reserve volume of alkane gases with abiogenic characteristics in these 26 gas wells in Songliao basin is over 500%108m3. This work is supported by the NSF of China, 40572087, the NS&TRP China, 96110010602. [1] Hu G.X. et al. (1998) Sci. in China Ser. D 41(2), 202–207. [2] Wang X.B. (2009) et al. Sci. in China Ser. D 52(2), 213– 226 [3] Bai Z.H. & Wang X.B. (1998) Chinese J Geochem 17(2), 103–113. [4] Wang X.B. et al. (1997) Chinese Sci. Bull. 42(16), 1327–1337. [5] Zhang M.J. et al. (2006) Natural Gas Geosci. 17(1), 31–35.

A1107

U-Th systematics in deep-sea red clays XIANFENG WANG1*, WALLACE S. BROECKER1, R. LAWRENCE EDWARDS2 AND HAI CHENG2 1

Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964, USA (*correspondence: [email protected]) 2 University of Minnesota, Minneapolis, MN 55455, USA We followed the pioneer study by Ku [1] and applied uranium and thorium analysis on three deep-sea red clay cores from the southwestern subtropical Pacific. With high-precision multi-collector ICP-MS techniques, only a few mg of clay samples (~10 ng of U) were digested for the analysis. The precision of our analysis is ~1%, mainly limited by weighing uncertainty. Using 23°Thexcess profile, extraterrestrial 3He flux, and Ar-Ar dating method on volcanic ash layers, we estimated a sediment mass accumulation rate of ~1-3 mm/kyr down the cores, and therefore, up to 10 million years of U and Th elemental and isotopic variations could be recovered from the ~10-meter long cores. We found that the #234U value (defined as ((234U/238U) activity – 1) * 1000‰) was close to 0‰ at the core top, rapidly decreased and then fluctuated between ~ -50‰ and -70‰ until ~7 m deep, and gradually came back to the equilibrium state in the lower portions. Our findings therefore confirmed the Ku’s observations, albeit now with better precision on much advanced techniques. The negative #234U values in the main portion of the cores suggest that 234U could be preferentially dispersed from red clay grains into marine pore water, due to the alpha-recoil effect. Such exchange of uranium between red clay and its surroundings could continue for a significant amount of time, only possibly been limited by the upward diffusion rate of 234U with the increasing depth in the cores. As red clay covers about half of the ocean floor, its preferential release of 234U into pore water, and subsequently into bottom seawater could have significant contribution in the uranium isotope budget in the ocean. Quantifying this 234U source will benefit our understanding of the history of seawater (234U/238U) activity; therefore help to screen coral samples for a reliable sea level reconstruction using their uranium-series ages. [1] Ku (1965) ‘An evaluation of the U234/U238 method as a tool for dating pelagic sediments.’ J. Geophys. Res. 70, 3457– 3474.

A1108

Goldschmidt Conference Abstracts 2010

Carbon, Oxygen and Strontium isotopic compositions of Lower to Middle Cambrian carbonates in the northwestern Tarim Basin, China XIAOLIN WANG, WENXUAN HU AND XIAOMIN XIE Department of Earth Sciences, Nanjing University, Nanjing, Jiangsu 210093, P.R. China (*correspondence: [email protected]) The Keping area in the northwestern Tarim Basin (nothwest China) has a good outcrop Lower to Middle Cambrian section, which is composed mainly of carbonates. In this study, 110 carbonate samples were analyzed for stable carbon and oxygen isotopes, and 14 samples for radioactive 87 Sr/86Sr isotopic ratios. The measured values generally have primary features of the rocks, as supported by two folds of evidences. First, the !18O values vary between -11.0‰ and -4.0‰ (PDB), averaging -5.8‰, greater than -10‰. Second, the !13C and !18O values have no clear positive correlation. The !13C values rise from 1.4‰ to 3.3‰ (peak I) from the late Meishucunian to late Nangaoan, punctuated by several fluctuations. After the peak I, the !13C values decrease to peak III (-4.2‰) from the Duyunian to the base of the Taijiangian, punctuated by a less negative peak (peak II, -3.0‰). The peak III marks the Lower-Middle Cambrian boundary, which has good correlation with other regions, such as South China [1] and Laurentia [2]. The !13C values rise to around 0 during the later part of the Middle Cambrian. The 87Sr/86Sr ratios exhibit a monotonic rise from the late Early Cambrian to Middle Cambrian, from ~0.7089 to ~0.7093. The rise of the 87Sr/86Sr ratios during this interval is interpreted to record uplift and attendant increased weathering associated with the Pan-African orogeny [3]. Subsequently, the 87Sr/86Sr ratios decrease to a minimum of ~0.7087 during the early Middle Cambrian, indicating an episode of widespread rifting [2]. The 87Sr/86Sr curve combined with the !13C curve defines the Early-Middle Cambrian boundary, which accords with the extinction of Redlichiid and Olenellid Trilobites. Thus, the data here provide clues and references for global isotopic and geological events from the Lower to Middle Cambrian as to global stratigraphic correlation. This research was supported by National S&T Special Project (grant no. 2008ZX05005-002-007HZ). [1] Zhu et al. (2004) Geobios 37, 287–301. [2] Montañez et al. (2000) GSA Today 10(5) 1–7. [3] Derry et al. (1994) EPSL 128, 671–681.

Absorption/desorption of soil phosphorus mobilization in a small watershed, China XIAOYAN WANG*, JIE YIN AND YANG YU College of Resources, Environment & Tourism, Capital Normal University, Beijing 100048, China (*correspondence: [email protected]) Understanding the soil mobilization mechanism is critical in controlling the phosphorus entering the water body for mitigating and preventing eutrophication.

Figure 1: Soil P absorption curves The dynamic curves of phosphorus adsorption can be well described with the two-constant dynamic equation. High phosphorus soil (TP > 0.9 mg·kg-1) occurred desorption all the time. The adsorption amount of low phosphorus soil (TP < 0.588 mg·kg-1) increased with increasing equilibrium concentration of solution. Absorption capacities of soil phosphorus were varied with different land use soil. The phosphorus absorption capacity of riverbed soil was the highest whereas that of slope grassland soil was the lowest. The main factors influencing the soil phosphorus absorption capacity were Clay, Fe-P, Al-P and Available Phosphorus (A.P.)[1-3]. The phosphorus releasing processes of high phosphorus soil occurred desorption all the time, which could be fit in well with by the dynamic equation. The phosphorus releasing processes of low phosphorus soil was an alternate dynamic process of adsorption - desorption, which could not be fit in well with by the dynamic equation. The soil phosphorus and clay content and water-soil ratio conditions affected desorption amount. With an increase in phosphorus solution concentration, soil phosphorus re-desorption capacity decreased gradually. This project is financially supported by the National Natural Science Foundation of China (40871219, 40971258) and the project of Beijing Municipal Commission of Education (KM200910028014) [1] Borggaard & Jqrgensens (1990) J. Soil Sci. 41, 443–449. [2] Amrani et al. (1999) Commun Soil Sci. Plant. Anal. 30, 1299–1314. [3] Katarina et al. (2001) Nutrient Cycling in Agroecosystems 59, 39–46.

Goldschmidt Conference Abstracts 2010

Uranium recovery from waste ores by an indigenous Acidithiobacillus ferrooxidans in laboratory XUEGANG WANG*, JINHUI LIU, ZHANXUE SUN, YAJIE LIU AND ZHIHONG ZHENG Department of Civil and Environmental Engineering, East China Institute of Technology, Fuzhou, Jiangxi, P. R. China (*correspondence: [email protected]) The feasibility of bioleaching recovery of uranium from the 721 Uranium Mine Shan-nan deposit waste ores, located in the Jiangxi Province, south of China, were investigated. A mesophilic iron oxidizing bacterium, Acidithiobacillus ferrooxidans has been isolated from the uranium mine ores. Bioleaching experiments were carried out in four columns. The effects of bacterial strain, pH, temperature, Eh and initial ferric concentrations on the uranium bacteria column leaching were evaluated. The results indicate that the efficiency of uranium extraction is dependent on all of the aforementioned variables. In addition, results show that the effects of ors size and temperature had more effect. The maximum uranium recovery was achieved 62% from waste ores which grade is 0.0245%, acid consumption are less than 4%, control the initial acidity concentration is 20g/L and spray amount from 20% to 15% in the acidification stage, initial ferric concentration from 5g/L to 3g/L and leaching solutions pH value less than 2.0 (avoid ferric precipitated) in the bacteria leaching stage, after 84 days. The uranium recovery was over 65% at the ore diameter less than 15mm. This work was supported by a grant from the National High Technology Research and Development Program of China (863 Program) (No.2007AA06Z120), the Ministry of Science and Technology of China International Cooperation Projects (No.2008DFA71760).

A1109

China geochemical baselines XUEQIU WANG Institute of Geopysical and Geochemical Exploration, CAGS, 84 Golden Rd., Langfang, Hebei 065000, China ([email protected]) China Geochemical Baselines (CGB) is an Earth science project to provide nation-wide geochemical baselines, spatial distribution and evolution of all elements, and finally to establish a Digital Element Earth in China. The first 5-year term for the CGB project was launched in 2008.

Goals The goals of the CGP project are to (1) establish China nationwide geochemical baseline data for rocks and soils, (2) display spatial distribution of nearly all elements in the crust, (3) explore evolution of elements with geologic times from Archeozoic to Quaternary, (3) trace sources of geochemical patterns, and (5) identify areas of interest for natural resources and environments.

China Geochemical Reference Networks The CGB Project is designed to divide each Global Reference Networks (GRN) [1] grid into 4 China Geochemical Reference Networks (CGRN) grids. Approximately 1500 CGRN grids cover the whole China mainland (9.6 millions km2). Primary (rocks) and secondary (soils) samples are both collected.

Chemical Analysis Nearly all natural elements (except gases) in the periodic table are determined by ICP-MS/AES following 4-acid digestion and XRF following fusion as backbone methods combined with other 10 methods. Analytical quality is under strict control by using standard reference samples.

Geochemical Database An Internet-based geochemical database will be established for Digital Element Earth, which can provide data and maps through the Internet. [1] Darnley et al. (1995) Earth Science 19, UNESCO Publishing (Paris) 122pp.

Goldschmidt Conference Abstracts 2010

A1110

New applications of in situ synchrotron x-ray techniques for studies of earth and planetary materials at high pressure and temperature YANBIN WANG GeoSoilEnviroCARS, The University of Chicago, 5460 S. Ellis Ave., Chicago, IL 60439 ([email protected]) The field of high-pressure earth and planetary sciences has changed dramatically over the last two decades, primarily owing to the increasingly sophisticated tools that are constantly being developed. Capabilities of modern synchrotron and neutron sources provide enormous opportunities for new types of experimentation at high pressure (P) and temperature (T). Accordingly, many new high-pressure devices have been developed to take advantage of these advances. This presentation will focus on a range of new developments for characterizing physical and chemical properties of minerals and rocks at simultaneous high P and T: (1) structures of crystals and liquids, (2) Elasticity of solids and potential applications for liquids, (3) rheological properties of minerals (poly- and single crystals) and melts. In addition, a high-pressure 3D tomographic imaging technique will be introduced, which has been used to study various phenomena, including (1) texture development in multi-phase materials under shear deformation, (2) segregation of Fe-rich melts from silicate, and (3) equations of state of melts. Future prospects will be discussed base on a few new initiatives.

Nonlinear dynamics of Banded Iron Formation precipitation YIFENG WANG1, HUIFANG XU2 AND ENRIQUE MERINO3 1

Sandia National Laboratories, P. O. Box 5800, Albuquerque, New Mexico 87185 2 Department of Geology and Geophysics and NASA Astrobiology Institute, University of Wisconsin, Madison, Wisconsin 53706 3 Department of Geological Sciences, Indiana University, Bloomington, Indiana 47405

Banded iron formations (BIFs) carry important information on the early evolution of the Earth. The actual mechanisms for their formation remain controversial. We have shown that the passage from predominant occurrence of BIFs in the Archaean-Early Proterozoic to their absence thereafter may have reflected compositional changes in the oceanic crust [1]. Fe-Si-rich geologic fluids can be generated only from Alpoor oceanic crust through hydrothermal leaching by seawater. Al enrichment in the oceanic crust after ~ 1.7 Ga ago tends to prevent BIF formation. We have further shown that periodic precipitation of iron and silica minerals in alternating bands can be induced by positive feedbacks among relevant chemical reactions as a Fe-Si-rich hydrothermal fluid mixes with ambient seawater [1]. Complexation of dissolved Fe (II) with silicic acid plays a crucial role in the selforganized process. Small-scale (< 1 cm) BIF bandings are thus attributed to the internal dynamics of the chemical system, rather than to an outside force such as surface temperature variations. In this presentation, we provide a detailed stability analysis of the model we developed to clarify the physical and chemical conditions for oscillatory precipitation of BIFs. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company for the US DOE’s NNSA under contract DE-AC04-94AL85000. [1] Wang et al. (2009) Nature Geoscience 2, 781–784.

Goldschmidt Conference Abstracts 2010

Enhanced mobility of fullerene (C60) nanoparticle in the presence of stabilizing agents Y. WANG1, Y. LI2, J. COSTANZA3, L.M. ABRIOLA1 1 AND K.D. PENNELL *

Even carbon-numbered n-alkanes predominance in lacustrine sediments and its climate significance in Linxia Basin, NE Tibetan Plateau, NW China

1

Dept. of Civil and Environ. Eng., Tufts Univ., 200 College Ave., Medford, MA 02155, USA (*correspondence: [email protected], [email protected], [email protected]) 2 Dept. of Civil Eng., Univ. of Nebraska-Lincoln, Nebraska Hall W356, Lincoln, NE 68588, USA ([email protected]) 3 U.S. Environmental Protection Agency, 1200 Pennsylvania Ave., Washington, DC 20460, USA ([email protected]) The effects of four stabilizing agents, tetrahydrofuran (THF), Suwannee River humic acid (SRHA), Suwannee River fulvic acid (SRFA), and Tween® 80, on the transport and retention of nC60 nanoparticles in water-saturated 40-50 mesh quartz sand was explored through a combination of experimental and mathematical modeling studies. To accurately determine the concentration of nC60 in aqueous suspensions containing either SRHA or SRFA, a novel analytical method was developed that involved liquid-liquid extraction and high performance liquid chromatography. At concentrations of up to 45 mg/L, the presence of THF, a transfer solvent used in the preparation of aqueous nC60 suspensions, did not alter nC60 transport and retention behavior. In contrast, the addition of SRHA (20 mg C/L), SRFA (20 mg C/L), or Tween® 80 (1, 000 mg/L) to influent nC60 suspensions greatly enhanced nC60 transport, as illustrated by coincidental nC60 and non-reactive tracer effluent breakthrough curves (BTCs), and minimal nC60 retention. Subsequent nC60 transport experiments revealed that the presence of adsorbed-phase Tween® 80 enhanced nC60 retention, characterized by retention profiles that exhibited exponential decay. A mathematical model that accounts for coupled surfactant and nanoparticle transport processes, including a spatially- and temporally-varying attachment rate coefficient, was able to accurately predict measured surfactant and nC60 effluent and solid-phase concentration profiles. These findings demonstrate that both natural and anthropogenic stabilizing agents have the potential to dramatically increase the transport nC60 nanoparticles in water-saturated quartz sand.

A1111

YONGLI WANG1,2, XIAOMING FANG2*, YUANMAO LI1, DAXIANG HE1, YINGQIN WU1, HUI YANG1 1 AND YOUXIAO WANG 1

Key Laboratory of Petroleum Resources Research, Institute of Geology and Geophysics, Chinese Academy of Sciences , Lanzhou 730000, China 2 Center of Basin-Mountain System and Environ-ment, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100085, China (*correspondence: [email protected])

n-Alkanes generally constitute the major fraction of saturated hydrocarbons and their distribution patterns are characterized by carbon-number ranges and predominances, depending on the nature of the source material and its microbial or geochemical alteration. In the present study we have identified such distributions for the first time in lacustrine sediments of continuous sedimentary section in the Linxia Basin, NE Tibetan Plateau, NW China, aging from 13Ma to 4.4Ma. Total n-alkanes of the sediments were characterized by two major groups. One was n-alkanes in the range n-C16 to n-C20 with a strong even carbon number predominance and a maximum at n-C18, the other, those from n-C27 to n-C31 with an odd carbon number predominance and a maximum at n-C29. We think that the even carbon-numbered n-alkanes in lacustrine sediments of the Maogou section have most likely a direct contribution from microorganisms. Based on various geochemical parameters and the correspondence between the strong even carbon number predominance of alkanes and warm-arid enviroment from bottom to top in study section, the most likely origin of n-alkanes is a kind of bacteria which preferenably live in the weak oxic-anoxic and warm-arid environments. And we suggest that n-alkanes with a high even carbon number predominance record information related to arid climate change. Supported by grants No. KZCX2-YW -104 (2), KZCX2YW-Q05-05, NSFC No.40672123, and 2005CB422001.

Goldschmidt Conference Abstracts 2010

A1112

Iron isotope fractionation during fluid exsolution and evolution

Trace elements and isotope dating from Devonian-Carboniferous boundary in China and its pale environment significance

Y. WANG AND X.K. ZHU Lab Isotope Geol., MLR, Inst. Geol., CAGS, Beijing, China ([email protected], [email protected]) It is an important issue whether Fe isotpes fractionate during the process of the fluid exsolution from magma and fluid evolution, as this kind of information is crucial in tracing the metal source and mineralization processes using Fe isotopes, and in understanding the evolution of Fe systematics during magmatic and ore-forming processes. Here we examine this issue by systmematic investigation of Fe isotope distribution in minerals separates and bulk samples from Xinqiao skarn deposit in Anhui province, China. Fe isotope compositions of mineral separates of magnetite, pyrite and chalcopyrite, as well as bulk samples of quartzmonzodiorite stock and skarn, were measured using a Nu Plasma HR MC-ICP-MS at high-resolution mode after purification using anion exchange chromatography. The results are expressed as deviations in permil from the same isotope ratios of the reference material IRMM-14. The skarn is the metasomatic product of magmatic fluid with carbonate country rock, and magnetite is among the earliest iron minerals precipitated from the ore-forming fluid. In this study, the !57Fe values of endoskarn and magnetite are ca.1.2‰ and ca. 0.3‰ lower respectively, relative to the quartz-monzodiorite stock. It has been documented both theoretically and experimentally that significant mass fractionation exists between Fe(II) and Fe(III) species, and Fe(III) enriches heavy isotopes of iron. Therefore, Fe isotope composition of the ore-forming fluid exsoluted from the magma must be even lighter than that of the diorite stock. The possibility that light Fe isotope composition of the oreforming fluid was resulted from mixing with country-rock can be ruled out because the carbonate country-rocks have Fe isotope compositions similar to those of the stock. Spatial and temporal zoning in !57Fe values is observed in Fe-sulfides, showing that early formed sulfides close to the stock are enriched in 54Fe compared to the late formed sulfides away from the stock. The most plausible explanation for the observed zoning is that Fe isotopes fractionate between Fesulfides and fluid during fluid evolution, and Fe-sulfides preferentially precipitate light isotopes. Thus the Fe isotope composition of residual fluid is becoming heavier with the progress of sulfide precipitation. The recognition that significant Fe isotope fractionation occurs during fluid exsolution and evolution provides important new insights into Fe isotope behaviour during magmatic evolution and deposit genesis.

Y.-X. WANG1*,2, Y.-Y. WANG3, Y.-J. CHEN2, M.-Q. ZHANG2 AND H.-M. LI1 1

State Key Laboratory of Mineral Deposit Research, Nanjing University, Nanjing 210093, China (*correspondence: wyxnu @nju.edu.cn 2 Center of Modern Analysis, Nanjing University, Nanjing 210093, China 3 Nanjing Institute of Geology and Paleontology, Academy of Sciences, Nanjing 210008, China

This paper makes an analysis of trace elements contained in 16 fossil samples and Rb-Sr dating from DevonianCarboniferous Boundary at the Nanbiancun section [1] in Guilin, China. The purposes are to research the pale environment significance and to quantitatively determine the paleoredox environment using the Ce anomaly (-0.49 to-1.7). The clay minerals may be fit in with the Rb-Sr isotopic determination of the boundary age. This is an important support to the conclusion that the section belongs to the Boundary strata and the clay mineral isochron age (361.0±4.1Ma) is reliable. Our studies showed that the clay is rich in 1Md illite, which is neither of detrital nor of diagenetic origin. This means that the homogenization time of Rb-Sr system can be assumed to be at or close to the sedimentary epoch, and the clay can be reasonably considered as representing the age of the Devonian-Carboniferous Boundary at Nanbiancun, Guilin.The range of 1000 Sr/Ca are 0.5 to 1.2 indicating a lower neritic to shallow bathyal environment. This study also demonstrates that the reliable age (361.0±4.1Ma) can be often obtained by using the clay mineral method. Sr isotopic initial ratio is 0.7079±0.0002. The pale environment significance is determined by the paleoredox environment using the Ce anomaly indicating an oxdized environment of carbonate sedimentation. This work is granted by the National Natural Science Foundation of China (No. 40872028) and by the Analysis Testing Foundation of Nanjing University [1] Yu, C.M. (ed) (1988) Science Press, Beijing, China.

Goldschmidt Conference Abstracts 2010

Oxygen isotope constraints on the origin of high-Cr garnets from Kimberlites ZHENGRONG WANG1, BRIAN SKINNER1 2 AND NOBU SHIMIZU

A1113

Geochemical evidence for crustal assimilation at mid-ocean ridges D. WANLESS1, M. PERFIT1, W.I. RIDLEY2, E. KLEIN3, P. WALLACE4, J.W.VALLEY5 AND C. GRIMES6 1

Dept. of Geological Sciences, Univ. of Florida U.S. Geological Survey, Denver, CO 3 Nicholas School of the Environment, Duke University 4 Dept. of Geological Sciences, Univ. of Oregon, 5 Dept. of Geoscience, Univ. of Wisconsin 6 Dept. of Geosciences, Mississippi State 2

1

Dept. of Geology & Geophysics, Yale University, PO Box 208109, New Haven, CT 06520 2 Dept. Of Geology and Geophysics, WHOI, MA 06517 The association between diamonds and high-Cr, sub-calcic garnets from kimberlites suggests these garnets have experienced high pressure and temperature conditions in the mantle. However, their oxygen isotope compositions were generally reported to be lower than those of coexisting olivines that have typical upper-mantle values, correlate negatively with their Cr-contents, and display subtle intermineral disequilibria [e.g. 1, 2, 3]. These observations require sub-calcic garnets either were derived from high-temperature hydrothermally-altered, Cr-rich crustal materials during deep slab subduction or have experienced cryptic metasomatism by high-Cr, high-Mg, but 18O-depleted melts during their ascent to the surface of the earth. We investigated the ‘Cr-effect’ on determining oxygen isotope compositions of high-Cr garnets. Mixtures of garnet standards (GMG-2) and various amounts of pure Cr-metal were measured for !18O-values by infrared-laser fluorination technique (ILFT). Experiments show that oxygen isotope compositions of sample mixtures vary systematically as a function of the Cr-content and O2-yield. Mass-balance and spectroscopic analyses indicate the correlation between the measured !18O-value and Cr-content is an analytical artifact mostly due to quantitative fractionation between the extractedO2 and chromium oxyfluorides in the sample chamber during the ILFT analyses (~0.086‰ for 1 wt. % Cr2O3 present). After applying our experimentally-calibrated correction method to garnets from South Africa and Canada [2, 4], our study reveals an equilibrium oxygen isotope fractionation between the Crpoor garnet and coexisting olivine (i.e. Garnet * Olivine). More importantly, the high-Cr garnets (Cr2O3>5%) have a !18O-value of ~6.0±0.1‰, suggesting the involment of 18Oenriched crustal materials during their formation. [1] D. Mattey, Lowry & Macpherson (1994) EPSL 128, 231– 241. [2] Klein-BenDavid & Pearson (2009) GCA 73, 837–855. [3] H.F. Zhang, Menzies & Mattey (2003) EPSL 216, 329– 346. [4] Schulze, Valley, Bell & Spicuzza (2001) GCA 65, 4375–4384.

While the majority of eruptions at spreading centers produce lavas with relatively limited basaltic compositions, dacites have erupted at several mid-ocean ridges (MOR). MOR dacites have remarkably consistent major and trace element trends and isotopic ratios, suggesting similar processes control their chemistry. The geochemistry of MOR dacites suggests that assimilation is important in their petrogenesis. These lavas are characterized by elevated Cl, U, Th, Zr, and Hf; low Nb and Ta and relatively low #18O (~5.6 vs. expected ~6.9). Petrologic modelling suggests that fractional crystallization and assimilation of altered crust will produce magmas consistent with MOR dacite compositions. Small amounts of partial meting and assimilation of oceanic crust may also be significant in the petrogenesis of evolved MORB. Thus, we investigate if these crustal processes affect interpretations of mantle source compositions by changing primary incompatible element concentrations and isotopic ratios. MOR dacites exhibit limited radiogenic isotope ratios that lie between ratios of spatially related basaltic lavas. We interpret this as geochemical homogenization of partial melts from a range of basaltic compositions within the crust during assimilation.

A1114

Goldschmidt Conference Abstracts 2010

Boron isotopic ratios from the Salar de Uyuni, Bolivian Altiplano as a paleoenvironmental indicator

The kinetics of binding of aspartic acid to aqueous calcium ion by molecular dynamics

N.R.WARNER1*, A. NUNNERY1, G.S. DWYER1, P.A. BAKER1, S.C. FRITZ2 AND A.VENGOSH1

D.M WARREN AND A.G. STACK

1

Division of Earth and Ocean Sciences Nicholas School of the Environment, Duke University, Durham, NC 27708 (*correspondence: [email protected]) 2 Department of Geosciences, University of Nebraska-Lincoln, Lincoln, NE

The Salar de Uyuni on the Bolivian Altiplano is the largest salt flat in the world with over half of the world’s lithium reserves and extensive borate deposits. The Salar fluctuated during the Late Pleistocene from being a dry salt pan to a deep (>100 meters) lake during periods of increased precipitation/inflow. The drier periods are recorded in the sediments as evaporites whereas the wetter periods are characterized by carbonate-bearing mud. We present new data on the boron concentrations and isotopic ratios recorded in fluids entrapped in sediment and evaporite deposits from the Salar. Boron concentrations and isotopic ratios were analyzed on over 40 samples collected from a core drilled in 1999; #11B values vary from -22‰ to -4 ‰. Present-day surface water in the Uyuni basin, including the major inputs of the Rio Desaguadero and the Rio Grande, have #11B values between -6‰ to +4‰. The #11B of evaporites deposited >50 ka fluctuates between -20‰ and -12‰. The transition from these evaporites to lacustrine sediments deposited during the wetter climate represented by paleolakes Minchin (~46-36 ka) and Tauca (~26-15ka)[1] is associated with a sharp change of #11B from -16‰ to -4‰, followed by a gradual decline to -14‰ in the lacustrine sediments. By contrast, the two most recent halite intervals have #11B of -4‰. The low #11B values recorded in the sediments are different from those of modern river water input and thus could reflect a contribution of an unknown water source with a distinguished high B and low #11B composition. We attribute this to an unmonitored geothermal source with high B, Li, and Mg contents. The relative contribution of this source predominates over surface inflows during drier periods >50 ka. The measurement of the boron isotopic ratios in fluids entrapped in sediments and evaporites offers a new paleoenvironmental proxy for reconstructing the hydrology of the basin. [1] Baker et al. (2001) Nature 409, 698–701.

School of Earth and Atmospheric Sciences, Georgia Institute of Technology ([email protected]) Specific amino acids such as aspartic acid play an important role in the mechanism of action of biomineralization proteins. Much research has been performed in the last several decades on elucidating the mechanisms by which these macromolecules affect morphology, phase selection, and kinetics of biomineral growth. Affecting all of these processes is the mechanism and rate that biomineralization proteins bind to the inorganic phase of interest. The interaction of aspartic acid and aqueous calcite surfaces has been studied widely in the field of biomineralization for their abundance in natural systems.[1, 2] However, despite the abundance of research in biomineralization, meaningful kinetic data at the molecularscale is still needed to understand reaction mechanisms. We analyzed the proposed binding mechanism of a carboxyl group of an aspartic acid to an aqueous calcium ion using molecular dynamics. Simulations were performed using the LAMMPS code using the DREIDING [3] force field for aspartic acid and a new model for aqueous calcium ions [4]. Rate expressions were computed using the reactive flux method metadynamics. The rates of attachment, detachment and binding energies of an aqueous calcium ion binding to the carboxyl of an aspartic acid have been calculated. Rate estimates were validated by estimating an equilibrium constant from the ratio of attachment to detachment rate and comparing to experimental information. This presents the first meaningful molecular level kinetic information for this system in solution. [1] Teng et al. (1998) Science 282, 724–727. [2] Elhadj et al. (2006) Proc. Nat. Acad. Sci. U.S.A 103, 19237–19242. [3] Mayo, Olafson & Goddard (1990) J. Phys. Chem. 94, 8897–8909. [4] Raiteri, Gale, Quigley & Rodger (in press) J. Phys. Chem. C.

Goldschmidt Conference Abstracts 2010

Microbial metal interactions – Thinking beyond the surface

Galapagos Islands – Tracing a volcanic groundwater system using noble gases

LESLEY A. WARREN1*, KELSEY L.I. NORLUND1 2 AND ADAM P. HITCHCOCK

R.B. WARRIER1*, M.C. CASTRO1, C.M. HALL1AND N. D’OZOUVILLE2

1

School of Geography and Earth Sciences, McMaster University (*correspondence: [email protected]) 2 Department of Chemistry, McMaster University

Our work combining field and laboratory integrated microbial geochemical investigation with high-resolution techniques enabling characterization and visualization at the bacterium scale (STXM), have indicated a repeated motif of socially organized microbial cooperation, ‘pod’ formation, that is directly linked to geochemical processes. Results will be presented from an integrated experimental approach including geochemical experimentation, scanning transmission X-ray microscopy (STXM), fluorescent in situ hybridization (FISH) [1], ecology and molecular genetics for our recent discovery of an environmental sulphur redox cycling consortium involving two common mine bacteria: Acidithiobacillus ferroxidans and Acidiphilium sp. The two bacterial strains are specifically spatially segregated within a macrostructure of extracellular polymeric substance (EPS), enabling coupled sulphur oxidation and reduction reactions confirmed by STXM results. Pod formation by type culture strains was induced and linked to ecological conditions and involves quorum sensing. The proposed sulphur geochemistry associated with this bacterial consortium produces 40-90% less acid than expected based on abiotic AMD models, with implications for both AMD mitigation and AMD carbon flux modeling. These results highlight how microbes cooperatively orchestrate their geochemical environment, underscoring the need to consider community activity in constraining their geochemical impacts. [1] Norlund, Southam, Tyliszcczak, Hu, Karunakaran, Obst, Hitchcock & Warren (2009) Environmental Science & Technology 43, 8781–8786.

A1115

1

Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan, USA (*correspondence: [email protected]) ([email protected], [email protected]) 2 Galapagos Islands Integrated Water Studies (GIIWS) ([email protected]) Noble gases dissolved in groundwater have been commonly used as conservative tracers to study sedimentary systems. Temperatures derived from dissolved noble gases in water have also been regarded as a potentially robust indicator of past climate. However, few studies have demonstrated the applicability of noble gases in identifying recharge sources and flow paths in volcanic systems. Our study attempts to characterize the hydrogeology of the volcanic islands of San Cristobal and Santa Cruz in the Galapagos archipelago. Of particular relevance is the identification of recharge areas and timing of recharge using the atmospheric component of noble gases. Water samples were collected from springs and groundwater for both islands as well as one lake in San Cristobal and analyzed for He, Ne, Ar, Kr, and Xe concentrations and isotopic ratios. For some samples, concentrations of noble gases indicate that equilibration with air saturated water (ASW) occurred within expected temperature and altitude range values. Specifically, altitudes between 250 and 730m and temperatures of 19 and 28°C are found for San Cristobal while altitudes between 160 and 870m and temperatures between 16 and 27.5°C are found for Santa Cruz, suggesting that these are the altitude and temperature range value at which recharge occurs. For other samples, recharge altitudes derived from measured noble gas concentrations are unexpected and extend above the peaks of these islands. Similarly, noble gas temperatures (NGTs) calculated for these samples using assumed recharge altitudes do not compare with expected temperatures in these islands. While some samples indicate high altitude and low equilibration temperatures, other samples indicate high altitude and high equilibration temperatures. Our preliminary results might suggest that re-equilibration of rain water with soil air, as in sedimentary systems, may be lacking here probably due to rapid water infiltration through fractures. Loss of noble gases by outgassing due to bacterial action might also be a factor.

A1116

Goldschmidt Conference Abstracts 2010

The mechanism of uranium isotope fractionation during adsorption to Mn oxyhydroxide

Evidence for the presence of cyanobacteria and thermophylic methanogens in a 3.46 Ga sea, Western Australia

L.E. WASYLENKI1, G.A. BRENNECKA1, J.R. BARGAR2 1,3 AND A.D. ANBAR

Y. WATANBE1*, M. HOASHI2 AND H. OHMOTO1

1

School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287-1404 USA ([email protected]) 2 Stanford Synchrotron Radiation Laboratory, 2575 Sand Hill Rd, Menlo Park, CA 94025 USA 3 Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287-1604 USA Recent studies have reported natural variations in the ratio of 238U/235U due to ‘stable’ isotope fractionation [1-3]. The largest observed fractionations are apparently associated with redox reactions, but a small fractionation between seawater and marine ferromanganese sediments suggested that adsorption of U (VI) from solution onto Mn and/or Fe oxyhydroxides also causes an isotope effect. Because adsorption to these substrates has critically important implications for U transport, understanding U isotope systematics during adsorption could lead to a useful new tool for monitoring this process in the environment. Previously we conducted simple U adsorption experiments with synthetic K-birnessite. We reported a fractionation matching that observed between seawater and natural ferromanganese sediments: #238U/235U of adsorbed U was 0.2‰ lighter than #238U/235U of dissolved U [4]. Because there is no redox reaction in this system, a difference in uranium’s coordination environment between dissolved and adsorbed U is likely responsible for isotope fractionation. We analyzed adsorbed U from our experimental study with extended X-ray absorption fine structure (EXAFS) spectroscopy. Comparison of our EXAFS spectrum with those for abundant aqueous U species reveals subtle, but important differences in the U-O coordination shell between dissolved and adsorbed U, specifically an increase in disorder in the bond distances to equatorial oxygens in the adsorbed complex. We hypothesize that these differences are responsible for the fractionation observed in our experiments and likely in nature, as well. [1] Weyer et al. (2008) GCA 72, 345. [2] Stirling et al. (2007) EPSL 264, 208. [3] Bopp et al. (2009) Geology, 37, 611. [4] Brennecka et al. (2008) GCA 72(12) Suppl. A114.

1

NASA Astrobiology Institute and Dept. of Geosciences, Penn State Univ., University Park, PA 16802, USA (*correspondence: [email protected]) 2 Dept. of Chemistry, Kyushu Univ., Fukuoka, 810-8560 Japan

The 3.46 Ga Marble Bar Chert/Jasper Formation (MBC) in the Pilbara Craton, Western Australia is a low-grade Algoma-type banded iron formaiton (BIF). It formed by mixing of submarine hydrothermal fluids (T <~250°C) and local seawater at depth >200m in a large (~30 km diameter) submarine caldera (Hoashi et al. 2009). The changes in paragenesis and abundances of Fe-bearing minerals (siderite, hematite, magnetite, pyrite) in a 160m-long MBC drill core suggest that the redox state of bottom water in the submarine caldera changed from anoxic during the major siderite precipitation stage to oxic (O2 content > 10 µM) during intensive hydrotehrmal activity that caused primary hematite precipitation. O2 in the deep water was most likely produced by oxygenic photoautotrophs (cyanobacteria) in the surface water. We have analyzed C/H/N/S ratios and #13C values of bulk rocks, extracted kerogens, and carbonates. The results indicate general trends from the anoxic to oxic (and increased hydrothermal activity) stages of: (1) decreasing organic C contents, from 0.7 to <0.1 wt%; (2) increasing #13Corg values from -27±5‰ to -20±5‰; (3) decreasing carbonate (siderite) contents from 3.7 to <0.1 wt% in Ccarb; (4) increasing #13Ccarb values from -2.4 to +5.8‰; and (5) increasing !13Ccarb-org values from 30 to 15‰. These data suggest that: (A) Organic matter accumulated on the seafloor during the anoxic stage was mostly remnant of cyanobacteria (#13C = -27±5‰); and (B) During the oxic (and intensitve hydrothermal) stage, remnants of cyanobacteria were decomposed within unconsolidated sediments to CH4 and CO2 by hetrotrophic methanogens; and this CO2, together with H2 from hydrothermal fluids, were used by thermophyllic chemolithoautotrophic methonogens to produce isotopically heavy organic matter. A variety of organisms that thrived in diffeerent chemical and thermal conditions (aerobes and anaerobes; photoautotrophs and chemolithoautotrophs; mesophylic and thermophylic) already existed 3.46 Ga ago.

Goldschmidt Conference Abstracts 2010

A1117

Platinum group element and Re-Os isotope systematics of cryogenian glacial terminations

Isotope separation by diffusion: Competing effects of chemical and isotopic exchange

CHRISTINE A. WATERS1*, BERNHARD PEUCKER-EHRENRBINK2 3 AND PAUL HOFFMAN

J. WATKINS1*, B. PETERSON1 AND D.J. DEPAOLO2

1

Department of Geological Sciences, University of Texas at El Paso, TX 79968, USA (*correspondence: [email protected]) 2 Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA ([email protected]) 3 SEOS, University of Victoria, BC, V8W2Y2, Canada Bodiselitsch et al. [1] hypothesize that significant extraterrestrial iridium anomalies (1.9 ppb) in terminal Cryogenian glacial sediments constrain the duration of the Marinoan and Sturtian glaciations at 3-12 million years. We present geochemical evidence against such significant extraterrestrial anomalies from three continuous sections (Canadian Cordillera, Namibia) across Marinoan glacial terminations. Platinum group element (PGE) and Re-Os isotope systematics of two continuous Marinoan deposits from the Otavi Platform and Hoanib Shelf basin in northwestern Namibia show mostly crustal-level Os concentrations for both sections (5.0-74 ppt) and lack significant anomalies. One sample from the Hoanib Shelf basin is an exception, with an Os concentration of 0.7 ppb. Osmium concentrations appear to vary inversely with sediment accumulation rates. However, samples with higher Os concentrations have less radiogenic Os, a signature consistent with binary mixing between terrestrial and extraterrestrial Os. These results confirm earlier results obtained from a continuous section from the Mackenzie Mts in NW Canada that also lacks a significant PGE anomaly at the end of the Marinoan glaciation. Our conflicting findings from Bodiselitsch et al. [1] prompted us to reevaluate the anomaly found in the Bodiselitsch et al. study. Reanalysis of the Bodiselitsch et al. sample with the 1.9 ppb Ir anomaly shows a concentration much lower than that reported and an isotope ratio, not yet age corrected, typical of crustal sediments. It is possible that the lack of evidence for a significant extraterrestrial anomaly reflects the general lack of such anomalies in most glacial/postglacial Marinoan deposits world-wide, or rather is linked to syn- and/or post-depositional conditions that prevented such a feature from either accumulating or from being preserved in the locations studied by us. [1] Bodiselitsch et al. (2005) Science 308, 239–242.

1

Univ. of California-Berkeley, Berkeley, CA 94720, USA (*correspondence: [email protected]) 2 Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA The traditional formulations of chemical diffusion - Fick's Laws - do not specifically account for the fact that chemical elements have isotopes, but it has been shown by experiment that isotopic species diffuse at different rates depending on mass, with especially large effects being generated in silicate liquids. To model these effects, it has been customary to treat each isotope as an independent chemical species, diffusing in response to its own chemical gradient. However, it must also be the case that gradients in the mole fraction of each isotope drive isotopic redistribution. During chemical diffusion, the equilibrium isotopic distribution is disturbed by the differing diffusivities of the isotopes, forming large transient variations in isotopic ratios. There must be concomitant diffusive fluxes related to isotopic exchange acting to erase these isotopic variations. The question that has arisen is whether the diffusivity describing the rate of isotope redistribution (Ds) is the same as that describing chemical diffusion (Dc). We studied Ca and Mg isotope separation by diffusion in silicate liquids using diffusion couples of natural and synthetic compositions. In all experiments, the initial isotopic composition is uniform and each isotope diffuses in the same direction down a substantial concentration gradient, enriching the Ca- or Mg-poor liquids in the lighter isotope by an amount dependent on the relative diffusion coefficients of the isotopes. We observe that diffusion-driven isotope separations extend beyond elemental diffusion profiles, suggesting that isotopic redistribution is more efficient than chemical redistribution by diffusion. We present a model in which isotopes diffuse in response to both elemental concentration and isotopic mole fraction gradients. In our model, the differing length scales of element and isotope ratio diffusion profiles can be explained if Ds is greater than Dc by a factor of 2 for Ca and 6 for Mg in albitic liquid at 1450C. This is consistent with previous observations that diffusive isotopic homogenization (self diffusion) is generally more efficient than elemental homogenization (chemical diffusion) in silicate liquids. The differences between Ds and Dc are inversely correlated with cation mobilities. We suspect that for fast diffusing cations, the mechanisms of chemical and self diffusion are similar and Ds/Dc approaches a value of unity.

A1118

Goldschmidt Conference Abstracts 2010

Quantifying nitrate migration and natural attenuation in a shale/saprolite pathway from a former waste disposal site D.B. WATSON1*, G. TANG1, J.C. PARKER2 1 AND S.C. BROOKS 1

Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA (*correspondence: [email protected], [email protected], [email protected]) 2 Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, TN, 37996, USA ([email protected]) Understanding and quantification of contaminant transport in preferential pathways are important for long-term stewardship of contaminated sites. Characterization, monitoring and research results over the past several decades show contaminant migration through a transition zone between saprolite and shale bedrock along strike for over 3000 ft from the former S-3 Ponds in Oak Ridge Tennessee during a 32-year operation period. The cross-bedding migration appears limited at least after the primary source was removed. Contaminant concentration decreases slowly due to natural attenuation (dilution and/or denitrification) in the past 27 years since the capping of the ponds. The contaminant concentration near the S-3 ponds remains very high, suggesting strong nonequilibrium processes, i.e. either diffusion between the highly permeable transition zone and the less permeable saprolite and shale, or between matrix and fractures, or a combination of both. A numerical model is constructed to quantify the diffusion processes, assess the natural attenuation rates, and evaluate the influence of recharge on the nitrate transport that has occurred for over half a century. Model results show that an equivalent porous medium model, with the transition zone as the fast flow pathway, and low permeable saprolite and shale as sink during plume emplacement and source after the primary source was removed, is sufficient in describing the major characteristics of the plume dynamics; the mass transfer between fractures and matrix in saprolite and shale may not be significant at this time scale of decades; dilution by recharge is the major mechanism that reduces nitrate concentration with natural attenuation rate not differentiable from dilution. These results help us improve our understanding of the controlling processes and provides a foundation for further investigation on the fate and transport of co-contaminants such as uranium, technetium, and mercury at the site.

Nanoparticle surface properties deduced from single crystal mineral/water interface studies G.A. WAYCHUNAS1*, J. SUNG2 AND Y.R. SHEN2 1

Earth Sciences Division, Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, CA 94720 USA (*correspondence: [email protected]) 2 Physics Department, University of California at Berkeley, Berkeley, CA 94720 USA

Nanoparticle properties are often controlled by their surface structure, and this can in-turn be affected by the detailed nature of surface ligands and surface functional groups. However determination of this structure even for synthetic analogs presents major experimental difficulties, and is also not readily accomplished with current simulation methods. One approach to understanding nanoparticle surfaces is afforded by the study of analogous or related single crystal mineral/water interfaces. In one such study we have analyzed the hydrogen bonding on the surfaces of C-plane and R-plane sapphire using nonlinear optical laser spectroscopy, and from such work can show why nanoparticles may have different acid-base properties from their single crystal analogs. In another study we have evaluated the overall details of the surface hydrogen bonding of R-plane sapphire and determined how this relates to surface structure as determined from x-ray reflectivity or crystal truncation rod diffraction. The technique is found to be highly complementary to the x-ray methods, and can be used as a test of model assumptions and type of surface termination.

Figure 1: Electron density of 1st shell H2O lone pair interacting with Fe3+(aq)[1]

Goldschmidt Conference Abstracts 2010

A1119

1St principle dynamical simulation of hydrogen bond structure, dynamics and simple reactions in the hydration shells of highly charged metal ions

Predicting the chemical and physical properties of geothermal fluids: Model development and molecular level theoretical understanding

JOHN H. WEARE1*, ERIC J. BYLASKA2, STUART BOGATKO1, EMILIE CAUET1 AND JOHN FULTON2

JOHN H. WEARE1*, NANCY MOLLER1, ZHENHAO DUAN2, EMILIE CAUET1 AND ERIC J. BYLASKA3

1

1

Chemistry and Biochemistry, UCSD, San Diego, CA, 92093 (*correspondence: [email protected]) 2 Pacific Northwest National Laboratory, Richland, WA, 99354 Highly charged (charge * 2+) metal ions are frequently encountered as important participants in geochemical processes involving aqueous solutions. Understanding the structure and dynamics of species in the structured hydration region surrounding these ions is critical to the interpretation of this chemistry. Because of the strong perturbation of the ion on the electronic structures of the neighbouring species conventional molecular dynamics based on assumed forms for the species interaction potentials have difficulty capturing important behaviours such as charge transfer, bond polarization, bond formation and breaking, etc, see figure of hydration shell charge transfer between a hydrating water to a transition metal ion (our simulation, left [1]). Simulation using parameter free 1st principle based methods (forces calculated directly from the electronic Schrödinger equation, Seq) will be presented. These results focus on hydrogen bonding, electronic structure and the description of simple reactions such as ligand and proton transfer, and the formation of ion pair species and agree well with data (X-ray, EXAFS etc.). Present simulation methods are based on local DFT solution to the Seq is which is known to be inadequate for many problems. Our efforts to efficiently implement higher levels of solution to the Seq will be described. [1] Bogatko, Bylaska & Weare (2010) J. Phys. Chem. A 114, 2189–2200.

Chemistry and Biochemistry, UCSD, San Diago, CA, 92093 (*correspondence: [email protected]) 2 Institute of Geology and Geophysics, Beijing, 100029, China 3 Pacific Northwest National Laboratory, Richland WA, 99354 The development of free energy based equation of state (EOS) models of geothermal fluids with emphasis both on developing predictive tools and the improvement of the molecular level understanding of the structural and chemical properties of hydrothermal fluids will be discussed. Our EOS models predict the solubility behavior of high and low density fluids in the system Na+-K+- H+-Ca2+-Al (H2O)63+-Cl¯-OH¯-SO42--CO32--H2O-H4SiO4-CO2 (aq/g)-H2S (aq/g)-CH3 (aq/g) to high T and ionic strength. For temperatures below the critical point of water this system is most accurately modeled in terms of a model consisting of a low density phase in the system H2O (g)-CO2-CH4 (g) in equilibrium with a high density liquid phase. The high density phase is described in terms of a specific interaction model accurate to high salt concentration with the inclusion of associated species where necessary. The new Al system model produces predictions with high accuracy for T to 300°C for a concentration range to 5m background salt. Our models of the low density phases and supercritical phases are based on a molecular level description via the application of thermodynamic perturbation theory and provide accurate predictions for reduced systems to much higher T and P. A major problem with the efficient use of hydrothermal resources and the development of reliable models is the lack of understanding of the structure and processes in aqueous solutions under extreme conditions. Progress in the development of new molecular level simulation tools that are providing new insights into the struture and chemistry of hydrotherms fluds will be discussed. These methods are based on the direct solution of the electronic Schrödinger equation and, provide parameter free predictions. Results agree well with observation where available (X-ray structure and EXAFS spectra). We describe our progress in the extension of these mehods to chemical processes occuring in the hydration shells of ions, and the structure and chemistry of ion associated and of oxo hydroxo polymeric species.

A1120

Goldschmidt Conference Abstracts 2010

Enrichment of gold in oceanic crust by the Iceland mantle plume: Constraints from the Reykjanes Ridge A. WEBBER1*, S. ROBERTS1, R. TAYLOR1 2 AND I.K. PITCAIRN 1

School of Ocean and Earth Science, National Oceanography Centre, University of Southampton, SO14 3ZH, UK (*correspondence: [email protected]) 2 Department of Geology and Geochemistry, Stockholm University, Stockholm, 10691 Sweden ([email protected])

It has recently been suggested that the subduction of goldenriched crust, such as oceanic plateaus and primitive basaltic crust, can increase the chances of developing gold mineralization in the overlying arc [1]. The Reykjanes Ridge is an ideal place to test the addition of Au to oceanic crust by plume activity because the mantle sources are well constrained by an extensive geochemical dataset. The ridge is under influence from the spreading Iceland plume head which progressively mixes with atlantic MORB southwards. Mixing can be identified primarily between three sources: enriched Iceland plume, depleted Iceland plume and depleted upper mantle [2]. We find this mixing process produces values between 0.22 and 1.67 ppb Au in the basaltic pillow lavas, with the highest values associated with the Iceland source members. These data correlate well with other mantle source indicators such as incompatible trace elements. Au proves to be a particularly sensitve tracer of mantle source mixing. However our lowest value of 0.22 ppb is ~4 times lower than the average of published Au data for atlantic MORB and we attribute this to the sensitivity of the analysis method used in this case. We suggest that the Iceland plume is enriching this portion of the Mid-Atlantic Ridge with respect to gold by up to 7 times. If it were to be subducted, a considerable amount of extra gold would enter the Arc system compared to subduction of MORB. [1] Bierlein et al. (2006) Mineralium Deposita 40(8), 874Ð 886. [2] Murton et al. (2002) Journal of Petrology 43, 1987Ð 2012.

Process oriented modelling of gas evolution in iron-based permeable reactive barriers A. WEBER1*, A.S. RUHL2 AND R.T. AMOS3 1

DGFZ e.V., Meraner Str. 10, 01217 Dresden, Germany (*correspondence: [email protected]) 2 Technische UniversitŠ t Berlin, Stra§ e des 17. Juni 135, 10623 Berlin, Germany ([email protected]) 3 University of Waterloo, 200 University Avenue West, Waterloo, Ontario, Canada ([email protected]) Geochemical conditions that determine rates of gas production and consumption within iron-based permeable reactive barriers are not well understood to date [1, 2]. Here we attempt to establish a numerical model representing dominant hydraulic and geochemical processes within zerovalent iron (ZVI) barriers. Initial simulations modeled the anaerobic corrosion of ZVI depending on I) the concentration of aqueous carbonate, which enhances iron reactivity, and II) mineral precipitates decreasing the reactive iron surface area. A version of the numerical model MIN3P [3, 4] that includes chemical gas production and consumption reactions is applied. A balanced degassing approach, which allows for gas storage and gas release was implemented. Thus the impact on residence time and chemical turnover is reflected. Results of laboratory ZVI filled columns, carried out under distinct conditions, delivered data for inverse modeling. After parameterization the model could reflect chemical conditions measured in the column effluent, gas evolution from the columns, and gas saturation within the columns. According to this stepwise approach the implementation of further processes into the model is planned.

Figure 1: Gas evolution and gas saturation in a column experiment with greycast, 4 mL/h DW + 40 mg/L TIC. [1] Kohn et al. (2005) Environ. Sci. Technol. 39, 2867Ð 2879. [2] Williams et al. (2007) Appl. Geochem. 22, 90Ð 108. [3] Amos & Mayer (2006) J. Contam. Hydrol. 87, 123Ð 154. [4] Jeen et al. (2007) Environ. Sci. Technol. 40, 6432Ð 6437.

Goldschmidt Conference Abstracts 2010

Microbially-mediated iron biogeochemistry KARRIE A. WEBER1,2 1

School of Biological Sciences, University of Nebraska, Lincoln, NE 68588 USA 2 Department of Geosciences, University of Nebraska, Lincoln, NE 68588 USA Iron is a nutritional requirement for life. However for many microorganisms iron is not only a nutritional necessity, but also serves as a source of energy or as a terminal electron acceptor in respiratory microbial metabolisms. Microbiallycatalyzed iron redox reactions between the Fe (III) and Fe (II) valence states play a fundamental role influencing modern environmental biogeochemistry in oxic, suboxic, and anoxic zones of aquatic, terrestrial, and subsurface environmental systems. The significance of iron redox cycling to the biogeochemistry of these environmental systems is well established. In the last decade, light-independent microbial Fe (II) oxidation has been recognized to contribute to iron redox cycling not only in the oxic environment but also in environments devoid of molecular oxygen with nitrate serving as the electron acceptor. To date, a diversity of microorganisms in the domain Bacteria and Archaea have been identified from various surface and subsurface environments that are capable of Fe (II) oxidation. These studies hint at the ubiquity of these Fe (II)-oxidizing microorganisms suggesting that metabolic, light independent Fe (II) oxidation reactions have the potential to contribute to suboxic and anoxic Fe (II) oxidative processes on a global scale provided that adequate concentrations of an electron acceptor are readily available. Some of these microorganisms are capable of oxidizing solid-phase Fe (II) bearing minerals including the products of microbial Fe (III) reduction. While oxidation of Fe (II) in suboxic and anoxic environments closes a gap in the iron redox cycle, the oxidative dissolution of these solid-phase Fe (II) minerals is additionally significant to understanding mineral weathering and dissolution reactions in these environments. These processes are not only important to modern biogeochemical cycling, but likely played a significant role throughout geologic time in surface as well as subsurface environments.

A1121

Biosignatures within iron-rich concretions originating in a sandstone paleoaquifer: Evidence of microbial oxidative dissolution of Fe(II)-carbonates KARRIE A. WEBER1,2*, TRISHA L. SPANBAUER1, RICHARD M. KETTLER2, DAVID LOOPE2, DAVID WACEY3 3 AND MATTHEW R. KILBURN 1

School of Biological Sciences, University of Nebraska, Lincoln, NE 68588 USA 2 Department of Geosciences, University of Nebraska, Lincoln, NE 68588 USA 3 Australian Microscopy & Microanalysis Research Facility, The University of Western Australia, Perth, Australia (*correspondence: [email protected]) Spheroidal concretions composed of an iron oxide-rich cemented outer rind and a weakly-cemented iron-poor sandstone core are abundant in the Jurassic Navajo Sandstone of the Colorado Plateau. Our recent work in south-central Utah has shown that abundant Fe (II)-carbonates were precipitated within the Navajo Sandstone at sites that lie downflow from massive CO2 reservoirs. The Fe (II)-carbonate concretions were subsequently altered to Fe (III)-oxide as oxidizing water was transported through the paleoaquifer. Microbial metabolisms have been demonstrated to promote the oxidative dissolution of Fe (II)-carbonate minerals. Elemental analysis of the specimens collected from Spencer Flat, east of Escalante, in south-central Utah revealed elevated carbon (C) as well as nitrogen (N) content with respect to the interior of the concretion (Rind, C, 0.06%, N, 0.006%; Interior, C, 0.009%, N, 0.003%). Elevated C and N values in the rind suggest C-N rich compounds consistent with biomolecules. Average #13C values measured from the organic carbon (OC) fraction in triplicate samples (-22.088‰) indicated the iron oxide crust contains OC consistent with a biogenic origin and CO2 fixation (-20 to -35 ‰). Structures morphologically consistent with bacterial cells have been observed via FE-SEM in association with a matrix that coated sand grains in the iron oxide-rich rind. Similar structures identified using NanoSIMS consists of high CN/C and FeO demonstrating a relationship of Fe minerals and C signature consistent with OC. Together these results support the presence of microorganisms and iron biomineralization in the spheroidal iron oxide concretions. Here we have presented evidence of biosignatures suggesting a role of microbial metabolism transforming the Fe (II)-carbonates which would have subsequently lead to carbonate dissolution in the paleoaquifer. Given the ubiquity of Fe (II)-oxidizing bacteria, this microbial catalyzed process is likely active in modern aquifers and other subsurface environments.

A1122

Goldschmidt Conference Abstracts 2010

Hawaiian plume source: Isotopic constraints from Mauna Loa DOMINIQUE WEIS1, J. MICHAEL RHODES2, MICHAEL O. GARCIA3 AND MARC NORMAN4

Permian-Triassic carbon isotopic signature from pedogenic carbonate, Ordos basin, China: Implications for pCO2 reconstructions

1

PCIGR, EOS, Univ. British Columbia, Vancouver BC V6T1Z4, Canada ([email protected]) 2 Geosciences, Univ. Massachusetts, Amherst, MA010039297, USA ([email protected]) 3 Geology & Geophysics, Univ. Hawai’i, Honolulu, HI 96822, USA ([email protected]) 4 ANU, Canberra, Australia ([email protected]) Significant heterogeneities have been documented in the Hawaiian mantle plume source, especially on the Loa trend. Mauna Loa itself, the largest Hawaiian volcano, had surprisingly few isotopic analyses. We carefully selected ~120 basalt samples for high-precision isotopic analyses (<200 ppm for Pb; <50 ppm for Hf, Nd and Sr) from the submarine southwest rift zone (up to ~500 ka), HSDP1, 2 (100-12 ka), radial vents (~47-0.148 ka), prehistoric (40-0.014 ka) and historical (1843-1984) Mauna Loa lavas. Our results show the presence of chemical heterogeneities at a range of scales in the plume source. About 10% of the analyzed lavas, all from the SW rift zone, including the Mile High-Section, do not define Pb-Pb lines and have high 208Pb*/206Pb*, lower 87Sr/86Sr, 143 Nd/144Nd and 176Hf/177Hf and higher Nb/Y, La/Sm than the other lavas. These older (>400 ka) lavas define separate binary geochemical and isotope trends compared to younger lavas. Their characteristics are not as enriched as the Koolau Makapuu component (i.e. recycled oceanic crust and sediment component). This indicates the presence of yet another component in the source of Hawaiian basalts. Older lavas from both Mauna Kea and Mauna Loa sample a more heterogeneous plume source (Loihi-like?) than younger shield lavas. Pb-Pb lines fan in opposite directions with age and in slope for younger, <100 ka, Mauna Loa and HSDP2 Mauna Kea basalts. Our large-scale isotopic study of Mauna Loa shield basalts confirms clear differences with Kea-trend volcanoes. This is maintained throughout the ~1 myr activity of these volcanoes and extends back in time on all the Hawaiian Islands (to ~5 Ma). Our study shows the presence of long-lasting geochemical heterogeneities in the plume source that are reflected in the erupted basalts, at the scale of individual volcanoes. The Loa-trend source is more heterogeneous in all isotopic systems by ~1.5 that the Kea-trend source and, Loatrend volcanoes systematically sample more enriched material, indicating an azimuthally zoned plume conduit.

AMY L. WEISLOGEL Department of Geological Sciences, University of Alabama, Tuscaloosa, AL 35487 ([email protected]) The end-Permian mass extinction is closely associated with a global carbon cycle instability thought to have been caused by volcanic eruptions and associated contact metamorphism of coal and carbonate crustal rocks. The current knowledge base of this event has mainly been reconstructed from marine sedimentary proxy records. Carbon isotopic composition of pedogenic carbonate from terrestrial deposits is another proxy for evaluating carbon cycle evolution and, assuming formation in equilibrium with the atmosphere, one that can be used to reconstruct atmospheric pCO2. Currently, terrestrial isotopic proxy data for the Permian-Triassic boundary are not sufficient for detailed modeling of the linked marine-terrestrial system response to carbon cycle fluctuations. The largely undeformed strata of the Ordos basin in north-central China include a robust, mostly conformable Upper Permian-Lower Triassic section bearing Calcic paleosols. The Permian-Triassic boundary in the eastern Ordos basin is defined lithologically as the contact of predominantly purplish mudstone and medium-bedded sandstone of the Upper Permian Shiqianfeng Formation with a thick-bedded red sandstone of the Lower Triassic Liujiagou Formation. Samples of pedogenic carbonate were collected across or near the Permian-Triassic boundary from 2 sections near the town of Wubu, Sha’anxi province, along with 2 additional sites near Hangcheng, Shanxi province. These samples were analyzed in the Alabama Stable Isotope Laboratory at the University of Alabama. Results from the Wubu area indicate high !13C values (~7-11‰ V-PDB) dominate the lower 70 m of the section; however approximately 30 m above the mapped Permian-Triassic boundary, !13C values exhibit a significant decrease to ~5-8‰ V-PDB. This decrease in !13C values results in a modeled increase in pCO2 of ~1000 ppmV. However, results from localities further south (~200 km) show markedly lower !13C values of ~3-5‰ V-PDB for upper Permian and lower Triassic samples. The decrease in !13C values corresponds to an increase in abundance of lacustrine facies in the section. This suggests basin hydrology, controlled primarily by tectonic basin evolution, may have influenced the !13C composition of soil carbonate. The north-south Permian-Triassic outcrop belt of the Ordos basin holds a unique opportunity to test possible basinal controls on pedogenic carbonate isotopic composition.

Goldschmidt Conference Abstracts 2010

Looking for the keys under the lamppost: Trace elements in fibrous diamonds Y. WEISS1*, W.L. GRIFFIN2 AND O. NAVON1 1

The Fredy and Nadine Herrmann Institute of Earth Sciences, the Hebrew University of Jerusalem, Israel (*correspondence: [email protected], [email protected]) 2 GEMOC, Macquarie University, NSW, Australia ([email protected]) Early analyses of trace elements in diamonds used destructive techniques. Recently, LA-ICP-MS has emerged as a new, less destructive tool for in situ analysis or for Ô off-lineÕ ablation. Much effort is being invested in bringing the detection limit of this method to a level that will allow the analysis of a wider range of elements in gem material. Here we report a study of fibrous diamonds that carry up to 1 wt% of submicron fluid inclusions. Combining EPMA, FTIR and LA-ICP-MS data the full composition of the trapped fluids is now available. Fluid composition varies between hydrous-saline, hydrous-silicic and two carbonatitic endmembers (high-Mg and low-Mg ones). Calculation of the trace element contents of the fluids reveals high enrichment of the Ô incompatibleÕ elements even in comparison with kimberlitic melts (up to a few thousand PM values). We distinguish two common patterns between Cs and La: Ô TablesÕ are rich in Ba, Th, U and LREE and depleted in alkalis, Nb and Ta, Ô BenchesÕ are smoother and devoid of significant anomalies. The two can be best distinguished by their U/Rb and La/Nb ratios.

Figure 1: Ô TableÕ and Ô BenchÕ patterns in silicic HDFs. A closer examination reveals unique features in patterns of diamond from some localities. For example, Ô TableÕ patterns in saline fluids from the Diavik mine exhibit higher Ba/Th ratios and steeper REEs compared with similar fluids from Koingnaas. Some analyses of gem diamonds reveal patterns that are close to the Ô TableÕ and Ô BenchÕ ones. Such unique provenance-controlled features in fibrous diamonds may prove useful in defining the source of gemmy diamonds.

A1123

Seasonal variation in the Mg/Ca ratio and !18O of the planktonic foraminifera, Globigerina bulloides: Results from the Gulf of Tehuantepec, Eastern Equatorial North Pacific K.E. WEJNERT1*, R.C. THUNELL1,2, E, TAPPA2, M. MACHAIN3, M.L. MACHAIN-CASTILLO3, F.R.G. ARGç EZ3, X.A. NAVA3 3 AND G. GONZç LEZ-CHAVEZ 1

Marine Science Program, University of South Carolina, Columbia, SC 29208, USA (*correspondence: [email protected]) 2 Department of Earth and Ocean Sciences, University of South Carolina, Columbia, SC 29208, USA 3 Instituto de Ciencias del Mar y Limnologia, Universidad Nacional Autonoma de Mexico, Coyoacan Mexico, DF, MEX 04510 Mg/Ca and !18O has been measured in the surface dwelling planktonic foraminiferal species Globigerina bulloides from weekly sediment trap samples collected from two depths (460 and 560m) in the Gulf of Tehuantepec (15¡ 38.826 N, 95¡ 16.905 W) between February 2006 and June 2008. The Gulf of Tehuantepec is a region of intense upwelling and undergoes significant seasonal changes in sea surface temperature (SST) (~ 24¡ Ð 31¡ C) and salinity (~ 33.3 Ð 34.5). Our results show that Mg/Ca and !18O are negatively correlated (r2 = - 0.34, p < 0.001) with most of the scatter occurring in the region of low Mg/Ca and high !18O values. A comparison of the Mg/Ca values with weekly sea surface temperature measurements yields a weak positive correlation (r2 = 0.23, p < 0.001), while no significant correlation exists between the !18O and SST. We attribute the latter to seasonal changes in the depth habitat of G. bulloides. Temperatures calculated from the Mg/Ca data range from 21¡ Ð 32¡ C and thus agree fairly well with the measured temperatures. Temperatures calculated from !18O are generally similar to those estimated from Mg/Ca.

A1124

Goldschmidt Conference Abstracts 2010

Impact of trace mineral phases on the total solute flux from andesitic volcanics

‘Invisible’ Ag and Au in supergene Cu-sulfides: EMPA, SIMS and TEM constraints

SUSAN A. WELCH*, STEVEN T. GOLDSMITH AND ANNE E. CAREY

M. WELDT1, M. REICH1*, S. CHRYSSOULIS2, A. DEDITIUS3, C. PALACIOS1, A. ZÚÑIGA4 1 AND M. ALVEAR .

School of Earth Sciences and Byrd Polar Research Center, The Ohio State University, Columbus OH 43210, USA ([email protected], [email protected] [email protected]) Recent work on high standing islands (HSIs) shows weathering rates based on stream water chemistry in andesitic terrains are comparable to rates determined for basalts, indicating that these areas might be much more important in drawing down atmospheric CO2 than previously recognized. We conducted batch dissolution experiments on andesitic material collected from +40, 000 year old tephra deposits from Dominica and ash from the 1991 eruption of Mt. Pinatubo, Philippines, to determine the dissolution rates of major and trace mineral phases. Dissolution experiments of months duration were conducted over a range of pH (3–7) on bulk samples and mineral separates. Dissolution rates at pH 4 based on Si release from the crystalline and glass-rich Dominica tephra separates were similar, ~4 to 8 *10-13 mol/g sec. Dissolution rates in water were lower, ~20–50% of rates measured at pH 4. Apatite, as inclusions within pyroxenes, composes only a few percent of the tephra but it contributes significantly to total solute flux. Solutes from apatite dissolution are ~1–6-fold greater than the solutes from silicate dissolution at pH 4, and ~0.1–1 times the solutes from silica dissolution in water. TDS from dissolution of the Pinatubo ash is 2 orders of magnitude greater than for the Dominica samples. Silica dissolution rates for Pinatubo ash are about an order of magnitude greater than those for the Dominica tephra, from ~1 to 8 *10-12 mol/g sec over pH 7–3. Apatite dissolution increases with increasing acidity, and is ~0.1–1 times silica dissolution. Over 90% of the solutes are derived from dissolution of trace amounts of CaSO4. Typically, the reactivity of Ca-bearing accessory minerals such as apatite or anhydrite has not been considered to contribute significantly to the overall Ca flux from weathering and subsequent CaCO3 precipitation. However, in our experiments the release of Ca ions to solution is dominated by the reactivity of these phases. In areas that experience rapid physical weathering the reactivity of trace mineral phases may contribute significantly to the total chemical weathering flux.

1

Dept. of Geology, University of Chile, Santiago, Chile (*correspondence: [email protected]) 2 Advanced Mineral Technology Laboratory, London, ON, Canada 3 CSIRO Division of Exploration and Mining, Kensignton, WA, Australia 4 Dept. of Mechanical Engineering, University of Chile, Santiago, Chile In this study, we used secondary ionization mass spectrometry (SIMS) and electron microprobe analyzer (EMPA) techniques to fully characterize the trace metal content of Ag-bearing supergene chalcocites from various Cu deposits in the Atacama Desert of northern Chile. SIMS and EMPA measurements reveal that, apart from hosting up to ~11, 000 ppm Ag, supergene chalcocite can incorporate up to part-per-million contents of Au (~6 ppm) and associated metalloids such as As (~300 ppm), Sb (~60 ppm), Se (~96 ppm) and Te (~18 ppm). The SIMS analyses show that Ag and Au concentrations strongly correlate with As, defining wedge-shaped zones in Ag-As and Au-As log-log spaces. SIMS depth profiling and high-resolution transmission electron microscopy (HRTEM) observations reveal that the anomalously high Ag/As and Au/As samples plotting above the wedge zone contain nanoparticles of metallic Ag and Au, while samples with lower ratios contain Ag and Au that is structurally bound to the Cu-sulfide matrix. The Ag-Au-As relations reported in this study strongly suggests that the incoporation of precious metals in Cu-sulfides formed under supergene conditions respond to the incorporation of a minor component, in this case As. Therefore, As might play a significant role by increasing the solubility of Ag and Au in supergene chalcocite and controlling the occurrence of Ag and Au nanoparticles. Considering the fact that supergene enrichment of Cu processes can be active from tens of millions of years (e.g. Atacama Desert), we conclude that As-bearing supergene chalcocite may play a previously unforeseen role in scavenging precious metals from undersaturated (or locally slightly supersaturated) solutions in arid to hyperarid areas.

Goldschmidt Conference Abstracts 2010

In situ immobilization of radionuclide and metallic contaminants in deep vadose zone environments via reactant microfoams 1,2

2

DAWN M. WELLMAN , LIRONG ZHONG , SHAS V. MATTIGOD2, JIM SZECSODY2 2 AND FRED ZHANG

A1125

New insights into the development of early clay grain coats JOANN E. WELTON1 AND GRANT Y. YIP1,2 1

ExxonMobil Upstream Research Company, P.O. Box 2189, Houston,TX 77252-2198 ([email protected]) 2 Currently, ExxonMobil Production Company, 800 Bell St., Houston,TX 77002 ([email protected])

1

U.S. Department of Energy, Office of Environmental Management, Germantown, MD 2 Pacific Northwest National Laboratory, 902 Battelle Blvd, PO Box 999, MS K3-62, Richland, WA 99352

Metal and radionuclide environmental contamination, at sites in which the capacity of the natural system to attenuate the contaminants is exceeded, is a critical issue plaguing water supplies globally. Within the United States, the most significant inventory is the results of legacy contamination within the Department of Energy complex. Long-lived radionuclides, 99Tc and U (VI), and highly toxic metals, Cr (VI), are of particular concern. Arid waste sites throughout the western United States, afford oxic, circum-neutral to alkaline geochemical conditions which maintain these contaminants as oxidized, highly mobile anions capable of migrating relatively unretarded through the subsurface. Moreover, the majority of the contaminant mass resides within deep vadose zone environments which present hydrogeologic challenges limiting access and remediation options. Heterogeneous deep vadose zone environments contain preferential flow paths. Generally, vertical migration of infiltrating remedial solutions is observed through high permeability zones and low permeability strata that are the dominant source of legacy contaminants are bypassed. Moreover, the wetting front of a water-based delivery can readily mobilize contaminants and potentially enhance transport to underlying aquifers prior to stabiliztion. In contrast, shear-thinning fluids (e.g. surfactants) can be used to lower the surface tension of liquids and create stabile foams. The flow of foam through a vadose zone environment can be directed by pressure gradient rather than gravity. Moreover, the use of foam as a delivery mechanism limits the volume of water (< 3% vol.) required for remedy delivery and emplacement, thus mitigating contaminant mobilization. We will present bench- and intermediate-scale laboratory results discussing the fundamental hydrogeochemical properties controlling the efficacy of utilizing RCMs for in situ stabilization of uranium, technetium, and chromium.

Clay grain coats have long been recognized as one of the key controls on the preservation of deep reservoir quality [1, 2, 3, 4]. However, most grain coat studies have emphasized high temperature cement growth, providing few insights into the initial processes responsible for early coat development. A fundamental question is, how and why does clay adhere to grain surfaces? The purpose of this research was to evaluate the primary controls on the development and distribution of early grain coats in a modern fluvial system. The Brazos River in Texas was selected for this study. It is a very clay-rich river, ranking 6th in terms of mean annual suspended sediment discharge (11mt/yr) in North America. It is a predominantly a meandering river system which extends approximately 850 miles through central Texas, crossing a diverse climate zone ranging from semi-arid to subtropical. The primary controls investigated include the impact of bedrock geology, fluvial style, climate, texture, pedogenesis, and the role of biological organisms in the development of clay and carbonate grain coats. Results confirmed that climate, texture, soil processes, and biological activity (e.g. microbial to land snails), do indeed play a critical role in the development of effective grain coats. Recognition criteria for identification of early grain coat processes in ancient sandstones will be discussed. [1] Pittman & Lumsden (1968) J. Sed. Pet. 38, 668–670. [2] Pittman, Larese & Heald (1992) SEPM Spec. Pub. 47, 241–255. [3] Ehrenberg (1993) AAPG 77, pp. 1260–1286. [4] Worden & Morad (2003) Int. Assoc. Sedimentol. Spec. Publ. 34, 3–41.

A1126

Goldschmidt Conference Abstracts 2010

Arsenic mitigation and safe water provisions in sedimentary basins of Northern China: Utilization of deep aquifer and piped water system DONGGUANG WEN1*, FUCUN ZHANG2, JIANQIANG GUO2, XUFENG LI2, ERYONG ZHANG1 AND YAN ZHENG3 1

China Geological Survey, 100037, Beijing, China (*correspondence: [email protected]) 2 Center for Hydrogeology and Environmental Geology, CGS, 071051, Baoding, Hebei, China ([email protected], [email protected], [email protected], [email protected]) 3 UNICEF Bangladesh, Dhaka 1000, Bangladesh ([email protected]) An estimated 3 million people were exposed > 0.05 mg/L As in drinking water in wells tapping shallow aquifers of Songneng, Hetao, Datong, Yinchuan and Kuitun Basins in northern China. The China Geological Survey conducted a series of investigations using remote sensing, geophysical, geochemical and hydrogeological surveys aimed to identify safe aquifers for drinking water supply. These low lying basins in arid or semi-arid climatic zones show similar hydrodynamics with sluggish flow down the flow path. Arsenic content in groundwater increases < 1 ,g/L from the advancing edge of the piedmont sloping plain to as much as 1820 ,g/L towards the center of plains. Although there is a large degree of spatial variation of arsenic content, high arsenic is usually found between 10m and 80m in a lacustrine sedimentary facies consisted of organic-rich, muddy, and silty fine sand. Low arsenic groundwater is found at depth below the arsenic containing shallow groundwater in confined aquifers, and also in shallow phreatic water in ancient channels and the sides of diversion canals. To avoid over exploration of low arsenic deep groundwater, the well spacing of production wells were designed considering well depth, diameter, pumping horizon, groundwater production. Corrosion resistant U-PVC pipes were used and the wells sealed to prevent shallow groundwater intrusion. The aquifer with low arsenic groundwater in piedmont alluvial sloping plain is characterized by coarse grain size with high yield. In areas where no deep groundwater production wells can be drilled, this aquifer was developed and piped water systems built. Our experience demonstrates that sustainable development of low arsenic aquifers can be achieved.

Hyperspectral mapping of mineral assemblages using spectral unmixing XING-PING WEN1*, RUN-SHENG HAN1,2 3 AND XIAO-FENG YANG 1

Faculty of Land Resource Engineering, Kunming University of Science and Technology, Kunming, 650093, P.R. China (*correspondence: [email protected]) 2 Southwest Institute of Geological Survey, Geological Survey Center for Non-ferrous Mineral Resources, Kunming, 650093, P.R. China 3 Research Center for Analysis and Measurement, Kunming University of Science and Technology, Kunming, 650093, P.R. China Hyperspectral remote sensing offers mineral exploration ability to map efficiently the distribution of various mineral assemblages [1]. The Pulang area, which is an important polymetallic enrichment zone in Yunnan Province in southwest China, is used as a case study. Access into this high altitude mountainous area is difficult and the ability to map indications of mineralization using spectral remote sensing is desirable. This study used EO-1 Hyperion remote sensing data. The hyperspectral image was first atmospherically corrected using the FLAASH model. Field spectra of typical mineral assemblage samples were measured in situ using the ASD FieldSpec 3 spectroradiometer. Background field spectra were acquired in large homogeneous areas. All field measurements were repeated 50 times and the mean spectra were computed as endmembers. It was assumed that the image spectra are linear combinations of endmember spectra. Then, the constrained Linear Spectral Unmixing algorithm was applied to the Hyperion data and abundances of mineral assemblages were obtained to generate a map of mineral assemblages. The results indicate that different mineral assemblages, particularly those associated with the polymetallic zone, can be identified successfully and they also partially coincide with soil geochemical anomalies. Future work would involve evaluation of abundances of mineral assemblages. This study was jointly supported by the NSF of Yunnan Province, China (KKSA200921019) and the innovation team of ore-forming dynamics and prediction of concealed deposits, KMUST, Kunming, China (2008). [1] Bierwirth et al. (2002) Economic Geology 97, 819–826.

Goldschmidt Conference Abstracts 2010

A1127

On the temperature dependence of mineral surface protonation and ion adsorption reactions

Dissecting the large-scale spatiotemporal variation in Ricinus communis (Castor Bean) seed oil # 2H

DAVID J. WESOLOWSKI1, MICHAEL L. MACHESKY2, SERGUEI N. LVOV3, MILAN PREDOTA4, MOIRA K. RIDLEY5 AND PETER T. CUMMINGS6

J.B. WEST1, H.W. KREUZER2 AND J.R. EHLERINGER3

1

Oak Ridge National Laboratory, Oak Ridge, TN 37831-6110, USA ([email protected]) 2 University of Illinois, Champaign, IL 61820, USA 3 The Pennsylvania State University, University Park, PA 16802, USA 4 University of South Bohemia, 370 05 Ceske Budejovice, Czech Republic 5 Texas Tech University, Lubbock, TX 79409, USA 6 Vanderbilt University, Nashville, TN 37235, USA The vast majority of mineral surface reaction studies have been conducted at room temperature. However, many processes of interest in the geosciences, materials and chemical sciences, electrical power generation, ore processing, chemical industries, etc., involve the interaction of aqueous solutions with mineral surfaces at elevated temperatures. Fortunately, recent advances in experimental, analytical, computational and theoretical approaches have greatly expanded our understanding of the temperature dependencies of surface protonation reactions and the resulting surface charge development. There is a smaller, but growing body of literature, including the extensive studies by this research team of rutile (alpha-TiO2), on the changes in ion adsorption equilibria with increasing temperature, which are intimately related to surface protonation equilibria. We will review these studies and demonstrate broad generalities relatable to the properties of homogeneous hydrothermal solutions. Ion pairing equilibria and the acid-base properties of aqueous species change profoundly, and have profound effects on system behaviour, with increasing temperature. Similarly, we show that ion adsorption is greatly enhanced at elevated temperatures and surface protonation equilibria have become both readily measurable and predictable. It is no longer necessary or appropriate to ignore temperature effects on surface reactions, and this information is critically needed to make fundamental advances in our understanding of, for instance, heterogeneous reaction rates and mechanisms.

This research team has been largely supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Geoscience Research Program through grants to Oak Ridge National Laborotory, which is managed for the U.S.D.O.E. by UT-Battelle, LLC under contract DE-AC05-00OR22725.

1

Department of Ecosystem Science and Management, Texas A&M University (*correspondence: [email protected]) 2 Pacific Northwest National Laboratory ([email protected]) 3 Department of Biology, University of Utah ([email protected]) Plant lipid isotope ratios record important aspects of environmental variation. For example, along with composition, the isotope ratios of lipids in sedimentary records yield insights to past species distributions and climate conditions. Lipids also have the potential to be useful for forensic reconstructions. Correctly interpreting these records requires that we understand what controls isotopic variation and in cases where inferences are to be made about geographic origins, an emphasis must be placed on understanding the primary drivers of large-scale spatial and temporal variability. Potential sources of variation include the isotopic composition of soil moisture, fractionations associated with biophysical processes such as transpiration, and biochemical processes such as photosynthesis and fatty acid synthesis. As part of a comprehensive evaluation of the large-scale spatiotemporal variation of castor bean isotopic composition, we report here results of an analysis of the global-scale variation of castor oil hydrogen isotope ratios. Over 250 seeds from plants grown in key castor bean growing regions, including Brazil, China, India, and many locations in the USA, as well as other locations in Europe and Central America were analyzed. We observed a significant correlation between spatial variation of seed oil #2H and that of modeled global precipitation #2H. A large amount of the observed variation remained unexplained by this simple relationship. Comparisons were made between our observations and spatiotemporal variations in climate by using the monthly climate grids (University of East Anglia, CRU TS 3.0) that revealed a significant influence of climate on an inter-annual basis. Correlations were also observed between seed oil #2H and seed characteristics, perhaps suggesting a role of either plant stress or seed maturity on seed oil #2H. A revised model, driven by both long-term modeled precipitation #2H and inter-annual variations in climate yielded improved explanatory power. The extent to which plant stress could mediate the hydrogen isotopic composition of seed lipids remains unclear and will be key to refining our understanding and predictive capacity.

A1128

Goldschmidt Conference Abstracts 2010

Biotic/abiotic controls on silica cycling in a grassland soil chronosequence

Stable isotopic evidence of climatedriven changes in methane cycling in northern peatlands

A.F. WHITE1, S. SCHULZ1, D. VIVIT1 AND R. EVETT2

J.R. WHITE1*, R.D. SHANNON2, J.F. WELTZIN3, J. PASTOR4 AND S.D. BRIDGHAM5

1

U. S. Geological Survey, Menlo Park, CA 94025 (*correspondence: [email protected]) 2 University of California, Berkeley, Department of Environmental Science, Berkeley, CA 94720

A soil chronosequence (65 TO 225 kA)), exposed to a coastal Mediterranean climate near Santa Cruz, California, provides ideal conditions to quantify both short and long-term patterns in silica mobility and cycling linked to seasonal variability in hydrology, pore water chemistry and growth patterns of the grassland vegetation. Superimposed on longterm silica release rates dominated by feldspar weathering and dependent on soil ages [1, 2] are additional patterns reflecting Si cycling between pore waters and grass biomass. While the seasonal uptake and release of mineral nutrients such as K and Ca involve the incorporation into and release from relatively labile organically-bound compounds, the cycling of Si involves the incorporation and slower release from phytoliths composed of amorphous silica. Annual Si fluxes between the soil and grasses (fSi) is 0.16 moles m-2 yr while the total phytolith soil mass (mphyto), whose distribution with depth reflects both bioturbation and chemical weathering, is 85 moles m-3. Assuming steady-state conditions, the phytolith residence time in the soil is t1 = 500 yr Alternatively, a phytolith residence time of t2 = 30 yrs is calculated based on a ‘shrinking sphere’ approach incorporating recently reported experimental dissolutions rates kr and estimates of surface roughness ! and molar volume Vo. The discrepancy in residence times (t1 > t2) either indicates non-steady-state conditions, i.e. phytoliths are currently dissolving much faster than in the past, or more likely, the natural rates are significantly slower due to the fact that pore waters are close to amorphous Si saturation. Such saturation inhibition is previously reported for silicate mineral weathering in the Santa Cruz soils [2]. Increases in amorphous Si, in excess of phytoliths with depth, and a close association with Al suggest that phytolith weathering is contributing to precursor clay formation. Addition insights are presented based on Ge/Si ratios and !3°Si distributions. [1] White et al. (2008) GCA 72, (36-68). [2] White et al. (2009) GCA 73, 2804–2831.

1

Indiana University, Bloomington, IN (*correspondence: [email protected]) 2 Pennylvania State University, University Park, PA ([email protected]) 3 USA National Phenology Network, Tuscon, AZ ([email protected]) 4 University of Minnesota, Duluth, MN ([email protected]) 5 University of Oregon, Eugene, OR ([email protected]) Boreal peatlands contain >30% of terrestrial organic carbon and are particularly vulnerable to changes in climate. Temperatures in boreal regions are predicted to increase during the 21st century which may affect soil microbial processes and plant communities. Plant community composition controls soil carbon quality, methanogenesis, methanotrophy and thus methane efflux. To date, these feedbacks have not been incorporated into carbon cycling components of GCMs. We investigated effects of soil warming and drying on methane cycling using lab incubations and field mesocosms. Bog and fen soil monoliths in northern Minnesota, received infrared heating crossed with water-table control for 6 years. Concentrations, fluxes and isotopic compositions of CH4 were measured as well as acetate, sulfate, ammonium, plant productivity and N retention. Shortterm (5-yr) perturbations in IR and water table affected CH4 cycling through changes in soil decomposition, root productivity, and N availability. We speculate that increase in labile substrates associated with root exudates and enhanced plant transport contribute to increases in methane efflux. Porewater stable isotopes support acetate fermentation as the principal pathway of methanogenesis in bogs (mean !13CH4 = -39.3‰). Under warm, wet conditions, the majority of the methane was isotopically heavy (mean !13CH4 = -28.1‰), consistent with methanotrophic activity throughout the soil column. Increases in mineralization of organic N to ammonium in porewater may enhance methane oxidation under low water table. To further improve our understanding of the dynamics of methane cycling in response to climate forcing, soil microbial communities and their interactions with plant communities must be studied in greater detail.

Goldschmidt Conference Abstracts 2010

Laser Raman Spectroscopy as a tool for in situ bio-geo-chemical analyses in the deep ocean S.N. WHITE Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA ([email protected]) Oceanography has historically been a science based on the collection of samples for ship- or shore-based analyses. While disciplines such as phycial oceanography and seafloor seismology have transitioned to sensing rather than sampling, disciplines such as geology, chemistry and biology have lagged behind. The development of deep-sea platforms such as remotely operated vechicles (ROVs), autonomous under-water vehicles (AUVs), and cabled observatories is driving the need for instruments capable of in situ, autonomous, real-time measurements in the deep ocean. This is particularly true for extreme environments such as seafloor hydrothermal vent systems. Laser Raman Spectroscopy is an optical technique capable of in situ molecular identification of solids, liquids and gases. A laser excites a target, and the spectrum of the energyshifted, backscattered light provides compositional and strucutral information about the target. Raman scattering is a weak effect – only 1 in 108 photons is Raman scattered – but it benefits in the deep ocean from the lack of ambient light. Because it is non-invasive and does not require reagents or consumables, laser Raman spectroscopy is well-suited to remote, deep-sea environments. While the potential is great, there are still a number of challenges to be addressed to effectively use laser Raman spectroscopy in the deep ocean. These include techniques to mitigate interference from fluorescence which can overwhelm the Raman signal; mechanisms to precisely position the laser spot; and approaches to extract background seawater signals from the spectra. A sea-going laser Raman spectrometer, Deep Ocean Raman In Situ Spectrometer (DORISS), has been deployed to collect spectra of seafloor shells; bacterial mats and clathrate hydrates at cold seep sites; minerals at hydrothermal vent and seafloor slump sites; and dissolved gases in controlled dissolution experiements. Laboratory Raman analyses of mineral species (e.g. carbonates, sulfates and sulfides) and dissolved gases (e.g. CO2 and CH4) of interest in seafloor hydrothermal systems has been undertaken to determine how to optimize sea-going Raman systems for hydrothermal applications. The goal is the development of miniature Raman instruments capable of monitoring hydrothermal vent fluid chemistry and geochemical processes in vent plumes.

A1129

Mass-independent fractionation of sulfur isotopes during experimental photolysis of sulfur dioxide and carbonyl sulfide A.R. WHITEHILL*, Y. LIN, E. CORDNER AND S. ONO Massachusetts Institute of Technology, Cambridge, MA 02139 (*correspondence: [email protected]) Sulfur mass independent isotope fractionation (MIF) has been observed in many Archean rocks. Photochemical reactions of atmospheric sulfur gases, particularly the UV photolysis of SO2, remain the most likely source of these sulfur MIF signatures. Understanding the isotope effects of the various photochemical reactions of sulfur gases, both theoretically and experimentally, can help reconstruct the atmospheric chemistry of the early Earth. Broad band photolysis of SO2 using a Xe lamp has yielded !33S/ !34S values of approximately 0.64. Additional photolysis experiments are being carried out on SO2 using a 200±30 nm bandpass filter. This isolates the 180-230 nm absorption band of SO2, which corresponds to the photodissociation of SO2 into SO + O. Preliminary results show !33S/ !34S values of approximately 0.62, similar to the fractionation caused by the full-spectrum photolysis. This suggests that 180-230 nm photodissociation is the primary cause of mass independent fractionation in SO2 photolysis. Photolysis experiments on SO2 using a 250 nm longpass filter are also being carried out to target the weaker photoexcitation band (260 – 340 nm) and exclude the strong SO2 photodissociation band. UV Photolysis of carbonyl sulfide (OCS) has shown small but measurable MIF signatures (!33S/ !34S = 0.533) [2]. Additional OCS photolysis experiments are being performed on OCS purified by gas chromatography and tested with full spectrum and 180-230 nm UV. [1] Ono et al. (2009) Eos Trans. AGU 90(52) Fall Meet. Suppl. Abstract V13G-05. [2] Lin et al. (submitted) Geophys. Res. Lett.

A1130

Goldschmidt Conference Abstracts 2010

Tracing sources of uranium contamination using minor isotopes

Challenges facing the production of RMs for geochemical microanalyses

E. WIDOM* AND D.C. KUENTZ

M. WIEDENBECK*

Department of Geology, Miami University, Oxford, Ohio 45406, USA (*correspondence: [email protected]) Isotopic signatures of uranium in environmental samples, including the minor as well as the major isotopes, can serve as highly sensitive tracers of environmental uranium contamination. Natural and non-natural sources of uranium contamination can sometimes be distinguished based on variations in the ratio of the major isotopes of uranium (235U/238U) because natural uranium has an essentially constant 235 U/238U ratio, whereas processed nuclear materials are generally relatively enriched or depleted in 235U. However, measureable variations in 235U/238U ratios occur only in response to relatively significant contamination with nonnatural uranium, and mixtures of enriched and depleted uranium can sometimes be obscured. Isotopic ratios involving the minor isotopes of uranium including (234U/238U) activity ratios and 236U/238U ratios can serve as complementary and significantly more sensitive tracers of uranium contamination from processed nuclear materials in environmental samples. The presence of measureable 236U, an essentially non-naturally occurring isotope of uranium formed by neutron-capture of 235 U in processed nuclear materials, is particularly diagnostic of anthropogenic uranium contamination. Tree bark, which effectively traps airborne dust and aerosols, serves as a natural repository of environmental contaminants, including uranium released to the environment during processing of nuclear fuel. We have analyzed the major and minor isotopes of uranium in nine tree bark samples from southwestern Ohio in the vicinity of the Fernald Feed Materials Production Center (FFMPC), where estimates of inadvertant releases of uranium dust to the atmosphere between 1951-1985 range from 200, 000 to 1 million pounds [1]. Our results show that tree bark as far away as 25 km from the FFMPC site contains measureable 236 U. Measured 236U/238U ratios increase progressively towards the FFMPC site, reaching ratios as high as 1.2 x 10-4. In addition, (234U/238U) activity ratios in most samples are below one and exhibit a strong negative correlation with 236U/238U, indicative of variable degrees of mixing between natural and depleted uranium, the latter enriched in 236U from nuclear fuel reprocessing. Depleted 235U/238U ratios were only detected in the more contaminated samples closer to the FFMPC site, demonstrating that the minor isotopes are significantly more sensitive tracers of anthropogenic environmental uranium contamination. [1] Makhijani (2000) Inst. Energy & Environ. Res. 5(3).

Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, Telegrafenberg, D-14473 Potsdam, Germany (*correspondence: [email protected]) The production of reference materials suitable for in situ microanalyses faces a number of challenges beyond those encountered for bulk sample applications. One obvious problem is the metrological requirement that RMs are only fitfor-purpose when using test portion masses at or above the levels for which the material’s homogeneity has been confirmed. Worldwide no materials currently exist for which the chemical composition has been certified at the µm sampling scale [1]. With the exception of the International Association of Geoanalysts’ protocol for the certification of geological reference materials [2, 3], the geochemical literature is largely silent about how this issue should be addressed. One approach is the characterization of a new material using bulk methods in conjunction with the homogeneity testing of the relative abundances of analytes using microanalytical methods. Such a strategy, however, is impacted by requirement that the intrinsic repeatability of the microanalytical method must be propagated to the expanded uncertainty assigned to the smaller test portion mass. Such an approach is unlikely to achieve the goal of an overall uncertainty which is no larger than 33% that of ‘routine laboratory measurements’ [2]. Only in rare cases is a direct determination of geochemical concentrations at sub-µg test portion masses metrologically possible (e.g. ion implantation in conjunction with SIMS depth profiling [4, 5]). Perhaps the greatest technical obstacle is the inability to determine the absolute mass of a test portion with low uncertainty – even the best of laboratory balances cannot determine a mass in the low µg range with an acceptable uncertainty. Here a method for crossing the µg-ng frontier is proposed. In contrast to using an isotopic spike for determining an element’s concentration, a spike approach could conversely be use to determine a sample’s mass in conjunction with assuming an absolute concentration for the given element in the material; large relative weighing uncertainties would thus be replaced by volumetric uncertainties associated with the spike solution. [1] http://www. nano-refmat. bam. de [2] Kane et al. (2003) Geostand. Newsletter 27, 227–244. [3] Kane et al. (2007) GGR 31, 285–288. [4] Keppler et al. (2003) Nature 424, 414– 416. [5] Shcheka et al. (2006) EPSL 245, 730–742.

Goldschmidt Conference Abstracts 2010

A1131

Nanoparticle aggregation state and aging: Implications for reactivity and toxicity testing

Geophysical constraints on heat transfer to mid-ocean ridge hydrothermal systems

M.R. WIESNER1,2 AND S.R. CHAE1,2

W.S.D. WILCOCK

1

Duke University, Civil and Environmental Engineering Department, 121 Hudson Hall, 27707, Durham, North Carolina, USA 2 CEREGE, UMR 6635 CNRS/Aix-Marseille Université, Europôle de l’Arbois, 13545, Aix-en-Provence, France 3 Center for the Environmental Implications of NanoTechnology (CEINT), Duke Univeristy, Durham, NC, USA

Within the gray zone between the atomic and bulk scales, the properties of nanomaterials may be expected to change due to the formation of nanoparticle clusters to an extent that is intermediate between those when atoms cluster of form molecules and when colloidal particles aggregate. In this communication, we discuss the effects of aging and aggregation on fullerene fate and transport, as well as the implications for nanoparticle reactivity and toxicity. The interplay between physical forces that bring nanoparticles in contact, the chemistry of nanoparticles surfaces and environmental factors that may transform these surfaces, play an important role in determining nanoparticle transport, fate and reactivity through their effects on aggregate structure. We discuss the role of environmental and physiological conditions in determining nanoparticle aggregation rates and aggregate structure as well as the impact of aggregate structure on removal by sedimentation. Using photosensitization by fullerene nanoparticles as an example, we show how differences in aggregate structure and heterogeneity that results over time may affect nanoparticle reactivity. The production of reactive oxygen species, microbial inactivation, and the mobility of the aggregates of the nC60 in a silicate porous medium all increased as suspensions were fractionated to enrich with smaller aggregates by progressive membrane filtration. These size-dependent differences are attributed to an increasing degree of hydroxylation of nC60 aggregates with decreasing size. As the quantity and influence of these more reaction fractions may increase with time, experiments evaluating fullerene transport and toxicity endpoints must take into account the evolution and heterogeneity of fullerene suspensions.

School of Oceanography, University of Washington, Seattle, WA 98195 (*correspondence: [email protected]) Seismic reflection surveys show that most fast and many intermediate spreading rate ridges are underlain at mid-crustal depths by a thin steady-state magma chamber [1]. The melt content varies from pure melt to a crystalline mush with higher melt fractions beneath sections of the ridge that support black smoker vent fields [2]. The observed heat fluxes of black smoker fields can substantially exceed the steady state heat fluxes necessary to form the lower oceanic crust but are consistent with the rates at which magma is supplied episodically to terrestrial volcanoes [3]. For black smoker systems, one-dimensional models of heat transfer show that the conductive boundary layer separating hydrothermal fluids from the magma chamber must be only a few meters thick [4]. Without magma replenishment the heat fluxes are sufficient to solidify the magma chamber in tens of years [5]. In order to preserve a steady-state magma chamber and maintain a balance between average hydrothermal heat fluxes and the heat of crustal formation, the conductive boundary layer must thicken considerably, perhaps to as much as a few hundred meters, along portions of the ridge with no black smoker fields. Microearthquake data collected beneath the Endeavour segment of the Juan de Fuca Ridge suggests that the injection of pressurized magma into mid-crustal magma chambers leads to significant fracturing of the overlaying rock carapace [6]. This fracturing provides a mechanism to maintain a thin conductive boundary that would otherwise thicken due to the clogging of cracks by hydrothermal alteration products. Thus it appears that a simple model of heat transfer in which the conductive boundary layer decreases in thickness by up to two orders of magnitude during intervals of magma injection and black smoker activity is consistent with geophysical observations. A challenge to the geochemical community is to determine whether this model is also consistent with the chemistry of hydrothermal fluids and reaction zone rocks. [1] Detrick et al. (1987) Nature 326, 35–41. [2] Singh et al. (1998) Nature 394, 874–878. [3] Humphris & Cann (2000) J. Geophys. Res. 105(28), 477–28, 488. [4] Lowell & Germanovich (1994) J. Geophys. Res. 99, 565–575. [5] Liu & Lowell (2009) J. Geophys. Res. 114, B02102. [6] Wilcock et al. (2009) Nature Geosci. 2, 509–513.

A1132

Goldschmidt Conference Abstracts 2010

Neutron diffraction studies of amorphous materials at high pressure

Extreme bone diagenesis: Implications for reconstructing palaeoenvironmental parameters

MARTIN WILDING1, MALCOLM GUTHRIE2, CRAIG BULL3 3 AND MATT TUCKER

C. TERRY WILLIAMS

1

Institute of Mathematical and Physical Sciences, Aberystwyth University, Aberystwyth, SY23 3BZ, UK ([email protected]) 2 Geophysical Laboratory, Carnegie Institute of Washington, Washington DC 3 ISIS neutron source, Rutherford Appelton Laboratoty, Chilton, Oxford, UK

Amorphous materials have been traditionally used to provide information on the structure of liquids. Neutron and X-ray diffraction provide unequivocal information on the structure of amorphous materials including coordination numbers and information on short and intermediate range ordering. There is however evidence to suggest that the structure of liquids and amorphous materials at high pressure are substantially different from the ambient pressure equivalents. This has important implications for any process dominated by liquids at high pressure, such as Earth formation and evolution in which structure dependent-properties such as viscosity may bear little resemblance to the same properties measured routinely at one atmosphere. The situation is further complicated because high pressure structures of glass cannot be quenched requiring in situ measurement. Diffraction studies of amorphous materials are challenging, the scattered signal is weak and interpretation requires data to high values of scattering vector Q in order to achieve good real space resolution. Diffraction studies at high pressure require the contributions from the sample environment to be removed, contributions that are pressure dependent and require careful correction. In this contribution we will present the results of studies of simple silicates compressed to pressure of up to 9GPa, illustrating that quantitative structure factor data can be obtained and insight into liquid behaviour achieved. We demonstrate the a silica poor magnesium silicate glass shows an abrupt change in structure between 9 and 9 GPa, this is an increase in Mg-O coordination and a corresponding change in the topography of the silicate network. We suggest that this change correlates with a decrease in viscosity and increase in the so-called melt fragility. We further discuss how the correction techniques and experimental protocols that we have developed can be applied to a wider range of compositions extending pressure ranges, using combined X-ray and neutron techniques to extract partial structure factors.

Department of Mineralogy, Natural History Museum, Cromwell Road, London SW7 5BD, UK ([email protected]) Palaeoenvironmental parameters can be established from studying both the concentrations, and distribution in fossil, or archaeological bone, of a range of trace elements, including Strontium, Rare Earth Elements and Uranium. However, overprinting from elements or isotopes derived from the burial environment can mask, or at worst case, completely destroy any inherent in vivo signals. In this presentation, examples will be shown of extreme diagenetic alteration in mammal bones in sites including Olduvai Gorge, Tanzania [1, 2], and from Pblined coffin burials at Spitalfields, London, UK [3]. These extreme examples instead, can provide information about the burial (or local) environment itself, and can identify characteristic signatures that establish the presence of diagenetic overprinting in fossil or archaeological bone. [1] Williams et al. (1997) Appl. Geochem. 12, 537–547. [2] Dauphin et al. (1999) J. Sed. Res. 69, 612–621. [3] Molleson et al. (1998) Bull. Soc. Géol. France 169, 425– 432.

Goldschmidt Conference Abstracts 2010

Copper stable isotopes as tracers of metal-sulphide segregation and impact melting processes on iron meteorite parent bodies

A1133

Formation of Selenium nanospheres accompanying bioremediation of a Uranium-contaminated aquifer KENNETH H. WILLIAMS1*, A. LUCIE N’GUESSAN2, MICHAEL J. WILKINS2 AND PHILIP E. LONG2

HELEN M. WILLIAMS1 AND COREY ARCHER2 1

1

Department of Earth Sciences, University of Oxford, Oxford OX1 3PR, UK ([email protected]) 2 Bristol Isotope Group, Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol BS8 1RJ, UK ([email protected]) We report high precision Cu isotope data for magmatic and non-magmatic iron meteorites, for which Fe isotope data are also available. The Cu isotope compositions of metals (#65CuM) and sulphides (#65CuFeS) range from -9.30 ‰ to 0.99 ‰ and from -8.90 to 0.63 ‰, respectively. Metal-troilite fractionation factors (!65CuM-FeS = #65CuM - #65CuFeS) are highly variable. In the non-magmatic (IAB, IIICD) irons, #65CuM and #65CuFeS show broad correlations with published metal Cu concentrations and correlations between #65CuFeS and !65CuM-FeS with troilite iron isotope compositions (#57FeFeS) and metal-troilite iron isotope fractionation factors (!57FeM-FeS) are also present. We propose that the range in #65CuFeS and !65CuM-FeS displayed by the non-magmatic irons is produced by kinetic stable isotope fractionation accompanying melting and diffusional transport of Cu, where the lighter isotope is preferentially concentrated into FeS. However, this process cannot explain the range in #57FeFeS and !57FeM-FeS values as unrealistically large amounts of Fe would need to be transferred. As concluded in an earlier study [1], we suggest that the range in !57FeM-FeS reflects incomplete isotopic equilibrium during cooling, where the irons with the largest !57FeM-FeS values are closest to Fe isotope equilibrium. These irons also display the smallest !65CuM-FeS values. We propose that these irons cooled the most slowly from magmatic temperatures, experienced minimal subsequent thermal perturbations, and are therefore the closest to isotopic equilibrium for both systems. The irons with the smallest !57FeM-FeS and largest !65CuM-FeS values experienced faster cooling such that Fe isotope equilibrium between metal and troilite was not reached, and were subject to later thermal events, which resulted in local melting and diffusional transport of Cu from metal to sulphide. The contrasting thermal histories that can be reconstructed for the IAB and IIICD irons using Cu and Fe isotopes are consistent with models that invoke episodes of impact related breakup and reassembly in the evolution of their parent bodies. [1] Williams et al. (2006) EPSL 250(3-4), 486–500.

Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA (*correspondence: [email protected]) 2 Pacific Northwest Nat. Lab., Richland, WA 99352, USA Removal of selenium from uranium-contaminated groundwater was documented during bioremediation activities at the Department of Energy’s Rifle Integrated Field Research Challenge (IFRC) site in Rifle, Colorado. Selenium was removed from groundwater and concentrated in its elemental form [Se (0)] within a mineralized biofilm attached to tubing used to circulate acetate in groundwater. Scanning and transmission electron microscopy revealed close association of spherical Se (0) precipitates and cell surfaces, with selenium aggregates having an average particle diameter of 50-60 nm. While total selenium in groundwater never exceeded 1.2 µM over the three-week treatment period, enrichment of Se (0) within the tubing (1580 µmol m-2) suggests a sorbed reservoir of selenium contributed to that concentrated within the biofilms. We propose that stimulation of iron-reducing microorganisms - as documented by increases in ferrous iron and a Geobacter-dominated microbial community - liberated an adsorbed pool of selenium following reductive dissolution of iron oxide sorbents, making it available for reductive immobilization by the tubing-associated, selenium-reducing microorganisms. The selenium removal process appeared to be the result of a mixed microbial community within the biofilm capable of coupling the oxidation of acetate to the reduction of oxygen, nitrate and aqueous selenium species. Phylogenetic analysis of the tubing-associated biomass revealed a community dominated by strains of Dechloromonas sp. and Thaurea sp., with isolates exhibiting genetic similarity to the latter group having been previously shown to reduce selenate to elemental selenium in laboratory studies. The predominance of Dechloromonas sp. in both the tubing biofilms and selenium-amended laboratory enrichment cultures suggests these well known perchlorate-reducing bacteria may also have the ability to reduce selenium or play a previously unrecognized role in the selenium removal process.

A1134

Goldschmidt Conference Abstracts 2010

Ex situ studies of nanominerals by Secondary Ion Mass Spectrometry

Micro total analysis system development for in situ chemical exploration of Titan and Mars

L.B. WILLIAMS1*, R.L. HERVIG1 AND J. SRODON2 1

Arizona State University, Box 871404, Tempe, AZ 85287, USA (*correspondence: [email protected]) 2 Inst. Geol. Sci PAN, Senacka1, PL-31 002, Krakow, Poland

Analyses of nanominerals that are difficult to separate from sediments in quantities sufficient for conventional isotopic analyses are well suited for analysis by SIMS because of the high useful yields for this technique. Separation of clay minerals <20nm is feasible [1], but requires several days of centrifugation to separate a few mg of fundamental clay particles. A 5µl suspension of 1mg pure, 20nm illite crystals in deionized water and dried on a glass slide provides ample material for multiple SIMS analyses. The surface tension of water orients the clays with basal (a-b) planes parallel to the surface, creating flat surfaces when dried. Using a defocused primary beam averages many crystals, and multiple analyses maximizes analyis precision. Such ex-situ analyses of an Ordovician bentonite from the Baltic Basin, were performed on different size fractions (<20nm, 20-100nm, 100-200nm) of illite-smectite (I-S). Isotope ratios varied up to 10‰ among the size fractions, relating to changes in fluid composition during crystal growth. Across the basin isotopic trends follow a paleo-temperature gradient [2]. Clay with isotopically heavy B (#11B ~ +10‰) occurs near higher temperature (200°C) parts of the basin grading to –3‰ in cooler regions (120 °C). In the same samples, Li-isotopes show an opposite trend; increasing from –10‰ (200°C) to +30‰ (seawater) in cooler sediments. The Cambrian Alum shale is a source rock for hydrocarbons (HC) in the Baltic Basin. The thermal maturity of this unit has been evaluated based on the H/C ratios and vitrinite reflectance [3]. A suite of samples ranging from immature (H/C = 1.16) to mature (H/C = 0.14) organic matter (OM) was evaluated for B and Li isotope composition in comparison to the bentonite. OM contributes 50% of the B and Li in the Alum shale. The OM #11B decreases from –0.4 to –28.4‰ with increasing maturity, while OM #7Li increases from –20 to +4‰. These opposing trends suggest that isotopically heavy B is first released from OM in the ‘oil window’ for hydrocarbons, while isotopically light Li is generated. Because the organic signatures of both elements are lighter than natural waters, isotopically light B and Li signatures in diagenetic illites may reflect inputs from organic sources during thermal evolution of the basin. [1] Clauer et al. (1997) Clay Mins. 32, 181–196. [2] Srodon et al. (2009) Clay Mins. 44, 361–387. [3] Buchardt & Lewan (1990) AAPG Bull. 74, 394–406.

P.A. WILLIS1, A.M. FISHER1, H.F. GREER1, M.F. MORA1, D. MAIR2 AND H. JIAO3 1

Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA (*correspondence: [email protected]) 2 Fluigence, LLC, Santa Clara, CA 95054, USA 3 Los Gatos Research Inc., Mountain View, CA 94941, USA This contribution summarizes our ongoing efforts in the design, fabrication, and implementation of micro total analysis (i.e. ‘lab on a chip’) systems intended for the payloads of future robotic explorers to destinations such as Mars or Titan. Chemical analyses performed in these microfluidic-based systems is aimed at the determination of the extent of past or present life on these worlds, or the extent of prebiotic chemical evolution that may have taken place. Samples are to be provided by the robotic platform carrying the instrument, either via drilling into regolith and treatment with liquid water (Mars and Titan) or possibly direct sipping from hydrocarbon lakes (Titan). Organic species are mixed with stored buffer solutions, and then separated from one another on-chip electrophoretically (via capillary electrophoresis or capillary electrochromatography) and detected via laser-induced fluorescence, or alternatively via nanoelectrospray ionization and mass spectrometric analysis. Automated capillary electrophoresis analysis of this type for Mars exploration was brought to an intermediate level of automation by Skelley using fluorescamine dye for labeling of amino acids. Current work focuses on the use of Pacific Blue dye, but now in an automated fashion, in which the derivitization process is performed on chip using dried reagents deposited in dedicated reaction reservoirs. Capillary electrochromatography (CEC) analysis is also performed for the determination of polycyclic aromatic composition, utilizing porous polymer monoliths as the separation medium. Nanoelectrospray ionization is performed using conventional pulled capillaries as well as micromachined nozzles. We perform required liquid sampling handling operations (mixing, derivitization, dilution, etc.) required for these automated analyses using circuits comprised of monolithic diaphragm valves. [1] Willis et al. (2008) Lab Chip 8, 1024–1026. [2] Aubrey et al. (2008) Astrobiology 8, 583–588. [3] Skelley et al. (2005) PNAS 102, 1041–1048.

Goldschmidt Conference Abstracts 2010

A1135

High-resolution X-ray tomography of fractionally-wet media: Drainage experiments

Assessing capture of atmospheric CO2 within mine tailings using stable isotopes and 14C

CLINTON S. WILLSON1* AND SETH BRADLEY2

S.A. WILSON1*†, G.M. DIPPLE1, S.L.L. BARKER1, I.M. POWER2, V. ATUDOREI3, S.J. FALLON4 2 AND G. SOUTHAM

1

Department of Civil and Environmental Engineering, Louisiana State University, Baton Rouge, LA 70803 (*correspondence: [email protected]) 2 ([email protected])

Numerous lab- and field-scale experimental studies have shown the strong impact of wettability on constitutive relations and how increased water repellency can lead to preferential flow paths and a heterogeneous water distribution in the vadose zone. Advances in high-resolution X-ray computed tomography (XCT) techniques now make it possible to nondestructively image opaque materials providing previously hard-to-observe qualitative and quantitative data and information. Concurrent with these advances has been an effort to quantify structure within these materials. Of particular interest in porous media research is the ability to now extract granular packing details and pore network structure along with the capability to correlate fluid phases and distribution within the pore structure. This level of detail provides insights into that pore-scale processes that impact macroscopic behavior and are proving useful for pore-scale modelers. Here we will discuss a series of experiments designed to obtain pore-scale details on the distribution of water in fractionally-wet media. A series of drainage experiments were conducted at the synchrotron-based tomography beamlines (i.e. APS/GSECARS and LSU/CAMD) where high-resolution XCT was used to image columns containing different fractions of water-repellant grains under similar capillary suction heads. A unique feature of these experiments was the ability to separate the water-wet from the water-repellant grains due to slight differences in their X-ray absorption properties. Following thresholding of the images (i.e. segmentation of the solid, water, and air phases), the granular packing and pore network structure were quantified along with the water volumetric content. In addition, the water distribution was correlated to the pore network structure and the individual water-wet and water-repellant grains providing valuable insights into the impact of pore-level wettability variations. Results indicate that grain-level differences in wettability have a major impact on the connectivity of the water phase during drainage. This leads to large differences in the drainage pathways and ultimate distribution of irreducible water.

1

Mineral Deposit Research Unit, Univ. of British Columbia, Vancouver, BC V6T 1Z4, Canada (*correspondence: [email protected]) 2 Univ. of Western Ontario, London, ON N6A 5B7, Canada 3 Univ. of New Mexico, Albuquerque, NM 87131-0001, USA 4 Australian National Univ., Canberra, ACT 0200, Australia † Current address: Indiana Univ., Bloomington, IN 474051405, USA Ultramafic tailings produced by some mining operations are capable of capturing CO2 directly from the atmosphere. Mineralization of CO2 within Mg-carbonate minerals in mine tailings can occur on a scale that is significant relative to the greenhouse gas emissions of a mine, and therefore may represent an offsetting of greenhouse gas emissions Stable C and O isotope data for secondary Mg-carbonate minerals within tailings from the Mount Keith Nickel Mine, Australia and the Diavik Diamond Mine, Canada fail to unambiguously fingerprint the source of CO2 within these minerals. The fractionation of stable C isotopes during precipitation of a hydrated Mg-carbonate mineral, dypingite, was examined using analogue experiments that simulate conditions in mine tailings storage facilities. Experimental results demonstrate precipitation of 13C-depleted dypingite from a dissolved inorganic carbon (DIC) pool that is out of C isotopic equilibrium with atmospheric CO2. These results provide a compelling explanation for the depleted, ambiguous stable C isotopic data for secondary Mg-carbonate minerals at Mount Keith. Furthermore, they suggest that equilibrium fractionation factors may fail to describe the #13C signature of mine process water DIC and the secondary Mg-carbonate minerals that precipitate from this DIC pool. Stable C and O isotope data for secondary Mg-carbonate minerals from mine tailings at Mount Keith and Diavik tend to reflect the processes by which C has been cycled rather than its provenance, making it difficult to fingerprint capture of atmospheric CO2. Alternatively, 14C provides an unambiguous measure of the amount of modern atmospheric C trapped within carbonate minerals. Using this more robust tracer, we have determined that >90% of C mineralized in secondary Mg-carbonate minerals at Mount Keith and Diavik was trapped from the modern atmosphere.

Goldschmidt Conference Abstracts 2010

A1136

Development of geochemcial reference materials: USGS experiences and future directions S.A. WILSON

Thermodynamic estimates for aqueous hydrocarbons TODD WINDMAN1 AND EVERETT SHOCK2 1 2

U.S. Geological Survey ([email protected]) Geochemcial Reference Materials (GRMs) are an integral part of any geochemcial program due to their role in methods development, quality control, and instrument calibration. Key aspects to a successful GRM program are to identify current and future needs, produce large quantities of reliable materials and develop new technologies that provide more efficient ways to produce GRMs. Benefiting from the early work of Flanagan and Kane, the USGS has developed a diverse set of 28 powdered reference materials. These materials originally developed to meet USGS programmatic needs have found widespread use in the international community as evidenced by the 12% average annual growth rate in GRM distribution over the past 15 years. Immediate USGS efforts will focus on developing replacements for several of our traditionalGRMs now that their 50 year lifetime is drawing to a close. Work is also planned for the preparation of new materials many in cooperation with outside organizations. The development of a national soil material, synthetic minerals, platinum ore, metalliferous black shale and marine sediment are a few examples. With expanding interst in trace element microanalysis using Laser Ablation ICP-MS has come a new set of challenges with respoec to the development of calibration and secondary QC materials. A key aspect of this work is the development of microanalytical reference materials (MRMs) that have a wide range of trace elements which are homogeneous at the 10-50 µm spot size. For many geolgic investigations these MRM needs are met through the use of either the MPI-DING, NIST (610, 612, 614) or USGS natural and synthetic basalt glasses. The use of LA-ICP-MS in the analysis of matrices such as coral, bone, sulfides, gems and organic matrices have generated a new urgency for matrix matched MRMs. To meet USGS needs in this area we have developed a series of pressed powders which allow for the quantative analysis of elements in a polymetallic sulfides, carbonates, sulfates, and phosphate matrices. The development of reference materials will continue to expand but a clearer understanding of what is needed and how best to produce/certify those materials will be important challenges. USGS efforts will focus on development of GRMs and MRMs that are not duplicated by other producers but serve an important role in understanding geological processes on earth and in our solar system.

([email protected]) ([email protected])

Aqueous hydrocarbons are involved in geochemical processes at conditions ranging from soils to sedimentary basins to hydrothermal systems. They are metabolized by microbes, transported in fluids, and involved in oxidationreduction reactions that can be coupled to mineral alteration, gas generation, and transformations of inorganic solutes including metals, as well as sulfur and nitrogen species. Although experimentally determined thermodynamic data are relatively limited, newly developed estimation methods make it possible to greatly expand the number and variety of aqueous hydrocarbons for which calculations are possible. A group estimation method for the thermodynamic properties of hydration of organic compounds [2] permits calculation of standard state properties of aqueous hydrocarbons at the reference temperature and pressure starting with ideal gas data. Corresponding properties at high pressures and temperatures are estimated with a correlation algorithm involving published [3] and newly developed relations among parameters in the revised-HKF equation of state. Estimates for aqueous hydrocarbons were combined with thermodynamic data for liquid hydrocarbons [1] to calculate hydrothermal hydrocarbon solubilities, and the results are in close agreement with experimental solubility data. With nearly 1000 aqueous alkanes, alkenes, and alkynes, as well as cyclic and aromatic hydrocarbons now available for use with SUPCRT92, equilibrium constants for diverse reactions involving hydrocarbons can be calculated over wide-ranging environmental and geologic conditions. [1] Helgeson et al. (1998) Geochimica Et Cosmochimica Acta 62(6), 985–1081. [2] Plyasunov & Shock (2000) Geochimica et Cosmochimica Acta 64(3), 439–468. [3] Plyasunov & Shock (2001) Geochimica et Cosmochimica Acta 65(21), 3879–3900.

Goldschmidt Conference Abstracts 2010

Is a biotic sulfur cycle isotopically necessary prior to ~2.45 Ga? BOSWELL A. WING McGill University, 3450 University St., Montreal, QC, H3A 2A7, Canada (*correspondence: [email protected]) The geological sulfur isotope record exhibits a bimodal character. Mass-independent isotopic fractionation distinguishes the record prior to ~2.45 Ga, and massdependent isotopic fractionation dominates the record afterwards [1]. Laboratory experiments [2] as well as theoretical calculations [e.g. 3] identify an atmospheric source for the mass-independent S isotope fractionation, while most of the isotopic variability in the record’s mass-dependent domain has long been taken to reflect biological processing [4]. This conceptual decoupling has carried over to interpretations of the full isotopic record in earliest Paleoproterozoic and Archean rocks, with isotopic anomalies exiting the atmosphere and much of the mass-dependent isotopic fractionation being associated with microbially-driven redox reactions [1, 5]. Exceptions to this framework are made only when there is a clear covariation of $33S values (- !33S -0.5 !34S) with associated #34S measurements [5]. Atmospheric processes, however, are well known to impart significant isotopic fractionation [e.g. 6], which may explain a substantial component of the full geological S isotope record prior to ~2.45 Ga. Despite early attention drawn to this possibility [1], the net consequences of mass-dependent atmospheric isotopic fractionation have not been explored. This contribution examines the conditions under which the geologic S isotope record reflects contributions solely from atmospheric processes. I use a minimal model of isotopic fractionation during transfer through an atmospheric reaction network, constrained by laboratory experiments on S isotope fractionation, published S isotope fractionation factors, as well as fractionation factors estimated from basic theoretical considerations. Surprisingly, this exercise indicates that the full isotopic character of the earliest Paleoproterozic-Archean S cycle could have apparently been set in the atmosphere. As a result, it is unclear whether the evolutionary history of microbial S metabolisms can be isotopically distinguished prior to ~2.45 Ga. [1] Farquhar et al. (2000) Science 289, 756–758. [2] Farquhar et al. (2001) JGR 106, 32829–32839. [3] Ueno et al. (2009) PNAS 106, 14784–14789. [4] Thode & Monster (1965) AAPG Mem. 4, 366–377. [5] Ono et al. (2003) EPSL 213, 15–30. [6] Eriksen (1972) Acta Chem. Scand. 26, 573–580.

A1137

Partial and biased preservation of the mantle signal in Icelandic phenocryst compositions B. WINPENNY AND J. MACLENNAN Department of Earth Sciences, University of Cambridge, Downing Street CB2 3EQ, Cambridge, UK ([email protected], [email protected]) The progression of mixing of heterogeneous mantle melts can account for the large range of incompatible trace element ratios observed in olivine-hosted melt inclusions in primitive Icelandic basalts and the decrease in this variability with degree of crystal fractionation. We show that melts sourced from different parts of the melting region follow different crystallisation paths in the Icelandic crust, controlling the ability of clinopyroxene to record the full range of melt compositions present in the magmatic system. Ion microprobe and LA-ICPMS trace element analyses were performed on high Mg# (85-92) clinopyroxene and high An content (80-90) plagioclase from the primitive Borgarhraun flow, N. Iceland. Major and trace element compositions were used to search for cpx-melt pairs close to equilibrium and thus suitable for thermobarometry. Thermobarometry results indicate that clinopyroxene crystallized at ~9 (±2) kbar, close to the Moho. The forsterite content of olivine in Mg-Fe equilibrium with the clinopyroxene and the trace element content of the equilibrium melt were estimated using crystal-crystal and crystal-melt partition coefficients. This conversion allows the compositions of clinopyroxene point analyses to be compared with those of melt inclusions and their host crystals. Both converted clinopyroxene compositions and olivine-hosted melt inclusion data show a wide range in incompatible trace element ratios close to Mg#~90, requiring mixing of mantle melts during crystal fractionation. However, the trace element enriched part of the range observed in the olivine-hosted melt inclusions is absent from clinopyroxene compositions. While the range in La/Yb of 92 olivine-hosted melt inclusions is 0.09-3.23, that for 167 converted clinopyroxene compositions is 0.11-1.29. Phase relations can explain this observation: deep-sourced, enriched melts have a long olivine-only crystallization path and cannot form high Mg# clinopyroxene prior to mixing with more depleted melts. The results have implications for the provenance of crystals hosted in basalts. Non-equilibrium textures, major and trace element compositions, or isotopic ratios differing from whole-rock values may not always be used to infer a simple xenocrystic origin. Instead, these features may be vestiges of the chemically and isotopically diverse mantle melts from which phases crystallized before melt mixing and eruption.

Goldschmidt Conference Abstracts 2010

A1138

Mg/Ca-derived temperatures for Neogloboquadrina pachyderma (s) in low temperature environments

Focused Ion Beam (FIB) combined with TEM reveals nano-scale processes in geosciences

K. WINSOR1*, A.E. CARLSON1 AND G. KLINKHAMMER2

RICHARD WIRTH

1

Dept. Geoscience, Univ. Wisconsin-Madison, Madison, WI 53706 USA (*correspondence: [email protected]) 2 College Oceanic & Atmospheric Science, Oregon State U., Corvallis, OR 97331 USA Reconstructing polar ocean temperature is vital for understanding the climate system response to past radiative and internal forcings. However, Mg/Ca paleothermometry in planktic foraminifera is generally limited to waters less than 3°C due to a poorly understood reversal of Mg/Ca temperature dependence [1]. We investigate the ability of a flow-through time-resolved analysis technique (FT-TRA) [2] to measure Mg/Ca in Neogloboquadrina pachyderma (sinistral) tests from core MD99-2227, located in the East Greenland Current [58°12.64 N, 48°22.38 W]. Our results show foraminiferal Mg/Ca values as low as ~0.5 mmol/mol. # 18ONpl (per mil) 4.66 4.21 4.61 4.20 4.16 4.15 3.71 4.01 4.28 4.70

Mg/Ca (mmol/mol) 0.498 0.529 0.530 0.537 0.539 0.544 0.547 0.552 0.558 0.559

T (°° C) -0.98 -0.37 -0.36 -0.22 -0.19 -0.09 -0.04 0.06 0.16 0.18

Table 1: Oxygen isotopes (#18ONpl) [3] and Mg/Ca-derived temperatures (T) [4] for ten N. pachyderma (s) samples with lowest Mg/Ca. Core intervals analyzed are from glacial Terminations I and II, with lowest Mg/Ca values surrounding the Last Glacial Maximum (~21 ka). Additionally, #18O of N. pachyderma (s) tests with very low Mg/Ca reflect glacial values for the North Atlantic [3]. We therefore suggest that the FT-TRA technique enables Mg/Ca paleothermometry to be performed on N. pachyderma (s) samples originating from waters at least as cold at -1°C, just above the freezing point of seawater. [1] Kozdon et al. (2009) Geochem. Geophys. Geosys. 10, Q03005. [2] Klinkhammer et al. (2004) Paleoc 19, PA403. [3] Evans et al. (2007) Geochem. Geophys. Geosys. 8, Q11007. [4] Mashiotta et al. (1999) Earth Plan. Sci. Let. 170, 417–432.

GFZ Potsdam, 3.3, Telegrafenberg, 14473 Potsdam, Germany ([email protected]) Phase transformations, mineral reactions and replacement reactions describe the P-T path of rocks. Occasionally it is difficult to decipher reactions that have occurred in minerals and rocks because phase transformations, mineral reactions and replacement reactions occurred at an atomic or nanometer scale. Fortunately, microscopic and much more frequently submicroscopic textures or microstructures are preserved in minerals indicating the mechanisms, which have operated during transformation, reaction or replacement reaction. Transmission electron microscopy (TEM) is the ideal tool to identify such structures. Modern TEM allows the measurement of the chemical composition with unsurpassed spatial resolution. High-resolution imaging and electron diffraction provide structural information from the same location. It is the combination of microstructure, crystal structure and chemical composition that fully characterizes the investigated mineral section. High-resolution elemental mapping or line scans with drift correction acquire complete EDX spectra pixel by pixel. Subsequent data evaluation allows connecting the spectrum with the respective elemental map/line scan and the image, thus illustrating spatially resolved chemical composition. Focused ion beam technique (FIB) is the appropriate TEM sample preparation method that allows the preparation of electron transparent foils with typical dimensions of 15 x 10 x 0.150 µm from locations of interest (site-specific). FIB sample preparation consumes only a small volume of the sample (approximately 2300 µm3), leaving most of the material completely unaffected. The large capability of FIB/TEM method is demonstrated with examples such as coupled dissolution/reprecipitation reactions, reactions (symplectite) and phase transformations.

Goldschmidt Conference Abstracts 2010

A new Early Carboniferous alkaline province in the crystalline basement of NE Poland J. WISZNIEWSKA1*, E. KRZEMI.SKA1, L. KRZEMI.SKI1, D. DEMAIFFE2, H. STEIN3,4 AND I.S. WILLIAMS5 1

Polish Geological Institute, Warsaw, Rakowiecka 4 (*correspondence: [email protected]) 2 Laboratoire Géochimie Isotopique (U. L. B.), DSTE (CP 160/02), 50, av. Roosevelt 1050 Bruxelles, Belgique 3 AIRIE Program, Colorado State University, Fort Collins CO 80525-1482 USA 4 Geological Survey of Norway, Trondheim 5 Research School of Earth Sciences, ANU, Australia Three alkaline magmatic complexes were discovered by deep drilling in northeastern Poland: the Tajno alkalinecarbonatite complex, the Elk alkaline-syenite massif and the Pisz gabbro-syenite intrusion. The complexes occur in a narrow E-W band along the southern rim of the Mazury Complex, NE Poland. An earlier Rb-Sr whole rock isochron for Elk syenites suggested an age of 355±4 Ma. K-Ar results estimate a Late Paleozoic age for the Pisz and Tajno complexes. Here we present new U-Pb zircon (SHRIMP, TIMS) and Re-Os sulphide (NTIMS) geochronology. The new U-Pb results are very consistent: 348±8 Ma for Elk, 346±5 Ma for Pisz (SHRIMP) and 348±15 Ma (TIMS) for Tajno. These ages point to an Early Carboniferous emplacement for platform mafic-alkaline magmatic activity in NE Poland. ReOs data for a sulfide sample (pyrrhotite) from the Tajno carbonatite yield an age of 348±2 Ma, calculated using an initial Os ratio of 0.2. The sample is LLHR (low level-highly radiogenic [1] with 187Re/188Os = 2466±5); thus, selection of the initial Os has minimal effect on the age calculation. Sr-Nd isotope signatures for the Tajno silicate rocks and carbonatites, with ISr (348 Ma) of 0.7033 to 0.7042 and /Nd (348 Ma) of +3.6 to +1.4, suggest possible involvement of two contrasting mantle components, DMM and EM1, in proportions of 95:5. The alkaline-ultramafic Tajno complex together with the Elk and Pisz intrusions are located on the extension of the Upper Devonian Pripyat-Dnieper-Donets (PDD) paleorift and may be comparable to the Late Devonian Kola Alkaline Carbonatite Province (KACP) and to the volcanic diatremes of the northern wing of PDD. [1] Stein et al. (2000) Economic Geology 95, 1657–1671.

A1139

Calcite growth rate and solution composition MARIETTE WOLTHERS1*, GERNOT NEHRKE2 1,3 AND PHILIPPE VAN CAPPELLEN 1

Department of Earth Sciences, Faculty of Geosciences, Utrecht University, P.O. Box 80021, 3508 TA Utrecht, The Netherlands (*correspondence: [email protected]) 2 Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany ([email protected]) 3 School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, 3032-0340, USA ([email protected])

The calcium to carbonate ratio of aqueous environments from which calcite crystals form can vary widely. For example, the free dissolved calcium to carbonate ratio in sea water is around 250 and in groundwater around 430, while during intracellular biomineralisation the ratio is is expected to be much smaller. Previous work has shown that the calcium to carbonate ratio (solution stoichiometry) affects the rate of crystal growth and dissolution. Nevertheless, models for crystal growth kinetics and dissolution generally ignore this effect. Here we present a model for calcite growth rate that takes solution stoichiometry and pH into account. The mechanistic growth model combines a surface structural model for divalent metal carbonates [1] with a growth model for binary symmetrical electrolyte crystals such as NaCl [2]. The latter model is extended to account for the different surface reactions taking place during growth. The resulting model describes step movement and kink formation rates and calcite growth rate depending on solution stoichiometry. Because bicarbonate is included in the model, pH is explicitly defined as well. The development of the mechanistic growth model is guided by the experimental data of Nehrke et al. [3] and further validated with previously published experimental data sets for calcite growth rates obtained over a wide range of solution composition in systems closed and open to the atmosphere. [1] Wolthers, Charlet & Van Cappellen P. (2008) American Journal of Science 308, 905–941. [2] Zhang & Nancollas (1998) Journal of Colloid & Interface Science 200, 131–145. [3] Nehrke, Reichart, Van Cappellen, Meile & Bijma (2007) Geochimica Cosmochimica Acta 71, 2240–2249.

A1140

Goldschmidt Conference Abstracts 2010

Nd isotopes as indicator of glacioeustasy, mid-Carboniferous boundary Arrow Canyon, NV

Advantages of combining geochronologic and trace element analyses using the SHRIMP-RG

STELLA C. WOODARD1*, DEBORAH J. THOMAS1,2, ETHAN GROSSMAN2, THOMAS OLSZEWSKI2, THOMAS YANCEY2, ANNE RAYMOND2 2 AND BRENT V. MILLER

JOSEPH L. WOODEN

1

Texas A&M University Dept of Oceanography (*correspondence: [email protected]) 2 Texas A&M University Dept of Geology & Geophysics

To better understand the effect of large-scale glaciation and sea level change on circulation in the epicontinental sea of western North America, we have generated a record of Nd isotopes spanning the mid-Carboniferous boundary using fossil apatite extracted from carbonate rocks collected in Arrow Canyon, Nevada. During the Carboniferous the Arrow Canyon lay near the equator within a foreland basin flooded by the North American epicontinental seaway. This region accumulated a thick, nearly continuous sequence of shallow marine sediments now recognized as the MississippianPennsylvanian GSSP [1]. However, sedimentological studies reveal a number of brief depositional hiatuses when the region experienced subaerial weathering and/or soil development [1, 2, 3, 4]. The 143Nd/144Nd isotopic signature of marine waters is controlled by weathering inputs from old crustal rocks (unradiogenic Nd) and young volcanic rocks (radiogenic Nd). Carboniferous 143Nd/144Nd values (expressed in epsilon notation and corrected for age, $Nd (t)) for the open ocean (Panathalassa/Rheic) were relatively radiogenic, -5 to –6, based on analysis of biogenic apatite in shallow marine rocks from Patlanoaya, Mexico, which was a small detached block moving northward from Gondwana during the Mississippian. We measured $Nd (t) values of approximately –7.6 for Arrow Canyon samples of mid-late Chesterian age suggesting that at this time a strong connection existed between the region and the open ocean. Upsection, $Nd (t) decreases to –9.4 in limestone topped by a paleokarst surface 2.5 m below the midCarboniferous (Chesterian-Morrowan) boundary [3], then increases back to ~7.6 across the flooding surface (identified by [2]). A similar decrease in $Nd (t), to –10.1, was measured about 3 m above in fossils extracted from a limestone bed directly overlying a green-brown shale containing root traces [3]. The decrease in Nd isotopic values near these exposure surfaces implies that circulation between the epicontinental seaway and open ocean became restricted as sea level fell. Enhanced contributions of water from interior basins of the mid-continent are the most likely source of the unradiogenic Nd. [1] Lane et al. (1999) Episodes 22, 272–283. [2] Bishop et al. (2009) Palaeogeogr Palaeocl 276, 217–243. [3] Barnett & Wright (2008) J Geol Soc London 165, 859–873. [4] Richards et al. (2001) in Carboniferous & Permian of the World, p.802.

SHRIMP Lab, Dept. Geol. Envir. Sciences, Stanford University, Stanford, CA 94305 ([email protected]) The combined high mass resolution and transmission of the SHRIMP-RG allows trace element determinations to be made without energy filtering. Standard U-Th-Pb analyses can be combined with trace element analyses by operation at 8000 MR (10% peak height). Acquisition tables for U-Th-Pb geochronology for zircon, titanite, and monazite routinely cover the mass range from 89 (Y) to 254 (UO) providing REE and other trace element data for each spot for which an age is determined and adding only an extra two minutes to the analysis time. More complete trace element analyses (Li to UO), done separately from geo- chronology, provide additional data, and can be invaluable in pre-screening individual grains and zones in grains for age analysis (U-ThPb and U-Th). In the last 4 years a large dataset has been developed for suites of zircons (smaller datasets for titanite and monazite) from samples representing diverse compositions and environments of formation. As a result of strong compositional zoning in individual grains and suites of grains the compositional data are most useful for understanding igneous and metamorphic processes and not for determining rock type. Some compositional characteristics are useful for fingerprinting MORB vs. continental, or crustal vs. lithospheric regions, or identifying specific sources. Divergence in established compositional trends can help confirm that a mineral suite is of mixed source and/or age which is increasingly important given the recognition of the common occurrence of inherited and antecrystic grains. Mineral thermometers for igneous zircon and titanite and the application of partition coefficients to compositional data allow the monitoring of melt composition and temperature during mineral growth. Age, temperature, and the specific minerals involved in metamorphic reactions (esp. garnet, feldspar) can be determined for zircon, monazite and titanite. Age and compositional data for inherited zircons can provide otherwise unobtainable information about the middle and lower crust.

Goldschmidt Conference Abstracts 2010

Response of marine aerosol to changes in phytoplankton induced by perturbations to aeolian iron input MATTHEW T. WOODHOUSE1*, ERIK BUITENHUIS2, GRAHAM W. MANN1, KENNETH S. CARSLAW1 3 AND OLIVIER BOUCHER

A1141

!34S isotopes from carbonate associated sulfate and chromiumreducible sulfur from the traditional Lower–Middle Cambrian T. WOTTE*, H. STRAUSS, A. FUGMANN, A. CORDING AND K. RABE

1

School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK (*correspondence: [email protected], [email protected], [email protected]) 2 LGMAC, ENV, University of East Anglia, Norwich, NR4 7TJ, UK ([email protected]) 3 Met Office Hadley Centre, FitzRoy Road , Exeter, EX1 3PB, UK ([email protected]) The sensitivity of marine aerosol to changes in dimethysulfide (DMS) emissions from the ocean resulting from pertubed iron deposition fluxes is investigated in sophisticated process models of atmospheric aerosol and the marine ecosystem. Primary production in large areas of the oceans is known to be iron limited. Additionally, bioavailable iron delivery to the ocean from the atmosphere is very poorly known, due to uncertainty in the emission, processing and deposition of aeolian dust [1]. DMS is produced by phytoplankton, and can influence the marine aerosol, cloud optical properties and climate [2]. There is therefore a possible link between cloud albedo and aeolian iron input to the ocean, via phytoplankton. The strength of this link is investigated in an offline model study in three parts. The first stage uses the detailed aerosol model GLOMAP [3] to calculate dust and bioavailable iron deposition to the oceans. The bioavailable iron deposition is used by the marine ecosystem model PlankTOM5 [4] to calculate global surface ocean DMS fields. Simple (doubling and halving) perturbations to the bioavailable iron field in PlankTOM5 provide an estimate of the sensitivity of the marine phytoplankton production of DMS to the bioavailable iron input. The surface ocean DMS concentrations calculated in PlankTOM5 are then fed back to the GLOMAP aerosol model, and the impact on aerosol is calculated. Early results with this approach suggest that the sensitivity of marine aerosol to bioavailable iron perturbations is quite low on a global scale. [1] Mahowald et al. (2009) Annual Review of Marine Science, 1, 245–278. [2] Charlson et al. (1987) Nature 326, 655–661. [3] Manktelow et al. (2007) GRL 34, L14803. [4] Vogt (2010) JGR-Oceans, accepted.

Institut für Geologie und Paläontologie, Westfälische Wilhelms-Universität Münster, Corrensstrasse 24, D-48149 Münster, Germany (*correspondence: [email protected]) We present high resolution !34SCAS and !34SCRS data from carbonate and mixed carbonate-siliciclastic successions from three Gondwanan sections and one locality from Laurentia respectively the Siberian Platform, covering the traditional Lower–Middle Cambrian boundary interval. !34SCAS values of Gondwana vary between 13.1 and 33.2‰, with CAS concentrations between 2 and 903 ppm, and !34SCRS data reaching from -5.1 to 26.5‰ with maximum CRS concentrations of 3706 ppm. !34SCAS data from Laurentia show a higher variation between -1.3 and 36.8‰. CAS concentrations are similar to those from Gondwana, ranging from 7 to 388 ppm. !34SCRS values varying between 11.3 and 43.7‰ with a maximum CRS concentration of 149 ppm. !34SCAS data from the Siberian Platform ranging from 0.2 to 29.9‰ with CAS concentrations up to 1552 ppm. !34SCRS values vary around 12.9‰ with a maximum CRS concentration of 7008 ppm. No correlation exists between sulfate abundance and sulfur isotopic composition. Whereas two of the Gondwanan sections show sympathetic shifts in their !34SCAS and !34SCRS curves, and thus indicate similar paleoenvironmental conditions, respective trends could be not observed for the other localities. Also a regional correlation of !34SCAS data seems possible, but is nonexistent on intercontinental scale. A diagenetic overprint can be largely excluded, based on respective proxies (!18O, Mn/Sr, Ca/Mg). These don’t show any correlation with !34SCAS. Hence, sulfur isotope values are considered as primary seawater values. Apparent differences in !34SCAS between the Gondwanan, Laurentian, and Siberian sections provoke a discussion whether the recorded sulfate sulfur isotope values reflect the global seawater signature.

A1142

Goldschmidt Conference Abstracts 2010

A novel in situ detection technique of metabolic enzymes in Black Sea methane seep microbial mats

Investigations of the influence of microbial cells on phosphate mineral precipitation

C. WREDE1*, C. HELLER2, J. REITNER2 AND M. HOPPERT1

KAREN WRIGHT1, YOSHIKO FUJITA1, JAMES HENRIKSEN1, NIC SPYCHER2 2 AND MARK CONRAD

1

Institute of Microbiology and Genetics, University of Goettingen, Grisebachstr. 8, 37077 Goettingen, Germany (*correspondence: [email protected], [email protected]) 2 Geoscience Centre, University of Goettingen, Goldschmidtstr. 3, 37077 Goettingen, Germany ([email protected], [email protected])

Microbial biofilms in natural habitats may contain a vast number of microorganisms with different metabolic features. Phylogenetic analysis and environmental genomics give insight into the various metabolic types present in biofilm consortia, but do not allow an assignment of expressed metabolic enzymes and hence metabolic pathways to certain microbial cells. With fluorescence in situ hybridization it is possible to locate organisms of distinct phylogenetic groups in biofilms by light microscopy, but metabolic key processes conducted by the organisms remain undiscovered. To overcome this drawback, we established a procedure for generation of probes, specific for metabolic enzymes in environmental biofilms, applicable for light as well as electron microscopy. For this purpose, degenerate primers were calculated for genes from protein families of interest. Primers were used for amplification of these gene sequences from biofilm DNA. The sequences were cloned in an overexpression vector. The protein was heterologously expressed in a host strain (like Escherichia coli). The purified protein was used for raising polyclonal antibodies in rabbits. Correlative light/electron microscopy [1] based on the antibody probe in combination with different markers was used for loacalization of the target proteins and, by this way, the metabolic feature connected to this protein, below the scale of a single cell. We used this method in particular to study microbial mats from deep sea methane seeps located on the Black Sea Crimean shelf. The key players of the anaerobic oxidation of methane (AOM), anarobically methane oxidizing archaea (ANME) as well as the sulfate-reducing bacteria (SRB) were analyzed by detection of the enzymes methyl-coenzyme M reductase (MCR) [2, 3] for (reverse) methanogens and the adenylylsulfate reductase for SRB. [1] Wrede et al. (2008) J. Microbiol. Methods 73, 85–91. [2] Heller et al. (2008) Geomicrobiol. J. 25, 149–156. [3] Krüger et al. (2003) Nature 426, 878–881.

1

Idaho National Laboratory ([email protected], [email protected], [email protected]) 2 Lawrence Berkeley National Laboratory ([email protected], [email protected])

The U. S. Department of Energy (DOE) is evaluating induced precipitation strategies to immobilize trace metals and radionuclides in the subsurface. One promising class of approaches is based on promoting the formation of phosphate minerals into which contaminants can partition. Phosphate minerals are relatively insoluble under conditions typical of many DOE sites, and thus contaminant sequestration within such minerals would be expected to be a long-term remediation strategy at these sites. A potential means of promoting subsurface mineral precipitation is stimulating microbial activity that releases phosphate ions from P-containing substrates. We have been investigating whether indigenous subsurface microorganisms can facilitate mineral precipitation by degradation of the compound triethyl phosphate (TEP). A mixed microbial culture derived from Idaho National Laboratory sediments was found to be capable of degrading TEP, and releasing soluble phosphate. However, mineral precipitation appears to be inhibited despite oversaturation with respect to minerals such as hydroxyapatite and octacalcium phosphate. To examine how microbial cells might impact calcium phosphate mineral precipitation, apart from the direct release of phosphate from TEP, we also conducted some abiotic experiments in which phosphate was added directly to the same synthetic groundwater as used for the TEP biodegradation experiments, in the presence and absence of Comamonas testosteroni cells. We also looked at the effect of adding organic acids that were detected in the TEP degrading cultures. Experiments where the phosphate concentration was increased incrementally over time (as would occur in the TEP degradation experiments) were conducted, as well as experiments where phosphate was added just at the beginning of the experiment. Results indicate that even in the absence of microbial cells, phosphate mineral precipitation in the synthetic groundwater is slow, but it is even more retarded by the presence of cells, as well as organic acids. The mineral phases formed initially are amorphous, but eventually appear to become more like hydroxyapatite.

Goldschmidt Conference Abstracts 2010

The structure of hydronium alunite: A first principles study K. WRIGHT1*, J.D. GALE1 AND K. HUDSON-EDWARDS2 1

Nanochemistry Research Institute, Department of Chemistry, Curtin University of Technology, PO Box U1987, Perth, WA 6845, Australia (*correspondence: [email protected]) 2 Department of Earth and Planetary Sciences, Birkbeck, University of London, Malet St, London WC1E 7HX, UK

A1143

Metabolic diversity and identification of soil microbial communities in mercury contaminated soil of Oak Ridge, TN KENDRA L. WRIGHT1, KAREN S.MCNEAL2 3 AND FENGXIANG X. HAN 1

([email protected]) ([email protected]) 3 ([email protected])

2

Minerals of the alunite supergroup are widely distributed and play significant roles in the storage and release of water, acidity and toxic elements. Although alunite can contain many different cations, a particularly interesting case is that where the A site is occupied by hydronium. Despite many different experimental studies, a recent paper concluded that the existance of hydronium immediately adjacent to several hydroxyl anions remains in question [1]. To date it has proved impossible to locate the positions of the hydrogen atoms and one paper has concluded that the problem may only be resolved by Ô rigorous numerical simulationÕ [2].

Figure 1: One possible ordered structure for H3O+-alunite. In order to probe the existence or otherwise of hydronium in alunite we have performed quantum mechanical simulations based on density functional theory [3]. Current proposals for the structure of H3O+-alunite suggest that the hydronium ions are arranged about an axis of rotational symmetry with the hydrogens pointing either up or down relative to the c axis of the hexagonal structure. Our research demonstrates that the hydrogens are actually distributed in a different manner to any of the experimental models and explain why it is unlikely that the protons will ever be accurately resolved using diffraction methods. [1] Nielson et al. (2007) Am. Miner. 92, 587Ð 597. [2] Lager et al. (2001) Can. Miner. 39, 1131Ð 1138. [3] Soler et al. (2002) J. Phys. Cond. Matter 14, 2745Ð 2780.

In the 1950s, the Department of Energy Y-12 Plant in Oak Ridge, TN used mercury in the production of nuclear weapons. Through the production process, mercury was released into the Oak Ridge environment. Mercury is known to cause serious health problems, and remediation efforts are on the forefront of the scientific research done in the area. To provide a better understanding of mercuryÕ s effects on microbial communities, the metabolic diversity of Oak Ridge grassland and woodland soil microbial communities were compared using Biolog Ecoplates and Anaerobic plates. Samples were taken from the field locations and analyzed in the laboratory. Also, the potential for mercury phytoremediation was examined in laboratory plants (Brassica juncea). Soil samples were taken from the rhizosphere and outermost potting soil, and metabolic diversity was measured. Microbial identification was completed for all sample types using Biolog GEN III MicroLog-M software. Preliminary data suggests laboratory soil treated with HgS2 or HgCl3 had significantly less metabolic diversity than the control samples. Furthermore, as mercury concentrations increase, field samples taken directly from the Oak Ridge site show variations in microbial diversity and community composition.

A1144

Goldschmidt Conference Abstracts 2010

Formation mechanism for the lanthanide tetrad effect in a topazand amazonite-bearing leucogranite pluton from Xinjiang, NW China

Sustainable development and utilization of groundwater resources considering land subsidence: A case study in Suzhou City, China

C.Z. WU1, S.H. LIU2, LX GU3, Z.Z. ZHANG3 1 AND R.X. LEI

JICHUN WU, XIAOQING SHI, SHUJUN YE, YUQUN XUE AND YUN ZHANG

State Key Laboratory for Mineral Deposits Research (Nanjing University), Shool of Earth Sciences and Engineering, Nanjing University, Nanjing 210093, China ([email protected]) 2 Zhoushan Entry-Exit Inspection and Quarantine Bureau of People’s Republic of China, zhoushan 316000, China 3 Eastern China Geological and Mining Organization for Nonferrous Metals, Nanjing 210007, China

State Key Laboratory of Pollution Control and Resource Reuse, Department of Hydrosciences, Nanjing University, Nanjing, 210093, China ([email protected])

1

The Baishitouquan (BST) pluton is a high F and Rb leucogranite pluton, and is situated in Xinjiang, northwestern China. This pluton exhibits five lithological zones gradational from the bottom upwards: leucogranite (zone a), amazonitebearing granite (zone b), amazonite granite (zone c), topazbearing amazonite granite (zone d) and topaz albite granite (zone e). Whole rock Chondrite-normalized rare earth elements (REE) patterns for above five zones from the BST pluton show clear convex tetrad effect, and the quantification factor (TE1, 3) for whole rock increases from zone a (1.02 ~ 1.16) to zone e (1.20 ~ 1.46). We analysis the REE content of major minerals and accessory minerals selected from all above five zone of the BST pluton through Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). Chondritenormalized REE patterns of minerals from zone a to zone e display clear convex tetad effect, and the TE1, 3 values of these different minerals are also increases from zone a to zone e as their host rocks without exception. Therefore, we conclude the minerals (such as plagioclase, zircon, garnet, monazite etc) inherit the REE signature of the melt and do not contribute to the bulk-rock tetrad effect via mineral fractionation, while their the tetrad effect develops during magma differentiation. Additionally, Ratios of some ionic twins with similar ionic radius and charge (such as K/Rb, Y/Ho and Zr/Hf) in whole rock decrease remarkably from zone a to zone e, and present negative correlation with their TE1, 3 values, which indicate that the tetrad effect develops as a result of the interaction between melt and magmatic hydrothermal fluid. The extraction of a coexisting fluid from a peraluminous melt during magma differentiation results in a M-shaped and a Wshaped REE tetrad effect in the residual melt phase and agmatic hydrothermal fluid, respectively.

Suzhou City, located at the lower reaches of the Yangtze River in southeastern Jiangsu Province, is a part of Su-XiChang area (including Suzhou, Wuxi and Changzhou Cities), which are one of the typical regions in China suffering from severe ground settlement caused by extensive groundwater exploitation. In accordance with the serious land subsidence, protection and management work for groundwater resource have been strengthened in Su-Xi-Chang area since 1995. By the end of 2005, an overall banning of groundwater pumping in Su-XiChang was realized and the land subsidence rate was slow down and groundwater level recovered gradually. On the other hand, the surface water#including lakes and rivers) have been increasingly polluted due to industrial and domestic wastewater and also agricultural runoff. In May 2007, Taihu Lake, the most important freshwater lake in SuXi-Chang area, was choked by blue-green algae, causing panic as over 200, 000 people found their tap water was undrinkable. This is China’s most serious case of drinking water pollution to date. Some thoughts on water supply crisis in Suzhou City induced by explosion of incident of large bloom of blue-green algae in Taihu Lake were developed. One of the main measures is to use groundwater as an emergency water supply source because of its fine quality. A research project was carried out to investigate this problem to develop groundwater resources reasonably under condition of controlling land subsidence. A 3-D finite element groundwater flow coupled onedimensional land subsidence model is established. The calibrated model is then used to assess the future evolution of land subsidence in the study area under different emergency water supply scenarios, which are helpful to design reasonable quantity of exploiting the groundwater to control the land subsidence. This research was supported by the National Nature Science Foundation of China grants No. 40702037 and 40725010.

Goldschmidt Conference Abstracts 2010

A1145

Equilibrium iron isotope fractionation between Fe(II) and hydrous ferric oxide

Organic geochemistry of Triassic mudstones in the central Junggar Basin, northwest China

LINGLING WU1,2, BRIAN L. BEARD1,2, ERIC E. RODEN1,2 1,2 AND CLARK M. JOHNSON

MING WU, JIAN CAO*, PING’AN SUN AND LEI XIE

1

University of Wisconsin-Madison ([email protected]) 2 NASA Astrobiology Institute The 56Fe/54Fe fractionation between aqueous Fe (II) and hydrous ferric oxide (HFO) was determined using the three isotope method. Experiments were conducted at 25°C at neutral pH in the presence of dissolved Si (2.14 mM), in order to prevent any phase transformation of HFO. XRD and TEM confirmed that the solid remains 2-line ferrihydrite through the course of the experiments (28 days). Four replicate experiments using either 57Fe-enriched aqueous Fe (II) or 57Feenriched HFO yielded an average Fe (II)-HFO equilibrium Fe isotope fractionation factor of -3.00 + 0.20 (2%) ‰. Combining previous aqueous Fe (II)-Fe (III) experimental results with the Fe (II)-HFO equilibrium fractionation determined here produced an equilibrium fractionation factor of 0‰ between Fe (III) and HFO. This important finding demonstrates that, under equilibrium conditions, the #56Fe value of Fe (III)aq will be directly reflected in the Fe isotope composition of poorly crystalline ferric hydroxides. This in turn confirms earlier inferences that in systems where the ferric hydroxide-Fe (II)aq fractionation is less than 3‰, kinetic isotope effects upon precipitation is the likely explanation. Counterintuitive to the reactive nature of HFO, only ~40% of isotope exchange occurred (Figure) after 28 days, presumably due to adsorption of Si to HFO surfaces.

Department of Earth Sciences, Nanjing University, Nanjing, Jiangsu 210093, P.R. China (*correspondence: [email protected]) The central Junggar Basin is a key petroleum exploration target of the basin, which is an important petrleum base and reseach highlights in northwest China. In previous studies, Permian mudstones are generally accepted as the effective source rock sequences. In this preliminary study, we reported the organic geochemistry of Triassic mudstones and discussed its geological implications. It is showed that the mudstones have a high abundance of organic matter, with TOC content more than 1%. The organic matter has a relatively high carbon isotopic value (25.70-28.13), indicating a type-II to –III kerogen type. Analyses on organic maturation show that the mudstones in the Mosuo are mature and highly mature, while the mudstones in the Madong area have not reached the oil generation threshold. Thus, it may be indicated that the Madong area has been a paleo-uplift since the Late Triassic. The analyses of biomarkers indicate that most hydrocarbons are generated from a brackish water or fresh water deposition environment whose redox changes from weak reduction to weak oxidation. In summary, the Triassic mudstones in the central Junggar Basin have high organic matter contents, are mature to highly mature in the sag areas; thus, the mudstones are good gasprone source rocks due to its humic organic-matter type. This set of mudstones should be laid enough emphasis in shaping the future petroleum exploration strategy.

A1146

Goldschmidt Conference Abstracts 2010

Trace elements and REE geochemistry of Liuju sandstone-type copper deposit, Yunnan, China

Experimental studies of microbial Fe(III)-phyllosilicate reduction in subsurface sediments

PENG WU, RUNSHENG HAN AND JING LI

TAO WU1*, EVGENYA SHELOBOLINA1, HUIFANG XU1, RAVI KUKKADAPU2 AND ERIC RODEN1

Kunming University of Science and Technology, Southwest Institute of Geological Survey, Geological Survey Center for Non-ferrous Mineral Resources, Kunming 650093, China (*correspondence: [email protected]) Liuju sandstone-type copper deposit is located in the Upper Cretaceous (K2ml1, K2ml2) continental red-bed basin of Chuxiong, Yunnan Province, China. Ore-bodies (average grade: Cu 1.25%, Ag >20g/t) are located in the interface between purple bed and grey bed. From purple bed to grey bed, the ore mineral horizontal zonality is hematite, chalcocite, bornite, chalcopyrite and pyrite. Based on geochemical data (by ICP-MS) of 9 drills in this deposit, the features of trace elements show that ore-bearing strata are riched in chalcophile elements such as Cu, Ag, Hg, Mo and depleted in Ta, Sc, Co, Ni, V. Ore-forming elements association is Cu, Ag, As, Sb, Hg (K2ml1) and Cu, Ag, As, Hg, Mo, Cd (K2ml2). Ore-bearing strata are beneficial to preliminary enrichment of metallogenic elements. The K2ml1 and K2ml2 are the dominant ore source bed. Compared with purple and grey bed, the copper ores are enriched in Cu, Ag, Hg, Mo with low content of high field strength elements (such as Nb, Ta, Zr and Hf). The average contents of copper ores 0REE=86.64%10-6, LREE/HREE=4.03, !Eu=0.85, !Ce=0.92. Chondritenormalized REE distribution patterns show oblique to the HREE side with the poor Eu and enrichment in LREE. From oxidized zone to transitional zone (purple bed!copper ore!grey bed), 0REE and !Ce decrease gradually with the increase of !Eu. The geochemical characteristics well indicate the change of oxidation and reducing environment. These were probably related to the water-rock interaction or infiltration metasomatism. Results of trace elements and REE analysis suggested that copper metallogenic in the deposit have experienced diagenesis preconcentration and reworked enrichment. Granted jointly by the project of State Crisis Mine (20089943) and the Distinguishing Discipline of KUST (2008).

1

Dept. of Geoscience, Univ. of Wisconsin-Madison, Madison, WI, 53706, USA (*correspondence: [email protected], [email protected], [email protected], [email protected] ) 2 Pacific Northwest National Laboratory, Richland, WA, USA([email protected])

The goal of this research is to compare and quantify experimentally the kinetics of Fe (III)-bearing phyllosilicate versus Fe (III) oxide reduction in natural sediments. A key first step was to separate phyllo-silicate and Fe (III) oxide phases in order to permit experimentation with phyllosilicates in isolation. Testing showed that physical separation through density gradient centrifugation did not adequately separate phyllosilicate and oxide phase present in sediment from Area 2 at Field Research Center at Oak Ridge National Laboratory (ORFRC). Hence we examined the ability of chemical extraction methods. Ammonium oxalate in the presence of a small amount of Fe (II) was used to extract both amorphous and crystalline Fe (III) oxides without changing the redox state of phyllosilicates. XRD analysis revealed, however, that both oxalate alone and oxalate with Fe (II) altered the structure of Fe (III)-bearing smectite in the Area 2 sediment. In contrast, citrate-dithionite-bicarbonate (CDB) extraction followed by reoxidation with hydrogen peroxide led to minimal alteration of smectite structures. Geobacter sulfurreducens was used to evaluate the microbial reducibility of Area 2 sediments extracted by different procedures. Ammonium oxalate+Fe (II) extracted sediments were reduced more than CDB extracted, H2O2 reoxidized solids, consistent with the apparent destabilization of smectite phases during oxalate-promoted dissolution revealed by XRD. CDB extraction was adopted to isolate Fe (III)-bearing phyllosilicates for microbial reduction experiments with ORFRC Area 2 and Atlantic coastal plain sediments from Oyster, VA.

Goldschmidt Conference Abstracts 2010

A1147

Sr–Nd isotopic characteristics of river sediments in the Tibetan Plateau

In situ biostimulation of U(VI) reduction and immobilization using emulsified vegetable oil

WEIHUA WU1,3*, JIEDONG YANG2, SHIJIN XU3, HONGWEI YIN3, HUAYU LU1 AND KAIJUN ZHANG3

W.-M. WU1*, D. WATSON2, T. MEHLHORN2, J. EARLES2, M. BOYANOV3, T. GIHRING2, C. SCHADT2, K. LOWE2, J. PHILLIPS2, K. KEMNER3, B. SPALDING2,

1

School of Geographic and Oceanographic Sciences, Nanjing University, Nanjing 210093, China (*correspondence: [email protected]) 2 Center of Modern Analysis Nanjing University, Nanjing 210093, China 3 State key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210093, China

Introduction Sr–Nd isotopic characteristics of different terranes in the Tibetan Plateau can be used to identify the attribute of tectonic units, reveal the geochemical heterogeneity of plateau lithosphere and the difference of evolution process of terranes. At present, isotope geochemical studies in the Tibetan Plateau mainly focus on granites, granulites and volcanic rocks. In this study, we provided a new perspective by using river sediments to reveal the isotopic characteristics and tectonic affinities of various terranes in the Tibetan Plateau. Sr-Nd isotopic characteristics We collected 40 river sediment samples in different terranes of the Tibetan Plateau and measured their Sr–Nd isotopic compositions. Three isotopic regions can be identified: (A) The Qilian Terrane and Himalaya Terrane. They have more negative /Nd (0) values (from -14.3 to -11.8 and from -20.64 to -13.26, respectively) and high 87Sr/86Sr values (from 0.719674 to 0.738818 and from 0.721020 to 0.824959, respectively), reflecting old and mature continental crust origin of these two terranes; (B) The southern Lhasa terrane. It is more radiogenic in /Nd (0) values (from -8.82 to -3.8) and low in 87Sr/86Sr values (from 0.711504 to 0.719489), implying the combined impact of the Neo–Tethys mantle and Himalaya old continental crust; and (C) other terranes. They have 87Sr/86Sr and /Nd (0) values between the above two. Tectonic implications Sr–Nd isotopic compositions of the Qilian Terrane are very close to those in the Yangtze Craton and are clearly different from the North China Craton, indicating that the Qilian Terrane was probably separated from the Yangtze Craton. Sr–Nd isotopic characteristics of the Songpan–Ganzi Terrane are similar to the Yangtze Craton and are remarkably different than the North China Craton, eastern Kunlun– Qaidam and the central Qiangtang metamorphic belt, implying that the provenance of the huge flysch complex of the Songpan–Ganzi Terrane may be the Yangtze Craton.

C.S. CRIDDLE1, P. JARDINE2 AND S. BROOKS2 1

Stanford University, Stanford, CA94305, USA (*correspondence: [email protected]) 2 Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA 3 Biosciences Division, Argonne National Laboratory, Argonne, IL60439, USA A field test was conducted in Area 2 of the DOE Oak Ridge Field Research Facility to reduce U (VI) using an emulsified vegetable oil (EVO) product containing 60% oil. Groundwater contained 5-6 ,M U; 1.0-1.2 mM sulfate; 0.21.5 mM nitrate; 2.5-4.0 mM Ca2+; with a pH of ~6.8. The hydrologic conditions were characterized by conducting a Brtracer test. Diluted EVO solution (20%) was then injected. The distribution of EVO injected and biogeochemical process was monitored through analysis of aqueous samples and surged samples of aquifer solids. A large fraction of the oil injected was trapped or adsorbed in the subsurface. The geochemistry was monitored over one year period. After oil injection, the sequential bioreduction of nitrate, Mn (IV), Fe (III) and sulfate occurred. Acetate was an intermediate in the oil degradation. U (VI) reduction was observed after 2-4 weeks of the oil injection and U concentrations were reduced to below 0.126 ,M (EPA MCL) at several well locations during the initial 100 days. The U concentration in groundwater seeps flowing into Bear Creek was decreased by >80% within a four month period and remained at less than 50% of original level after >365 days, indicating that the U migration was reduced substantially. Dissolved methane concentration increased after the oil injection, indicating the enhancement of methanogenic activity. After the oil was consumed, rebound of U in groundwater was observed together with the rebound of sulfate concentrations as acetate concentrations approached below detection limits. Rebound of U in downgradient wells were slow as the oil was sequentially consumed in upgradient locations. U (VI) reduction to U (IV) in situ during the field tests was confirmed by XANES analysis. The change of U valence in sediment samples corresponded with the changes in groundwater geochemistry. Known U (VI)-and Fe (III)reducing bacteria and a diversity of sulfate-reducing bacteria were stimulated after the oil injection.

A1148

Goldschmidt Conference Abstracts 2010

Does carbonic anhydrase affect the fractionation of stable carbon isotope YANYOU WU*, KUAN ZHAO AND DEKE XING Institute of Agricultural Engineering, Jiangsu Univ., Zhenjiang, 212013, China (*correspondce: [email protected]) The samples were obtained from leaves of plants. Foliar stable carbon isotope, carbonic anhydrase (CA) activity and bicarbonate concentration were measured. CA catalyzes the reversible conversion of bicarbonate to CO2. There are significant positive correlation between the CA activity and !13C value in the leaves from different plant species at the same site. The higher the activity of CA in the leaves of plant is, the greater the variability of !13C. The variability of !13C in the leaves of Broussonetia papyrifera (Bp) and Orychophragmus violaceus (Ov) are great because of their high CA activity compared to Brassica juncea (Bj) (Tables 1). The high correlation between foliar CA activity and !13C value is involved in that which plants with high CA activity can effectively use bicarbonate in the leaves as the carbon source for photosynthesis. The variation of !13C is also related to which plant alternately use bicarbonate and atmospheric CO2 as the carbon source for photosynthesis. Ov Bj Bp CA activity 1350 246 3450 Mean -26.805 -27.683 -29.656 Std Dev 1.207 0.234 0.794 Min -29.125 -28.132 -30.920 Max -24.254 -27.343 -28.842 n 20 10 10 CV/% 4.503 0.845 2.677 Bicarbonate 2.03 2.06 2.64 concentration Table 1:: The variation of 13C value, the 13C value (‰ vs PDB), bicarbonate concentration (µmol g-1FW) and CA activity (WAU g-1FW) in the leaves from some plants species. This work was supported by NSFC (No. 40973060).

Subsurface heterogeneity of high and low arsenic aquifers delineated by high resolution geophysical survey in Datong Basin, Shanxi, China YI WU, QINGJUN ZHU, FENGZHE LI AND GUOZHAN LI Center for Hydrogeology and Environmental Geology, CGS, 071051, Baoding, Hebei, P.R.China (*correspondence: [email protected], [email protected], [email protected]) The Datong Basin located in northeastern Shanxi province is a Cenozoic fault basin. A number of the tectonic and climatic changes during Quaternary have resulted in a complex hydrogeological structure of the aquifers with low water storage. Groundwater arsenic concentration increases from the Piedmont to the central basin, reaching 4.435 mg/L. This arsenic gradient corresponds to a lithological change from coarse sediment to fine, organic rich sediment. Studies have found that the smaller the sediment particle size, the higher the sediment arsenic loading. a high resolution, large depth exploration features. Sediment particle size in generally influences the resistivity. We show that audio-frequency magnetotelluric sounding method (EH-4 electrical conductivity imaging system) can be used to obtain high resolution subsurface sediment texture and to assist identification of high and low arsenic zones. Resistivity value of + 30ohm-m indicates loam-based clay where the water is poor; resistivity value of between 30-50 ohm-m corresponds to silt with weak water potential; resistivity value * 50ohm-m is fine to coarse sand with gravel with high water yield. These high water yield zones are < 200 m deep, and are located along the hillside or the steep slope of the terrains at the head of the alluvial fan with rapid flow. In contrast, the aquifer in the low lying areas to a depth of 300 m is consisted of fine grained sediment with low quality water and low yield. Test bore holes drilled along the hillside and in the central plains confirm the grain size inferred by resistivity results, suggesting that this can be a valuable tool to help locate low arsenic aquifer in alluvial basins.

Goldschmidt Conference Abstracts 2010

Multi-stage evolution and fluid activity of HP-UHP rocks from the western Dabie Mountain, central China: Evidence from zircon trace element, U-Pb age and Hf isotope composition YUANBAO WU AND LAISHI ZHAO State Key Laboratory of Geological Processes and Mineral Resources, Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China (*correspondence: [email protected]) The Dabie-Sulu UHP terrain is the largest UHP orogen on earth. Despite intensive study for more than 20 years, controversies still exist about the location and number of sutures and the timing of collision and their subsequent evolution. The Hong’an Block, that forms part of the western Dabie Mountains, is one area critical to decipher the tectonic evolution of the Qinling-Dabie-Sulu orogenic belt, as it is located at the junction between the western and eastern sections of the orogenic belt, and forms the transition between zones exposing low-pressure and ultra-high pressure rocks. Zircon trace element, U-Pb age and Hf isotope composition were determined for HP and UHP rocks from the Huwan HP and the Xinxian UHP units in the western Dabie Mountains. The results demonstrate that a Carboniferous eclogite-facies metamorphism in Siluro-Devonian oceanic protoliths occurred in the Huwan HP zone. Whereas the UHP rocks from the Xinxian UHP zone were mostly derived from the Neoproterozoic basement rocks in Yangtze Block, and have experienced prograde and retrograde eclogite-facies metamorphism at 239 ± 2; 227 ± 2, and 216 ± 3 Ma, respectively. They can be used to constrain a two-stage exhumation process with average exhumation and cooling rates at ca. 0.33 cm/y and 8 °C/ Ma and at 0.67 cm/y and 65 °C/ Ma. Two episodes of fluid activity have also been dated for quartz veins within around eclogites at 224.7 ± 1.3 and 217 ± Ma, which might have been accompanied with the two periods of exhumation process of the UHP rocks.

A1149

Noninvasive geophysical imaging of ureolytic CaCO3 precipitation YUXIN WU1*, JONATHAN AJO-FRANKLIN1, RYAN ARMSTRONG2 AND SUSAN HUBBARD1 11

Cyclotron Road, Berkeley, CA 94720 USA (*correspondence: [email protected]) 2 Oregon State University, 103 Gleeson HallCorvallis, OR 97331([email protected])

Calcium carbonate (CaCO3) minerals are a key family of compounds that frequently precipitate during natural and engineered subsurface processes. Carbonate precipitation has utility in both environmental remediation, as a means to sequester hazardous radionuclides including Strontium 90, and in geotechnical engineering as a tool for improving soil strength or decreasing rock permeability. Characterization of both the spatial extent and temporal dynamics of subsurface precipitation is critical for both of these applications. Wellbore geochemical sampling is the currently accepted monitoring strategy for stimulated precipitation experiments. However, the spatial and temporal variability of the induced process often make it difficult to assess the efficacy of the treatments over time and space using wellbore data alone. Recent studies have explored the potential of geophysical, especially electrical and seismic, methods as monitoring tools for induced precipitation processes during bioremediation. Specifically, distinct electrical signatures have been observed during abiotic precipitation of well crystalized calcite. The combination of wellbore geochemical sampling and spatially extensive geophysical data could significantly improve our understanding of the evolution of induced in situ precipitation processes. Urea hydrolysis is one mechanism used to induce in situ CaCO3 precipition. Here, we explore the electrical and seismic signatures produced by ureolytic CaCO3 precipitation using the model organism Sporosarcina Pasteurii. Our data revealed a significant increase in electrical signatures due to CaCO3 precipitation, and changes in both P-wave seismic attanuation and velocity corresponding to the initiation and accumulation of CaCO3 over time. Calcium concentration was monitored regularly and used to calculate precipitate mass and establish petrophysical correlations to geophysical attributes. Postmortum scanning electron microscopy (SEM) revealed the size and morphology of the precipitates which differered significantly from previous abiotic experiments. Our results demonstrate the sensitivity of electrical and seismic methods to microbial CaCO3 precipitation and suggest a complementary geophysical approach for monitoring induced in situ precipitation treatments.