Goldschmidt Abstracts 2010 – R

Goldschmidt Abstracts 2010 – R

Goldschmidt Conference Abstracts 2010 Evaluating arsenic adsorption in a low arsenic aquifer in Bangladesh using in situ and laboratory methods K.A. ...

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Goldschmidt Conference Abstracts 2010

Evaluating arsenic adsorption in a low arsenic aquifer in Bangladesh using in situ and laboratory methods K.A. RADLOFF1, Y. ZHENG1,2, H.A. MICHAEL3, M. STUTE1,4, I. MIHAJLOV1, K.M. AHMED5 AND A. VAN GEEN1 1

LDEO, Columbia Univ., Palisades, NY 10964, USA (*correspondence: [email protected]) 2 Queens College, CUNY, Flushing, NY 11367, USA 3 University of Delaware, Newark, DE 19716, USA 4 Barnard College, New York, NY 10027, USA 5 Dhaka University, Dhaka 1000, Bangladesh Deep tube wells tapping low arsenic aquifers are a widely used strategy for reducing exposure to arsenic contained in shallower groundwater in Bangladesh. The Dupi Tila aquifer, characterized by orange-colored sand deposited during the Pleistocene, has been used for arsenic mitigation in Dhaka and the surrounding rural areas. Regional groundwater flow modeling of the Bengal Basin has shown that in some areas deeper aquifer zones are vulnerable to the migration of shallow high arsenic water (Michael et al. this session), thus arsenic sorption could be important for resource sustainability. We compare here results from adsorption experiments initiated in the field using freshly collected sands with in situ experiments to provide robust estimates of the rate and extent of As adsorption on orange aquifer sands. The batch adsorption experiments indicate little difference between As (III) and As (V) adsorption, an equilibrium partitioning coefficient (K) of 30 to 70 L/kg, and an adsorption capacity of 40 mg/kg. In parallel, shallow groundwater intrusion, ~200 ppb As (III) or As (V), into the Pleistocene aquifer was simulated in the field using push-pull tests and monitored over time. Both batch and in situ experiments show that the rate of As adsorption is limited by the diffusion into smaller pore spaces. Analysis of results from the in situ experiments requires an equilibrium partioning coefficient (K) and an estimate of the exposed spaces. Values for K are similar to the batch experiments when small pore spaces, which were nearly unaffected by the experiment, account for 95 to 98% of the total adsorption sites. This is not unreasonable given the rapid flow induced in the in situ experiments. Under the most conservative scenario, with ratelimited sorption, the K would be 0.5 to 2 L/kg for As (III) and As (V), respectively. These results demonstrate the ability of orange sands to retard contamination of the Pleistocene aquifer and extends its potential usefulness for at least decades (Michael et al. this session).

A843

Trace and rare earth element characteristics of Vindhyan (NeoProterozoic) sandstones of Bhopal region, Central India R.S. RAGHUWANSHI Govt. Motilal Vigyan Mahavidyalaya, Bhopal (M.P.) India 462008 ([email protected]) The study area, Bhopal (Lat. 23°10' - 23°20'N and Long. 77°17' - 77°30'E) in Madhya Pradesh, India is represented by sandstones intercalated with shales and intra formational conglomerates belonging to Upper Vindhyans of Neoproterozoic age and basaltic lava flows affiliated to the Deccan trap igneous activity of Cretaceous period. The observed La/Sc, Th/Sc, Th/Co, Th/Cr, Cr/Th ratios after Cullers [1, 2]; Cullers and Podkovyrov [3]; Cullers et al. [4] and Taylor and McLennan [5] and concentration levels of other trace elements like Zr, Ni, V and Sc strongly suggest that these sandstones were derived principally from the felsic source rocks. The Th/Sc versus Sc bivariate and La-Th-Sc triangular plots support this interpretation. The rare earth element (REE) patterns of these rocks further confirm their derivation from felsic source rocks. Interestingly, these rocks exhibit higher LREE/HREE ratios (average 9.19) confirming the felsic igneous rocks as a possible source rocks. [1] Cullers, R.L. (1994) Chem. Geol. 113, 327-343. [2] Cullers, R.L. (2000) Lithos. 51, 181-203. [3] Cullers and Podkovyrov (2000) Precambrian Res. 104, 77-93. [4] Cullers, Basu and Suttner (1988) Chem. Geol. 71, 335-348. [5] Taylor and McLennan (1985) Blackwell, Oxford, UK, 349 p.

A844

Goldschmidt Conference Abstracts 2010

Targeting a safe aquifer in the Arsenic contaminated alluvial deposits M.T. RAHMAN1*, A. MANO1, K. UDO1 2 AND Y. ISHIBASHI 1

Disaster Control Research Center, Tohoku University, Sendai-980-8579, Japan (* [email protected]) 2 Tohoku Gakuin University, Miyagi 985-8537, Japan The present study aims to investigate the sorption and mobility of As in the contaminated sediment-groundwater (GW) interface to find out a likely safe aquifer beneath the Holocene deposit. The results show that the deeper sediment (> 100 m) comprising of partly oxidized, brownish medium sand (As, 0.76 !g/g) that accommodates much natural adsorbing surfaces like Fe and Al, was found to provide considerably low As (4 !g/L) water. A relatively faster in situ reaction rate, Kr (2.72 " 10-16 /sec) derived by using inverse mass balance model could also enhance the essential As releasing process from the upper source sediment. The distribution of As in the sediment-water interface was recognized by computing a partition coefficient, Kd-As by employing in situ, batch adsorption and flow through column techniques separately and was found to vary ranging between 10 and 250 L/kg. Additionally, a parametric equation to predict that Kd-As (R2 = 0.67) was postulated from the GWpH and logarithm of leachable Fe and Al contents in sediments. Incorporating these Kd and Kr, a 1-D finite difference numerical model was applied which showed that even after 80 years (Fig.1) not only the upper leached As could be immobilized against reaching the deeper aquifer due to the presence of a natural filter (oxidizing sand and adsorbing minerals Fe, Al), but also much of its GW As (83%) might get reduced. Finally, the deeper aquifer could be considered as the sustainable source of safe and adequate water to meet the urgent demand. Figure 1: Prediction of As scenario after 80 years

Towards accurate modeling of the growth and nucleation of carbonates P. RAITERI1, J.D. GALE1*, D. QUIGLEY2 AND P.M. RODGER3 1

Nanochemistry Research Institute, Dept. of Chemistry, Curtin University of Technology, PO Box U1987, Perth, WA 6845, Australia (*correspondence: [email protected]) 2 Dept. of Physics and Centre for Scientific Computing, Univ. of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK 3 Dept. of Chemistry and Centre for Scientific Computing, Univ. of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK

The nucleation and growth of CaCO3 is of significant interest in a number of fields, including biomineralization. In order to understand the atomic detail of how such processes occur, it is valuable to perform computer simulations alongside experimental studies. Our ability to perform accurate dynamical simulations of the aqueous CaCO3 system is hindered by two aspects. Firstly, the challenge of correctly describing the phase diagram of calcium carbonate; it is well known that the competition between calcite, aragonite, vaterite and amorphous precursors is very sensitive to particle size and conditions. Secondly, there is the issue of speciation; when does the interconversion between bicarbonate and carbonate occur and how does this influence growth processes?

Figure 1: Solvated nanoparticle of CaCO3. In this study we propose new force-field based methods [1] to address both of the above problems, thereby offering a route towards the accurate simulation of this system. To illustrate this, results for the properties of CaCO3 nanoparticles in water (Figure 1) will be presented. [1] Raiteri et al. (2010) J. Phys. Chem. C, in press.

Goldschmidt Conference Abstracts 2010

Hydro and pedogeochemistry in relation to landuse/landcover in Mungi village, Medak District, Andhra Pradesh, India S. RAJITHA AND PRAVEEN RAJ SAXENA Department Of Applied Geochemistry, Osmania University, Hyderabad, India ([email protected]) The study area Mungi village forms a part of deccan basalt terrain where mostly the soils are laterites. Lot of inorganic fertilizers is being used in the agricultural fields thus causing possible contamination in soils and groundwater. Soil and groundwater contamination by heavy metal ions is one of the most serious environmental problems. Thus keeping this fact twenty nine groundwater and twenty four soil samples have been analyzed using Perkin Elmer Sciex ELAN DRC II ICPMS. In the groundwater samples Pb ranged between 0.01 and 13.31µg/l with an average concentration of 1.82 µg/l the permissible limit of 10 µg/l. Ni contents ranged between 1.76 µg/l and 393.14 µg/l with an average of 38.29 µg/l which exceeds the permissible limit of 20 µg/l. As ranged between 0.09 µg/l and 2.42 µg/l with an average of 0.40 µg/l this is within the permissible limit of 10 µg/l. Zn ranged between 4.79 µg/l and 204.09 µg/l with an average of 33.68 µg/l. Cd ranged between 0.005 µg/l to 0.49 µg/l with an average of 0.06 µg/l this is within the permissible limit of 3 µg/l. With regard to the soil concentration Ni ranged between 32.92 mg/kg and 79.90 mg/kg with an average of 44.30 mg/kg. Pb ranged between 5.22 mg/kg and 14.45 mg/kg with an average of 10.21 mg/kg. Zn ranged between 124.42 mg/kg and 196.14 mg/kg with an average of 161.05 mg/kg. Co ranged between 29.64 mg/kg and 72.28 mg/kg with an average of 46 mg/kg.

A845

Electronic structure of Ti, Zr, Hf and Sn containing garnets – Materials for immobilization of actinides ZSOLT RAK, RODNEY C. EWING AND UDO BECKER Department of Geological Sciences, University of Michigan, Ann Arbor, MI 48109, USA Garnet, A3B2X3O12, have recently been considered as a candidate for actinide-bearing host matrices [1-3]. The presence of three different cation sites (A, B, and X), permits the incorporation of numerous elements into the structure. This not only gives rise to a large variety of naturally-occuring garnets, but also opens up the possibility of synthesizing artificial actinide-bearing phases with garnet structure. Present efforts are focused on structures that are derivatives of the fluorite structure, e.g. pyrochlore [1-4]. Garnets with high levels of Zr and Ti, such as kimzeyite and schorlomite have been found in nature, and their synthetic analogues have been ivestigated experimentally as nuclear waste form materials [4]. In order to potential of garnet to incorporate actinides, it is crucial to obtain a basic theoretical understanding of the bonding and electronic structure. We have investigated the crystal structure, nature of interatomic bondings, and electronic structure of Ca3 (Ti, Zr, Hf, Sn)2Fe2SiO12 garnet, using first-principles calculations within the density functional theory (DFT). The calculated equilibrium lattice parameters and the interatomic distances are close to the available experimental values, with a slight overestimation due to the generalized gradient approximation (GGA) used in our calculations. The theoretical total density of states (DOS) and its projections onto the atomic orbitals are presented and analyzed for different values of the on-site Coulomb interaction (Hubbard U) within the Fe d states. In order to quantify the strength of the interatomic bonds, we have performed Bader analysis of the charge density. The result of this analysis provides insight into the relative radiation resistance of garnet as a function of composition. [1] Omel’yananko et al. (2007) Geol. Ore Dep. 49, 137-193. [2] Livshits (2008) Geol. Ore Dep. 50, 470-480. [3] Laverov et al. (2010) Geochem. International 48, 1-14. [4] Whittle et al. (2006) J. Solid State Chem. 180, 758-791. [5] Utsunomoiya et al. (2005) J. Nucl. Mater. 336, 251-260.

A846

Goldschmidt Conference Abstracts 2010

Sorption of oxytetracycline on magnetite-water interface S. RAKSHIT1*, P. PUNAMIYA1, R. DATTA2 AND D. SARKAR1 1

Montclair State University, 1 Normal Ave (ML 116), Montclair, NJ 07043 (*correspondence: [email protected], [email protected] [email protected]) 2 Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931 ([email protected]) Oxytetracycline (OTC) is one of the most common veterinary antibiotics detected in wastewater, surface water, and soils. Few reports are available on the environmental fate of OTC. While there are some studies on the sorption of OTC on iron oxides [1], little information is available regarding its interaction with magnetite (Fe3O4) - an iron oxide with mixed oxidation state. This information would be essential in modeling the fate and transport of OTC in environments where Fe3O4 dominates. In addition, Fe3O4 appears as a secondary product in treatment technologies that employ zerovalent iron as a sorbent for permeable reactive barriers. The primary objective of this study was to elucidate the sorption behavior of OTC on Fe3O4. Batch sorption experiments were carried out as a function of equilibration time (1 min-48 h), pH (3-10), ionic strength (0.01-0.5 M KCl) and initial OTC concentration (0.1-2 mM OTC) under anerobic conditions. Magnetite was used at a concentration of 20 gL-1 in all sorption studies. Preliminary results indicate that sorption of OTC by Fe3O4 is rapid and nearly complete at 5 h. Sorption isotherm reached a plateau within 48 h. The pH-edge data indicate that with increasing pH, OTC sorption by Fe3O4 decreased, suggesting a possible combined effect of Fe3O4 surface charge and OTC speciation on sorption. Sorption isotherm data was fitted to the Langmuir model. A range of Langmuir parameters (b= 0.081-0.047 mMg-1, k = 39-191 LmM-1) for ionic strengths ranging from 0.01-0.5 M were obtained. The effect of ionic strength on sorption was negligible at initial OTC concentrations ranging between 0.1-1 mM. However, at higher initial concentrations (>2 mM), OTC sorption was a function of ionic strength, possibly indicating a different sorption mechanism. Surface complexation modeling of Fe3O4–OTC interactions is currently in progress. Spectroscopic studies are necessary to elucidate sorption mechanism. Preliminary results from this study indicate potential for use of Fe3O4 as a sorbent for OTC. [1] Figueroa & Mackay (2005), Environ. Sci. Technol. 39, 6664-6671.

Assessment of heavy metal pollution in sediments of Kazipalli watershed, northwest of Hyderabad (India) by wavelength dispersive X-Ray fluorescence spectrometry K. RAMA MOHAN*, A. KESHAV KRISHNA, N.N. MURTHY, P. VENKATESWARA RAO, A. SANTOSH KUMAR, P. SRIHARSHA AND S. YASHODA Environmental Geochemistry Division, National Geophysical Research Institute (Council of Scientific & Industrial Research), Habsiguda, Hyderabad-500606, A.P, India (*corresponding author: [email protected]) The contamination of natural systems by heavy metals is of major concern especially in many industrialized countries because of their toxicity, persistence and bioaccumulative nature. The objective of this study is to investigate the contamination levels and dispersion pattern of heavy metals (As, Cd, Co, Cr, Cu, Ni, Pb, V and Zn) in sediments of Kazipalli watershed, northwest of Hyderabad, India. The Kazipalli watershed consists of an industrial area comprises intense chemical, pharmaceutical and pesticide manufacturing industries. The watershed is spread over 37.15 sq km with crisscrossed by intermittent streams and their water conserved in a chain of small picturesque lakes called ‘cheruvus’. Sediments were collected (n = 23) from different lakes and streams flowing into the lakes, have been analyzed for their heavy metal content using Wavelength Dispersive X-Ray Fluorescence (WD-XRF) Spectrometry. The results show that sediments from the lake ‘Kazi cheruvu’ and streams connecting to this lake contain highest concentrations of As (961.7 mg/kg), Cd (116 mg/kg), Cr (512.8 mg/kg), Pb (2043.6 mg/kg) and Zn (504 mg/kg) than the other lakes in the study area. Concentrations of heavy metals found in sediments are exceeding the prescribed limits by Regulatory agencies. The correlation analysis of concentration data showed positive correllations (r2 = 0.99) among As, Cd, Zn, Pb, Co Cu, Vand Ni indicating that the contamination is from the identical source. These elevated heavy metal concentrations were ascribed to the untreated open discharge of industrial waste water via streams in to the lakes. Further studies will be required for speciation of various chemical forms of the heavy metals to assess their bioavailability and toxic effects to the aquatic life.

Goldschmidt Conference Abstracts 2010

A847

Mining wastes – Water quality deterioration and its impact on environment in Southern India

The genetic pathway for high level chromium resistance in Shewanella sp. strain ANA-3

H.K. RAMARAJU

JEANIE RAMOS1 AND CHAD SALTIKOV2

Professor and Head of Civil Engineering Department, Dayananda Sagar College of Engineering, Kumaraswamy Layout, Bangalore-560078, Karnataka, South India, ([email protected]) Water is the basic amenity of life which is finite and precious. India’s sanitation systems both in urban and rural areas are water based. Rapidly growing population and rising income levels have put severe pressure on natural resources. Karnataka state contains vast major mineral deposits of gold, silver, platinum, iron etc. Land degradation is one of the significant impacts arising out of mining and quarrying activity which is mainly in the form of alteration of land structure due to excavation, stacking of top soil and loss of land due to dumping of mine waste and overburden soil. The continuous mining activity of the last 100 years in this area has resulted in stress, deteriorated and contaminated with heavy metals from historic mining and mineral processing operations. A field study was carried out in Kolar Gold Field mining residential area. The main objective of this study is to assess the impact of mining. It is observed from results that the quality and quantity of surface /ground water got affected through various factors like surface hydrology, soil texture, terrestrial vegetation and huge dumps of mining waste depending on the quality of leachates generated from the overburden material whether acidic in nature or rich in mineral content, thereby warranting adoption of appropriate control measures. Interventions are needed to ease the human pressure on natural resources and to ensure sustainable –use. In this paper, we have attempted to understand the process of overdevelopment of groundwater and its impact on environment in the mining area, agriculturally and industrially advanced district of Kolar, in the southern part of India.

University of California, Santa Cruz, Santa Cruz, CA 95064, USA ([email protected], [email protected]) Hexavalent chromium [Cr (VI)] is highly soluble in groundwater and toxic to most organisms. Cr (VI) reduction to Cr (III) is proposed to be a remediation strategy for Cr (VI) polluted water because Cr (III) tends to form insoluble oxides at neutral pH. Cr (VI) can be directly reduced by bacteria or indirectly by reacting with Fe (II) produced by Fe (III)reducing bacteria. We are investigating the metal-reducer Shewanella sp. ANA-3 as a model Cr (VI) bioremediation organism. ANA-3 was shown to resist Cr (VI) exposures up to 2 mM. Moreover, direct Cr (VI) reduction was also observed in cultures grown aerobically. Other Shewanella species showed considerable sensitivity to Cr (VI) relative to ANA-3. Anaerobically grown cultures of ANA-3 were extremely sensitive to Cr (VI). No growth was detected at Cr (VI) concentrations above 2.5 micro molar in anaerobic cultures grown with fumarate. Genetic work in ANA-3 showed that aerobic Cr (VI) resistance was conferred by the chrA gene, which encodes for a chemiosmotic pump the extrudes chromate out of the cell. The chrA gene appears to be present only in ANA-3 and not other Shewanella strains with sequenced genomes. Moreover, chrA is associated with a mega-plasmid and is part of a putative operon, chrBAC. Gene expression studies indicated that chrA was inducible by Cr (VI) relative to no chromate. These results point to chrA as a key component in ANA-3 to withstand chromium toxicity. Current work is aimed at understanding why ANA-3 exhibits acute anaerobic sensitivity to Cr (VI). This work contributes to the possibility of using microbes to sequester Cr from contaminated sites.

A848

Goldschmidt Conference Abstracts 2010

Study of changes in physiochemical properties of soil by the addition of cement

Understanding natural perchlorate formation by ozone and UV-oxidation of aqueous Cl species

M. RAMZAN* AND A. FAROOQI

B. RAO1*, W.A. JACKSON2, J.K. BÖHLKE3, P.B. HATZINGER4, B. GU5 AND NEIL STURCHIO6

Fatima Jinnah Women University, Rawalpindi, Pakistan (*correspondence: [email protected], [email protected])

Solution for Atmospheric dust and Problematic soils The effect of cement on physiochemical properties of three types of soils i. e garden soil, agricultural soil and roadside soil was investigated. The ordinary Portland cement was used. The amount of cement added to soil samples, as dry mass percentage was 20%.The results of analysis showed that the addition of cement is capable of bringing about changes in physiochemical properties of soil. The electrical conductivity and organic matter content in three soils get decreased by the addition of cement. While the pH, bulk density and water holding capacity of soils after the addition of cement gets increased. The soil found most suitable to be treated with cement was roadside soil. It was concluded that cement can be used to change the physiochemical properties of soil and this technique has great utility in improving the quality of problematic soils. This technique has great utility in controlling the loss of valuable cover of top soil by binding the lose particulate matter in cement matrix. Natural (wind and water erosion, landsliding etc) as well as anthropogenic disturbances (construction etc) which allowed the dissimination of particulates in air can be overcomed by using soil cement mixing techniques. Further more, small bricks were also made from these three types of soil and the brick with lowest organic matter i. e roadside soil plus cement mixture showed greater stablity then others. This idea of brick making from cheap resource which is abundant in nature i. e soil, can be used to in making of earthquake resistant buildings. As statellites cannot see through soil structures so by making buildings with soil-cement bricks, can enchance the security of nations as well. Soil cement mixing can be used in making of high ways and for reclamation of problematic soils.

1

Texas Tech University, TX (*correspondence: [email protected]) 2 Texas Tech University, TX ([email protected]) 3 US Geological Survey, Reston, VA ([email protected]) 4 Shaw Environmental, NJ ([email protected]) 5 Oak Ridge National Laboratory, TN ([email protected]) 6 University of Illinois at Chicago, IL ([email protected])

Recent studies have demonstrated that natural perchlorate (ClO4-) ubiquitously occurs throughout the world. However, currently there is little understanding of the production pathway (s) that is responsible for natural ClO4- formation. Our work has systematically examined the production of ClO4formed by both O3 mediated oxidation and photo-oxidation of aqueous oxy-chlorine anions (e.g. Cl-, OCl-, ClO2-, ClO2) including evaluating the impact of major environmental parameters such as pH, reactant concentration, and irradiation wavelength. Further, we have evaluated the stable isotopic composition of the produced ClO4-. ClO3- is not an effective reactant as neither O3 nor photolysis produced ClO4- under the experimental conditions studied. ClO4- production yield (0.18 to 0.006 %) were in general greater for higher incident radiant wavelength when ClO2- was used as the initial reactant. Ozone oxidation of ClO2- and ClO2 produced the highest yields of ClO4- (0.6 to 2.7 %) compared to other reactants evaluated. Perchlorate production yields (0.0016 to 0.00012 %) were much lower for both ozonation and photolysis of HOCl/OCl-. Ozonation but not photolysis of Cl- solutions produced ClO4-. Chlorine dioxide is considered to be the critical intermediate in the formation of ClO4-. ClO4- produced from ozonation of OCl-, and ClO2exhibited non-mass-dependent O isotopic variation (preliminary #17O values around 20 and 12 ‰, respectively), whereas ClO4- produced by photolysis of OCl- and ClO2exhibited largely mass-dependent O isotopic variations. The $18O values of ClO4- products were higher than those of the Cl-O reactants for all processes except photolysis of OCl-. New insights about the relative importance of these potential formation pathways may be gained by comparing isotopic compositions of experimentally produced ClO4- with reported isotopic compositions of natural ClO4-.

Goldschmidt Conference Abstracts 2010

Reno river, Northern Italy: geochemical composition of water and suspended river sediments

Automated domestic online monitor of water pollution P. RASHMI REDDY, G.SATYA SWAROOP AND KARTHIK RAVI TEJA. M*

1

DIMITRA RAPTI-CAPUTO , DONATELLA PAVANELL2 AND CARMELA VACCARO1 1

University of Ferrara, Department of Earth Sciences. Via Saragat, 1, I-44100 Ferrara Italy ([email protected]) 2 University of Bologna. DEIAgra, Facoltˆ di Agraria. Italy

The preliminary results aimed to defining the environmental conditions of the hydrographic basin and based on geochemical and hydrological methods are presented. The discussed case study is represented by the Reno river, northern Italy, where its environmental conditions are initially determined with a analysis of lithological, hydrological and land use of the watersheds of the hydrographic basin, integrated with granulometric composition and geochemical analysis of the solid suspended material and of the water, during extreme flow events, in 8 monitoring stations. Additionally, a geochemical monitoring has been carried out for two of the major hydrographic sub-basins: a) Lavino river, with areal extension of 82, 6 km2 and mean annual discharge of 0.62 m3/s (period 1998-2004) and b) Savena river, with areal extension of 168, 9 km2 and mean annual discharge of 2.8 m3/s (period 2000-2004). In particular, the chemical analysis of the collected solid material by means of an X-rays method and of the waters by means of ICP-MS standard procedures allowed to define i) the principal mean concentrations of both water and sediments and their comparison with the Italian and European legislative limits; ii) the variations in ionic concentration of both sediments and water, therefore enabling to infer the degree of erodibility of the rocks outcropping within the hydrographic basins, their relation with the amount of precipitation and corrivation times of the water at the monitoring sections; iii) the present-day background values of the principal chemical elements.

A849

CVR College of Engineering, JNTUH, AP, India. 1 ([email protected], [email protected], *correspondence: [email protected]) The principle of working of conducting plates is used in the paper. When the conducting plates are ON, the conducting media, water conducts, and the different ions present in the water are responsible for conductivity. The other constraint is temperature as conductivity depends on it, hence RTD is used for temperature sensing and thus equivalent voltage is obtained. These voltages are given to the microprocessor which on processing gives the required result. The model can be divided into three basic parts: Conducting plates, RTD and Micro-processor

Figure 1: Block Diagram. Water quality

Conductivity range (S/m)

Excellent quality Good quality Poor quality

5.5 x 10-5 to 0.046 0.046 to 0.141 0.141 to 0.188

Table 1: The conductivities of water at different qualities From the table given above, the quality of water is decided based on the conductivity values. The quality poor imply that, by consuming water of this quality for a considerable period of time it may cause health problems [1], [2]. Thus the water quality is being observed periodically to avoid health hazards. [1]

http://www.laleva.cc/environment/water.html

http://www.who.int/household_water/en/

[2]

A850

Goldschmidt Conference Abstracts 2010

Os isotope systematics of Jorullo Lavas, Mexico: Petrogenetic implications C. RASOAZANAMPARANY1*, E. WIDOM1, C. SIEBE2, G. VALDEZ3, S. SALINAS2 AND M.-N. GUILBAUD2

Insights into anaerobic respiration from the genome of the selenate respiring bacterium “Desulfurispirillum indicum” strain S5

1

Department of Geology, Miami University, Oxford, OH 45056 USA (*correspondence: [email protected]) 2 Departamento de Vulcanologia, Instituto de Geofisica, UNAM, 04510 México, D.F., México 3 Unidad Académica de Ciencias de la Tierra, UAGRO, Taxco, Guerrero, México

I. RAUSCHENBACH*, N. YEE, M.M. HÄGGBLOM AND E. BINI Rutgers University, New Brunswick, NJ 08901, USA (*correspondence: [email protected])

Background Arc lavas are generally radiogenic in 187Os/188Os compared to depleted mantle, which has been variously attributed to crustal assimilation [1] or to addition of subduction components to the mantle wedge [2]. However, the low Os abundances in most arc lavas make the Os isotope signatures highly susceptible to crustal assimilation. The 1759-1774 eruption of the Jorullo volcano in the Michoacán Guanajuato Volcanic field (MGVF), Mexico produced relatively primitive lavas that can potentially help address the origin of radiogenic Os in arc magmas. Os concentrations in Jorullo lavas vary from 18 to 173 ppt, and 187Os/188Os ranges from 0.13031 to 0.14066. A previous regional Os isotope study of MGVF cinder cones invoked lower crustal assimilation to explain such elevated ratios [1, 3]. However, our preliminary work on Jorullo lavas shows a lack of correlation between 187Os/188Os and indices of fractionation (e.g. MgO, SiO2), suggesting a limited role for crustal assimilation processes in their petrogenesis. In addition, a positive correlation between 187 Os/188Os and 2°6Pb/2°4Pb argues against lower crust assimilation assuming typical lower crustal compositions. Instead, 187Os/188Os is positively correlated with elemental ratios characteristic of slab derived fluids (e.g. Ba/Zr, Sr/Ta), thus apparently consistent with addition of a slab-derived fluid containing radiogenic Os to the overlying mantle wedge. In addition, the negative correlation between the 187Os/188Os and some incompatible elements (e.g. Ta) appears to be inconsistent with upper crustal assimilation, and may reflect variable degrees of partial melting of a mantle source, in which greater fluid addition to the mantle wedge results in more radiogenic Os and higher degrees of melting. [1] Chesley et al. (2002) Earth Planet Sci. Lett. 195, 211–221. [2] Saha et al. (2005) Earth Planet Sci. Lett. 236, 182-194. [3] Lassiter & Luhr (2001) G3 2, 1525-2027.

The bioreduction of dissolved selenate and selenite oxyanions to sparingly soluble elemental selenium is one of the primary processes by which selenium can be detoxified in contaminanted environments. In order to employ Se-reducing bacteria for in situ bioremediation purposes, reliable models must be developed to predict microbial behavior, including when they are active, what mechanisms are involved, and under what conditions the mechanisms function. ‘Desulfurispirillum indicum’ strain S5, a novel species belonging to the family of Chrysiogenes, is capable of respiring selenate, selenite, arsenate, and nitrate. The annotation of its whole genome sequence enabled us to identify and characterize the reductases and molybdoenzymes involved in selenate, arsenate, and nitrate respiration.

Methods To process the genome sequence information of ‘Desulfurispirillum indicum’ and make possible predictions about the function of genes, the JGI databases (IMG) and various other tools, such as BLAST and Artemis were used. The genome data analysis was set in the comparative context of multiple microbial genomes to identify homologous genes, open reading frames and proteins.

Results and Discussion Genome analysis uncovered 17 sequences carrying the signatures of molybdoenzymes. Two of the molybdoenzyme sequences were found to cluster with the respiratory arsenate reductase Arr, the alpha subunit of the membrane-bound nitrate reductase NarG, and the periplasmic nitrate reductase subunit NapA, respectively. Further analysis of the genome context revealed the presence of additional sequences encoding operons of each enzyme, and a gene organization resembling typical arr, nar, and nap operons. Homologs of YnfE and YnfG, known to be involved in selenate reduction in Escherichia coli and Salmonella, were also identified in the S5 genome. The results of this genomic analysis provide a springboard for further investigations into metabolic pathways for energy production in contaminated environments, and how these pathways are regulated depending on the availability of oxyanions.

Goldschmidt Conference Abstracts 2010

A851

Sustainability of groundwater abstraction in the Arsenic-affected Bengal Basin, Bangladesh and West Bengal (India)

Geochemistry of granitoids of the Kerala Khondalite Belt, Southern India – Magmatic petrogenesis in an arc-accretion setting

PETER RAVENSCROFT

G.R. RAVINDRA KUMAR* AND C. SREEJITH

Entec UK Ltd, Trinity House, Cambridge Business Park, Cowley Road, Cambridge, CB4 0WZ. ([email protected]) In the Bengal Basin, groundwater supplies drinking water to >100 million people and irrigates the most important food crop, with irrigation accounting for 90% of groundwater abstraction. The region suffers the world’s worst case of arsenic pollution, where >20 million people still drink water containing >50 ppb As, predominantly from shallow aquifers. Moreover, As is accumulating in the food chain and; in some areas, contributing to similar levels of exposure and declining yield in rice. The use of groundwater is also constrained by salinity, iron, manganese, boron, barium, and microorganisms. Each constraint generates complex feedback mechanisms that further threaten the presently safe aquifers, most of which, for various social and economic reasons, will resulting in increased abstraction from deeper aquifers that are, at best, partly renewable resources. Based on population projections, estimates of annual potential recharge are sufficient to satisfy projected demand, but without intervention water quality constraints may make this impossible. Arsenic in shallow aquifers is being redistributed, polluting safe wells, but also being attenuated, such that As concentrations are simultaneously increasing and decreasing in different parts of the aquifers. The greatest threats to the sustainable use of deep aquifers come from the lateral and vertical migration of arsenic and of residual salinity, plus excessive drawdowns. As shallow groundwater is drawn into deeper aquifers, natural attenuation will contribute to the gradual clean-up of the shallow aquifers. However, there is significant doubt whether the present abstraction scenarios are sustainable. Nonetheless, sustainability, or at least greatly increased resource life may be achieved through managed natural attenuation of As; artificial recharge in urban and rural areas; river bank infiltration; in situ removal of As, Fe and Mn; reduced distribution losses from piped water supplies from deep aquifers; and changes in agronomic practices and cropping patterns.

Centre for Earth Science Studies, Trivandrum, India (*correspondence: [email protected]) The Kerala Khondalite Belt (KKB) is an important lower crustal segment of the southern Indian granulite terrain. Most studies consider KKB to be of supracrustal origin. Tectonomagmatic framework is not well-constrained due to lack of comprehensive datasets for the entire KKB. In this study we bridge this gap by interpreting major- and traceelement data and REE systematic on major (> 70%) granitoid lithounit of the belt as related to the magmatic petrogenesis in an arc-accretion setting. The granitoids of KKB can be classified as sodic and potassic groups based on K2O/Na2O ratios. The sodic group has geochemical affinity to Archaean tonalities with low-K, calc-alkaline, metaluminous to peraluminous chemistry. Compositionally contrasting K-rich rocks are essentially of granitic composition. Most oxides in both the groups, with exceptions of K2O and Na2O, show negative correlation with SiO2. The sodic group is enriched in Sr and depleted in Rb and Th. They exhibit geochemical features similar to those of Archaean tonalite and trondhjemite [1] with enriched LREE and depleted HREE with positive and/or no Eu anomaly. On the other hand, potassic group show enrichment in large ion lithophile elements in relation to the high field strength elements and sharp negative anomalies of Eu, Nb, Sr, Zr, and Ti with fractionated REE patterns, implying significant fractionation of plagioclase into the residue and strong effects of intracrustal differentiation [2]. Complimentary patterns of Eu and Sr anomalies in both groups, also suggest an event of intracrustal magmatic differentiation in the presence of plagioclase. The most plausible tectonic model that explains the generation of sodic group is through melting of hydrous basaltic material at the base of a thick crust and that of potassic granites by partial melting of meta-igneous source rocks [3]. We speculate subduction zone related arc accretion setting followed by intracrustal melting for the evolution of KKB, which may therefore represent the deep-section of a collisional orogen. [1] Taylor & McLennan (1995) Rev. Geophys. 33, 241-265. [2] Gromet & Silver (1987) J. Petrol. 28, 75-125. [3] Pati%o Douce (1999) Geol. Soc. London, Spec. Publ. 168, 55-75.

A852

Goldschmidt Conference Abstracts 2010

Reconstructing the marine Os record: Lessons from pelagic sediments GREG RAVIZZA, FRANCOIS PAQUAY AND DENYS VONDERHAAR Deparment of Geology and Geophysics, SOEST, University of Hawaii, Manoa, 1680 East-West Rd. Honolulu, HI 96822. ([email protected], [email protected], [email protected]) Our recent work performing bulk sediment analyses of Cenozoic and late Cretaceous deep sea sediments reveals clear whole ocean shifts related to impact events, flood basalt volcanism and long-term climate evolution. In addition, new high resolution records reveal systematic offsets in 187Os/188Os between widely separated sites, suggesting regionally heterogeneous 187Os/188Os in the open ocean on the order of 5%. This finding is significant because it implies that the Os isotope systematics of pelagic sediments record both whole ocean reservoir shifts in response to changing global inputs, as well as regional contrasts that are potentially useful for reconstructing ocean circulation. Thus, marine Os isotope records may be conceptually more analogous to marine carbon isotope records, than to either marine Nd or Sr isotope records. In order to further explore this possibility three important issues must be addresses. First our ability to distinguish between lithogenic, particulate extraterrestrial and hydrogenous components of sediment Os budgets must improve. Second, multiple high resolution records of Os isotope variations from nearby, well-correlated sites must be used to better understand the nature of very brief transient excursions in 187Os/188Os. Third, direct analyses of Os in pore fluids is needed to evaluate the potential influence of diagenetic Os redistribution. New and recently published data from the deep sea sediments recovered by ocean drilling will be used to illustrate the importance of these topics. Importantly our work integrates data from a variety lithologies.

Rapid Os isotope analyses of carius tube digestions by sparging GREG RAVIZZA, FRANCOIS PAQUAY, DOUG PYLE AND DENYS VONDERHAAR Deparment of Geology and Geophysics, SOEST, University of Hawaii, Manoa, 1680 East-West Rd. Honolulu, HI 96822. ([email protected], [email protected], [email protected], [email protected]) We have developed a method that integrates carius tube digestion of sediment samples with Os isotope analysis by sparging. The objective of merging carius tube digestion with the sparging method was to develop a procedure that eliminated the need for all post-digestion Os separation. To achieve this goal required abandoning digestion solutions based on nitric and hydrochloric acids in favor of nitric acid hydrogen peroxide mixtures. The sparging method involves direct introduction of OsO4 vapor into the plasma with an Ar carrier gas bubbled through solutions resulting from carius tube digestion. Not only does this approach eliminate the need for laborious Os separations, it has rapid sample through put, 4 -5 analyses per hour, relative to N-TIMS. Using an Element2 single collector ICPMS for analysis routinely yields precisions between 0.5% and 1.5% 2 sigma uncertainties for 187Os/188Os ratios measured on 100 pg of analyte. Tests have been conducted using a variety of marine sediments including glacial diamictites, composed almost exclusively of silicate detritus, deep sea oozes, composed of >90% CaCO3, and organic-rich sediments, strongly enriched in authigenic Os. Comparisons of carius tube digestions to total digestion by NiS fire assay indicate that the nitric peroxide mixtures liberate nearly all of the Os contained in the samples, including >50% of the of silicate associated Os contained in the glacial diamictites.

Goldschmidt Conference Abstracts 2010

Homogeneous and heterogeneous sediment experiments using fiber optic sensing technology for detecting gas hydrate formation C.J. RAWN1*,2, J.R. LEEMAN3, S.M ULRICH4, J.E. ALFORD5, M.E. MADDEN3 AND T.J. PHELPS5 1

Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA (*correspondence: [email protected]) 2 Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996 USA 3 School of Geology and Geophysics, University of Oklahoma, Norman, OK 73019 USA 4 Department of Environmental Science and Engineering, Colorado School of Mines, Golden, CO 80401 USA 5 Environmental Science Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA The 72 liter Seafloor Processing Simulator (SPS) was developed as a mesoscale apparatus to bridge laboratory scale characterization of gas hydrates and seafloor conditions. Originally during an experiment the overall pressure and temperature of the SPS were monitored with traditional thermocouples and 1-2 pressure transducers and hydrate formation/dissociation was viewed visually using multiple ports with sapphire windows. Recently we have added a fiberoptics temperature/strain sensing system to observe temperature changes that correspond to gas hydrate formation (exothermic) or dissociation (endothermic) throughout the system. The optical fibers have Bragg gratings every 1 cm so that each fiber has around 150 – 200 gratings matching the spatial scale of natural hydrates occurrences in nature. In addition to adding spatial resolution data can be collected at specified time intervals resulting in time-resolved 3-D temperature monitoring. Experiments have been conducted where the optical fibers were buried at various levels above and below a gas diffuser outlet and used to observe methane hydrate formation. During one experiment the fibers were buried in a homogeneous sediment column (Ottawa sand only) and during a second experiment the fibers were buried in a heterogeneous sediment column split vertically with one side being Ottawa sand and the other side being slit. The results of these experiments indicate the the fiber optic sensors are a viable technology for sensing hydrate formation and that hydrate formation takes place preferentially in the the more porous sediment. Research sponsored by the U.S. DOE, Office of Fossil Energy under FWP FEAB111. ORNL is managed by UTBattelle LLC, for the U.S. DOE.

A853

Multi-element laser mapping of geological materials: Improving data collection, image production and analysis using time series and innovative inference techniques A.M. READING*, L. DANYUSHEVSKY, S. MEFFRE AND S.E. GILBERT CODES CoE and School of Earth Sciences, University of Tasmania, Private Bag 79, Hobart, TAS, 7001, Australia (*correspondence: [email protected]) Laser ablation ICP-MS imaging ‘laser mapping’ is a flexible technique which has been applied to find the spatial distribution of a wide range of elements in medical, zoological, archaelogical and geological samples. Geological applications include the mapping of element concentrations and isotopic ratios in zoned minerals [1, 2, 3], which are often characterised by element concentration variations over orders of magnitude on small spatial scales. They also present a combination of sharp changes and gradational zones in element abundance. We present the results of investigative work which aims to improve three distinct parts of the laser mapping process: 1) Data collection, 2) Image production and 3) Image analysis. Our investigations concerning data collection, the first of these stages, are in the form of an adaptive process whereby the laser operation and scanning procedures are optimised for the following image production stage. In the second stage, strategies from geophysical time-series analysis are used to minimise the influence of data collection procedures. The interaction between extreme count regions and mass spectrometer response is responsible for unwanted artifacts in laser mapping images and these are again minimised using geophysical time-series strategies. At the end of stage two, the aim is to produce an image in which the laser scanning history is substantially removed. In the third and final part of the process, we investigate the application to geological samples of some of the innovative spatial data inference techniques which have emerged from the digital imaging revolution. In particular, we show techniques which make use of correlations between the related images produced by multi-spectral techniques. [1] Woodhead et al. (2007) Geost. Geoanal. Res., 31, 313343. [2] Large et al. (2009) Econ. Geol., 104, 635-668. [3] Ulrich et al. (2009) Can. Mineral., 47, 1001-1012.

A854

Goldschmidt Conference Abstracts 2010

A case-study of 3He-3H dated groundwaters to reconstruct atmospheric 36Cl inputs R. REBEIX1*, C. LE GAL LA SALLE1, A. MAYER2, R. FINKEL2 AND R. SIMLER3 1

GIS/CEREGE, Université de Nîmes 30035 Nîmes cedex 1, France (*correspondence: [email protected]) 2 CEREGE, Europole de l’Arbois, BP80, 13545 aix en provence, France 3 UMR EMMAH 11144 INRA Université d’Avignon France 3 H-3He systems of groundwaters allows precise dating of modern recharges and determination of mixing % with older groundwaters. In this study, we show the benefit of this method to reconstruct the 36Cl inputs from rainfall for a mid latitude setting (Venice, Italy). The sampled groundwaters have been dated using 3H-3He and 14C (Mayer et al. this volume). Comparison between tritiogenic 3He and 3H record of Vienna (IAEA) enabled us to determine mixing % between modern (3He-3H- dated) and old (14C- dated) component in mixed recent groundwaters. The large span of residence times allowed building a coherent attenuation signal of 36Cl on the whole last 50 years, since nuclear tests in the 1950s, when a large amount of 36Cl was introduced in the atmosphere, inducing a thousand fold increase of the input signal. The built attenuation curve shows a maximum peak value of 7, 960 at. m-2. s-1 and a current deposition between 123 and 251 at. m-2. s-1 with maximum attenuation between bomb pulse and 1980 and slower lowering between 1980 and current deposition rate. Moreover, 36Cl in old groundwaters, corrected for decay and addition of secular neutrogenic 36Cl, allowed to estimate natural deposition up to 12, 000 BP, with a local mean value of 53 at. m-2. s-1. Gap between current and calculated natural deposition rate was investigated. A possible way of overproduction by stratospheric activation of CFCs by neutron is proposed. Finally, our samples and a wide range of literature data were compared to investigate the impact of the latitude on the attenuation of the bomb pulse.

Dynamics of mineral precipitation in mixing zones in porous media GEORGE REDDEN1, DON FOX1, TSIGABU GEBREHIWET2, HAI HUANG1, LUANJING GUO1 AND YOSHIKO FUJITA1 1

Idaho National Laboratory ([email protected], [email protected], [email protected], [email protected], [email protected]) 2 University of Idaho-Idaho Falls ([email protected]) Stimulating in situ precipitation of minerals to immobilize metal contaminants is a promising approach for subsurface remediation. However, predicting and controlling the spatial/temporal distribution of reactant mixing and precipitates remains a challenge. Fluid flow, dispersive/diffusive transport of reactants, biogeochemical reactions and changes in porosity-permeability are tightly coupled, in a non-linear fashion, and at multiple scales. Chemical gradients within the mixing zones will determine local reaction rates, products, and possibly changes in hydrodynamic characteristics of the porous media. Transients in mineral precipitate distributions that arise from these gradients in multi-component mixing zones can influence: 1) the longer term outcomes of reactions in the affected region, and 2) the ability of models that employ volume averaging at some scales to predict changes in local properties of the system, such as extent and rates of reactions. We have conducted physical experiments, along with model simulations, to investigate the dynamics of mineral precipitation in two types of mixing geometries in porous media. One is double diffusion where reactants, calcium and either carbonate or phosphate, mix in gel or granular media through diffusive transport. Precipitation band formation occurs as expected, but with evolving local structures that affect permeability and chemical conditions on either side of the precipitation zone. The process coupling also affects the precipitation products. In the second type of mxing geometry, carbonate ion is formed in situ by enzymatic hydrolysis of urea in a porous media column where calcium is introduced along with the urea. A precipitation zone forms downstream of the head of the immobilized enzyme zone, which causes reduction in permeability and flow, changes in the chemical composition along the column, and eventually compression of the reaction and precipitation zone. Both examples illustrate challenges in controlling precipitation events as well as in predicting mixing and precipitation using volume averaging modeling approaches. Modeling results for the experiments from a fully coupled, fully implicit reactive transport simulator will also be presented.

Goldschmidt Conference Abstracts 2010

Identification of geochemical facies and processes of fluoride enrichment in ground water of fracture granitic aquifer of Chimakurthy watershed, Southern India A.G.S. REDDY1 AND D.V. REDDY2 1 2

Central Ground Water Board, Hyderabad National Geophysical Research Institute, Hyderabad

The genesis of fluoride rich ground water is a combination of complex processes involving many dynamic factors with variant magnitude. Aquifer chemistry, mineralogical makeup of host rock, pressure-temperature conditions of solute play a deciding role in ground water attaining a saturated status with respect to fluoride assimilation which again is under constant modifications in space and time. Understanding the multivariant hydrochemical processes of high fluoride aquatic enrichment in a fractured, semi-confined aquifer system could give more clarity to this much debated subject. Fluoride content is vary high in this closed Pre-cambrian granitic water shed reaching as high as 11ppm with a mean of 1.70ppm. Limited seasonal variation in fluoride content is noticed but it varies widely in space as higher content of fluoride in ground water is noticed at the contact zones of granite gneiss and Norite gabbro which occurs as an enclave amidst leucocratic, feldspar rich granites. The fluoride do not exhibit distinct relation with any of the analyzed elements including Ca. Trace element chemistry is also unique in this area as Sr and Zn are very high. Rock chemistry, in which fluoride content varies between 202 and 612ppm indicates that weathering processes, water-rock interaction and fluoride rich aquifer material together with favourable semi-arid climate could be responsible for high fluoride content in ground water of this water shed.

A855

Structure model of synthetic amorphous calcium carbonate R.J. REEDER1*, A.L. GOODWIN2, F.M. MICHEL3, B.L. PHILLIPS1, D.A. KEEN4 AND M.T. DOVE5 1

Department of Geosciences, Stony Brook University, Stony Brook, NY 11794 USA (*correspondence: [email protected]) 2 Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, UK 3 Department of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305 USA 4 ISIS Facility, Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0QX, UK 5 Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK Formation and subsequent transformation of amorphous calcium carbonate (ACC) are widely recognized as integral steps of biomineralization in certain calcifying invertebrates, and this strategy has been exploited for bio-inspired synthesis. An incomplete understanding of structure in ACC has posed challenges for identifying the mechanisms by which additives control ACC stabilization and influence crystallization behavior. Adopting a model approach, we explore a combination of methods for determining structure in ACC over a wide range of length scales. Whereas several different varieties of ACC are known from biogenic and synthetic sources, our initial work focuses on synthetic, hydrated ACC. Pair distribution functions obtained using synchrotron X-ray total scattering data reveal the presence of medium-range order (up to 15 Å) in biogenic and synthetic ACC. Results of reverse Monte Carlo refinement of the total scattering data reveal that the ACC consists of a porous calcium-rich framework that supports interconnected channels containing water and carbonate molecules. The existence of a previously unrecognized nanometer-scale channel network suggests mechanisms of how additives can be accommodated within the structure and provide temporary stabilization, as well as influence the crystallization process. Moreover, while lacking long-range order, the calcium-rich framework in ACC contains similar Ca packing density to that present in calcite, aragonite and vaterite, yielding clues of how the amorphous material converts into the different crystalline forms. The new structure model is found to be consistent with Ca EXAFS and NMR data, and provides a new starting point for examining interactions of additive molecules with ACC structure and their structural role in controlling stabilization and crystallization. This method should also find application to other varieties of ACC.

A856

Goldschmidt Conference Abstracts 2010

Using direct-current and complex electrical conductivity to monitor biogeochemical redox reactions A.B. REGBERG1, K. SINGHA1, D.R. BOND2 Q. ZHENG3, F. PICARDAL3, E.E. RODEN4 AND S.L. BRANTLEY1

Mineral precipitation from geothermal brines during reservoir activities – Example Groß Schönebeck (Germany) S. REGENSPURG, J. BANKS AND G. ZIMMERMANN

1

Department of Geosciences , Pennsylvania State University, University Park, PA 16802 USA ([email protected]) 2 Department of Microbiology, University of Minnesota, St. Paul, MN. USA 3 School of Public and Environmental Affairs, Indiana University, Bloomington, IN. USA 4 Department of Geology and Geophysics, University of Wisconsin, Madison, WI. USA

Direct-current electrical conductivity measurements can be correlated across scales to changes in chemical concentrations due to redox reactions if reaction stoichiometries are understood. In batch experiments, reaction rates for dissimilatory iron reduction calculated from geophysical and geochemical changes were similar to within +25%. In flow-through reactors, initial conductivity changes corresponded to changes in fluid chemistry. However, under iron-reducing conditions a three-fold increase in electrical conductivity (0.02 S/m – 0.06 S/m) was recorded over 10’s of cm. after 11 weeks. An even larger increase (0.02 S/m – 1.2 S/m) was recorded under nitrate-reducing conditions. Models based on percolation theory are consistent with the measured conductivity increase if biofilms are 33 times more conductive than pore fluid. To confirm this hypothesis we performed electrochemical experiments that involved growing iron reducing bacteria directly on an electrode surface. Preliminary data from these experiments demonstrate a thousand-fold increase in the DC electrical conductivity of respiring biofilms. Similar column experiments are being run while collecting complex conductivity measurements (an alternating-current method) in an attempt to further characterize this phenomenon.

GFZ German Reserach Center for Geosciences- International Center for Geothermal Research, 14473 Potsdam, Germany, ([email protected], [email protected], [email protected]) Between 2001 and 2009 various reservoir operations have been conducted at the two geothermal wells of Gro! Schönebeck (North German Basin) to increase fluid production and injectivity. Simultaneously, fluid samples have been collected (at 4100-4235 m depth) and analyzed for their chemical composition. The aqueous phase is nearly saturated with calcium, sodium and chlorine, which represent altogether 98 % of its salt content. During fluid production the initial (reservoir) pressure and temperature conditions (" 150 °C and " 45 MPa) change, causing shifts in the chemical equilibrium of the fluid. Consequently, various minerals such as sulfates or silicates are oversaturated and their precipitation in pipes of the geothermal plant or in the pores of the reservoir can be expected. In addition, other minerals could be formed due to slight changes of pH- and redox conditions (e.g. iron-, manganese-, or lead- hydroxides). In this study, changes in fluid chemistry were related to geothermal reservoir activities (engineering). It was found that concentration variation of most elements (e.g. Na, Ca, K, Cl, Li) over time was mainly due to dilution of the formation fluid with filtered freshwater used for water-frac stimulations or injection tests. However, iron, lead, barium, sulfate and bicarbonate concentrations did not correlate with dilution indicating that precipitation-, dissolution-, and/ or redox reactions took place. Direct evidence for scaling induced by well operations was found for the element lead (Pb), which occurs normally in the unprocessed Groß Schönebeck fluid in concentrations of about 0.8 to 1 mM. During pumping tests, redox conditions in the vicinity of the pump changed and Pb concentration decreased dramatically (< 0.0002 mM). Additionally, a grey scale consisting mainly of native lead and laurionite (Pb (OH)Cl) as identified by X-ray diffraction, precipitated on the pump.

Goldschmidt Conference Abstracts 2010

Trace elements in mantle olivine and orthopyroxene from the North Atlantic and Kaapvaal Cratons TATJANA REHFELDT1,2, STEPHEN F. FOLEY1, DORRIT E. JACOB1 AND D. GRAHAM PEARSON3 1

Universität Mainz, Becherweg 21, 55099 Mainz, Germany (*correspondence: [email protected]) 2 Universität Erlangen, Schloßgarten 5a, 91054 Erlangen, Germany 3 Durham University, Durham DH1 3LE, Great Britain We present olivine (ol) and orthopyroxene (opx) trace element data of garnet peridotite xenoliths from West Greenland (North Atlantic Craton), Jagersfontein and Kimberley (Kaapvaal Craton), representing samples of Archaean subcratonic lithospheric mantle. Peridotites from both cratons experienced high degree partial melting. However, while West Greenland peridotites are mostly pristine [1], Kaapvaal peridotites have experienced silicaenrichment and crystallization of secondary diopside [2, 3]. This is discernable e.g. from differences in texture, whole-rock Al/Si (0.001-0.02 and 0.002-0.08, respectively) and modal opx content (8±7 vol.% and 28±9 vol.%, respectively). Mn, Co, Ni, Cu, Zn and Ga in ol and opx correlate with Mg# = Mg/(Mg+Fe). Slightly higher values in West Greenland peridotites compared to Kaapvaal peridotites, probably reflects the more refractory composition of the former, since these elements are compatible. B, Al, Sc, V, Cr and Y in ol are moderately enriched in West Greenland compared to Kaapvaal peridotites. These elements do not correlate with Fo content, but most of them correlate with Ca content reflecting possible pressure dependency. In opx these elements have similar concentrations in peridotites from both localities. Al, V and B in opx decrease with increasing Mg# and may reflect correlation with the degree of melt depletion. Compared to West Greenland peridotites, trace element contents in Kaapvaal opx are mostly low, which may be due to inheritance from replacement of primary ol. Secondary ionisation mass spectrometry analyses of opx show overall rare earth element (REE) enrichment in Kaapvaal peridotites, especially light REE, compared to West Greenland peridotites. This might be genetically related to light REE-enrichment in secondary diopsides in Kaapvaal peridotites that crystallized from light REE enriched mantle melts [3]. [1] Wittig et al. (2008) EPSL 274, 24-33. [2] Simon et al. (2007) J. Petrol. 48, 589-625. [3] Rehfeldt et al. (2008) GCA 72, 5722-5756.

A857

Cd isotope constraints on nutrient cycling in the Southern Ocean M. REHKÄMPER1, Z. XUE1, T. VAN DE FLIERDT1, R. MIDDAG2 AND H. DE BAAR2 1

Department of Earth Science and Engineering, Imperial College, London SW7 2AZ, UK 2 Royal Netherlands Institute for Sea Research, NL-1790 Den Burg, The Netherlands

The marine geochemistry of Cd is of particular interest because its distribution in seawater is correlated with the macronutrient phosphate. Recent investigations have furthermore revealed considerable Cd isotope fractionations in the oceans as a consequence of biological utilization. Nutrient depleted surface waters exhibit &114/110Cd values as high as +40, whilst the deep ocean is characterized by &114/110Cd ' +4 (&114/110Cd is reported relative to JMC Münster Cd). In this study, cadmium concentrations and isotope compositions were determined for 46 seawater samples from the 2008 IPY GEOTRACES expedition ‘Zero & Drake’ aboard RV Polarstern (ANT 24-3). This includes samples from 3 depth profiles (in the Drake Passage, and northwestern & central Weddell Sea) as well as 13 surface waters from the Zero Meridian between 62° and 69°S. The Southern Ocean seawater samples display a good correlation of &114/110Cd with Cd contents, which suggests that Cd cycling is dominated by closed-system uptake at the surface and remineralization at depth. The Cd concentrations of the surface waters are high at about 0.4 to 0.7 nM, which is typical for this HNLC region, whilst Cd isotope compositions are only moderately fractionated (&114/110Cd ' +5 to +8) due to limited nutrient (and Cd) utilization. These samples provide a particularly well-defined correlation of &114/110Cd with [Cd] that is indicative of biological fractionation at ( ' 1.0005. Water samples from below 1 km depth have similar Cd contents of 0.77 ± 0.04 nM and relatively constant Cd isotope compositions of &114/110Cd ' +3.5 ± 0.5 (1s, n = 15), in excellent agreement with published global deep water data. The Drake Passage profile reveals significant Cd isotope fractionation at 250-500 m depth with &114/110Cd values of about +5. This may reflect influx of Antarctic mode water from the west. The &114/110Cd values of about +2 to +3 for depths of 200-400 m at the two Weddell Sea stations are also unusual and are indicative of remineralization of biological material with low/negative &114/110Cd, due to incomplete nutrient utilization at the surface. Taken together, these results show that Cd isotope data provide new constraints on marine nutrient cycling and may be a useful paleoceanographic proxy of nutrient utilization.

A858

Goldschmidt Conference Abstracts 2010

Sources and sinks of iodine in the Atacama Desert, northern Chile: Insights from the nitrate ore fields and supergene zones of Cu deposits M. REICH1*, G. SNYDER2, U. FEHN3, C. PALACIOS1, G. VARGAS1 AND E.M. CAMERON4

Orogen-scale thermochronologic trends of the Central Andes P.W. REINERS1, A. VERNON1, M. ZATTIN2, S.N. THOMSON1, D. PEARSON1 AND W. CAVAZZA3. 1

Dept. of Geosciences, Univ. of Arizona, Tucson, AZ 85721 Dipt. di Geoscienze, Univ. di Padova, Padova, Italy 35137 3 Scienze della Terra, Univ. di Bologna, Bologna, Italy 40126 2

1

Dept. of Geology, University of Chile, Santiago, Chile (*correspondence: [email protected]) 2 Department of Earth Science, Rice University, Houston, TX 3 Department of Earth and Environmental Sciences, University of Rochester, Rochester, NY 4 Eion Cameron Geochemical Inc., Carp, ON, Canada

Iodine is a strongly biophilic element and its global distribution is dominated by the marine system, in particular marine sediments. Because iodine is rarely incorporated into minerals, the occurrence of iodine minerals in continental settings is rare, with the exception of hyperarid areas such as the Atacama Desert of northern Chile. Currently, the Atacama region is the world’s premier iodine production province, where the occurrence of iodine minerals is exclusively restricted to: (a) The extensive nitrate-iodine deposits located along the eastern side of the Coastal Range, and (b) The supergene zones of Cu deposits. The presence of iodine in copper and nitrate deposits is enigmatic and has been seriously underlooked over the years. Little information is available about the source (s) of iodine in the Atacama region, and only a few studies have reported data on the mineralogy, geochemistry and isotopic composition of iodine in these deposits. Preliminary iodine-129 (129I) data of nitrate ores of the Atacama Desert show that the isotopic signature of this element in the nitrates is not consistent with a marine fog origin, as previously thought. These low 129I/I ratios, comprised between 75 and 200#10-15, are similar to previously reported ratios of forearc fluids, suggesting that the iodine component of nitrate deposits may have a different origin than atmospheric or marine (e.g. deep source). Moreover, the occurrence of iodine minerals in supergene zones of copper deposits nearby (e.g. the stratabound Cu deposit Mantos de la Luna) indicate that reducing iodine-rich waters were involved in supergene enrichment of copper. In the light of these new evidences, alternative source(s) for the iodine that is contained in copper and nitrate deposits in the Atacama Desert are presented. This information is of utmost importance to better understand the processes that have led to iodine enrichment in northern Chile, and its relation with the tectonic/seismic/metallogenic history of the area and changes in climate, particularly the desiccation of the Atacama region.

The central Andes between ~21-28°S record Mesozoic to Recent evolution of arc magmatism and development of an associated 700-km-wide Cordilleran style retro-arc wedge formed by east-directed thrusting of the orogen over the South American plate. Several features of this region have attracted attention of wedgeologists, including: 1) an extreme orographic precipitation gradient (~zero on the west flank) that may influence deformation patterns, 2) evidence for punctuated episodes or cycles of uplift potentially linked to lithospheric convective instability, and 3) extension and subduction erosion at the western pro-arc side of the orogen. To better constrain the large-scale dynamics of this part of the Andes, we combine apatite and zircon (U-Th)/He and FT ages from ~30 new samples with published data to create several cross-orogen transects recording bedrock cooling between ~21-26°S. All systems show decreasing ranges of cooling ages and increasing minimum ages from east to west across the range: zircon He from ~15-385 Ma in the east to ~120 Ma in the west, apatite FT from ~15-200 Ma in the east to ~45-100 Ma in the west, and apatite He from ~5-50 Ma in the east to ~35-60 Ma in the west. Just to the south (~2628°S), AFT ages are 3-180 Ma in the east to ~45 Ma in the west. We interpret these trends with a simple model of frontal accretion and relative westward motion of rocks through an eroding (stationary and steady-state) wedge. Although the model has too many free parameters to uniquely constrain detailed dynamics, it provides several insights into the significance of thermochronologic trends at this scale. The overall form of most of these data is consistent with erosion at ~0.5-0.7 mm/yr within only a ~100-km wide region on the east flank; to the west rocks are advected through a noneroding wedge at roughly 6 mm/yr to decretion at the Pacific margin. Only locally on the east flank is cumulative erosion high enough to expose fully reset zircon He ages. Younger apatite He ages within the range interior require localized and possibly punctuated episodes of erosion to depths <~2 km. To the south, AFT age trends require more rapid erosion (~1 mm/yr) focused in a narrower eastern zone (~50 km), and predict the presence of very young apatite He ages but few to no reset zircon He ages.

Goldschmidt Conference Abstracts 2010

Transformation products from inorganic ligand promoted oxidation/dissolution of silver nanoparticles B.C. REINSCH1,3, R. MA1,3, C.S. KIM2 AND G.V. LOWRY1,3* 1

Carnegie Mellon University, Pittsburgh, PA 15213, USA (*correspondence: [email protected]) 2 Chapman University, Orange, CA 92866, USA 3 Center for Environmental Implications of NanoTechnology Silver nanomaterials are being used in a range of commercial products, thus increasing their potential for introduction into the environment. The lifetime and persistence of silver metal nanoparticles will be determined in part from their oxidation and dissolution rates and in part from the types of phase transformations that may occur in the presence of organic and inorganic ligands. In this study manufactured silver nanoparticles, both coated and uncoated, were exposed to several environmentally relevant aqueous inorganic ligands (S2-, CN- Br-, Cl-, and I-) and dissolved oxygen to determine their effects on the rate of silver oxidation/dissolution. Synchrotron-based X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (XAFS) spectroscopy and TEM were used to elucidate the amount of zero-valent silver that remained as the particles were oxidized by the inorganic ligands and to determine the speciation of the products formed. These results have implications for the persistence, transport, bioavailability, and fate of silver nanoparticles in the environment.

A859

The immobilisation of toxic heavy metals by biofilms in mine drainage groundwater outflow regions JIE REN1* AND GORDON SOUTHAM1 1

Department of Earth Sciences, The Univ. Of Western Ontario, London, ON N6A5B7, Canada (*[email protected])

The biooxidation of metal sulfides in mine wastes, e.g. tailings, leads to the generation of acidic solutions possessing toxic heavy metals [1]. Bioremediation of heavy metal contamination is an active area of research because it represents a green technology with the potential for high efficiency at a low cost. There is a wide range of active and passive biogeochemical processes that bacteria can employ to immobilise toxic heavy metals from solution, all of which can occur within biofilms. Biofilms, containing aerobic heterotrophic and dissimilatory sulfate reducing bacteria, from 14 locations in an active uranium mine site were examined for their capacity to immobilise metals from solution. Most (eight) of the samples had pH values ranging from 5 to 8. However, five of them were below pH 5 and one has pH value of 12.35, which did not support sulfate reducing abcteria. Using ICP-AES, the concentration of metals in groundwater samples, and in 2% nitric acid extracts from biofilms collected at the groundwater outflow sites revealed that the biofilms possessed higher concentrations of metals than the groundwater Ô feedingÕ them. For example, one of the biofilms was found to contain 33 times higher concentration of Pb as well as 19 times higher Ni, 135 times higher As, 588 times higher Cd and 436 times higher Hg, respectively. Examination of the biofilms using transmission and scanning electron microscopy has demonstrated the presence of secondary minerals entrapped within exopolymer materials. A laboratory-based column treatment system, employing dissimilatory sulfate reducing bacteria is being evaluated to determine the maximum bioremediation efficiency versus this field system and the ability of sulfate reducing bacteria to form mixed metal sulfides. [1] Nordstrom, D.K., and G. Southam. (1997) Rev. Mineral 35, 361-390

Figure 1: EXAFS linear combination fit of Ag(0) nanoparticles aged in 5mM Na2S solution for 24 hours with the species and percent contribution of individual model compound spectra listed. The original particle contained ~90% Ag(0) and 10% Ag2O. The resulting material does not contain significant amounts of Ag2O.

A860

Goldschmidt Conference Abstracts 2010

Late Triassic volcanic activities at the northwest margin of Junggar Basin, Xinjiang, China

Li/Ca ratios of ostracod shells as a paleoenvironmental indicator at Lake Qinghai, NE Tibetan Plateau

M. REN1* J.M. HU2 H.J. QU2AND J.X. YANG3

S. REN1,2,3, Z. ZHU1,2,3*, J. MO2 AND Y. SHUANG2

1

Department of Geology, University of Texas at El Paso, El Paso, TX 79912 (*correspondence: [email protected]) 2 Institute of Geomechanics, Chinese Academy of Geosciences, Beijing 100081 ([email protected], [email protected]) 3 College of Earth Science and Resources, Chang'an University, Xi'an 710054 ([email protected]) The studied volcanic rocks are located at the southeast of Jeminay town, on the northwest margin of Junggar Basin and the south Altay Mountain, Xinjiang, China. Based on the attitude of the volcanic flows, we divide them into two groups. The slight synclinal dipping and nearly vertical fractures at one of the sampling location for the upper unit may represent a near venting area. The mineral chemistry, whole rock major, trace, and RbSr, Sm-Nd isotope compositions have been analyzed. Both groups are calc-alkaline series with matalunimous to slightly peraluminous characters. The discrimination diagrams show that both groups possess ‘volcanic arc’ characteristics. The zircon U-Pb age for the lower group is around 320 Ma. The Rb-Sr isochron age for lower series is 319 Ma. The zircon UPb age for the upper group is 226 Ma. This is the first late Triassic volcanic activity reported in this area. By late Carboniferous time, the Altay region was under convergent action with the relative shearing movement of Baltica with respect to Siberia (Sengor et al., 1993 [1]). The volcanic variation pattern is basaltic to intermediate to felsic from south to north in Jeminay region (Xinjiang Geological Institute, 1983 [2]); this pattern might be the result of this late Carboniferous tectonic collage. The late Triassic volcanic eruption observed from this study might be the result of compression resulting from the Cimmeride collision [1]. [1] Sengor et al. (1993) Nature 364, 299-307. [2]Xinjiang Geological Institute (1983) Report of regional geological survey L-45-II (1:200,000) 252 p.

1

Chongqing Institute of Geology and Mineral Resources, Chongqing 400042, China 2 Key Laboratory of Geology for Mineral Resources & Environment, Chongqing Administration of Land, Resources and Housing, Chongqing 400042, China 3 Chongqing Research Center of State Key Laboratory of Coal Resources and Safe Mining 400042, China (*correspondence: [email protected])

During the processes of carbonate precipitation, Lithium (Li) is commonly incorporated into calcite crystals. Previous investigation has demonstrated that Li is preferentially incorporated into the 0001 face in calcite, which is exothermic in calcite compared with other faces, and is likely to be favoured at lower temperatures. Therefore, Li is easily incorporated into calcite crystals at lower temperature with carbonate precipitation, and Li/Ca ratios of carbonate are potentially capable of providing reliable paleotemperature records. With the purpose to explore the potential of Li/Ca ratios of ostracod shells as an indicator in lacustrine sediments and to avoid the interspecies effects, here, we analysed for the first time Li/Ca ratios of monospecific ostracod shells Eucypris inflate in the lacustrine sediment core from Lake Qinghai, NE Tibetan Plateau. The results showed that Li/Ca ratios of ostracod shells is a reliable paleotemperature proxy, which is testified by comparisons of variations of Li/Ca ratios and temperature inferred from meteorologic records and tree ring widths in Dulan and Qilianshan. Li/Ca ratios of ostracod shells negatively correlate with temperature. High temperature corresponds with low Li/Ca ratios, and vice versa, suggesting that Li/Ca ratios of ostracod shells is an effective proxy to deduce paleotemperature variations. Our ongoing in-depth investigation is using Li/Ca ratios of carbonates in more lakes to further reveal its paleienvironmental implications.

Goldschmidt Conference Abstracts 2010

A861

Geochronology of the Xiaoxinancha Cu-Au deposit in NE China: Insights from molybdenite Re-Os dating

Improved calibration of the 40Ar/39Ar geochronometer: Consequences for thermochronology

YUN-SHENG REN*, HUA-LEI ZHAO AND HUI WANG

PAUL R. RENNE1,2

College of Earth Sciences, Jilin University, Changchun 130061, China (*correspondence: [email protected]) There is still a divergence on metallogenic age of the Xiaoxinancha large copper-gold deposit associated with the Mesozoic granitic intrusion. The 4°Ar-39Ar isochrone age of Cu-Au-quartz veins is 123.35±0.8Ma [1], whereas the SHRIMP U-Pb dating of zircons constrained the emplacement of ore-hosting granitic complex between 112Ma and 104Ma [2]. A molybdenite-quartz vein discovered recently supplies a more appropriate isotopic dating to the deposit. It occurs within the granitic intrusion and parallel to adjacent lode CuAu ore bodies, indicating that they are controlled by the common structure system. In the ore, metal minerals are dominated by molybdenite, pyrite, chalcopyrite and minor arsenopyrite, which are accordant to mineral assemble of the early stage of Xiaoxinanxha deposit. Primary inclusions in quartz grains from the vein include low-density gas, highdensity aqueous two-phase and daughter mineral inclusions. They are coexistent and their homogeneous temperature is approximate (340~380)), leading to a conclusion that the fluid evolved the similar process of boiling as ore-forming fluid in the early stage of major Cu-Au mineralization [3]. Molybdenite Re-Os dating of six samples obtains the model ages from 109.2±3.4Ma to 110.8±4.0Ma and an isochrone age of 111.1±3.1Ma, which are consisting with newly isotopic dating of ore-forming granitic intrusions. It suggests that the large copper-gold mineralization take place at the end of the early Cretaceous and resulted from the subduction of the Pacific Ocean slab to the Eurasia plate. [1] Meng et al. (2001) Jilin Sci.& Tec. Pub. House: 44-77. [2] Sun et al. (2008). Mineral Deposits, 27(3): 319-328. [3] Li & Chen (1995). Mineral Deposits, 14(2):151-173 (in Chinese).

1 2

Berkeley Geochronology Center ([email protected]) Univ. of California, Berkeley, Dept. of Earth and Planetary Science

Thermochronology almost invariably involves comparison of data from different radioisotopic systems, and the extent to which these different chronometers are accurately intercalibrated poses limits on the validity of thermal histories derived from multi-system data sets. The 40Ar/39Ar system is pivotal to many thermochronologic studies because ample diffusion data and models exist for various minerals with closure temperatures between ~200 and ~500 °C. A new calibration of the 4°Ar/39Ar system (Renne et al. this conference) renders older ages than most previously used decay constants, the magnitude increasing with age. Consequently, discrepancies e.g. between 40Ar/39Ar biotite and U/Pb zircon ages for granitoids decrease by an amount that increases with age. Previously inferred mean cooling rates over the ~800 to ~300 °C range turn out to be higher than previously inferred, the more so with age. For example, consider two hypothetical plutons intruded at equivalent depth in a coherent terrane with U/Pb zircon ages of 1527 Ma and 2860 Ma, and biotite 40Ar/39Ar cooling ages of 1502 Ma and 2835 Ma respectively, based on the decay constants of Steiger and Jäger (1977) and standard calibration of Renne et al. (1998). The 40Ar/39Ar ages recalculate to 1512 Ma and 2848 Ma, respectively. Assuming 800°C zircon saturation temperatures and a 300 °C closure temperature for biotite, mean cooling rates of 20 °C/Ma for both the younger and older plutons based on the old calibration recalculate to 33 °C/Ma and 42 °C/Ma, respectively. Thus one might infer exhumation/uplift or a decreasing thermal gradient over the time spanned by the two intrusions, whereas thermochronology previously betrayed no changes in cooling rates over the same temperature interval. Old meteorites are especially sensitive to the new calibration, though not as much as allowed by decay constant uncertainties based on activity data (e.g. Renne, 2000) because the revision indicates an increase in the probability of !- and decrease in probability of electron capture decays. An age of 4543 Ma based on Steiger and Jäger (1977) and 1073 Ma for the Hb3gr standard (now 1080 Ma) is revised to 4556 Ma, thus imposing a speed limit for rapidly cooled meteorites.

Goldschmidt Conference Abstracts 2010

A862

Unleashing the full potential of the 40 Ar/39Ar geochronometer

First principles investigation of coupled substitution in Galena

PAUL R. RENNE1,2, ROLAND MUNDIL1, GREG BALCO1,2, KYOUNGWON MIN3 AND KENNETH R. LUDWIG4

D. RENOCK* AND U. BECKER University of Michigan, Ann Arbor, MI. 48109, USA (*correspondence: [email protected])

1

Berkeley Geochronology Center ([email protected]) 2 Univ. of California, Berkeley, Dept. of Earth and Planetary Science 3 Univ. of Florida, Dept. of Geological Sciences 4

°Ar/39Ar geochronology has long suffered from large systematic errors arising from imprecise K and Ar isotopic data for standards and imprecisely determined decay constants for the branched decay of 40K by electron capture and !emission. This study presents a statistical optimization approach to improving the situation, using constraints from 40 K activity data, K-Ar isotopic data, and 16 pairs of 238U-206Pb zircon and 40Ar/39Ar data for rigorously selected volcanic rocks as inputs for estimating the partial decay constants (! and ! ) of 40K and the 40Ar*/40K ratio (K) of the widely used Fish Canyon sanidine (FCs) standard. The 238U-206Pb ages were corrected for 90 ±77 ka mean pre-eruptive residence time (Simon et al. 2008). The optimized results yield values of K = (1.6418 ± 0.0046) x 10-3, ! = (0.5755 ± 0.0016) x 10-10/a and ! = (4.9737 ± 0.0092) x 10-10/a; all uncertainties stated at one sigma. These results improve uncertainties in the decay constants by a factor of >5 relative to values derived from activity data alone. Uncertainties in these variables determined by our approach are highly correlated and error propagation must include their covariances [cov (K,! ) = 7.3620 x 10-19, cov (K,! ) = -6.8299 x 10-19, cov (! ,! ) = -3.4811 x 10-26] or use Monte Carlo-type simulations. Age errors estimated from these results are significantly improved relative to previous calibrations, i. e., producing smaller age errors than the astronomical calibration of Kuiper et al. (2008) for ages >6 Ma, up to a factor of 10 smaller than the latter at 4.5 Ga. The age we derive for FCs is 28.305 ± 0.031 Ma. Age errors are smaller for a comparable level of analytical precision in isotope measurement data than those produced by the 238 206 U/ Pb system. Thus ironically, despite being partly calibrated by it, the 40Ar/39Ar system is now capable of accuracy comparable to and even exceeding that of the 238 206 U/ Pb ‘gold standard’ in certain circumstances. A case in point is the Permo-Triassic boundary, whose new 40Ar/39Ar age (recalculated from Renne et al. 1995) is 252.27 ± 0.08 Ma, compared with a 238U/206Pb age of 252.40 ± 0.33 Ma (Mundil et al. 2004), including systematic errors in both. "

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Coupled substitution is an important mechanism responsible for Ag enrichment in galena. Studies show that the concentration of Ag in galena will tend to equal the sum of the concentrations of Sb and Bi [1]. The thermodynamic mixing properties of the binaries Pb2S2-AgSbS2, Pb2S2-AgBiS2, and Pb2S2-AgAsS2 have been investigated using first-principles and Monte-Carlo calculations similar to the method used by Reich et al. [2]. Quantum mechanical methods were used to account for electron transfer between the substituting species. Total energies for different substitution configurations were used in Monte-Carlo calculations to derive the excess enthalpy of mixing (#Hexcess), entropy of mixing (#Sexcess), and free energy of mixing (#Gexcess) at temperatures ranging from 200 °C to 700 °C. #Gexcess was used to calculate phase diagrams that can be compared with experiment. Miscibility gaps dominate the Pb2S2-AgSbS2 and Pb2S2-AgAsS2 binaries for XAg < 0.25, whereas Pb2S2-AgBiS2 has a complete solid solution at temperatures >200°C, in rough agreement with experiments [3]. Electron transfer between Ag and either Sb, Bi, or As is shown to affect cation-ordering in these systems. Quantum mechanical simulations allow for visualization of specific orbitals that are predominantly responsible for this electron transfer. Intermediates of the Pb2S2-AgBiS2 solid solution tend to order into alternating Ag-rich layers parallel to {111} and Pb/Sb-rich layers. [1] Hoda, S.N., Chang, L.L.Y. (1975) Am. Mineral. 60, 621633. [2] Reich, M.R., Becker, U.(2006) Chem. Geol. 225, 278290. [3] Chutas, N.I., Kress, V.C., Ghiorso, M.S., Sack, R.O. (2008) Am. Mineral. 93, 1630-1640.

Goldschmidt Conference Abstracts 2010

Microbial biominerals: Role in radionuclide remediation

Sulfate standards for in situ high spatial resolution SIMS measurements

J.C. RENSHAW1*, S. HANDLEY-SIDHU1 2 AND L. MACASKIE

M. REUSCHEL1, M.J. WHITEHOUSE2, A. LEPLAND3, V.M. MELEZHIK3 AND H. STRAUSS1

1

School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK (*correspondence: [email protected], [email protected]) 2 School of Biosciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK ([email protected]) Bacteria form a range of biominerals, which can immobilise radionuclides through sorption or precipitation [1, 2]. Biomineralisation can be stimulated in situ by injecting nutrients, offering a potential remediation mechanism using indigenous microorganisms. Studies so far have focussed on simplified, pure culture systems. This study is investigating the effect of three biomineralisation processes on radionuclides using natural microbial consortia under complex geological and geochemical conditions, as would be found at contaminated sites. The processes are:

Carbonate precipitation Bacterial ureolysis produces NH4+ and HCO3- and can form biogenic calcite [3]. NpV and PuIV carbonates are insoluble and so could be precipitated through ureolysis, whilst SrII can be incorporated into biogenic calcite [3]. Calcites have also been found to sorb radionuclides [4, 5].

Phosphate precipitation Bacterial hydrolysis of organophosphate can precipitate SrII, AmIII, ThIV, PuIV and UVI as phosphates [1]. Coupling of phosphate biomineralisation and ureolysis could enhance actinide precipitation by forming highly insoluble ammonium phosphates [6, 7]. In addition, bacterial hydroxyapatite is an effective sorbent for Sr (II) [8].

Manganese Oxide formation Mn oxides have high sorption capacities and redox activity, and can immobilise a range of metals and radionuclides [2]. They can sorb significant amounts of Pu [9] and UVI can be incorporated in biogenic Mn oxides [10]. This investigation will be a critical step in the development of novel in situ bioremediation technologies. [1] Lloyd & Renshaw (2005), MIBS 44, 205-240. [2] Tebo et al. (2004), Annu. Rev. Earth Planet. Sci. 32, 287-328. [3] Warren et al. (2001), Geomicrobiol. J. 18, 93-115. [4] Parkman et al. (1998), GCA 62, 1481-1492. [5] Meece & Benninger (1993), GCA 57, 1447-1458. [6] Yong & Macaskie (1995) J. Chem. Technol. Biotechnol. 64, 87-95. [7] Yong & Macaskie (1995), J. Chem. Technol. Biotechnol. 63, 101-108. [8] Handley-Sidhu et al. (2010), in prep. [9] Powell et al. (2006), EST 40, 3508-3514. [10] Webb et al. (2006), EST 40, 771-777.

A863

1

Westfaelische Wilhelms Universitaet, Corrensstrasse 24, 48153 Muenster, Germany (*correspondence: [email protected]) 2 Swedish Museum of National History, Box 50007, SE-10405 Stockholm, Sweden 3 Geological Survey of Norway, Leiv Eriksons vei 39 N-7491 Trondheim, Norway Sedimentary sulfates are a valuable proxy for determining the seawater sulfate concentration and isotopic composition of ancient oceans, in particular providing constraints on the redox state of the ocean water. This knowledge is important especially for Precambrian sediments, where the redox state of atmosphere and hydrosphere changed significantly. However evaporites of Precambrian age are rare and often inaccessible with conventional geochemical analytical techniques. The secondary ion mass spectrometry (SIMS) technique facilitates in situ measurements of even small amounts of sulfate minerals with a spatial resolution *15 um. Application of the method to sulfates is however limited due to the absence of well-documented, homogeneous, matrix-matched reference materials. We present multicollector (three Faraday) SIMS measurements of sulfate $34S and %33S for selected Phanerozoic and Precambrian age sulfate minerals (anhydrite, barite and celestine) to test their suitability as potential sulfate reference materials. Replicate conventional S isotope analyses were performed on these minerals prior to the SIMS study to determine their sulfur isotopic composition. The SIMS study illustrates that the selected sulfate minerals do not exhibit significant heterogeneties in their sulfur isotopic composition, typically yielding external precision of 0.2-0.3 ‰ (1 std. dev.) on both $34S and %33S from a *15 um analysed area. Measurements on several randomly oriented pieces enable us to exclude the possibility of crystallographic orientation effects at this level of precision. The selected minerals thus provide reliable reference materials for in situ high spatial resolution sulfur-isotope measurements by SIMS.

A864

1 2

Goldschmidt Conference Abstracts 2010

U-Pb dating of zircon, Rb-Sr and Sm-Nd isotopic analysis of layered intrusion Kivakka (N. Karelia)

Expression of Shewanella sp. str ANA-3 metal reduction genes in response to iron(III) and arsenate

N. REVYAKO1,2, M. ANOSOVA2, YU. KOSTITSYN1,2 1,2 AND YA. BYCHKOVA

CAROLINA REYES, JULIE N. MURPHY AND CHAD W. SALTIKOV1,2,3

MSU, Moscow, Russia ([email protected]) GEOKHI RAS, Moscow, Russia ([email protected])

Results of Rb-Sr and Sm-Nd isotopic analysis of the 38 samples of Kivakka layered basic-ultrabasic pluton and country rocks and in situ U-Pb dating analysis of 13 zircon grains from two zones of norites, gabbro-norites and subzone of interstratification of bronsitites and norites are presented. Kivakka cone shaped body consists of four main zones: (topdown) gabbros, gabbro-norites, norites and olivinites. Country rocks are migmatized biotitic and amphibolic gneisses, granite-gneisses and granite-diorite-gneisses of upper Archean. U-Pb isotopic analysis were done using LA-ICP-MS. Zircon grains an age of 2443 ± 5 Ma (MSWD = 0.006). Obtained age are in good agreement with data of many layered intrusions of the eastern Baltic Shield [1] and age of one zircon fraction from gabbro-norites of Kivakka intrusion (2445±2 Ma) [2]. Initial Nd and Sr isotopic rations were calculated using obtained U-Pb age. We have found clear inverse correlation between initial Nd isotopic composition and Nd content in the Kivakka layered rock suite. Variations of Nd initial isotopic ratios could be interpreted as a result of parent basic melt interaction with country acid rocks in the magma chamber during crystallization. Many similar layered intrusions at the North Karelia have Nd isotopic composition shifted toward crustal significances. Thus, it is possible that discovered interaction between basic melt and country rocks accompanied formation other layered intrusions in Karelia too. 1. Amelin Y.V., Semenov V.S. 1996. CMP. 124: 255-272. 2. Barkov A.Y. et. al. 1991. Abstract of the conference Isotopic geological techniques. 21-23 (on Russian).

1

([email protected]) ([email protected]) 3 ([email protected]) 2

The expression of genes associated with metal reduction have the potential of serving as indicators of biological activity linked to geochemical conditions. In arsenic contaminated sediments arsenate is often associated with iron (III) hydroxides and can be released or sequestered through microbial iron (III) dissimilatory reduction or arsenate respiration. Shewanella sp. str. ANA-3 utilizes an arsenate respiratory reductase (encoded by the arrA/B genes) to reduce arsenate to arsenite coupled to oxidation of an electron donor. Additionally, ANA-3 has a cluster of metal reducing genes (mtrCABDEF/omcA) that encodes c-type decaheme cytochromes and non-cytochromes, some of which are involved in reduction of soluble and insoluble metal oxides such as iron and manganese hydroxides. Previous studies have primarly focused on the expression of the mtrCAB/omcA cluster in the presence of iron and manganese oxides but questions remain about the function of the MtrDEF proteins and whether the mtr/omc cluster also responds to other metals and metalloids. The goal of our study was to investigate the expression of the mtr/omc gene cluster in the presence of arsenate, soluble and insoluble iron (III). ANA-3 cells were grown aerobically or anaerobically with arsenate, iron (III)citrate, iron (III)oxide, iron (III)oxide-arsenate, RNA extracted and quantitative RT-PCR (qRT-PCR) used to monitor the exrepssion of the mtr/omc cluster. Our results showed that the mtrCAB/omcA genes were expressed highest with arsenate compared to cells grown with iron (III)-citrate. Expression of mtrCB was highest compared to mtrA/omcA in samples grown with iron (III)oxide. The mtrc/omc cluster was not expressed in samples grown under oxygen conditions. In contrast, little to no expression of the mtrDEF genes was detected in samples grown anaerobically with iron (III) citrate, iron (III) oxide or arsenate conditions. These results show that the mtrCAB/omcA genes are expressed in the presence of arsenic and iron and imply that their expression is repressed in the presence of oxygen. More work is needed to determmine if changes in varying iron-arsenic concentrations, redox states and mineral phases leads to changes in the expression of the mtr/omc and arrA genes.

Goldschmidt Conference Abstracts 2010

A865

Silicate weathering and Si isotope fractionation in a glacial, granitic catchment

Lithium and oxygen isotopes and oxidation state of lower oceanic crust: Atlantis Massif, 30°N

B.C. REYNOLDS1*, E. LEMARCHAND1,2, R. HINDSHAW1,2, E.T. TIPPER1,3 AND B. BOURDON1

V.S. REYNOLDS1*, E.J. CRAPSTER-PREGONT1, M.D. DYAR2, E. JAWIN2, W.F. MCDONOUGH3, L. QIU3, D. RUMBLE 4 AND J. TUCKER 2

1

Institute of Geochemistry and Petrology, ETH Zurich, Switzerland (*[email protected]) 2 Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Switzerland 3 Dept. of Earth Sciences, University of Cambridge, UK Chemical weathering of silicate rocks consumes CO2, affecting climate on geological timescales, and it releases dissolved cations and silicon (Si). Stable isotope variations of such elements can now be used to investigate the processes controlling chemical weathering and subsequent cycling within ecosystems. Here we utilize the potential of stable Si isotopes to characterize the release of Si from granitic rocks under glacial conditions in a small mountainous catchment. The Damma glacier in the central Swiss Alps erodes the Central Aar Granite massif, and the glacial retreat is known over the last 150 years, providing a chronosequence of soil development and vegetation growth. The soil and water chemistry has been extensively studied as part of a large multi-disciplinary investigation of the chronosequence (BigLink http://www. cces. ethz. ch/projects/clench/BigLink). Soil samples collected along the chronosequence gradient have similar chemical compositions to the underlying lithology as little chemical weathering has occurred. Water sampling included biweekly sampling of the main streams in the snow-free summer months. Depositional inputs from snow and rain are negligible for Si. The dissolved stable Si isotope compositions were analyzed using a Nu Plasma 1700, after removal of the cation matrix. Streamwater Si isotope compositions are much heavier (> 0.3‰ $3°Si) at all times of the year compared to the rocks and soils. The Si isotope compositions are lightest (closest to the granitic minerals) in summer when Si concentrations were at a minimum and discharge was fed by melt waters, and heaviest during autumn and winter, when flow was severely limited and Si concentrations were highest. Significant Si isotope fractionation into the dissolved phase within the sub-glacial environment is clearly evident, even though the waters are undersaturated with respect to secondary clay minerals. These results are in agreement with similar results from rivers draining basaltic lithologies, and with the hypothesis that secondary clay formation during mineral dissolution, or adsorption onto iron oxides are the main causes of Si isotopic fractionation.

1

Department of Geology, Colby College, Waterville, ME 04901 (*correspondence: [email protected]) 2 Department of Astronomy, Mount Holyoke College, Hadley, MA 01075 3 Department of Geology, University of Maryland, College Park, MD 20742 4 Geophysical Laboratory, Carnegie Institution, Washington, DC 20015 The greatest proportion of oceanic crust is presently forming along slow-spreading centers (<55 mm/year full rate). Lower magma supply rates result in periods of non-magmatic extension, whereby faults extend deeper into the crust and provide extensive pathways for deep seawater circulation. Understanding the depth and degree of seafloor alteration is important in elemental flux calculations. Although upper oceanic crust has been well characterized, the lower oceanic crust remains somewhat enigmatic due to limited exposure in ophiolites and the rarity of lower crust sampled by deep-sea drilling projects. The Atlantis Massif, an oceanic core complex located at 30 N along the mid-Atlantic ridge represents a block of lower oceanic crust exposed at the seafloor by detachment faulting [1].

Methods For this study, 26 samples were selected from the lowermost 1000 m of IODP Hole U1309D drill core [2] for whole rock chemical characterization by ICP-OES and Fe3+/Fe2+ determination by Mössbauer spectroscopy. Wholerock oxygen ($18O) and lithium ($7Li) isotopic compositions were measured for a subset of 10 samples (2 diabases and 8 gabbros).

Results $18O ranges from +1‰ to +5‰ (rel. to SMOW), with an average of +3.0‰. Most samples record $7Li between -2.6‰ and +2.6‰, (rel. to LSVEC). Two samples record significantly heavier $7Li values of +6.1‰ and +7.1‰. Percent Fe2+/&Fe ranges from 73-94, with one sample yielding a value of 56. Downhole variation trends for $18O, $7Li, and Fe2+/&Fe are remarkably similar; all three variables are positively correlated with one another. Discussion of these trends and further comparisons with bulk chemistry and petrography will be presented. [1] Blackman et al. (2002) Mar. Geophys. Res. 23, 443-469. [2] Ildefonse et al. (2006) Scientific Drilling 3, 4-11.

Goldschmidt Conference Abstracts 2010

A866

Thirty years of deep-sea hydrothermal microbiology: Where are we now?

Densities of dilute adenosine solutions to 50 MPa and 373.15 K G.W. RHETT1, J.C. SEITZ1*, M.D. SCHULTE2 AND A.S. HALL1

A-L. REYSENBACH 1

Portland State University, Portland, OR 97201, USA Over the past 30 years, microbiologists have explored deep-sea hydrothermal vents, describing new species, identifying symbioses and establishing upper temperatures limits for life. In the early 1980’s, Holger Jannasch and others, established the chemosynthesis framework for the basis of the microbial food chain at vents, and subsequently much of the research discoveries revolved around autotrophy and symbioses. With the temperature of hydrothermal fluid exceeding 100°C, several hyperthermophiles were isolated, setting temperature records for life, and challenging our imagination of life in this solar system. However, it was only with the advent of the use of molecular biological approaches (and now high throughput sequencing technologies) to describe the diversity associated with hydrothermal vents that we are truly beginning to appreciate the extent of the microbial life at vents. These inventories have helped guide cultivation attempts of novel and endemic lineages from deepsea vents. Coupling diversity patterns to biogeochemical measurements and geological processes is also providing insights into the factors that might influence microbial colonization at deep-sea vents. I will trace the history of microbial research at deep-sea vents, highlighting some milestones, recent research and possible future directions.

Cal. State Univ., East Bay, Hayward, CA 94542 USA (*correspondence: [email protected]) 2 Univ. of Missouri, Columbia, MO 65211 USA ([email protected]) Adenosine is a nucleoside formed from the attachment of ribose to the nucleobase adenine. It plays an important role in cellular metabolism as a structural component of ATP (the molecular unit of currency for energy transfer in cells). Determining its thermodynamic properties is essential for understanding the potential for its formation and reaction properties in high P-T environments that host extremophiles and may have hosted the emergence of life. The volumetric properties of dilute aqueous solutions of adenosine (0.00284 m, 0.00486 m & 0.007924 m) were obtained using an Anton Paar DMA HP vibrating tube densimeter. Reproducibility of density measurements was <±0.0001 g·cm-3, exceeding propagated errors associated with uncertainty in the measurement of temperature, pressure, and fluid concentration. Comparison of densities for dilute adenosine solutions at 0.1 MPa and 288.15-333.15 K from this study and [1] shows excellent agreement. Experimentally determined volumetric properties for adenosine solutions at elevated pressure and/or temperature are not available in the literature; this study extends the database to 373.15 K and 50.0 MPa.

Figure 1: Experimentally determined densities for 0.00792m adenosine solutions to 50 MPa and 373.15 K from this study. Lines represent simple linear regression fits to the data. [1] Dyke & Hedwick (2008) J. Chem. Thermo. 40, 957-965.

Goldschmidt Conference Abstracts 2010

A867

Mineralogy and magnetic parameters of burning coal waste pile materials: A preliminary insight

New 40Ar/39Ar and geochemical constraints on São Jorge Island, Azores

J. RIBEIRO1, H. SANT’OVAIA1, C. GOMES2, H. CORRÊA-RIBEIRO1, Z. LI3, C. WARD3 AND D. FLORES1

L.P. RIBEIRO1*; A. CALVERT2, Z. FRANÇA, B3. RODRIGUES4 AND M.P. ABREU1

1

Centro Geologia UP, DGAOT, FCUP, R. Campo Alegre, 4169-007 Porto, Portugal ([email protected]) 2 CGUC, DCT, Universidade Coimbra, Portugal 3 School of Biological, Earth and Environmental Sciences. University of New South Wales. Sydney, Australia This work describes the changes in mineralogy and magnetic parameters of the waste pile materials from burning and unburned zones in the S. Pedro da Cova, Midões and Lomba areas of the Douro Coalfield, Portugal. X-ray diffraction analysis has provided information about the mineral phases and the reactions that occurred during the combustion process, and hence been used to identify the temperatures reached. The unburned coal waste materials contain quartz, illite, mica (mainly muscovite) and in many cases pyrophyllite. Some of the burnt coal waste samples have similar mineralogy to the unburned materials, but some contain mullite and cristobalite, suggesting that higher temperatures were involved in the combustion process. Lowfield magnetic susceptibility (') and isothermal remanent magnetization (IRM) determinations were used to indicate the source of the magnetic mineralogy and the waste material contamination in burning parts of the S. Pedro da Cova and Lomba piles. In S. Pedro da Cova, the two highest values of ' (1217.60 and 556.22 x10-8 m3/kg) were found in zones where the temperature was higher than 200°C, and in Lomba the two highest values (705.84 and 211.67 x10-8 m3/kg) were found where the temperature was higher than 70°C. These temperatures were measured with a digital infrared thermometer when the samples were collected. In unburned zones ' ranges from 13.58 to 16.62 x10-8 m3/kg. The IRM values of the S. Pedro da Cova samples show that remanence saturation was achieved at a magnetic field lower than 300 mT, suggesting the presence of a low-coercivity structure, magnetite-like phase. However, in the samples from Lomba, the imparted field was insufficient to achieve remanence saturation, probably because ‘hard magnetic structures’ are also present. The ‘Index of Geo-accumulation’ at S. Pedro da Cova and Lomba shows that the samples represent a strong to very strong contamination. Here the highest ' occurs where the combustion temperature was also very high, suggesting that the burning process was the main cause of the magnetic enhancement.

1

EMEPC, Lisbon, Portugal ([email protected]) U.S. Geological Survey, Menlo Park 3 Azores University, Portugal 4 Aveiro University, Portugal 2

Twelve new 40Ar/39Ar ages, major and trace element geochemical data from several lava sequences at São Jorge Island, Azores, are presented. These data improve the temporal constrains on the volcanic and geochemical evolution of the island. Overall, in the Azores context, São Jorge was constructed by fault-controlled fissural volcanism, dominated by 150°N and the 120°N regional fault systems. The stratigraphic and geomorphologic division of São Jorge into three main volcanic complexes (Topo, Rosais and Manadas [1, 2]), is congruent with most of the new and previous [3] geochronological data, however some adjustments are required. The new 40Ar/39Ar ages of 1310 and 1284 ka on São João lava sequence, the early sub-aerial volcanic phase, are within the time interval presented by [3]. When compared with the rest of the island, São João is a timeisolated volcanic event presenting high growth rates, a system of dikes trending 150°N, a geochemical signature distinct from the other complexes and lavas with a singular lithological composition [4], thus it should be considered as a separated volcanic unit from Topo. A second volcanic phase, building up Topo Complex, started at least at 757 ka lasting at least until 543 ka ago, despite some scarce late eruptions. Topo presents a strong alkaline affinity with a predominant basaltic composition. This stage is followed by the onset of the Rosais alkaline complex forming the western side of São Jorge at least until 117 ka ago. Rosais presents relative enrichment in K2O and P2O5, and shows evidences for coeval volcanism across the complex as verified by the lava sequences at Fajã do Ouvidor, starting at 368 ka [3] and at João Dias, estimated to have started at 360 ka and continued after 215 ka ago. The early Manadas eruptions are not constrained by this study, but volcanism is concentrated on the center of the island and remains active until present day with two sub-aerial historical eruptions, 1580 and 1808 A.D. The new data shows that these alkaline lavas have a tendency to be sub-saturated. [1] Forjaz & Fernandes (1975) Portuguese Geological Services; [2] Madeira, (1998) PhD Thesis [3] Hildenbrand et al., (2008) EPSL [4] Ribeiro et al., (2007) Geoph. Res. Abst.

A868

Goldschmidt Conference Abstracts 2010

Zn-rich hercynite-magnetite assemblage in gneiss and metasedimentary rocks from Lavadores (Northern Portugal)

A group additivity approach to describe the complexation of radionuclides by fulvic acids in geochemical modeling studies

M.A. RIBEIRO*, H. SANT’OVAIA AND A. DÓRIA

LAURENT RICHARD1, CAROLINA SABATER1, AMBROSE KIPROP2,3, EMILIE POURTIER3 AND CHINH NGUYEN-TRUNG3

Centro Geologia Universidade Porto, DGAOT, FCUP, R. Campo Alegre, 4169-007 Porto, Portugal (*correspondence: [email protected]) This study describes the occurrence of hercynite in metapelitic and gneiss-migmatitic rocks outcropping in Praia de Lavadores (Northern Portugal) as metamorphic host rocks of the post-tectonic granite, ‘Granito de Lavadores’. The spinel hercynite occurs mainly in pelitic and quartz-pelitic metasedimentary lithologies (micaschists and quartzmicaschists) in paragenetic association with quartz, sillimanite (fibrolite) and magnetite- ulvospinel series. In the gneissmigmatitic rocks, the occurrence of hercynite is restricted to small restitic nodules with granoblastic texture, and is associated with magnetite-ulvospinel series, andalusite, quartz, cordierite and biotite. The semi-quantitative mineralogical study of the hercynite has pointed out a relatively constant composition, with values of Al2O3, very close to 56%, FeO total between 20 and 21% and a component of ZnO between 11 and 12%. The Zn-rich hercynite-magnetite-fibrolite assemblage in the metapelitic rocks points out one of two possibilities: (i) that the biotite was consumed in a dehydration reaction, which generated hercynite, Fe-oxides Ti (magnetite-series ulvospinel) and ‘melt’[1]; or (ii) that the spinel is as a result of dehydration of Zn-rich staurolite [2]. The magnetite-rich pelitic rocks, as it has already been evidenced by the high values of magnetic susceptibility and isothermal remanent magnetization curve [3], and its association with a Zn-rich spinel shows the correlation of these rocks with staurolite-rich metapelitic, occurring to the east of this coastal zone [4].The geological context, the paragenetic assemblage, either in metaspelitic or in gneiss-migmatitic rocks and the Zn-rich hercynite, indicates HT/L to MP metamorphic conditions in anomalous high thermal gradient in a late-orogenic setting. These conditions can be intensified by magmatic and/or metamorphic fluids advection over a late-orogenic period of crustal thinning, accompanied by processes of migmatization. [1] Nex et al. (2001) Jour. Afric. Earth Scs. 32, 471-469. [2] Stoddart (1979) Amer. Miner. 64, 736-741; [3] Sant'Ovaia et al. (2009). CGA 73, A1115. [4] Ribeiro et al. (2008) Memórias 13, 39-43.

1

Amphos21, Pg. García i Fària 49-51, 08019 Barcelona, Spain, [email protected] 2 Moi University, Department of Chemical and Process Engineering, P.O. box 3900, 30100 Eldoret, Kenya 3 Nancy-Université, G2R, 54506 Vandoeuvre-lès-Nancy cedex, France Clay formations which are considered by a number of countries as potential sites for high-level nuclear waste storage often contain a significant amount of organic carbon mostly present under the form of kerogen. A possible scenario considered in feasibility studies for nuclear waste storage is water seepage through the concrete walls of a storage site. It has been shown that complex mixtures of soluble (including fulvic acid-like) organic compounds are generated from kerogens under conditions of alkaline perturbation [1]. These organic compounds are potentially able to complex and transport radionuclides around nuclear waste disposal sites. Knowledge of the equilibrium constants of complexation reactions of radionuclides by fulvate anions is therefore of primordial interest for performance assessment exercises. New developments in analytical chemistry have resulted in improved knowledge of the molecular structure of fulvic acids [2]. Structural models of individual fulvic acids have been proposed [3], for which thermodynamic properties can be estimated using group additivity techniques (e.g. see [4]). Equilibrium constants at infinite dilution published in the literature for complexes of radionuclides with low-molecularweight organic compounds can be used to develop group additivity algorithms for calculating the standard molal Gibbs energies of formation of radionuclide-fulvate complexes. The latter properties can help in the interpretation of laboratory experiments on the complexation of radionuclides by natural organic matter. They can also be incorporated in geochemical models of nuclear waste repositories. [1] Claret et al. (2003) Sci. Total Environ. 317, 189-200. [2] Sutton and Sposito (2005) Environ. Sci. Technol. 39, 90099015. [3] Stenton et al. (2003) Anal. Chem. 75, 1275-1284. [4] Amend and Helgeson (1997) Geochim. Cosmochim. Acta 61, 11-46.

Goldschmidt Conference Abstracts 2010

Magmatic metal fluxes in convergent and collided margins

Evolution of the Siberian Platform; Constraints from diamondiferous xenoliths of Nyurbinskaya

JEREMY P. RICHARDS Dept. Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, Canada, T6G 2E3, [email protected] Oceanic plate subduction causes water and other crustal materials to be recycled into the mantle via hydrated oceanic crust and wet sediments. This water (and other fluid-soluble components) is released into the overlying mantle wedge where it acts to lower the solidus of peridotite, causing partial melting and the formation of hydrous arc basalts. Fractionation of these basalts near the upper plate Moho and interaction with crustal rocks and partial melts, generates magmas of intermediate, hydrous, calc-alkaline composition. Arc magmas are also uniquely oxidized (typically %FMQ+2) and S-rich (dissolved mainly as SO2), reflecting seafloor oxidation of the subducting oceanic plate. Despite these high fO2 conditions, high fS2 may also result in the stabilization of small amounts of sulfide in the asthenospheric mantle source region and in fractional crystallization products (amphibole-rich cumulates) at the base of the crust. These trace sulfides will preferentially partition highly siderophile elements (HSE) such as Au and PGE from the flux of magma over the life of the arc, and will become progressively enriched in these elements. Throughgoing magmas may lose some of their complement of HSE, but concentrations of more abundant and less strongly siderophile/chalcophile elements such as Cu and Mo will be largely unaffected. Thus, these magmas are potential sources of porphyry Cu-Mo-(Au) deposits and related high sulfidation epithermal Au deposits. In contrast, the residual subduction-modified mantle wedge and lower crust represent enriched reservoirs of HSE, locked up in trace sulfide phases. The asthenospheric reservoir is unlikely to persist long after subduction ceases (due to mantle convection), but the lithospheric reservoir has greater permanence. During or after arc or continent collision, a variety of tectonic processes, such as crustal thickening, lithospheric mantle delamination, and post-collisional rifting, can cause a second stage of melting in amphibolitic former-arc crustal roots, giving rise to magmas that are similar (but typically somewhat more alkaline) to arc magmas. Such conditions (now under lower fS2 because of the absence of a flux of new S from active subduction) may cause re-dissolution of HSE-rich trace sulfides, and consequent enrichment of the melts in these metals. Collisonal and post-collisional magmas are thus associated with Au-rich porphyry and alkalic-type epithermal Au deposits.

A869

AMY J.V. RICHES1*, YANG LIU1, ZDISLAV V. SPETSIUS2, JAMES M.D. DAY3 AND LAWRENCE A. TAYLOR1 1

Planetary GeoSciences Institute, Department of Earth & Planetary Sciences, University of Tennessee, Knoxville, TN 37996, USA *[email protected] 2 Institute of Diamond Industry, ALROSA Company Ltd., Mirny, Yakutia, Russia 3 Department of Geology, University of Maryland, College Park, MD 20742, USA

This study provides evidence of subducted crust underlying the Siberian Platform, and supports models of lithosphere formation by subduction-zone stacking. Garnets in a large suite of highly diamondiferous mantle xenoliths (121) entrained by the Nyurbinskaya kimberlite have a unique distribution of oxygen isotope compositions, where >82 % of the xenoliths contain garnets with $18O-values above the mantle range [1]. This xenolith suite presents an opportunity to constrain the nature of diamond-bearing mantle protoliths, and provides a snap-shot of the Siberian mantle lithosphere. Geochemical characteristics of these garnet grains fall into 3 distinct groups: 1) Harzburgitic garnets with high Mg#, lowREE abundances, sinusoidal REE-patterns, and $18O-values within the mantle range; 2) Type-1 eclogitic garnets that are LREE-depleted, with modest positive and negative Euanomalies, and $18O-values commonly above the mantle range; and 3) Type-2 eclogitic garnets with lower HREEconcentrations and higher Mg# than Type-1 eclogitic garnets, display convex-upward REE profiles with a peak at Sm, and ~70% have mantle-like oxygen isotope compositions. Trace-element compositions of these garnets, in addition to those resulting from kimberlite-interaction, record metasomatic processes operative in the lithosphere beneath Yakutia. Type-1 eclogitic garnets are derived from crustal precursers altered at low-temperature. In contrast, harzburgitic garnets are derived from highly-depleted mantle materials that have interacted with a carbonatitic-melt, and similar processes may account for Type-2 eclogitc garnets. These results indicate that a significant portion of Nyurbinskaya mantle xenoliths are of crustal origin, with some modified by infiltrating metasomatic melts/fluids. Similar geochemical characteristics are observed in xenolith populations across Yakutia and are common features of diamond-inclusions. These observations suggest subducted lithosphere is present in all terranes of the Siberian Platform, and indicate that ubiquitous small-volume metasomatism may be linked to diamond growth in this region. [1] Spetsius et al., (2008) Eur. J. of Min. 20; 375-385

A870

Goldschmidt Conference Abstracts 2010

Silver nanoparticles: Effects on microbial denitrification ALLISON RICK* AND YUJI ARAI 1

Clemson University, Clemson, SC 29634, USA (*correspondence: [email protected])

Nanoparticles (d < 100 nm) are increasingly common in consumer technology. Nanosilver particles, in particular, are used for their well-known antimicrobial properties in a wide range of consumer products ranging from socks to washing machines. These particles kill gram negative bacteria by disrupting the cell membrane [1]. Bacteria-driven nutrient cycles in soils and sediments may be impacted by the introduction of nanosilver particles via discharge from water treatment plants and/or sludge amendments on agricultural land. Nanosilver could possibly threaten the (de)nitrification cycle in soil-water environments. Choi et al. [2] reported in a recent study that the nitrification process was suppressed in solution systems when the aerobic bacteria were exposed to nanosilver particles (1 mg/L) [2]. However, our preliminary experiments showed no antibacterial effect on anaerobic denitrifers at nanosilver concentrations as high as 5 ppm, while dissolved silver exposure at 1-5mg/L showed the complete inhibition. This suggests that solubility and stability of nanosilver particles in the soil systems might be controlling the toxicological effects on denitrifiers. This research will further explore the antibacterial effects of nanosilver particles on denitrifiers under various redox conditions prior to anaerobic denitrification experiments, as well as the fate of silver nanoparticles in soil-water environments. Both saturated soil and solution systems will be used to assess the solubility/stability of nanosilver with respect to the overall antimicrobial effects. [1] Sondi and Salopek-Sondi (2004) J. Colloid Interface Sci. 275, 177-182. [2] Choi et al. (2008) Water Research 42, 30663074.

Adsorption of strontium at nano- and micro-crystalline titanium-dioxide interfaces: Interpreting surface speciation using charge distribution and the MUSIC model M.K. RIDLEY1*, M.L. MACHESKY2 3 AND D.J. WESOLOWSKI 1

Department of Geosciences, Texas Tech University, Lubbock, TX, USA ([email protected]) 2 Illinois State Water Survey, Champaign, IL, USA 3 Oak Ridge National Laboratory, Oak Ridge, TN, USA The surface speciation of specifically adsorbed ions at metal (hydr)oxide surfaces is dependent on mineral surface structure and solution chemistry. Theoretical simulations and X-ray techniques provide molecular-scale detail of adsorption complexes and mineral surfaces. Whereas, the effects of solution chemistry on ion adsorption, particularly pH, are best investigated using macroscopic experimental techniques. Surface complexation models (SCM) provide a framework for integrating molecular-scale detail with macroscopic experimental results. Such integrated approaches have been applied successfully to better understand the specific adsorption of ions onto various micro-crystalline metal (hydr)oxide phases. For example, potentiometric titration data, X-ray measurements and theoretical calculations for the adsorption of Sr2+ on micro-crystalline rutile ((-TiO2) have been integrated successfully using the MUSIC model in combination with the charge distribution (CD) model. The surface reactivey of nano-crystalline materials have not been studied as extenisively, thus fewer compariable integrated studies have been performed. This contribution will present adsorption results of Sr2+ on nano-crystalline anatase (TiO2). The sorption of Sr2+ was studied as a function of nanoparticle size (3–40 nm diameter), pH and loading in NaCl media at 25°C. Moreover, the experimental solution conditions were selected carefully so as to evaluate Sr2+ sorption on nano-particles relative to compariable macroscopic phases. The development of proton charge curves with the adsorption of Sr2+ were similar for all nano-samples, when normalized to their respective pHznpc values. Furthermore, the charging curves for Sr2+ sorption on the nano-sized anatase were similar to compariable adsorption curves for micro-crystalline rutile. Adsorption charging curves change as funtion of surface loading, suggesting a change in surface speciation. All experimental results were rationalized using a CD-MUSIC model combination. Moreover, the SCMs for Sr2+ sorption on rutile were used to help constrain all nanocrystalline anantase modeling efforts.

Goldschmidt Conference Abstracts 2010

A871

REE geochemistry of deep ocean sediments in Brazil Basin

Characterization of sea spray OM from selected algal cultures

M. RIMSKAYA-KORSAKOVA* AND A. DUBININ

M. RINALDI1*, S. DECESARI1, E. FINESSI1, D. CEBURNIS2, M. ZACHARIAS3, S. CONNAN3, D.B. STENGEL3, C.D. O’DOWD2 AND M.C. FACCHINI1

P.P.Shirshov Institute of Oceanology RAS, Moscow, Russia (*correspondence: [email protected]) 1

Geochemical studies are essential for understanding the processes of sedimentation and diagenesis in Brazil Basin in Quaternary. Brazil Basin (South Atlantic) is characterized with low sedimentation rate and the low organic matter concentration in sediments that leads to oxidizing diagenesis. Here we focus on REE geochemistry in the surface and subsurface sediments obtained from 8 sediment cores along 24° W in the Basin from the depths 4500-5800 m. The recovered sediments are represented with red clays, partly reduced hemipelagic clays and carbonate and ethmodiscus oozes. The sediments at southern stations of the profile are oxidized and reveal the presence of Mn (IV) oxyhydroxide. Shale normalised REE patterns are flat and have positive Ce anomaly. Phosphorus concentrations are low (0.02-0.08%) relative to typical red clays. Sediments of northern part of profile bear evidence of hydrothermal influence: high Fe and Mn concentrations and the characteristic REE pattern. This implies that REE concentrations are increased relative to south station sediments and REE patterns have negligible Ceanomaly. Phosphorus concentrations are also increased probably due to sorption by hydrothermal Fe-oxyhydroxides. Sources of hydrothermal matter could be volcanic structures at the Basin bottom at 12°W observed during seismic profiling. Reduced sediments with traces of pyrite were recovered on two stations. They reveal both the absense of Ce-anomaly coupled with Mn-Fe reduction and the anomal preservation of Ce-enrichment. In first time there were examined REE composition of ethmodiscus oozes of Brazil Basin. The oozes are enriched with manganese that propably controlls the positive Ce anomaly. In this study it has been observed the anomal Ce enrichment of REE in Brazil Basin sediments relative to World Ocean sediments. Positive Ce anomaly is controlled by scavenging on Fe-Mn-oxyhydroxides. Presence of hydrothermal oxyhydroxides leads to reduction of Ce-anomaly and slight HREE enrichment.

Institute of Atmospheric Sciences and Climate, National Research Council, Bologna, Italy (*correspondence: [email protected]) 2 School of Physics, National University of Ireland Galway, Galway, Ireland 3 Botany and Plant Science, School of Natural Sciences, National University of Ireland Galway, Galway, Ireland

Recent investigations showed that submicron sea spray, generated from biologically productive waters, can be extremely enriched in organic matter [1, 2]. Selected microalgal cultures, namely Emiliania huxleyi and Leptocylindrus danicus, in the exponential phase of growth, were used to produce sea spray aerosol in bubblemediated laboratory experiments, with a similar setup as described by Facchini et al. [1]. After six hours, seawater were characterized by higher particulate organic carbon (POC) and lower dissolved organic carbon (DOC), as compared to oceanic water samples collected during a cruise in the north-east Atlantic [1]. Aerosol particles generated by bubble bursting show an organic matter (OM) contribution less than 10% of the total submicron sea spray mass, very low compared to the sea spray aerosol generated by the oceanic water samples [1, 2]. Nevertheless, some of the sea spray features described in sea spray aerosol generated by natural waters have been confirmed: submicron sea spray OM resulted mainly water insoluble (WIOC). 1 H NMR analysis highlighted that the WIOC in E. huxleyi sea spray consisted of unsaturated lipids, less complex and less oxidized with respect to the oceanic water sea spray [1]. Identical features characterizes the spectra of POC extracted from the bubbled water. Aerosol WSOC resulted extremely different from WIOC, and its composition is consistent with a mixture of lipopolysaccharides, proteins and aminoacid derivatives (metabolites), which plausibly derived from DOC. These results confirm that the chemical components of phytoplankton exudates and the biological hydropbobic material (e.g. membrane lipids) forming POC are efficiently transferred to air-sea surface films and into sea spray particles. [1] Facchini et al. (2008) Geophys. Res. Lett. 35, L17814. [2] Keene et al. (2007) J. Geophys. Res. 112, D21202.

A872

Goldschmidt Conference Abstracts 2010

Using ToF-SIMS isotope mapping to constrain dissolution/reprecipitation and redox reactions in experimental CO2-sequestration studies S. RINNEN1, C. STROTH1, A. RISSE2, K. HEESCHEN2, C. OSTERTAG-HENNING2 AND H.F. ARLINGHAUS1* 1

Physikalisches Institut, Westfälische Wilhelms-Universität Münster, 48149 Münster, Germany (*correspondence: [email protected]) 2 Bundesanstalt fuer Geowissenschaften und Rohstoffe, 30655 Hannover, Germany ([email protected])

The sequestration of CO2 gas streams of different origins into e.g. deep saline aquifers opened a major area for geochemical research on gas-fluid-rock interaction at elevated, in situ pressures and temperatures. Besides the inherent problems of experimental approaches to constrain the kinetic parameters of the slow dissolution processes of silicates in highly saline brines, the often conincident dis-solution and precipitation reactions hamper the determination of precise dissolution or precipitation rates in more complex experimentat approaches, e. g flow-through experiments. To facilitate the precise determination of the amount of dissolved ions incorporated into newly formed precipitates within the reaction chambers, a spatial analyses of incorporation of isotopically-labelled elements/ions (e.g. 18O) into mineral precipitates is beeing developed by using high resolution ToF-SIMS techniques. With this technique it is possible to simultaneously image the elemental, isotopic, and molecular composition in rocks with high spatial resolution. Also, the elemental and isotopical distribution as a function of depth can be monitored. To set up a database of a variety of rock-forming minerals, ToF-SIMS spectra were recorded in different measurement modes - either on individual crystal grains of less than 500 µm diameter or in thin sections from rocks envisaged as potential storage formations in Germany. Furthermore, a calibration of the isotopic scale has been performed by measuring artificially prepared minerals with different percentages of isotope labels incorporated. Thereby, the distinction of the incorporation of ions from dissolution (e.g. 99% 16O) in contrast to those from the synthetic brine (e.g. 99% 18O) is possible. In addition, using e.g. 18O labels as atomic oxygen ions, the isotopic composition in larger molecules such as CO3 could be used to unambigously identify the mineral, into the labeled oxygen has been incorporated (e.g. clay minerals or carbonates).

Extracellular electron transport coupling biogeochemical processes centimeters apart N. RISGAARD-PETERSEN1, H. FOSSING2, P.B. CHRISTENSEN2, M. SAYAMA3 AND L.P. NIELSEN4 1

Center of Geomicrobiology, Aarhus University, DK-8000 Aarhus C, Denmark (*correspondence: [email protected] ) 2 Department of Marine Ecology, National Environmental Research Institute, Aarhus University, Vejlsøvej 25, DK8600 Silkeborg, Denmark ([email protected], [email protected] ) 3 National Institute of Advanced Industrial Science and Technology (AIST), 16-1 Onogawa, Tsukuba 305-8569, Japan ([email protected] ) 4 Department of Biological Sciences, Aarhus University, Ny Munkegade 114, DK-8000 Aarhus C, Denmark ([email protected]) Recent observations in marine sediment have revealed conductive networks transmitting electrons from oxidation processes in the anoxic zone to oxygen reduction in the oxic zone [1]. The electrochemical processes and conductors seem to be biologically controlled and may account for more than half of the oxygen uptake in laboratory incubations of initially homogenized and stabilized sediment. Using microsensors and process rate measurements we further investigated the effect of the electric currents on sediment biogeochemistry. Dissolved sulfide readily donated electrons to the networks and could be depleted below detection limit in a several cm thick layer below the oxic zone. Subsequent dissolution of iron sulfide was indicated by mobilization of ferrous iron being precipitated again as ferric iron at the oxic-anoxic interface. Lowered sulfate reduction rates in the upper centimeters of the sediment confirmed the depth range of the electric communication and indicated donation of electrons directly from organotrophic bacteria. The separation of oxidation and reduction processes created steep pH gradients eventually causing carbonate precipitation at the surface. The results indicate that electron exchanging organisms have major biogeochemical importance as they allow widely separated electron donors and acceptors to react with one another. [1] Nielsen et al 10.1038/nature08790

(2010)

Nature

463,

DOI

Goldschmidt Conference Abstracts 2010

A873

The role of Archaea in low temperature dolomite formation

Boron isotopes in Southern Ocean deep sea corals

J.A. ROBERTS*, P.A. KENWARD, D.A. FOWLE AND N. KINNEBREW

LAURA F. ROBINSON1*, B€ RBEL H… NISCH2 1 AND MAUREEN E. AURO

Department of Geology, University of Kansas, Lawrence, KS 66045, USA (*correspondence: [email protected], [email protected], [email protected], [email protected])

1

Pervasive in the ancient rock record, primary dolomite remains scarce in modern systems at low temperatures (< 50¡ C), even those systems supersaturated with respect to dolomite. This scarcity is attributed to kinetic inhibition of precipitation including ion complexation, hydration spheres and the presence of sulfate. No longer considered a purely geochemical problem, the impacts of live bacteria on the controls of dolomite formation have been extensively studied and disordered phases have been documented [1]. Recent work has demonstrated that methanogenic Archaea can also influence low temperature dolomite formation producing ordered, stoichiometric phases [2, 3]. Using both pure cultures and mixed consortia in controlled laboratory experiments we have demonstrated that Archaea uniquely influence dolomite precipitation at low temperature. Methanogenic Archaea impart stable isotopic signatures indicative of specific metabolisms and precipitates form from solutions slightly supersaturated with respect to dolomite and at Mg:Ca ratios ~1. Utilizing other, non-methanogenic Archaea we demonstrate that, while often key in supersaturating conditions, metabolic activity is not necessary for dolomite formation and rather nucleation on the cell wall is the primary mechanism of precipitation (Figure 1). Our characterization of these Archaeal cell walls indicates that they are not only unique in their composition compared to bacterial cell walls but also possess distinctive surface functional group characteristics.

Today the Southern Ocean is experiencing changes in carbonate chemistry with potential impacts on calcifying fauna. Similarly there were likely to have been large changes in pH in the past, associated with transient shifts in upwelling. Studying past changes in Southern Ocean carbonate chemistry, and its effect on calcifying organisms may help to better assess their fate in the light of anthropogenic ocean acidification. Carbonate formed by marine organisms incorporates boron, and the speciation of boron and fractionation of its isotopes are sensitive to the pH of seawater. In order to test a new archive for past seawater pH we have analysed the boron chemistry of modern stylasterid corals collected from 130m to 2000m in the Drake Passage where there is a pH gradient with depth. Stylasterid corals have a global distribution and concentrically banded skeletons, but little is known about their growth rates or biomineralisation. Boron concentrations range from ~60-160ppm and vary between species. The $11B values also show a large range, which again appear to be species dependent. Single species exhibit lighter values with decreasing pH (increasing water depth) similar to empirical calibrations of benthic foraminifera and theoretical predictions. The high boron concentrations provide the possibility of using these corals for ultra-highresolution reconstruction of deep and high latitude pH in the past, but will require analyses of additional modern samples to confirm the pH-boron calibration.

Figure 1: TEM (left) nano-crystals of dolomite forming on lysed cells of H. sulfurofontis. EDS (right) of circled area. This evidence lends strong support for a role for Archaea in low temperature dolomite formation and identifies a key mechanism in the formation of ordered primary phases. [1] Vasconcelos et al. (1995). Nature 377, 220Ð 222. [2] Roberts et al. (2004) Geology 32, 277Ð 280. [3] Kenward et al. (2009) Geobiology 7, 556-565.

Woods Hole Oceanographic Institution, Woods Hole, MA, (*correspondence: [email protected]) 2 LDEO, Columbia University, Palisades, NY

A874

Goldschmidt Conference Abstracts 2010

New approach for the determination of a mantle end-member of N-MORB-like component in oceanic basalts: Metallogenic implications KACEM ROCHD1*, ABDELLATIF JOUHARI1, NASSER ENNIH1, ABDELLAH MOUTTAQI2, MINA NASLOUBI3 1

Chouaib Doukkali University, El Jadida, Morocco (*correspondence: [email protected], [email protected], [email protected]) 2 ONHYM, Rabat, Morocco, ([email protected]) 3 CMT, Tighza Mine, Morocco Pb isotope data for the Bou Madine volcanogenic deposit, located in the Anti-Atlas domain of Morocco, display a linear trend, on a standard 207Pb/204Pb vs. 206Pb/204Pb plot, with a MORB-like component. Considering the age of 552 Ma of rhyolites associated Bou Madine, together with calculations based on U/Pb systematics, the present-day Pb isotopic composition of the mantle source intercept with the northern hemisphere reference line (NHRL) is: 206Pb/204Pb = 18.6043 and 207Pb/204Pb = 15.5078. We regard these values to be the best estimate for the mantle end-member of oceanic basalts lying between the primitive mantle and the FOZO mantle on the NHRL. This model, when applied to other deposits related to mantle-derived rocks in North Africa and West Europe

Diffusion retardation due to decreasing micro-channel width in a 2-D micromodel K.A. ROD1*, D.M. WELLMAN1 AND M. FLURY2 1

Pacific Northwest National Laboratory, 902 Battelle Blvd, Richland WA, 99352, USA (*correspondence: [email protected]) 2 Washington State University, Pullman WA, 99164-6420, USA

Introduction and Methods Dissolution of uranium minerals within fractures has been found to be a diffusion rate limited process; thus, diffusive mass transfer in sediment micro-factures significantly affects the fate and transport of uranium in the subsurface [1]. In 1-10 !m micro-fractures, the diffusion coefficient of uranium contaminated waste water into pore water has been estimated as low as 10-11 m2 s-1 [1], which is 2% of the measured diffusion coefficient for uranyl, 4.26"10-1° m2 s-1 [2]. The objective of this investigation is to investigate diffusion retardation as a function of micro-fracture size. A micro-fluidics model was engineered by inductively coupled plasma-deep reactive ion etching system [3]. It had a linear main channel with micro-channels, 0.5 mm long and 5 !m - 30 !m wide, coming off the main channel. A continuous stream of water was pumped through the main channel. Water was spiked with fluorescent dye tracer, microspheres, or uranium phosphorous complex. Diffusion was calculated from image analyses obtained using a Nikon Epiphot 200 epifluorescent microscope with 10" objective, and a RT Spot CCD digital camera [3].

Results and Discussion

(e.g., Assif El Mal and Erdouz deposits in western High Atlas of Morocco, Maria Luisa and Puebla de la Reina deposits in Ossa Morena Zone of Spain, and Iberian Pyrite Belt in the south Portuguese Zone), provides ages in good agreement with ages determined by independent methods. Consequently, we recommend this model for dating deposits that are associated with N-MORB-derived magmatic rocks and whose Pb isotope data fall along mixing lines with N-MORB-like components.

Initial results demonstrate that diffusion of fluorescein dye into a 5 !m channel was reduced by 19% at 30 seconds and 30% at 7 minutes, compared to a 30 !m channel. While the time frames of these experiments are short, the results suggest the significance of microfractures in subsurface sedimentary material on the transport and fate of contaminants. Knudsen diffusion, surface drag, and adsorption can combine to reduce effective axial diffusion. Consequently, dissolution of intraparticle contaminant source phases and release to pore fluids will be reduced. Moreover, local saturation indices within the microfractures will result in precipitation of secondary phases, which, in turn, will sustain contaminant concentrations beyond conventional transport models predictions. [1] Liu et al. (2006) Water Resour. Res., 42 1-15. [2] Lide (2003) CRC Handbook of Chemistry and Physics. [3] Willingham et al (2008) Environ. Sci. Technol. 42, 3185-3193.

Goldschmidt Conference Abstracts 2010

Microbial reduction of solid-phase humic substances and electron shuttling to Fe(III) oxide

Simulating crystal nucleation: Seeing the infrequent with Molecular dynamics

ERIC RODEN1, ANDREAS KAPPLER2, IRIS BAUER2, JIE JIANG2, ANDREA PAUL3, REINHARD STOESSER4, HIROMI KONISHI1 AND HUIFANG XU1

P.M. RODGER,1 D. QUIGLEY, 2 J.H. HARDING3 3 AND C.L. FREEMAN

1

University of Wisconsin-Madison, Madison, WI, USA ([email protected], [email protected], [email protected]) 2 Eberhard-Karls-University, Tuebingen, Germany ([email protected], [email protected], [email protected]) 3 BAM Federal Institute for Materials Research and Testing, Germany ([email protected]) 4 Humboldt University Berlin, Berlin, Germany ([email protected]) A selection of Fe (III)-oxide stripped soils and sediments (freshwater wetland, saltmarsh, agricultural soil, and coastal plain peat) were screened for the presence of microbially (G. sulfurreducens) reducible solid-phase humics using an electron shuttling assay originally designed to detect dissolved reduced humics. All materials contained detectable quantities (5-50 µmol per g) of microbially reducible solid-phase humics. The solid-phase humics could also be reduced abiotically by H2 in the presence of a palladium catalyst. Electron spin resonance showed that reduced sediments had higher signals in the range of organic radicals than nonreduced sediments. The abundance of radicals increased with increasing pH, which suggested the presence of semiquinone radicals. Addition of small amounts of humics-containing freshwater wetland sediment increased amorphous Fe (III) oxide reduction rate constants by a factor of two. Experiments conducted with cultures amended with freeze-dried surface sediment vs. cultures prepared with surface sediment porewater suggested that solid-phase humic substances were primarily responsible for the acceleration of microbial HFO reduction. Combustion of the freeze-dried sediment eliminated the stimulatory effect on Fe (III) oxide reduction. Additional experiments showed that inorganic sediment components (e.g. sand, clay, Fe (II)) were not responsible for the observed stimulation of Fe (III) oxide reduction. Experiments with pure cultures of Geobacter and Shewanella provided direct evidence for the ability of solid-phase humic substances to accelerate reduction of amorphous Fe (III) oxide. Our results suggest that microbial reduction of solid-phase humic substances may have a substantial impact on the kinetics of Fe (III) oxide reduction in organic-rich anoxic soils and sediments.

A875

1

Department of Chemistry & Centre for Scientific Computing, University of Warwick, UK 2 Department of Physics & Centre for Scientific Computing, University of Warwick, UK 3 Department of Engineering Materials, University of Sheffield, UK Simulating the spontaneous onset of crystalline order with molecular resolution has been a longstanding challenge, particularly for molecular systems where the nucleation and subsequent growth may be controlled by the presence of complex macromolecules. This is seen most clearly in biomineralisation, where the use of biomolecules in nature to direct the path of crystal growth leads to a degree of polymorph and morphology control that far surpasses anything that can currently be effected in a laboratory. An ability to model the onset of crystal formation at a molecular level would considerably enhance our ability to understand, and potentially to mimic, how such exquisite control of crystal form is brought about; unfortunately, the timescales on which crystal nucleation occurs is much longer than the timescales accessible to standard molecular simulation methods. This talk will show how the metadynamics method can be adapted to simulate the onset of crystal formation with statistical reliability, to extract rigorous thermodynamic information about the nucleation process and to characterise how chemical additives can modify the nucleation and subsequent growth. Several examples of applications of the method will be given, including spontaneous formation of ice in constant pressure simulations, methane hydrate formation, calcite crystallisation on self-assembled monolayers and the role of ovocleidin-17 (a protein found in the chicken eggshell) in the eggshell formation.

A876

Goldschmidt Conference Abstracts 2010

Characteristics of produced waters and biogeochemical processes for effective management using constructed wetland treatment systems J.H. RODGERS, JR. AND J.W. CASTLE* Clemson University, Clemson, SC 29634, USA ([email protected], *correspondence: [email protected]) Waters associated with energy production, including extraction of oil and natural gas, may require renovation prior to discharge or reuse. Treatment of these waters to transfer or transform constituents of concern may limit production at marginal sites. Constructed wetland treatment systems can treat a variety of constituents to achieve performance criteria for discharge or reuse in many situations. A wide range of chemical, physical, and risk characteristics are present in produced waters. Produced waters can range from fresh to hypersaline. Cations found in produced waters commonly include sodium, calcium, magnesium, and potassium; anions present often include chloride, sulphate, and bicarbonate. Reverse osmosis (RO) is sometimes used to reduce concentration of the cations and anions. However, specific constituents can pass through RO membranes and require further treatment. One of these constituents is ammonia, which may be treated through nitrification and denitrification. Metals that are of concern in produced waters can include any or all of the following: iron, manganese, zinc, cadmium, copper, lead, nickel, zinc, and others. These metals in produced waters can be treated through specific biogeochemical processes such as oxidation and reduction. Other constituents of concern identified in produced waters include arsenic and selenium. These ‘metalloids’ are amenable to treatment in specifically designed constructed wetland systems through targeted biogeochemical processes. Produced waters can contain a range of organic constituents from oil and grease to low molecular-weight aromatic hydrocarbons. Concentrations of dissolved and dispersed organic constituents can be decreased by oxidation. Depending on the designated post-treatment use for a produced water and its composition, various combinations of inorganic and organic constituents can be specifically targeted for treatment in constructed wetland systems. To achieve treatment of targeted constituents, constructed wetland systems are designed to promote specific biogeochemical processes including oxidation, reduction, nitrification, and denitrification.

The mechanism of ACC nanoparticle transformation to vaterite J.D. RODRIGUEZ-BLANCO1, P. BOTS1, N.J. TERRILL2, S. SHAW1 AND L.G. BENNING1 1

School of Earth and Environment, Univ. of Leeds, Leeds. LS2 9JT, UK ([email protected]) 2 Diamond Light Source Ltd, OX11 0DE, UK

The formation of calcium carbonate (CaCO3) minerals is a key part of the global carbon cycle. Crystalline CaCO3 phases (e.g. vaterite, calcite) often form via a poorly-ordered metastable precursor, amorphous calcium carbonate (ACC). The transformation of ACC nanoparticles to the CaCO3 polymorphs vaterite (Vat) is usually extremely fast i. e., seconds - minutes. Here we demostrate the use of an in situ time-resolved synchrotron-based scattering approach (i. e. SAXS/WAXS) combined with SEM imaging to quantify the fast kinetics and mechanisms of Vat crystallization. Experiments were carried out on station I22 at the Diamond Light Source, UK. The precipitation of ACC was induced by mixing molar solutions of Ca2+ and CO32- at 20°C and the crystallization was monitored via simultaneous SAXS/WAXS patterns acquisition at 1s time frames. In addition the effects of Mg2+ and SO42- on the crystallization reactions were studied. The WAXS data (Fig 1, 3D plot) shows that the transformation from ACC to Vat occurred within ~100s. The SAXS patterns revealed that the initial spherical ACC nanoparticles (~36nm) transform to Vat nanoparticles (~10nm) which agrregate to form ~1µm clusters. The crystallization of these Vat nanoparticle subunits likely occurs via an internal reordering and dehydration process. The aggregated Vat crystallites then continue to grow via Ostwald ripening until they reach ~50nm in size (after ~ 3000s). These sizes were confirmed via SEM observations (Fig 1, insets at right).

Figure 1: 3D WAXS plot and SEM images showing ACC-Vat transformation.

Goldschmidt Conference Abstracts 2010

Effects of ionic strength and multivalent cations on humic substances G.M. ROGER2,3,*, S. DURAND-VIDAL1, O. BERNARD2, G.MERIGUET1, S. ALTMANN3 AND P. TURQ1 1

UPMC Univ Paris 06, PECSA, F-75005 Paris, France CNRS, UMR 7195, PECSA, F-75005 Paris, France (*correspondence: [email protected]) 3 ANDRA, F-92298 Châtenay-Malabry Cedex, France 2

ANDRA is currently directing a research program aiming at providing the necessary data for assessing the feasibility of a deep reversible geological storage for High-Level and Long Lived (HLLL) nuclear waste at a depth of 500 m in the eastern of the Paris basin. It has been proved that the exposition of the host rock to concrete generates fulvic and humic acids [1]. The size and the charge of humic substances are key parameters to access their transport properties and their potential ability of complexation of radionuclides in the soil We have already shown that an original method - high precision conductimetry coupled to a suitable transport theory [2] - give access, at various pH, to the size and the effective charge of reference humic substances and their analogues [3]. The results were confirmed by two independent techniques : atomic force microscopy (AFM), dynamic light scattering (DLS). We now present the results obtained by conductimetry at different ionic strengths and in the presence of multivalent cations: (i) present in the host rock poral water (Ca2+, Mg2+), (ii) models for fission products (Cs+) and actinides (Eu3+) [4]. The mobility of the eventually formed complex is analyzed and the first results of this study are presented. Sizes and effective charges of reference humic substances measured in these various conditions of ionic strength will be discussed together with AFM, DLS and also zetametry measurements. [1] Claret et al. (2003) Sci. Tot. Env. 317 189. [2] G.M. Roger et al. (2009) J. Phys.Chem. B 113 8670. [3] G.M. Roger et al., (2010) Colloid Surf. A, in press (doi:10.1016/ j.colsurfa.2009.12.029) [4] ANDRA (2005) Dossier 2005 : Évaluation de la faisabilité du stockage géologique en formation argileuse, Châtenay Malabry

A877

Cr(VI) removal from alkaline COPR leachate using Green Rust C.M. ROGERS1*, S. SHAW1, I.T. BURKE1 AND I.A. AMED2 1

School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK (*correspondence: [email protected]) 2 Lancaster Environment Centre, University of Lancaster, Lancaster, LA1 4YQ, UK Green rust materials have the potential to decontaminate Cr (VI) waste liquor especially at elevated pH, where other materials are ineffective. Chromium ore processing residue (COPR) produces highly alkaline leachate contaminated with chromate. Often a remediation strategy involves permeable reactive barrier (PRB) technology with zero valent iron (ZVI) as the reactive material. However ZVI does not immobilise Cr (VI) solutions of pH 12, typical of COPR leachate. Laboratory based batch experiments were used to evaluate the effectiveness of ZVI and several different green rust formulations in removing Cr (VI) from anoxic chromate solutions over a range of alkaline pH values. Figure1 demonstrates the fast (103 s) removal of Cr (VI) from chromate solutions when reacted with carbonate green rust at pH 12. This behaviour is contrasted with the lack of Cr (VI) removal in the experiments with ZVI at the same pH over a timescale of 106 s.

Figure 1: Rate of chromate removal at pH 12 The removal mechanism is presumed to be via reduction to Cr (III). Insoluble Cr (III) products precipitate onto the reactive material and can be removed. Therefore Green Rusts are ideal candidates for immobilising Cr (VI) from leachate at alkaline pH levels. They may also have an application in ‘remediation by reduction’ of other brownfield and radioactive contaminants such as U, Se, Tc and even recalcitrant organic contaminants such as tetrachloroethene.

A878

Goldschmidt Conference Abstracts 2010

Kingston fossil plant ash release – Assessment at one year WILLIAM J. ROGERS, NEIL E. CARRIKER AND ROCK J. VITALE1,2,3

Continuous 520,000-year sea-level record in 250-year timesteps, on an independent radiometrically calibrated chronology

1

Tennessee Valley Authority, P.O. Box 1010, Muscle Shoals, AL 35660 ([email protected]) 2 Tennessee Valley Authority, 1134 Swan Pond Road, Harriman, TN 37748 ([email protected]) 3 Environmental Standrds, Inc., P.O. Box 810 • Valley Forge, PA 19482 ([email protected])

Initial and ongoing investigations of environmental impacts of the December, 2008, Kingston Fossil Plant Ash Release are summarized for the first year after the release. Since the release, air and surface water have been analyzed on a continual basis. Various characterizations of the released ash (chemical, physical, and radiological properties, aquatic toxicity, geomorphology and transport) will be presented. Results of seasonal fish studies and initial assessments of other biota will also be discussed. Surface water analytical results showed no discernable impact except during high rainfall events where re-suspension of silt-sized sediment transported the materials downstream. Air monitoring data indicate that dust suppression efforts have been extremely effective in preventing off-site impacts. Plans for long-term biological monitoring to assess potential effects on the ecosystem and for investigating chemically and biologically mediated arsenic and selenium transformations will be presented.

EELCO J. ROHLING School of Ocean and Earth Science, National Oceanography Centre, Southampton SO14 3ZH, UK ([email protected]) We present a sea-level record for the last 520, 000 years based on stable oxygen isotope analyses of planktonic foraminifera and bulk sediments from the Red Sea, with a mean temporal resolution of 250 yr [1]. It reveals a strong signal similarity with the EPICA Dome C ice-core record of Antarctic temperature variations. The orbital-scale variability in the sea-level record is expressed on its own chronology [2], which is independent of ice-core chronology and which does not involve any assumptions for astronomical tuning. This is achieved by a straightforward (linear) calibration with radiometrically dated coral and speleothem sea-level benchmarks. Despite being achieved by a simple linear transformation, the new chronology for our continuous sealevel record remains within 1.5% of radiometric datings throughout the last 520, 000 years. The sea-level record on the radiometrically calibrated chronology is available from http://www. soes. soton. ac. uk/staff/ejr/ejrhome. htm#2010. [1] Rohling et al. (2009) Nature Geoscience 2, 500-504. [2] Rohling et al. (2010) Earth and Planetary Science Letters 291, 97-105.

Goldschmidt Conference Abstracts 2010

A879

In situ boron isotopic measurements in cultured foraminifera: Implications for $ 11B vital effects

Sorption of Pu onto hematite colloids at various total sorbate concentrations

C. ROLLION-BARD1 AND J. EREZ2

A.YU. ROMANCHUK*, S.N. KALMYKOV AND R.A. ALIEV

1

CRPG-CNRS, BP 20, Vandoeuvre-lès-Nancy, France, ([email protected]) 2 The Hebrew University, Jerusalem, Israel, ([email protected]) The boron isotope composition of marine carbonates is considered to be a seawater pH proxy. Nevertheless, the use of $11B has some limitations such as the knowledge of the fractionation factor ((4-3) between boric acid and the borate ion and the amplitude of ‘vital effects’ on this proxy that are not well constrained. Using secondary ion mass spectrometry (SIMS) we have examined the internal variability of the boron isotope ratio in the shallow water, symbionts bearing foraminiferan Amphistegina lobifera. Specimens were cultured at constant temperature (24±0.1 °C) in seawater with pH ranging between 7.90 and 8.45. Intra-shell boron isotopes showed large variability with an upper limit value of '30 ‰. Our results suggest that the fractionation factor (4-3 of about 0.974 (Klochko et al. 2006) is in better agreement with our experiments and with direct pH measurements in seawater vacuoles associated with the biomineralization process in these foraminifera. Despite the large variability of the skeletal pH values in each cultured specimen, it is possible to link the lowest calculated pH values to the experimental culture pH values while the upper pH limit is slightly below 9. This variability can be interpreted as follows: foraminifera variably increase the pH at the biomineralization site to about 9, as it is measured by micro-electrode. This increase above ambient seawater pH leads to a range in $11B (%11B) for each seawater pH. This %11B is linearly correlated with the culture seawater pH with a slope of -12.9 per pH unit, and is independent of the fractionation factor (4-3, or the $11Bsw through time. It may also be independent of the pKB (the dissociation constant of boric acid) value. Therefore, %11B in foraminifera can potentially reconstruct paleo-pH of seawater.

Lomonosov Moscow State University, Leninskie Gory, Moscow 119991, Russia (*correspondence: [email protected], [email protected], [email protected])

Introduction Molecular level understanding of radionuclide/colloid interactions under different geochemical conditions is necessary for prediction of their migration in the enviroment. Most of the laboratory scale experiments were done at the total concentrations of Pu that were significanlty higher than values typical even for contaminated environments, i. e. 10-12 – 10-16 M. At this concentration interval, no spectroscopic methods exist for direct Pu speciation. The redox speciation could be done only after acid leaching by further application of solvent extraction, co-precipitaton or other separation techniques. At the same time the examination of features like position of pH sorption edges, kinetics of sorption and desorption, leaching behavior could be used to derive mechanisms of sorption. The purpose of this investigation was to define the mechanisms of plutonium sorption onto hematite colloids at total concentration of < 10-13 M and to compare with Pu sorption behavior at total concentration higer than 10-10 M.

Experiment Synthesized hematite colloids were used in all sorption experiments. To study plutonium sorption at different total concentrations, isotopes with different specific activities were used – 237Pu (T1/2 = 45.2 d.) and 239Pu (T1/2 = 2.41·104 y.). In this study Pu (IV) and Pu (VI) pH sorption edges, kinetics and redox speiation were examined at three radionuclide concentration ranges, i. e. femtomolar (~10-14 M), nanomolar (~10-1° M) and micromolar (~10-6 M).

Discussion of results It was established that Pu in high valence states was reduced to Pu (IV) upon sorption onto hematite at all examined radionuclide concentrations. In case of Pu (IV) at very low total concentration, e.g. ~10-14 M, the fast sorption of monomeric Pu (OH)n (4-n)+ species occurred, while in case of Pu (VI), the sorption was kinetically controlled by slow reduction on the surface. Other mechanisms of sorption were proposed for Pu at total concentration of ~10-10 - 10-9 M and 10-6 M. We suppose that upon sorption and reduction Pu (IV) could polymerize as a resuts of increase of its concentration near the surface, that could strongly affected both kinetics of sorption and leaching behavior.

A880

Goldschmidt Conference Abstracts 2010

Interactions at the cell-mineral interface

New opals from Wollo, Ethiopia: Geochemical characterization

M.E. ROMERO-GONZALEZ*, Z. ZHANG, J.S. ANDREWS, M. GEOGHEGAN, L. SWANSON, J. SCHOLES, S. ROLFE AND S.A. BANWART

B. RONDEAU1*, E. FRITSCH2, B. TOK3 AND F. MAZZERO4

Cell-Mineral Research Centre. Kroto Research Institute. The University of Sheffield, Sheffield S3 7HQ, UK (*correspondence: [email protected]) The physical and chemical interactions of cell macromolecules with solid substrata is a primary mechanism essential to an enormous range of microbial processes in microbial geochemistry, microbial biotechnology and biomedical engineering and. These phenomena are strongly influenced by the pioneer encounters of macromolecular structures of the cell wall with solid substrata such as mineral surfaces. We have developed an integrated approach to studying cell surface chemistry that includes simplified chemical systems of pure compound biopolymers as models of the cell wall. The specific polymer selected to construct the model cell surface is based on the known physiology of key classes of bacteria. Our work has focussed on specific strains of the genera Rhodococcus, Pseudomonas and Sphingomonas. These biological models are selected due to their respective cell wall structures. Chemical characterisation of polysaccharides, proteins and nucleic acids present in outer layers of these bacterial strains were extensively studied by FT-IR and Raman microspectroscopy, zeta potential, potentiometric titrations and XPS. These were also compared with quantification of attached growth in live cultures. The interfacial physical chemical changes that occurred due to interactions with a range of minerals were also studied. Mycolic acids were studied by AFM since they are proposed to play a key role in the adaptation of Rhodococcus to effectively anchor cells to solid substrata with a range of surface properties. Parameterisation of mathematical models of colloidal force interactions using the Extended DVLO theory, allowed a quantitative interpretation of the contribution of ionic charge and solvent interactions to cell binding at the mineral surface. These studies have shown that for diverse organisms, general characterisation of cell and substratum properties (i.e. hydrophobicity) did not strongly distinguish between the tendency for attachment to a surface and subsequent biofilm growth. Microscopic and spectroscopic techniques showed that extracellular macromolecules influential in cell attachment to surfaces, biofilm formation and structure were genus specific within the strains tested. The future challenge is then to elucidate the role of common model compounds on cell binding mechanisms.

1

Université de Nantes, CNRS-UMR 6112, BP9208, 44322 Nantes, France (*[email protected]) 2 Université de Nantes, IMN, CNRS-UMR 6205, BP 32229, 44322 Nantes, France 3 Institute of Geological Sciences, Bern, Switzerland 4 Opalinda, 56 rue Lafayette, 75009 Paris, France A new deposit of precious opal has been discovered in 2008 close to Wegel Tena, Wollo Province, Ethiopia [1]. It occurs about 350 km North of the deposit of Mezezo, Shewa Province, which is mined since the 1990’s. Opals from Wegel Tena occur in a specific horizontal level of a thick rhyolitebasalt sequence about 30 Ma old. These volcanics are related to the East-African rift. When unaltered, the opal host-rock is an alkaline rhyolite. At the contact with the opal veins, quartz is absent (it has probably been dissolved to form opal) and some feldspars grains are apparently etched: this suggests that opal formed through an alteration process of the rhyolite. We measured the chemical composition of opals using a SEM equipped with EDS and a LA-ICP-MS for major and trace elements respectively. Opals from Wegel Tena contain minor amounts of Al (1000 to 1900 ppm), Ca (350 ppm) and K (250 ppm). Trace elements are present in amounts comparable with those in opals from Mezezo [2], with the following notable exceptions: Y (0.1 ppm), Nb (1 to 3 ppm) and Th (<0.01 ppm) are lower in Wegel Tena material, whereas Sc (1.5 to 2 ppm), Rb (40 to 75 ppm), Sr (70 to 160 ppm) and Ba (140 to 230 ppm) are higher. The high Ba concentration in opals from Wegel Tena is surprising: compared to opals from all over the world [2], all opals formed in a volcanic environment usually have a low Ba concentration (below 100 ppm) whereas those formed in a sedimentary environment are Ba-rich (100 to 300 ppm). [1] Rondeau et al. (2009) Gems & Gemology, 45, 59-60. [2] Gaillou et al. (2008) Ore Geology Reviews, 34, 113-126.

Goldschmidt Conference Abstracts 2010

A881

Recognition of a HIMU-like reservoir beneath northwest Ethiopia

Coupled arsenic and sulfur speciation in semi-arid mine tailings

TYRONE O. ROONEY1* LAURE DOSSO2 AND WENDY NELSON3

ROBERT A. ROOT*, SARAH M. HAYES, CORIN SCHOWALTER AND JON CHOROVER

1

Dept. Geological Sciences, Michigan St. Univ., E. Lansing, MI 48824, USA (*correspondence: [email protected]) 2 Centre National de la Recherche Scientifique, UMR 6538, Domaines Océaniques, Plouzané, France 3 Dept. of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC 20015, USA

The initiation of Cenozoic magmatism throughout East Africa has been attributed to mantle plume activity; however the number and composition of these plumes has remained controversial. The recognition of the ‘C’ mantle reservoir in Afar magmatism and a radiogenic Pb isotope signature in Kenya basalts have been interpreted as manifestations of the African superplume. A radiogenic Pb isotope signature is also commonly observed in magmas erupted on the African and Arabian plates, highlighting the importance of spatial and temporal isotopic studies in developing an understanding of the interaction of the African superplume with the continental lithosphere. Distinguishing between these reservoirs has proven difficult using traditional Sr, Nd and Pb analyses, though the increasing quantity of Hf isotope analyses has highlighted some differences. We present new Sr, Nd, Pb and Hf isotopic data on a Miocene series of silica under saturated (10-16% normative nepheline) mafic (6-8% MgO) flows from the northwestern Ethiopian Plateau. These samples are particularly enriched in the most incompatible trace elements (e.g. 120 ppm Nb, 100 ppm La) and display some of the most elevated TiO2 values (4.1-5.2%) in the region. Measured 2 6 ° Pb/2°4Pb values extend to ~20 and are coupled with unradiogenic &Hf (~0.8-1.8). These magmas exhibit linear mixing arrays that reflect assimilation of the continental lithosphere by a magma with a radiogenic Pb isotopic signature. The position of these samples well below the &Nd&Hf mantle array and towards the St. Helena HIMU field, precludes a significant role for either the ‘C’ mantle reservoir or the radiogenic Pb component evident in the Arabian lithosphere in the generation of these magmas. These data show conclusively that a HIMU-like component is present in the Ethiopian mantle and that it can be distinguished from other reservoirs using Hf isotopes, though its location remains poorly constrained. The major and trace element characteristics of these Miocene Ethiopian magmas are comparable to those interpreted as partial melts of a metasomatized lithospheric mantle (Getra Kele - S. Ethiopia; Kajong – N. Kenya). Whether this HIMU-like signature is an inherent component in the lithospheric mantle or the result of plume-lithosphere interaction is the subject of ongoing study.

Department of Soil, Water and Environmental Science, University of Arizona, Tucson AZ, USA (*correspondence: [email protected]) Arsenic is a potential airborne hazard when populations are exposed to fine-aerosolized particles. Dust from a high As (>5000 mg kg-1) tailings pile blows into residential areas flanking the Iron King mine, a federal Superfund site, in semiarid central Arizona, USA. Phytostabilization of the historic tailings pile is being implemented to reduce surface wind velocity and runoff to limit dispersion of respirable particulates and decrease contaminant transport. The tailings are acidic (pH = 1.9-2.2), and generally homogenous; a redox gradient has developed from surface oxidation of the sulfidic tailings that were initially deposited. Core samples were collected from the top meter to examine the As-S-Fe system speciation with X-ray absorption spectroscopy (XAS), and investigate the mobility of As in the tailings. In the top 0-25 cm, As XANES shows a single peak at 11875 eV, indicating As (V) dominates in the upper 25 cm of the tailings; sulfur NEXAFS shows sulfate as the dominant sulfur species, fit as gypsum and jarosite, with residual pyrite present (Fig.1). A change in speciation, reflected concurrently in As and S, occurs at 25 cm. At 25-55 cm, two distinct As peaks at 11869 and 11875 are observed, indicating As (V) and As-sulfide species, with the noted absence of As (III). The S NEXAFS at 25-55 cm show pyrite as the dominant S species. Weathering of the tailings, indicated by sulfur speciation, controls the mobility and speciation of contaminants, such as arsenic, in the tailings and has important implications for the health risks to nearby communities.

Figure 1: Arsenic XANES and sulfur NEXAFS as a function of depth in the tailings pile.

A882

Goldschmidt Conference Abstracts 2010

Solubility of carbon dioxide in rockbuffered aqueous fluids JÖRGEN ROSENQVIST1*, CHRISTOPHER A. ROCHELLE2 1 AND BRUCE W.D. YARDLEY

Redox-dependent, diffusion-driven fractionation of Fe isotopes in silicate melts and its structural controls M. ROSKOSZ1, C.M.O’D. ALEXANDER2, K. SIO3, J. WANG2, H.C. WATSON4, N. DAUPHAS3 AND B.O. MYSEN5.

1

School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK (*correspondence: [email protected]) ([email protected]) 2 British Geological Survey, Keyworth, Nottingham NG12 5GG, UK ([email protected]) Modelling of CO2 behavior in geological storage reservoirs suggests that significant amounts of CO2 will dissolve in the formation water within periods of years to hundreds of years and that ‘solubility trapping’ will be important in the overall trapping of CO2. However, the interactions between the fluid phase and the surrounding rock, and their influence on CO2 solubility, are not well constrained. Most potential CO2 storage reservoirs involve formation waters with considerable concentrations of Ca2+, and the addition of acidity will result in enhanced dissolution of reactive minerals within the rock, potentially leading to even higher Ca2+ concentrations. This will significantly affect the solubility of CO2 (c. f. [1]). At the same time, dissolution of the rock will neutralize some of the added acidity, and this pH-shift will also affect the solubility. We perform solubility measurements in rock-buffered fluids, at both supercritical and subcritical CO2 pressures. These experiments have been conducted using a number of pure mineral phases, as well as crushed North Sea sandstones. Intermittent sampling of the fluid phase (in lower-pressure experiments coupled with pH measurements) also allow us to follow the evolution of the system with time. At constant pCO2, mineral reactions result in elevated pH relative to the pure fluid system, but different minerals respond at different rates. For typical sandstone formations, the initial dissolution of calcite in response to CO2 injection will be followed by Ca-Na exchange with clays and further reaction with feldspars. Exchange experiments with Naexchanged SWy-2 montmorillonite indicate that the Ca:Na ratio of the fluid will adjust on a timescale of days. The results also indicate that while the presence of divalent cations lower the solubility of CO2, the difference in pH between rockbuffered fluids and unbuffered fluids might actually lead to an increased solubility in rock-buffered fluids. [1] Duan & Sun (2003), Chemical Geology 193, 257-271.

1

UMET, UMR 8207, U. Lille 1. ([email protected]) 2 DTM, CIW, Washington, DC 3 Dept. of the Geophysical Sciences, The U. of Chicago 4 Dept. of Geology and Env. Geoscience, N.I.U 5 Geophysical Laboratory, CIW, Washington, DC Chemical diffusion of cations and atoms in silicates and metals can promote large isotopic fractionation [1]. Iron isotopes can be used, therefore, to probe various differentiation processes. Here, we evaluate experimentally the effect of the redox state of Fe on diffusion-driven isotopic fractionation. Diffusion couples were prepared from CaMgSi2O6 and Fe–bearing CaMgSi2O6 glasses. Experiments were done in a piston-cylinder apparatus at 1 GPa and 1630°C. Samples were either loaded in C capsules to produce melts with all Fe reduced to Fe2+ or in a double Pt capsules with PtO2 buffers to produce melts with oxidized iron (high Fe3+/Fe2+) and to avoid isotopic fractionation during diffusion of Fe into Pt capsules [2]. There is a significant difference between diffusion coefficients of ferrous and ferric ions - Fe2+ diffuses faster than Fe3+ by a factor of 1.5. Also, Fe isotopes appear more fractionated by diffusion in reduced melts than in oxidized melts. Relating the diffusion coefficients of 56Fe and 54Fe to their mass ratios through an empirical coefficient, ! to model our data, we find that !Fe2+>!Fe3+. Because Fe2+ and Fe3+ do not have the same structural roles in molten silicates [3], our data allows us to provide an interpretative framework to understand and predict variations of ! values for a broad range of elements in various materials [1] Richter et al. (2009) Chem. Geol. 258, 92-103. [2] Roskosz et al. (2006) Earth Planet. Sci. Lett. 248, 851–867. [3] Mysen et al. (1985) Am. Min. 70, 317-322.

Goldschmidt Conference Abstracts 2010

A883

Oxidation of added Mn(II) in soils as observed by the Cr Oxidation Test ( XANES spectroscopy and Mn K(

New insight into the phase diagram, structure and viscosity of iron at core conditions

DONALD S. ROSS1* AND ANTONIO LANZIROTTI2

MARVIN ROSS AND REINHARD BOEHLER

1

Dept. of Plant & Soil Science, Hills Bldg., Univ. of Vermont, Burlington VT 05405 USA (*correspondence: [email protected]) 2 Univ. of Chicago CARS, National Synchrotron Light Source, Beamline X26A, Brookhaven National Lab, Upton NY 11973 USA ([email protected]) Soil manganese oxides control the behavior of many contaminant metals through sorption and, in some cases, oxidation. The ability of a soil to oxidize added Cr(III)Cl3, the Standard Net Cr Oxidation Test (COT), has been used as a tool to assess soil Mn surface reactivity (1). Synchrotronbased Mn K( XANES spectroscopy allows determination of Mn oxidation state on field-moist soil samples. It avoids drying-induced changes in soil redox status (2), although x-ray beam-induced reduction (3) needs to be minimized. While the COT measures only surface reactions, Mn K( XANES measures the average oxidation state of the near-surface region. For a better understanding of the behavior of soil Mn(III)/Mn(IV) oxides and their ability to regenerate, we used both tools in an investigation on the oxidation of added Mn(II). We hypothesized that, over time, increases in Mn oxidation state would mirror the increases in surface reactivity as measured by the COT. The soils studied had a wide range in total Mn (0.04 to 1.75%), COT (0.03 to 4.9 mmol Cr(VI) kg-1 soil), pH (4.6 to 7.2) and organic carbon (3 to 27%). Addition of Mn(II)SO4 resulted in both an immediate decrease in the COT (as the added Mn (II) blocked reaction sites for Cr oxidation) and the presence of a Mn(II) peak in the XANES spectra. Over a 50-hour period, the COT increased linearly to higher than original and the XANES spectra shifted to nearly the original proportion of Mn(III)/Mn(IV). The rate of change in both measurements were similar but the final location of the Mn K( absorption edge (higher with a higher proportion of Mn(IV):Mn(III) in the oxide) was often lower than original. The COT measured the overall capacity for oxidation while Mn K( XANES spectroscopy measured average oxidation state. Surface reactivity, as measured by the oxidation of added Cr(III), was greatly enhanced by prior addition and oxidation of Mn(II), likely through the increase in Mn oxide surface area. [1] Bartlett & James (1993) Adv. Agron. 50, 151-208. [2] Ross et al. (2001) Soil Sci. Soc. Am. J. 65, 744–752. [3] Ross et al. (2001) Soil Sci. Soc. Am. J. 65, 736–743.

By combining diamond-anvil-cell measurements, and calculations of the iron melting curve, with sound speed measurements made in shockwave experiments, we present a new understanding of the phase diagram, structure and viscosity of iron up to the inner-outer-core boundary (IOCB) of the Earth near 330 GPa (~5000K). Based on the experimental evidence, drawn from diamond-anvil and shockwave measurements, we conclude that the outer core must be that of a viscous structured liquid. The inner core is likely a plastic solid textured by local structures, or clusters, readily distorted in the direction of the magnetic field, as an explanation for the observed seismic anisotropy of the Earth’s inner core.

A884

Goldschmidt Conference Abstracts 2010

Influence of adsorbed water on energetics of cassiterite nanoparticles

Landweber-EXAFS structural analysis of aqueous polynuclear U(VI) complexes with tartaric acid

N.L. ROSS1*, E.C. SPENCER1, S.F. PARKER2, A.I. KOLESNIKOV3, J. BOERIO-GOATES4, B.F. WOODFIELD4 AND A. NAVROTSKY5

A. ROSSBERG1,2, C. LUCKS1, S. TSUSHIMA1 1,2 AND A.C. SCHEINOST

1

VirginiaTech, Blacksburg, VA 24061, USA (*correspondence: [email protected]) 2 ISIS, Rutherford Appleton Laboratory, Didcot, OX11 0QX, U.K. 3 Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA 4 Brigham Young University, Provo, UT 84602, USA 5 University of California at Davis, Davis, CA 95616, USA Water is ubiquitous on the surface of oxide nanoparticles, displaying varying degrees of deviation from bulk water structure and dynamics, and can exert a profound influence on the thermodynamic properties of the oxide [1]. We have used inelastic neutron scattering (INS) to investigate the structure and vibrational density of states (VDOS) of the surface water of SnO2 (cassiterite) nanoparticles with differing size distributions and differing levels of hydration. The INS spectra of the water adsorbed on the surface of 1-2 nm, 6-7 nm and 40-50 nm SnO2 nanoparticles were measured at 4 K over the 0-500 meV range using TOSCA, an INS time-of-flight spectrometer at ISIS. The results from this study show that surface confinement on the surfaces of cassiterite nanoparticles of different sizes strongly influences water vibrations. The VDOS derived from the INS spectra have been used to compute the heat capacity and entropy of the surface water. We will present a comparison of INS measurements with calorimetric data that will provide additional insight into the structure and dynamics of water confined on the surface of SnO2 nanoparticles. These results will also be compared with our previous results of the influence of adsorbed water on the energetics of TiO2 (rutile and anatase) nanoparticles [2-3]. [1] Boerio-Goates et al. (2006) Nano Lett., 6, 750-754. [2] A. A. Levchenko et al. (2007), J. Phys. Chem. A, 111, 1258412588. [3] E. C. Spencer et al. (2009) J. Phys. Chem. A, 113, 2796-2800.

1

Forschungszentrum Dresden-Rossendorf, P.O. Box 510119, 01314, Dresden, Germany (*correspondence: [email protected]) 2 Rossendorf Beamline at ESRF, B.P. 220, 38043 Grenoble Cedex, France

In coordination chemistry, an open question is if the structure of an aqueous metal complex is equal to the structure of its solid form. While the structure of the solid can usually be determined with great reliability and precision by XRD, determination of the structure in solution by EXAFS may be much more biased. An intrinsic problem of EXAFS shell fitting is that the radial pair distribution function (RPDF) is approximated by Gaussians functions imitating the coordination shells. Different combinations of shells can yield different structures with similar fit quality, thereby making the structural solution non-unique. Even the so-called F-test often does not yield a unique solution. Therefore, we developed two methods which enable the direct calculation of the RPDF and the spatial structure of metal complexes in solution. Solely based on the FEFF scattering theory, the Landweber inverse method [1] yields the RPDF for the aqueous bi- and tri-nuclear U (VI)-tartaric acid complexes without predefined assumptions about the form of the RPDF. With this information and density functional theory (DFT) calculations, the spatial structures of the complexes are refined by Monte Carlo Target Transformation Factor Analysis [2], which also include the calculation of higher order scattering events. Using this combinatorial structural analysis, we were able to show that in the (UO2)3 (H-1Tar)3 (OH)25- complex a central equatorial oxygen atom at a radial U-O distance of 2.22 Å connects the three uranium atoms symmetrically. Consequently, the formula of the aqueous complex corresponds to its stoichiometric equivalent (UO2)3 (µ3-O)(H-1Tar)35-. [1] Rossberg & Funke (2010), J. Synchr. Rad. 17, 280-288. [2] Rossberg et al. (2005), Anal. Bioanal. Chem. 383, 56-66.

Goldschmidt Conference Abstracts 2010

A 87Rb decay constant accumulation experiment

Molecular composition of terrigenous dissolved organic matter after long-term degradation (2.4 years) P.E. ROSSEL1*, A.V. VÄHÄTALO2., M. WITT3 1 AND T. DITTMAR 1

Max Planck Research Group for Marine Geochemistry, University of Oldenburg, ICBM, Oldenburg, Germany (*correspondence: [email protected]) 2 Department of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland 3 Bruker Daltonics, Fahrenheitst. 4, Bremen, Germany Large amounts of terrigenous dissolved organic matter (DOM) are transported from the continents to the ocean. To investigate the role of photochemical and microbial processing of DOM on the continental shelves, we performed a long-term (2.4 years) experiment with DOM leached from Juncus effusus, as a representative for terrigenous DOM [1]. Leachates were analyzed as bulk and after solid phase extraction (SPE-DOM) by Fourier-transform ion cyclotron mass spectrometry (12 Tesla FT-ICR-MS, Bruker-Daltonics, [2]).

A885

E. ROTENBERG1*, D.W. DAVIS1 AND Y. AMELIN2 1

Department of Geology, University of Toronto, 22 Russell St., Toronto, ON M5S 3B1 CANADA (*correspondence: [email protected]) 2 Research School of Earth Sciences, ANU, Building 61 Mills Road, Canberra ACT 0200 Australia

Mounting evidence suggests that the actual value of the Rb decay constant (+87) is 1-2% lower than the conventional value of 1.42 " 10-11 a-1 [1]. We have re-determined +87 by laboratory accumulation of 87Sr in a batch of purified RbClO4 over a ca. 30 year time span. To improve precision in fractionation correction of highly radiogenic Sr isotopic compositions, we used a 84Sr-86Sr double spike along with conventional 84Sr single spike. A weighted average of the )87 measurements (Fig. 1) yields 1.3991 " 10-11a-11 ± 0.0010 (MSWD = 78). The data scatter outside of their analytical errors in what appears to be an upwardly biased distribution from an unknown source. The scatter is reduced by averaging the 19 lowermost measurements (1.3966 ± 0.0003, MSWD = 2.8) but is still outside of error. A Bayesian statistical approach assuming a unidirectional half-gaussian bias gives a best estimate for the decay constant of 1.396 ± 0.001 " 10-11a-1 (35% probability of fit) including spike calibration errors. This is in agreement with recent estimates for U-Pb age comparisons of 1.398 ± 0.003 [2] and 1.396 ± 0.006 [3] and the most recent laboratory counting estimate of 1.396 ± 0.009 [4]. We propose that it be used for all Rb-Sr age determinations in place of the previously accepted value. 87

Figure 1: Mass spectrum of SPE-DOM for one exemplary nominal mass. (a) fresh leachate, (b) dark control after 898 days, (c) sterile sample after 459 days exposed to sunlight and (d) photodegraded sample after 439 days biodegradation. The molecular composition of bulk DOM was similar in all samples, indicating that a group of abundant molecules survive the harsh long-term treatment. We could identify a larger number of molecules in SPE-DOM (Fig. 1), compared to bulk DOM, and strong molecular changes became evident in the different treatments. The results also indicate that photodegradation has a stronger effect than microbial alterations on the molecular composition of DOM. [1] Vähätalo & Wetze, 2008 Limnol. Oceanogr. 53, 13871392. [2] Dittmar & Paeng, 2009 Nat. Geoscie. 2, 175-179.

[1] Steiger and Jager (1977) EPSL 36, 359. [2] Nebel et al. (2006) Fall AGU abst. V21A-0558. [3] Amelin and Zaitsev (2002) GCA 66, 2399. [4] Kossert (2003) Appl. Rad. Isot. 59, 377.

A886 142

Goldschmidt Conference Abstracts 2010

Nd anomalies in the Nuvvuagittuq supracrustal belt revisited

Sorption and wetting properties of pore fluids probed by neutron scattering techniques

A.S.G. ROTH1, B. BOURDON1, T. KLEINE2, S.J. MOJZSIS3 4 AND M. TOUBOUL

GERNOT ROTHER1*, JUSKE HORITA1, KENNETH C. LITTRELL2 AND DAVID R. COLE1

1

Institute for Geochemistry and Petrology, ETH Zurich, 8092 Zurich, Switzerland ([email protected]) 2 Institut für Planetologie, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany 3 Department of Geological Sciences, University of Colorado, Boulder, CO 80309-0399, USA 4 Department of Geology, University of Maryland, College Park, MD 20742, USA Coupled 147, 146Sm-143, 142Nd systematics are a powerful tool to trace the earliest differentiation of the silicate. While early mantle depletion has been well documented as positive 142Nd anomalies in Eoarchean rocks from West Greenland and Western Australia [1-3], first evidence for an enrichedreservoir reported as negative 142Nd anomalies in pre-3750 Ma rocks from the Nuvvuagittuq supracrustal belt (NSB) in Québec [4] is controversial [5]. Here we report new Nd isotopic data for rocks from the NSB. Samples are from five different lithologies and comprise amphibolites, cummingtonite-rich amphibolites, granodiorites, tonalites, and trondhjemites [6]. They cover a range of Sm/Nd ratios from about 0.14 to 0.32. Sm and Nd were separated from bulk rock samples by standard ion-exchange chromatography [2] and Ce was efficiently removed from Nd by liquid-liquid extraction [7]. Nd was measured as Nd+ using the Thermo Triton (TIMS) at ETH Zurich in dynamic mode. Repeated measurements of the JNdi-1 standard yield an external precision of ±5 ppm (2 SD) for the 142Nd/144Nd ratio over a period of two years (n=82). Over the course of this study the external precision was ±4 ppm (n=35). To further test the accuracy of our method we analyzed samples from the Isua supracrustal belt and Itsaq Gneiss for which positive 142 Nd anomalies have previously been reported [2]. Our data are in excellent agreement with those reported earlier. In contrast to an earlier study [4], our new data show no resolvable 142Nd anomalies in rocks from the NSB. This is consistent with a ca. 3.8 Ga 147Sm-143Nd age of these rocks. To further explore the potential occurrence of 142Nd anomalies in the NBS we are currently analyzing several samples (same sample powders) that were also analyzed by O’Neil et al. [4]. [1] Harper and Jacobsen (1992) Nature 360, 728-732. [2] Caro et al. (2006) GCA 70, 164-191. [3] Bennett et al. (2007) Science 318, 1907-1910. [4] O’Neil et al. (2008) Science 321, 1828-1831. [5] Andreasen and Sharma (2009) Science 325, 267-(). [6] Cates and Mojzsis (2007) EPSL 255, 9-21. [7] Rehkämper et al. (2009) Chemical Geology 129, 201-208.

1

Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6110, USA (*correspondence: [email protected]) 2 Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, TN37831-6393, USA

The physical properties of pure and binary fluids confined in nanopores of porous materials play an important role in both geological and technological processes such as carbon dioxide sequestration, the uptake,, storage, and transport of geologic fluids, and chromatography. Detailed studies of pore processes on the molecular to microscopic levels are required to understand the interplay of sorption, wetting, and confinement effects. Neutron scattering experiments probe the pore structure and dynamics of pore fluids and provide detailed information about density and volume of fluid phases, sorption properties, as well as species mobility and self diffusion characteristics [1]. We will discuss Small-Angle Neutron Scattering (SANS) studies of confined pure fluids [2] and mixtures, and present different experimental and analysis techniques to extract physical quantities of pore fluids from these data. Mixtures of iso-butyric acid (iBA) and water (W) serve as model systems for binary pore fluids, including geologic fluids such as CO2+water or hydrocarbon +water [3]. This particular system was chosen because the critical temperature of the iBA + W system is near room temperature, and both components are liquids with very similar mass densities, diminishing the effects of gravitational demixing. A H/D contrast variation study of the demixing properties of this binary liquid inside the pores of mesoprous Vycor 7930 material with 3 nm average pore size was conducted on the GP SANS instrument at ORNL. Analysis was performed in terms of contrast variation SANS [4] as well as a modified 3-phase model based on the consideration of the scattering invariant [5]. [1] D.R. Cole, E. Mamontov, G. Rother, In: Neutron Applications in Earth, Energy, and Environmental Sciences, R. Rinaldi, L. Liang, H. Schober (Eds.), Springer (2009) [2] G. Rother, Y.B. Melnichenko, D.R. Cole, H. Frielinghaus, G.D. Wignall, J. Phys. Chem C 111, 15736 (2007) [3] S. Schemmel, G. Rother, H. Eckerlebe, G.H. Findenegg, J. Chem. Phys. 122, 244718 (2005) [4] H. Endo, Physica B 385386, 682 (2006) [5] W.L. Wu, Polymer 23, 1907 (1982)

Goldschmidt Conference Abstracts 2010

Oxidation state and temperature influences Cr sorption with struvite ASHAKI A. ROUFF* AND DAVID MAZA School of Earth and Environmental Sciences, Queens College, CUNY, Flushing NY 11367, USA (*correspondence: [email protected]) Struvite (MgNH4PO4·6H2O; MAP) occurs naturally in animal and human kidney stones, poultry litter, bat guano and phosphate deposits [1]. It is produced anthropogenically in soils as a fertilizer by-product, and is a common precipitate in wastewater treatment processes, with optimal precipitation occurring within a 180-240 °C temperature range [2]. Substitution of the toxic metalloid chromium (Cr) into MAP structures has been reported [3], however Cr-MAP sorption processes are not completely elucidated. Oxidation state and resultant speciation dictates Cr mobility. While Cr (III) tends to interact strongly with solid particles, Cr (VI) is more mobile and easily transported in solution [4]. Sorption experiments were conducted with Cr (III, VI) in the presence of MAP at temperatures ranging from 25-300 °C. At 25 °C, ~70 and 2 % Cr (III) and Cr (VI), respectively is removed from solution. Insignificant sorption of Cr (VI) may be due to competition with P species for similar sorption sites. With increasing temperature, removal of both Cr (III) and Cr (VI) is enhanced, maximizing at 90 and 85 %, respectively at 300 °C. Increased removal of Cr (VI) with temperature is suggestive of an enhanced or altered sorption mechanism, which may be accompanied by a change in oxidation state. Preliminary results from x-ray absorption near-edge spectroscopy (XANES) studies suggest similarities in Cr-MAP sorption complexes regardless of initial oxidation state. Results of this research provide insight into Cr-MAP associations in low and high temperature biological, geochemical and anthropogenic systems. [1] Abdelrazig & Sharp (1988), Thermochim. Acta 129, 197215. [2] Arakane et al. (2006) Water Sci. Technol. 54, 81-86. [3] Ravikumar et al. (1999) Cryst. Res. Technol. 34, 911-914. [4] Fendorf (1995) Geoderma 67, 55-71.

A887

Chlorite formation during hydrotermal alteration of Troctolite: An experimental study at 420°C and 500bars MIKAELLA E. ROUGH* AND WILLIAM E. SEYFRIED, JR. University of Minnesota Geology and Geophysics Department, 310 Pillsbury Dr. SE 55455 (*correspondance: [email protected]) The >360°C high temperature Rainbow system vents fluid enriched in H2, CH4, and Fe fluids that can be accounted for by hydration of ultramafic rock assemblages, although the distinctly low pH, high Ca and Si concentrations are greater than would be expected for such a process. The coexistence of these rocks with plagioclase-bearing gabbro, however, could provide Al and Si for chlorite formation needed for pH lowering, while at the same time dissolved H2 could be buffered by chlorite-magnetite fluid equilibria. Gabbro intrusions into ultramafic lithologies are often associated with detachment faults at slow spreading mid-ocean ridges. Accordingly, chlorite and amphibole bearing assemblages may be more pervasive than serpentine in rocks altered at greenschist to amphibolite-facies conditions [1]. To test the role of gabbro (troctolite) alteration on mass transfer reactions during hydrothermal alteration, we conducted a series of hydrothermal experiments 420°C, 500 bars and monitored changes in fluid chemistry. Dissolved H2 increased rapidly to >20mmol/kg before slowly decreasing to concentrations of approximately 7 mmol/kg. Preliminary examination of alteration minerals indicates chloritization of the olivine and plagioclase bearing reactants. [1] Blackman, Ildefonse, John, Ohara, Miller, MacLeod (2006) Proceedings of the IODP, 304/305

A888

Goldschmidt Conference Abstracts 2010

Inorganic geochemical composition of Appalachian Basin formation waters – Preliminary examination

Climate sensitivity to atmospheric CO2 during the Phanerozoic DANA L. ROYER1, JEFFREY PARK2 AND ROBERT A. BERNER2

ELISABETH L. ROWAN1* AND MARK A. ENGLE2 1 1

USGS, 12201 Sunrise Valley Dr., M.S. 956, Reston, VA 20192, USA (*correspondence: [email protected]) 2 USGS, Reston, VA 20192, USA ([email protected])

Unlike many oil and gas producing basins in the U.S., inorganic geochemical data for Appalachian Basin formation waters are scarce. In a preliminary effort to characterize the formation waters, we have examined publically available data for five states: NY, PA, OH, WV, and KY, e.g. [1, 2]. The samples were obtained from oil/gas wells producing from Pennsylvanian – Cambrian age reservoirs, with the majority of samples taken from reservoirs of Devonian and Silurian age. The median salinity is ~250, 000 ppm TDS (total dissolved solids), and values range to nearly 400, 000 ppm. Piper diagrams show that the waters are predominantly Na-Cl type, with Na/Ca mole ratios of >3; concentrations of K, Mg, SO4, and HCO3 are comparatively minor. Cl/Br and Na/Br ratios in samples from eastern Ohio indicate that evaporative seawater concentration was the dominant salinity source, rather than dissolution of evaporites. Although, thus far, we lack the Br analyses needed for a similar investigation of the formation waters from the other states, strong similarities in total salinity, Na/Ca, and other major element ratios across the data sets suggest a common origin for the brines. Additionally, we examined fluid inclusion salinity data published in studies of MVT (Mississippi Valley type) ore deposits (commonly of Late Paleozoic age) within and at the margins of the Appalachian Basin. Fluid inclusions preserve microscopic samples of formation fluid trapped during the growth of the host crystal. The inclusion fluids are similar to the formation waters in several ways: 1) high total salinities, generally 150, 000–350, 000 ppm TDS, 2) Na-Cl type fluids with Na/Ca ratios similar to those of the formation water samples, and 3) Cl/Br ratios indicative of surface evaporative concentration of seawater as the salinity source. These observations suggest that highly saline formation waters in the Appalachian Basin might be remnants of Paleozoic connate fluids. Unravelling their history may help in predicting the distribution of brines within the basin. [1] Sanders (2001) AAPG Bull. 75, 1593-1608. [2] Breit (2002) http://energy. cr. usgs. gov/prov/prodwat/index. htm.

Department of Earth and Environmental Sciences, Wesleyan University, Middletown, CT 06459, USA ([email protected]) 2 Department of Geology and Geophysics, Yale University, New Haven, CT 06520, USA

The equilibrium temperature response to doubled atmospheric CO2, a common measure of climate sensitivity, provides a wealth of information about the climate system because it integrates a wide variety of climate feedbacks such as clouds and other greenhouse trace gases. In deep geologic time, over Myr timescales, an equilibrium temperature response includes additional feedbacks, for example the waxing and waning of ice sheets and the chemical weathering of silicate minerals. This long-term climate sensitivity is sometimes called Earth system sensitivity. In an earlier study, we calculated an average Earth system sensitivity of 2.8 °C per CO2 doubling for the past 420 Myrs. This was done by minimizing the misfit in CO2 between proxy records and GEOCARBSULF, a long-term carbon- and sulfur-cycle model that includes Earth system sensitivity as a parameter. However, because a single mean value was calculated, it was not clear whether Earth system sensitivity was constant or variable during the Phanerozoic. We will report an extension of the earlier study using an updated CO2 proxy data set and carbon cycle model (GEOCARBSULFVOLC) to calculate a more finely-resolved record of Earth system sensitivity (~50 Myr time slices). In particular, we focus on potential differences in sensitivity during glacial and non-glacial times. We will compare with independent estimates of Cretaceous and Cenozoic Earth-system sensitivity that correlate proxy estimates of CO2 and tropical sea surface temperature.

Goldschmidt Conference Abstracts 2010

Melting and refertilization in peridotites: What happens to Os? ROBERTA L. RUDNICK* AND RICHARD J. WALKER Dept. of Geology, Univ. of Maryland, College Park, MD 20782 USA (*correspondence: [email protected]) Most peridotites, be they from massifs, xenoliths or the ocean floor, are more refractory than estimates of the Earth’s primitive mantle (i. e., they have lower Al2O3 and CaO). Suites of peridotites commonly form linear arrays on plots of MgO vs. Al2O3 or CaO, which are often interpreted as melt depletion trends. However, it has been appreciated for some time [e.g. 1] that some (many?) of these trends may also reflect melt refertilization. This point was recently brought home when it was recognized that lherzolite from its type locality in the Pyrenees is the product of refertilization of harzburgite [2]. How melt refertilization affects the Re-Os isotope system in peridotites depends on the timing of refertilization relative to melt depletion. We argue here that most refertilization observed in peridotite suites is a product of adiabatic melting processes – i. e., the refertilizing melts originate from deeper in a rising melt column and infiltrate overlying harzburgite. We term this process autorefertilization [3]. Auto-refertilization increases Re/Os ratios in harzburites, but because the process occurs nearly coincident with melt depletion, it will not change 187Os/188Os at the time of the event. With time, the resulting refertilized peridotites will form linear trends on Al2O3 vs. 187Os/188Os or Re-Os isochrons. The resulting ages will reflect the time of partial melting/refertilization. By contrast, refertilization of ancient harzburgites occurring significantly after melt depletion will produce strongly curved arrays on Al2O3 vs. 187 Os/188Os plots [4]. Some lherzolitic xenoliths from the Kaapvaal Craton show such a trend [5]. In the absence of fugitive sulfide melts in the upper mantle, for which we argue there is little evidence, Os isotopes in whole rock peridotites may often be faithful recorders of melting episodes in the upper mantle. [1] Elthon, 1992, J. Geophys. Res. 97: 9015-9025. [2] Le Roux et al., 2007, EPSL 259: 599-612. [3] Rudnick and Walker, 2009, Lithos 112: 1083-1095. [4] Reisberg and Lorand, 1995, Nature 376: 159-162. [5] Simon et al., 2007, J. Petrol. 48: 589-625.

A889

Isotopic and geochemical tracers for evaluating the environmental impact of the Tennessee Valley Authority coal ash spill in Kingston, TN LAURA S. RUHL*, AVNER VENGOSH AND GARY S. DYWER Duke University, Division of Earth and Ocean Sciences, Durham, NC 27708 (*correspondence: [email protected]) Systematic monitoring of the environmental impacts of the largest coal ash spill in US history at the Tennessee Valley Authority (TVA) coal-burning power plant in Kingston, TN has revealed that interaction of the coal combustion products (CCPs) with natural waters mobilizes leachable coal ash contaminants (LCACs) such as boron, arsenic, selenium, strontium, and barium [1]. We have monitored the quality of water and sediments in downstream segments of the Emory and Clinch Rivers near the spill site, which revealed several distinctive patterns (1) surface waters in areas of restricted water exchange show high LCACs levels (e.g. As: 9- 95 µg/L). Removal of ash from this area and diversion of surface water has led to a reduction of the LCACs concentrations with time; (2) downstream Emory and Clinch Rivers show low LCACs concentrations below the EPA maximum contaminant level (As=10 µg/L), but with levels (e.g. As ~4 µg/L) above the baseline of the upstream rivers; and (3) pore water extracted from bottom sediments of the downstream Emory and Clinch Rivers with significantly high LCACs levels (e.g. As 9-285 µg/L). Our field and leaching experiments data show that boron is one of the sensitive indicators for CCP contaminants’ leaching, with boron content up to 1276 µg/L in pore water relative to the upstream river water (6 to 9 µg/L) and $11B values of -12‰ and -16‰ (relative to NIST951). This isotopic composition is significantly different from that of meteoric boron. Overall, we show that while significant dilution reduces the LCACs’ impact in the Emory and Clinch Rivers, leaching continues to occur at the bottom sediments and mobilizes LCACs to the underlying pore water. [1] Ruhl, et al. (2009) Env. Sci. Tech 43, 6326–6333.

A890

Goldschmidt Conference Abstracts 2010

Authentic inquiry into gas chromatography for a chemistry laboratory class CHRISTOPHER V. RUHS AND KAREN S. MCNEAL ([email protected], [email protected]) Educators must teach environmental science concepts effectively to college-level students in order to produce capable citizens, able to understand and address current and future environmental concerns. Authentic inquiry-based laboratory classes have been shown to be more effective than classical ‘cookbook’ style laboratory classes at transferring conceptual knowledge and experience to students, and should be considered by educators. Therefore, in order to investigate the potential benefits of employing authentic inquiry in a pilot study, the chromatography module from an introductory chemistry laboratory class was redesigned to include the use of an authentic inquiry approach. The experimental class was compared with a control group using pre- and post-tests to assess students’ progress; our results revealed that students exposed to the redesigned module showed greater improvement in content knowledge and reflected more positive attitudes toward chromatography.

Effect of extracellular polymeric substances (EPS) on Cd adsorption to Shewanella oneidensis and Pseudomonas putida: X-ray absorption fine structure study X. RUI1, J.P.L. KENNEY2, J.B. FEIN2 AND B.A. BUNKER1 1

Department of Physics, University of Notre Dame, Notre Dame, IN, 46556 ([email protected]) 2 Department of Civil Engineering and Geological, University of Notre Dame, Notre Dame, IN, 46556 Extracellular polymeric substances (EPS) can bind a number of metal species and may affect metal binding and distribution in biofilms. Ueshima et al. (2008) studied the role of EPS in binding Cd in a bacterial biofilm, and concluded that Cd was bound to EPS to a similar extent as to the bacterial cell walls. This result has not been tested with other bacterial species, nor has the underlying mechanism been determined to explain the similarity in binding. In this study, we use X-ray absorption fine-structure spectroscopy (XAFS) to determine the molecular-scale mechanisms responsible for Cd-EPS binding, and we compare these mechanisms to those responsible for Cd binding onto the cell wall of the bacteria that produced the EPS. We studied 2 types of biomass samples: 1) bacterial biofilms exposed to aqueous Cd under a range of pH conditions; and 2) the same bacterial biofilms with EPS removed, exposed to the same Cd and pH conditions. The difference in the signals is ascribed to Cd-EPS binding. S. oneidensis and P. putida were grown to yield biofilms containing both cells and attached non-soluble EPS. One portion of each biofilm was washed with 0.1M NaClO4 only, while the other portion of each biofilm, prior to washing, was treated with glucoamylase, effectively cutting the EPS from the cell walls. Each biomass was then suspended in a 10 ppm Cd, 0.1M NaClO4 solution at pH 5, 7, or 8 for 2 h. Cd-edge XAFS spectra revealed, for both bacteria species, Cd ion binding to carboxyl and sulfhydryl sites for the bare cell walls as well as the cells with EPS. However, the contribution from the two sites varied for the cell walls and EPS. For both bacteria species, more sulfhydryl site binding was observed for the sample with EPS, except for the enzyme-treated P. putida at pH 7, where the cell walls had more sulfhydryl sites. pH also affected the binding mechanisms, with sulfhydryl sites being more important at low pH. Although differences exist, the Cd binding environments of the EPS and bacterial cells are broadly similar, likely explaining the similarities in extents of binding of these two types of bacterial sorbents.

Goldschmidt Conference Abstracts 2010

Effect of phosphonates on calcitesolution reactions ENCARNACIÓN RUIZ-AGUDO1*, CHRISTINE V. PUTNIS1, DEVIS DI TOMMASO2, NORA H. DE LEEUW2 AND ANDREW PUTNIS1. 1

Institut für Mineralogie, Universitat Münster, 48149, Münster, Germany (*correspondence: [email protected]) 2 Department of Chemistry, University College London, London, WC1H 0AJ, United Kingdom

Increasing amounts of anthopogenic phosphonates are entering the environment as a result of their use as chelating agents, herbicides or inhibitors of calcite scale formation in porous oil reservoirs [1, 2]. Phosphonates released into the environment may interact with minerals in rocks, soil or oil reservoirs. These compounds are also key components of the marine dissolved organic phosphorus. Recently, it has been proposed that an important source of phosphonates into the ocean is nitrogen-fixing cyanobacteria. These organisms bloom in warm, CO2-rich environments, which suggests that phosphonate concentration in oceans may increase in the future [3]. Thus phosphonate interaction with carbonates may also be relevant for biomineralization processes taking place in marine environments. This study has used AFM in situ dissolution experiments on calcite in the presence of HEDP (hydroxy ethylene diphosphonic acid) at pH 8 in order to get insights into the kinetics and mechanisms of nanoscale processes occurring during the interaction of calcitephophonate bearing solutions. Rhombohedral calcite etch pits appeared tear-shaped and dissolution rates were drastically reduced in the presence of phosphonate, although they increased with additive concentration. Stabilization of polar steps as well as increased frequency of water exchange in the hydration shell of Ca2+ (as shown by molecular dynamics simulations) may explain such observations. The nucleation and growth of a Ca-HEDP phase on calcite surfaces was also observed. The reaction must be controlled by a fluid boundary layer at the mineral-solution interface, which as a consequence of calcite dissolution, became supersaturated with respect to the phase that precipitated (although the bulk solution was undersaturated). The reaction stopped when the calcite surface was covered. However, when Na+ is present in solution, a fibrous, highly porous Na-Ca-phosphonate phase which is loosely attached to the calcite surface, seems to be able to fully replace the parent crystal. [1] Pairat et al. (1997) Langmuir 13, 791-798. [2] Jonasson et al. (1996) Chem. Geol. 132, 215-225. [3] Dyhrman et al. (2009) Nature Geoscience 2, 696–699.

A891

Influence of MgO nanoparticle size on available surface area for carbonation A.M. RUMINSKI AND J.J. URBAN* Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (*correspondence: [email protected]) It is widely accepted that anthropogenic carbon dioxide (CO2) emissions are a leading cause of global warming and that there is an urgent need to develop methods for CO2 capture and sequestration [1]. Metal oxides are an attractive material for CO2 fixation. CO2 reacts with metal oxides forming thermodynamically stable solid metal carbonates suitable for long term storage. In this work we investigate the storage capacity of magnesium oxide nanocrystals as a function of particle size. Synthesis of spherical MgO nanocrystals with a narrow size distrubtion and tunable diameter has recently been reported [2]. Surface area is measured through N2 adsorption [Figure 1] using the BET method. The small diameter of the particles studied (2 – 7 nm) results in large surface areas up to 2200 m2/g. CO2 physisorption and chemisorption capacities will be examined through alternate thermal cylcing of CO2 and N2 purge gases using a thermal gravimetric analysis (TGA) instrument.

Figure 1: N2 adsorption/desorption isotherms for MgO nanoparticles ranging from 2 to 7 nm in diameter. [1] Metz et. al. (2005) Special Report on Carbon Dioxide Capture and Stoarage, Intergovernmental Panel on Climate Change. [2] Moon et. al. (2009) Angew. Chem. Int. Ed. 48, 6278-6281.

Goldschmidt Conference Abstracts 2010

A892

Composition of organic matter stabilised by mineral interactions in subsoil horizons CNRS, BIOEMCO, Campus AgroParisTech, Bâtiment EGER, Thiverval-Grignon, France ([email protected]) Subsoil horizons located below the A horizon are known to store important amounts of organic carbon characterised by high mean residence time. The organic matter compounds present in subsoil horizons are mainly stabilised by mineral interactions [1, 2]. The aim of this paper is to report the composition of SOM in close interaction with soil minerals in several soil types under temperate as well as tropical climate. Bulk chemical composition of SOM in subsoils is soil type specific and suggests, that pedological processes determine the stabilisation of specific compounds. Analytical pyrolysis showed, that polysaccharides, as well as nitrogen containing compounds can contribute in higher amounts to SOM stabilised by mineral interactions Wet chemical analysis showed, that plant-derived aromatic compounds, such as lignin were not stabilised by mineral interactions in subsoil horizons. The characterisation of hydrolysable polysaccharides emphasises the importance of microbialderived compared to plant-derived compounds for carbon stabilisation by mineral interactions in subsoil horizons (Fig. 1) [3]. GM/A X /*)

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J.C. RUSHTON* AND V.J. BANKS1 1

CORNELIA RUMPEL

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Characterisation of mine waste: A case study of Frongoch tailings

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Figure 1: Relationship between the 14C activity and the microbial versus plant-derived sugars (GM/AX ratio) of bulk soil horizons and the dense fractions (data from [3]). [1] Rumpel et al. (2002) Org. Geochem. 33, 1131-1142. [2] Eusterhues et al. (2007) Org. Geochem. 38, 1356-1372. [3] Rumpel et al. (2010) SBB 42, 379-382.

British Geological Survey, Keyworth, Nottingham, NG12 5GG, UK (*correspondence [email protected])

Results are presented of a petrographic examination of mine wastes collected from a tailings lagoon at the abandoned lead-zinc, Frongoch Mine, in the Ystwyth catchment, midWales, UK. The ore mineralisation is derived from quartzsulphide vein deposits associated with ENE trending faults and fault breccias in Silurian turbidite host rocks. Characterisation of mine waste is fundamental to determining the contaminant source and flux (in this case leachable lead and zinc), which is required for catchment scale prioritisation of remediation. We have used specialist sampling and sample preparation techniques to enable detailed petrographic analysis of the tailings deposits to aid the interpretation of the hydraulic testing. This established that despite the structured nature of the tailings, laboratory determined vertical hydraulic conductivities of undisturbed samples were relatively high (3.4 x 10-4 to 2.5 x 10-1 m/day). The presence of vertical flow paths was also indicated by field observations of soluble eflorescent minerals at the tailings surface during the hot, dry summer of 2006. Undisturbed samples were collected, using Kubiena tins, from the walls of a trench cut into the tailings. The undisturbed samples were resin impregnated within the tins using a process of sequential liquid displacements that retains the internal structures of unconsolidated sediments [1]. Petrographic thin sections and polished blocks were prepared for optical and scanning electron microscope analyses. The tailings consist of finely bedded muds, silts and sands comprising highly angular fragments of vein minerals and country rock. Vegetative matter from surrounding peat deposits is intermixed. Parallel lamination is common. There are also ripples, cross-beds and erosional surfaces. Fluid escape structures, fine scale (mm) slumping, rare burrowing, syneresis fracturing and sub-vertical fracturing associated with larger scale (cm +) slumping are identifiable. Fluid movement is expected to be mainly channelled along bedding planes. Deformation structures provide vertical pathways; this is illustrated by the presence of secondary deposits, primarily lead sulphates derived from oxidative alteration of sulphides, lining many of these structures. There is an association between the secondary deposits and vegetative matter. This is published with the permission of the Executive Director of British Geological Survey (NERC). [1] Smart and Tovey (1982) Oxford Un. Press.

Goldschmidt Conference Abstracts 2010

A893

The valence state of iron in chromite from the Luobusa massif of Tibet: Mössbauer spectroscopy studies

Applications of LA-ICP-MS in geoanalysis – New technologies and future perspectives

T. RUSKOV1*, I. SPIROV1, M. GEORGIEVA2, S. YAMAMOTO3, H. GREEN4, C. MCCAMMON5 4 AND L. DOBRZHINETSKAYA

R.E. RUSSO1,2 AND J. GONZALEZ1,2

1

Institute for Nuclear Research and Nuclear Energy, Bulgaria (*correspondence: [email protected] ) 2 University of Sofia, Bulgaria 3 Tokyo Institute of Technology, Tokyo, Japan 4 University of California, Riverside CA 92521, USA

The Mössbauer spectroscopy studies show that chromites from massive ore are characterized by Fe3+/,Fe = 0.42, and chromites from nodular and disseminated ores contain Fe3+/,Fe = 0.22, all are from a Tibetan ophiolite. The massive ores record traces of ultrahigh pressure minerals: diamond, exsolution lamellae of coesite and diopside in chromite, inclusions of metal-nitrides, SiC and Fe°, the latter indicate a strongly reducing environment. In contrast, chromites from nodular and disseminated ores contain abundant low-pressure OH-bearing mineral inclusions whose formation requires a more oxidizing environment. The high value of Fe3+/,Fe in the ‘reduced’ massive ores is explained by stabilization of Fe3+ in a high-pressure polymorph of spinel deep in the upper mantle through a mechanism such as charge coupled substitution, or creation of oxygen vacancies, accompanied by Fe disproportionation to balance charge. We suggest that the massive chromitite and their host peridotite were transported in the solid state from a highly reduced deep mantle (>300km) to an ocean spreading center. In this shallow environment they partially reacted with their host peridotite in the presence of hydrous melt, yielding the nodular and disseminated chromitite ores as proposed previously. Given that the high pressure highly-reduced mineral assemblage within the Tibetan massive chromitite is not unique, similar examinations of chromitites worldwide and high-pressure experiments on reduced Cr-rich systems should help to decipher further the missing history of the deep mantle processes that are involved in their formation.

1

Lawrence Berkeley National Laboratory, Berkeley, CA 94720 ([email protected]) 2 Applied Spectra, Inc. 46660 Fremont Blvd, Fremont, CA 94538 Advances in laser ablation sampling have allowed this technology to become mainstream in many laboratories, with most users to date in the geochemical sciences. Laser ablation provides direct solid sample chemical analysis, without requiring sample preparation or consumables and without generating waste solvents. For laboratory measurements, femtosecond laser ablation with ICP-MS can provide accuracy and precision comparable to that achieved using conventional liquid nebulization; although using much less sample than would be required for digestion [1, 2]. Current developments in laser ablation are showing promise for field use and for nanometer spatial scale resolution. The use of near-field optics or femtosecond far-field focusing can provide the ability to measure grains and grain boundaries, with sub-micron spatial resolution [3]. For field use, laser induced breakdown spectrosopy (LIBS), a laser ablation process, can be configured into in suitcase-sized, battery operated self contained system. LIBS offers the geologist the ability measure light elements (Li, Be, etc) in the field, in real time [4]. This presentation will sumarize state of the art capabilities in laboratory laser abaltion ICP-MS and field LIBS based capabilities for geoanalysis. [1] Baudelet (2009) SPIE 7214 72140-10. J Archeological Science 36 461-466. Analytical & Bioanalytical Chemistry Piscitelli (2009) Spectrochimica Acta Spectroscopy 64 147-154.

[2] Brostoff (2009) [3] Zorba (2010) 396 173-180. [4] Part B: Atomic

A894

Goldschmidt Conference Abstracts 2010

Iron isotope fractionation at the hematite-water and goethite-water interface JAMES R. RUSTAD AND DAVID A. DIXON 1

Department of Geology, University of California, Davis, Davis, CA USA 95616 2 Department of Chemistry, University of Alabama, Tuscaloosa, AB USA 35487

Density functional theory electronic structure calculations are used to compute equilibrium constants for iron isotope exchange among Fe2+(aq), Fe3+(aq), and hematite (a-Fe2O3). The hematite is represented in both bulk and surface environments. The iron-isotope fractionation between Fe2+(aq) and Fe3+(aq), determined using a range of exchangecorrelation functionals and basis sets, is in good agreement with experimental measurements. The calculated reduced partition function ratio for bulk hematite is very close to previous estimates based on Moessbauer and inelastic nuclear resonance X-ray spectroscopy. However, the calculated fractionation between hematite bulk and the aqueous species Fe3+(aq) and Fe2+(aq) differs from experimental measurements carried out at the aqueous-hematite interface. We find a heavy iron enrichment trend in the order Fe2+(aq) < hematite bulk ' hematite surface < Fe3+(aq). It is surprising that the aqueous environment is predicted to be richer in heavy iron. The reason for this is that coupling of Fe-fractionating modes to wagging motions of water molecules near 1000 cm-1 give rise to a significant increase in the predicted reduced partition function ratio for the aqueous phase, while the highest-frequency motions in hematite are below than 700 cm-1. In contrast to experimental studies, we find a significant positive fractionation (heavy enrichment) for Fe3+(aq) relative to hematite, regardless of whether the hematite is represented by a bulk or a surface model. Our calculations indicate how isotope signatures might possibly be used constrain surface structures, and indicate that it is unlikely that the aqueous interfacial structure of hematite is a simple termination of the bulk structure. Calculated goethite-water interfacial fractionations are very close to those predicted for hematitewater.

Iron isotope fractionation in the lower mantle JAMES R. RUSTAD AND QING-ZHU YIN Department of Geology, University of California, Davis, Davis, CA USA 95616 At the pressures of the Earth's lower mantle, crystalline and melt phases should preferentially take up heavy isotopes as bonds are compressed and vibrational frequencies increase. For the iron isotopes, the possibility of spin collapse may be expected to result in additional bond shortening which could further facilitate enrichment in heavy isotopes. A large fraction of the iron in the earth's lower mantle is dissolved in ferropericlase and ferroperovskite. The distinct coordination environments in these phases (6-fold versus 8-fold) and their influence on the spin state of iron would be expected to give rise to a fractionation of iron isotopes between these phases, most likely enriching heavy iron in the tighter six-fold coordination environment. In addition, during the crystallization of the mantle, these phases would have been in equilibrium with silicate melt exhibiting a variety of coordination environments for iron. Pressure effects on the fractionation will be counteracted to an unknown extent by increasing temperatures in the mantle. Using density functional theory we have calculated isotope fractionation factors between these phases to pressures and pressures near the core-mantle boundary. We find that in ferropericlase, the predicted reduced partition function ratio (RFPR) is a strong function of the spin state. In contrast, the predicted RFPR of ferroperovskite is hardly affected by the spin transition. This appears to result from the asymmetric coordination environment of intermediate and low-spin Fe in perovskite, in which some bonds are lengthened and some are shortened relative to high-spin Fe. Surpisingly the RPFR values are very similar between ferropericlase and ferroperovskite. Although the immediate Fe-O bonds are indeed weaker in the eightfold coordination site, vibrational coupling of Fe-fractionating modes to Si-O stretching vibrations at high frequency raise the RPFR for Fe in ferroperovskite, compensating for the higher coordination environment. Ab initio molecular dynamics simulations of Fe in MgSiO3 melt at lower mantle pressures give rise to a variety of coordination environments intermediate between ferropericlase and ferroperovskite. The presence of water in the melt seems to have little effect on the predicted isotopic signature.

Goldschmidt Conference Abstracts 2010

The PGE contents - !13C correlation in Native Fe(-Pt) ores, Dzhaltul, The Siberian Platform 1

1,2

V.V. RYABOV , V.A. PONOMARCHUK *, D.V. SEMENOVA1 AND A.A. LAPKOVSKY1 1

Institute of Geology and Mineralogy SB RAS, Novosibirsk, Acad. Koptyyug av., 3, Russia. 2 Novosibirsk State University, Novosibirsk, Pirogov st., 2. (* correspondence:[email protected]) Native Fe (-Pt) ores are appeared in gabbro-dolerites in the form of native iron nodules [1, 2]. The main minerals of the ores are kamacite, ferrite, cohenite and copper and the minor Ð C-containing phases: cohenite, graphite, cliftonite anthraxolite, carbonaceous matter and moissanite. PGE are presented as isomorphous admixtures in the native Fe(-Pt) ores. The direct correlation dependence between noble and base metals contents are determined in the native Fe(-Pt) ores [1, 3]. Carbon isotope composition of C-containing phases in Dzhaltul native Fe(-Pt) ores were determined using the Thermo Finnigan 253 mass spectrometer equipped with the Finnigan Elemental Analyser (EA)+ConFlo III preparation unit. In special cases of smaller sample amount, the speciallyconstructed line in combination with the Finnigan Gas Bench II were used [4, 5]. The data obtained shows weighting of $13C values among coexistent minerals in order: cohenite -30.9ä, cliftonite -25ä, anthraxolite -22.8 ä. It is interesting, that the inverse trend of $13C values were determined for coexistent Ccontaining minerals in native iron of island Disco (Greenland): -24.0ä; -26ä i n cohenite and -22ä; -28ä i n graphite [6]. The extensive study of the Dzhaltul native Fe(-Pt) ores have shown that the accumulation of platinoids in native iron is accompanied by the variable $13C values of organic matter: when PGE contents are changed from 0.08 to 8.3 ppm, $13C of organic matter increases from -27.6 ä t o-18.0 ä. The data obtained are agreed with the author's PGE formation model. The important elements of the model are: a) migration of base and noble metals in form of metalloorganic compounds; b) carbon isotope composition of reducing fluids evolved during oreformation process. The study is supported by Russian Academy Foundation (grant 09-05-12015-ofi-m and grant 09-05-00728). [1] Ryabov et al (1999) Geology and Geophysics 40, 162-174. [2] Oleinikov et al., (2000). Domectic geology 5, 21-23. [3] Ryabov et al. (2000) Magmatic formation of the NorilÕ sk region 1, 408. [4] Semenova & Ponomarchuk (2009) Geochim. Cosmochim. Acta 73,.A1193. [5] Talibova et al., (2007) Geochim. Cosmochim. Acta. 71. A997. [6] Smith et al. (1992) Lunar Planet. Sci. XXXI, 81-82.

A895

Amorphous magnesium stabilized calcium carbonate C.A. RYAN*, K. YACCATO, M. GINDER-VOGEL AND B. CONSTANTZ Calera Corporation, Los Gatos, CA, 95032, USA (*correspondence: [email protected])

Calera Process The Calera Process is focused on capturing CO2 from industrial sources (such as coal flue gasses) and sequestering it in the built environment. In order to create novel carbonate materials for cements and aggregates (two of CaleraÕ s first products) we have looked to meta-stable forms of calcium carbonate, such as amorphous calcium carbonate (ACC), vaterite, and aragonite.

Laboratory Investigation of Amorphous Carbonates During our investigation of carbonates sequestered from flue gas, we have performed laboratory experiments aimed at understanding carbonate morphology and properties. Precipitation of carbonate minerals from Na2CO3 solutions mixed with CaCl2 and MgCl2 is a proxy for process conditions of interest to Calera. The Ca:Mg ratio of these solutions can be expected to affect carbonate morphology [1]. Several Ca:Mg solution ratios were investigated which generated amorphous phases with varying stability. At Ca:Mg = 0.2, long-term stability of the amorphous material was observed, while lower ratios resulted in less stable materials.

Raman spectroscopy of the sample matches the characteristics seen in amorphous calcium carbonate observed in biological specimens [2]. TGA coupled with FT-IR evolved gas analysis of these materials demonstrates the production of H2O and CO2. Additionally, these materials will be characterized using HR-TEM. [1] Loste, et. al (2003) Journal of Crystal Growth 254, 206218. [2] Raz, et. al (2002), Biological Bulletin, 203, 269-274.

Goldschmidt Conference Abstracts 2010

A896

Integrating microbeam research instrumentation into the classroom to teach mineralogy and petrology: Outcomes

Novel continuous flow-cavity RingDown spectroscopy systems for high-precision bulk and compoundspecific 13C/12C measurements

JEFFREY G. RYAN

NABIL SAAD

Department of Geology, University of South Florida 4202 East Fowler Ave., Tampa, FL 33620, ([email protected]) A range of activities have been employed in Mineralogy and Petrology courses involving the use of analytical research instrumentation [1, 2], all dealing in different ways with the logistical and instructional challenges this entails. Using Webbased remote operation technologies, classroom access to microbeam instruments (SEM and EPMA; electron microprobe [3]) can now become routine, permitting easy integration of research activities into instruction. My students use EPMA as part of term projects examining suites of metamorphic/igneous rocks collected in the field, following a studio classroom instructional model [4]. EPMA use is introduced via lectures and whole-class participatory activities before students collect their own imagery and mineral chemistry data. Students work in teams choosing the samples to study, preparing and polishing thin sections, conducting optical petrography, and doing EPMA measurements in class during lab periods and/or scheduled times outside of class. The project seeks to measure: 1) student impressions of the experience. Three years of survey data indicate strongly positive student perceptions, as has been observed in other projects [1]. 2) Student learning of mineralogy and petrology. Pretest/post-test results using both content-specific questions and a subset test from the GCI [5] indicate overall better understanding of the course content. 3) Student interests: ~20% of students have taken a postcourse, permit-only Senior research class focused on EPMA/SEM use, and thus far five students have presented EPMA research results on metamorphic petrology at sectional GSA meetings. [1] Beane (2004) J. Geosci Ed. 52, 250-253; [2] Argast and Tennis (2004) J. Geosci. Ed. 52, 213-217; [3] www.fiu.edu/ ~emlab/home.html; [4] Perkins (2005) J. Geosci. Ed. 53, 101109; [5] Libarkin and Anderson (2005) J. Geosci. Ed., 53, 394-401.

Picarro, Inc., Sunnyvale, CA 94085 ([email protected]) Light stable isotope analysis is a valuable tool to elucidate pathways and provide a better insight into physiological, biochemical and geochemical processes. Isotope ratio mass spectrometry (IRMS) is usually used for these measurements; however, here we present the results of both bulk stable isotope analysis (BSIA) of soil organic matter (SOM) and compound-specific isotope analysis (CSIA) of short chain hydrocarbons using two novel laser-based systems: the world’s first combination of either a bulk combustion module (CM) or gas chromatography-combustion (GC-C) interface with an isotopic CO2 cavity ring-down spectroscopy analyzer (CRDS) for the measurement of 13C/12C BSIA and CSIA, respectively. CRDS is a highly sensitive optical spectroscopy technique due to a highly reflective optical cavity with many kilometers effective path length. It first measures the quantities of each isotopologue independently using their distinct ro-vibrational spectra, and then infers the stable isotopic ratios in the analyzed small molecules. The Combustion Module was interfaced to the CRDS analyzer using Liaison, an innovative multi-tasking interface that runs three operations simultaneously; it automatically collects the generated combustion gas from the current analyzed sample in one bellows for isotopic homogenezation, it diverts a second bellows’ gas content from the previous collected sample for isotopic measurement with CRDS, and it purges a third bellows with high-purity nitrogen gas in preparation for the next sample combustion and the collection of its generated gas. The SOM samples analyses using the compact and easyto-use CM-CRDS system were rapid and achieved an average precision of 0.1permil. On the other hand, using the novel GCC-CRDS system, we analyzed a mixture of methane, ethane, and propane for 13C/12C isotopic ratio without the need for water removal. Measurements were achieved with a precision of 0.95 permil or better. Compared with IRMS, the current Continuous Flow-CRDS systems are robust, simpler to operate, and could be made field-portable. We anticipate that advances in spectroscopic analysis will improve the precision of the GC-C-CRDS isotopic measurements, making it comparable with CM-CRDS.