An experimental study of the diffusion of C and O in calcite in ...

Goldschmidt Conference Abstracts 2010

A553

An experimental study of the diffusion of C and O in calcite in

mixed CO2-H2O fluid T.C. LABOTKA1*, D.R. COLE2, M.J. FAYEK3

AND T. CHACKO4 1Department of Earth and Planetary Sciences, University of

Tennessee, Knoxville, Tennessee 37996-1410

2Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6110

3Department of Geological Sciences, University of Manitoba, Winnipeg MB R3T 2N2

4Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton AB T6G 2E3 The diffusivity of C and O in calcite in mixed CO2–H2O

fluid was determined over the range in xCO2 from 1.0 to about 0.2 primarily at 700 °C, 100 MPa, with selected experiments conducted at pressures to 250 MPa and temperatures of 600 and 800 °C. The diffusivity of C, DC, varies little with xCO2, although there is some evidence for a slight increase in DC from ~ 5 ! 10–18 to ~ 5 ! 10–17 cm2/s with decreasing xCO2. Despite the large uncertainty, we observed that DO increases from ~ 2 ! 10–16 to ~ 5 ! 10–14 cm2/s with xCO2 decreasing from 1.0 to 0. There is a good correlation at 700 °C between log DO and log fH2O regardless of the total pressure, matching the observations of previous workers. The data are consistent with a simple model for the diffusion of O in calcite with two components in the fluid phase, one for diffusion in the presence of CO2 and one for the presence of H2O: DO = DO

CO2 + DO

H2O aH2O. The activity of H2O is relative to the fugacity at 100 MPa, 700 °C. DO

CO2 is 3.45 ! 10–16, and DOH2O

is 3.8 ! 10–14 cm2/s. The model implies that there is little dependence of the diffusivity on pressure over the range investigated. With this model and the values of DO in pure CO2 and in pure H2O, the value of DO is predicted over the temperature range 600--800 °C and pH2O up to 300 MPa, the range of the data. Calculated closure temperatures for O-isotope exchange between calcite and fluid are reduced by about 150 °C in the presence of an aqueous fluid (figure).

Particulate matter pollution: An environmental magnetism study with biological collectors in urban

areas of Northern Portugal M.J. LACERDA1, H. SANT’OVAIA1* AND C.R. GOMES2

1Centro de Geologia da Universidade Porto, DGAOT, FCUP, R Campo Alegre, 4169-007 Porto, Portugal (*correspondence: [email protected])

2CGUC, DCT, Universidade de Coimbra, Portugal This work presents an evaluation of the pollution levels in

plant leaves from five selected sites, 4 in urban areas (2 zones in Porto, 1 in Valongo and 1 in Braga towns) and one in a rural area. An environmental magnetism study was used with particle biological collectors, leaves from Nerium oleander, Quercus spp., Tilia spp. and Platanus spp. The sampling was conducted in July, August, October, November and December 2009 and January 2010. A total of 34 samples was obtained. Magnetic parameters, low-field magnetic susceptibility (") and isothermal remanent magnetization (IRM) determinations, were used to indicate the source of the magnetic particles.

The magnetic susceptibility (") values are comprised between 2.54 and 17.17 E-8 m3kg-1 in Porto, 3.78 and 5.70 E-8 m3kg-1 in Braga, 2.85 and 8.28 E-8 m3kg-1 in Valongo and, finally, between -0.66 and -0.21 E-8 m3kg-1, in the rural area. The town of Porto shows the higher " comparing to Braga and Valongo. The samples of the rural area showed always negative values of " and very low values of IRM1T. The values of IRM1T, measured for the Tilia spp. in Porto and in the rural area have a relationship 9.92:1.00. In Porto, when comparing neighbouring trees of different species (Platanus spp, Quercus spp. and Nerium oleander) in the same area, the highest values of " are always obtained in the Quercus leaves. A comparison of the values of " for the different months shows that in the month of December, these values are, on average, higher. In November, compared with October, there was a decrease of ", which can be explained by the rainfall which had the effect of removing particles from the leaves. In January, it seems to have had an increase of ", although the sampling had been limited to evergreen species. The average values of S-300 was 0.96 (N=26), indicating the presence of ferrimagnetic particles magnetite-like. The values of S-25 (mean=0.27, N=26) were consistent with the presence of particles with a PM10 diameter. The results pointed out the contrast between areas with high traffic and the countryside. We come to the conclusion that Quercus leaves showed a higher efficiency to accumulate particles than the Platanus leaves.

Goldschmidt Conference Abstracts 2010 A554

Hg stable isotopes in human hair as a tracer for dietary Hg exposure

LAURE LAFFONT1, JEROEN E. SONKE1, LAURENCE MAURICE1, YUBA S. BACCAREZA2

AND PHILIPPE BEHRA3 1Univ. de Toulouse, UPS, CNRS, IRD, LMTG, France 2Universidad Mayor de San Andrés (UMSA), La Paz, Bolivia

3Univ. de Toulouse, INPT, INRA, LCA, ENSIACET, France Since mercury (Hg) and methylmercury (MMHg) toxicity

for humans is known, scientists try to evaluate its impacts on health. Dietary MMHg exposure, via food comsumption of marine and freshwater fish, can be evaluated by hair Hg analysis. However, populations exposed to elevated atmsopheric Hg° levels, such as goldminers, may have important respiratory Hg uptake. In addition inorganic Hg° can also be adsorbed at the hair surface. In this study, we use speciation analysis to evaluate inorganic Hg and MMHg concentrations in hair and isotopic analysis of Hg to trace sources of MMHg. Different people from the Beni River basin in Bolivia were studied: native gold-miners, alluvial gold-miners and indigenous people. Native gold-miners do not eat fish while alluvial gold-miners and indigenous people do. For comparison, hair of European colleagues with a dominant marine fish MMHg exposure were also analyzed.

Hg speciation analysis, by species-specific isotope dilution GC-ICPMS show that the percentage of MMHg in human hair varies between 60 and 90% in native people and Europeans and between 10 and 93% in gold-miners. These results show presence of inorganic Hg adsorbed on hair surface. Variations in total Hg stable isotopic composition measured by cold-vapor MC-ICPMS reveal large variations in #2°2Hg (relative to NIST 3133) and $2°1Hg respectively between —0.87‰ and +0.19‰ and +0.04‰ and +0.99‰ for gold-miners hair. Native people hair have homogenous isotopic signatures; #2°2Hg=+1.18±0.24‰ (2SD, n=10) and $2°1Hg=+0.25‰ close to average $2°1Hg of the Beni basin fish. Europeans hair present #2°2Hg between +1.87‰ and +2.59‰ and $2°1Hg between +0.55‰ and +1.02‰ which is close to published marine fish #2°2Hg and $2°1Hg. Previously we showed that absorption of MMHg via fish consumption is followed by metabolic MDF of +2‰ of #2°2Hg for hair [1].

Three types of Hg exposure for gold-miners can be deduced from combined MDF/MIF signatures: Hg adsorbed on hair surface from vapor Hg (0), MMHg from local Beni basin fish consumption and MMHg from imported marine fish. Combined Hg isotopic and speciation analysis emerges as a powerfull tool to trace sources of human Hg exposition.

[1] Laffont, L. et al. (2009) Environmental Science & Technology 43, 8985–8990.

Influence of CO2 on New Albany Shale composition and pore structure

R.W. LAHANN, M. MASTALERZ* AND J.A. RUPP Indiana Geological Survey, Indiana University, 611 North

Walnut Grove Ave., Bloomington, IN 47405-2208, USA (*correspondence: [email protected]) To determine the possible influence of CO2 on the pore

structure and mineralogy of the New Albany Shale (Devonian-Mississippian), experiments were conducted utilizing Indiana shale samples of varying total organic carbon content under various conditions. After the shale samples were heated as high as 150°C in Teflon-lined high-pressure reaction cells with either distilled water or NaCl brine and CO2, the reaction products were characterized by mesopore and micropore analysis, X-ray diffraction and scanning electron microscope analysis of the shale residue, and fluid chemistry analysis of the reactant brine. Results from CO2-saturated shale and distilled water showed no changes in shale pore structure relative to shale samples without CO2 surface saturation. A second series of experiments was run at 80°C, using 50, 000 ppm NaCl brine, 60-mesh ground shale (2:1 by mass), and varying amounts of solid CO2 (dry ice). The pressure in the reaction cells was controlled by the partial pressure of CO2 and ranged from 100 to 3500 psi (0.69 to 24.13 MPa). Post-reaction brine samples showed up to thousands of ppm of K, Mg, and Ca in solution. The concentration of Ca and Mg in the brine tended to increase in proportion to the increasing partial pressure of CO2. The same experiments using chips of shale from the New Albany Shale showed lower concentrations of the cations in solution, but displayed a similar pattern of elevated increasing Ca and Mg with increasing CO2 pressure. Scanning electron microscope examination of the shale chips confirmed the dissolution of carbonate-mineralized biogenic structures in the shale.


A555

Bacterial biogeochemistry revealed by submicron X-ray fluorescence

spectroscopy B. LAI*

X-ray Science Division, Argonne National Laboratory, Argonne, IL 60439, USA (*correspondence: [email protected]) The microenvironment around actively metabolizing

bacteria can be significantly different from the bulk environment, with steep chemical gradients developed over very short distance. Submicron x-ray fluorescence (XRF) microprobes are ideally suited for studying the local chemistry and elemental distribution at or near the microbe-mineral interface. Investigations have ranged from the respiratory role of mixed-valence intracellular Fe granules formed in Shewanella putrefaciens [1], formation of extracellular UO2 nanoparticles by Shewanella oneidensis [2], increased resistance of surface adhered Pseudomonas fluorescens to Cr (VI) [3], to mechanisms of gold biomineralization in Cupriavidus metallidurans [4]. These x-ray microprobe analyses, together with high resolution electron microscopy, have revealed the remarkable respiratory versatility and sophisticated metal regulation mechanisms developed by bacteria. These studies were made possible because XRF microprobes offer high elemental sensitivity (attogram), high resolution (150 nm), high penetration power (through whole cells and fluid layer), and spectroscopic capability (µ-XANES). Currently minimal sample preparartions are required, but as the spatial resolution improves, possibly approaching 20-30 nm in the near future, radiation damage will be the main limiting factor and strategies for cryogenic sample handling will need to be considered.

[1] S. Glasauer et al. (2007) Appl. Environ. Microbiol. 73, 993–996. [2] M.J. Marshall et al. (2006) PLoS Biol. 4, 1324–1333. [3] K. M. Kemner et al. (2004) Science 306, 686–687 (2004). [4] F. Reith et al. (2009) Proc. Natl. Acad. Sci. of the USA 106, 17757–62.

XPS results pertaining to the applications of nanomodified

vermiculite T. LAIHO1*, O. EKLUND2, A. SHEBANOV3

AND V.N. RUDASHEVSKY4

1Lab. of Materials Science, Department of Physics and Astronomy, University of Turku, Finland (*correspondence: [email protected])

2Department of Geology, University of Turku, Finland

3GeoSmart, St. Petersburg, Russia

4CNT Mineral Consulting Inc., St. Petersburg, Russia

Background A research group at the University of Turku has developed

a new simple nanomineralogical method for removing ammonium ions from waste waters. This novel method is based on modified vermiculite mineral obtained in result of high-tech manipulations with the crystalline lattice.

Method

X-ray photoelectron spectroscopy (XPS) was used to perform a chemical characterisation of the chemically treated samples of nanomodified vermiculite. It is a method for analysing elemental composition and chemical states of atoms. Because of its applicability for chemical analysis, the method is also called ESCA (Electron Spectroscopy for Chemical Analysis). Discussion of Results

We have studied absorption on nanomodified vermiculite in different chemical environments. We now report studies concerning ammonium ion sorption from ammonium acetate solution, urine and waste water.

XPS is our main analysis method. Elemental composition before and after chemical treatment is reported and detailed chemical analysis of samples is peformed based on the analysis of XPS spectra. The O 1s, Si 2p, Al 2p and Mg 2p photoemission lines are presented in detail and N 1s and other photoemission lines resulting from absorption products are analysed. Flow injection analysis (FIA) method is used to complete time-dependent quantitative analysis.

Time-dependence, effect of other than ammonium ions and tempereture-dependence are considered and results are presented.


Imaging nanoparticle transport with magnetic resonance imaging

LAKSHMANAN SUSITHRA1, W.M. HOMES2, W.T. SLOAN3 AND V.R. PHOENIX1

1Department of Geographical and Earth Sciences, University of Glasgow, G12 8QQ, UK ([email protected])

2Wellcome Surgical Institute, University of Glasgow, UK ([email protected])

3Department of Civil Engineering, University of Glasgow, UK ([email protected]) While most renowned for its use in medicine, magnetic

resonance imaging (MRI) has tremendous potential in the study of environmental processes. Its ability to non-invasively image inside materials that are opaque to other imaging methods is a particular strength. MRI has already been used, for example, to study fluid flow in rocks and image mass transport and biogeochemical processes in biofilms [1-4]. Here, we report on the application of MRI to image nanoparticle transport through porous geologic media. Commercially available paramagnetically tagged nanoparticles are used; the paramagnetic tag making the nanoparticle visible to MRI. In this study, packed columns of quartz or marble based gravels or sands were first imaged to check their suitability for MR imaging. The paramagnetic nanoparticle GadoCELLTrack (BioPAL), was then prepared and pumped through the sand/gravel column. MR images were collected as the nanoparticle solution was transported through the system. These images can be calibrated to provide fully quantitative maps of nanoparticle concentration at regular time intervals throughout the column. Such data can be used to help develop models of nanoparticulate transport.

[1] Holmes, Packer (2003) Magnetic Resonance Imaging 21, 389–391[2] Seymour et al. (2004) Journal of Magnetic Resonance 167, 322–327 [3] McLean et al. (2008) ISME, 2, 121–131 [4] Phoenix et al. (2008) Appl. Environ. Microbiol, 74, 4934–4943

Geochemistry, Sr-Nd isotope abundances and magnetic studies in

some Deccan basalts and their bearing on mixing processes

T. LALA1, S.K. PATIL, D.K. PAUL AND A.K. CHAUDHARY

1([email protected]) The Deccan Volcanic Province predominantly consists of

tholeiitic flows and dykes. The flows attain a thickness of about 1.2 km in the western part but the thickness decreases towards east. The mafic dyke swarms occur in abundance in the western, central and northern parts of the volcanic province. The dykes are medium to coarse grained, porphyritic with phenocrysts of clinopyroxene (Wo31-39 Fs14-25 En42-46), plagioclase (An 43-78) set in a groundmass of clinopyroxene (Wo28-39Fs21-54En17-39), plagioclase (An 63-65), olivine and opaque minerals.

We present new isotope data (Nd, Sr) and other geochemical data on some mafic dykes from the easternmost part of Deccan Volcanic Province (DVP).The mafic dykes have a restricted composition in the basaltic field. Because of restricted composition, it is difficult to relate the flows to the dykes. The rare earth element abundances of the dykes are similar to some important dyke swarms of the western part and the eastern dykes. The elemental abundances of some incompatible elements and a weak Eu anomaly suggest fractionation-induced effects. Initial 87Sr/86Sr ratios in the mafic dykes vary from 0.704625 to 0.806359 and 143Nd/144Nd varies from 0.512629 to 0.513382. The !Nd values of the dykes are positive varying from +1.46 to +16.1. The Sr, Nd isotopic data do not conform to any of the fields established for the Deccan stratigraphic formations of the Western Ghats, but form a flat array in a 87Sr/86Sr vs !Nd plot. The high Sr and Nd isotopic ratios of the dykes, perhaps accentuated during long distance magma migration, require complex contamination of a depleted source with an unusual enriched crustal component. Magnetic susceptibility and IRM measurements revealed that titano-magnetite was the major magnetic mineral in the samples. Detailed AF and thermal demagnetizations on oriented samples yielded ChRM directions which were similar to those of the Deccan super Pole.


A557

Transition element abundances in Banded Iron Formations record the

Great Oxidation Event STEFAN V. LALONDE*, ERNESTO PECOITS AND

KURT O. KONHAUSER Department of Earth and Atmospheric Sciences, University of

Alberta, Edmonton, AB, T6G 2E3, Canada (*correspondence: [email protected]) Banded Iron Formations, ancient marine deposits

originally consisting of iron- and silica-rich chemical sediments, preserve a record of the evolution of seawater by shifts in their composition over time. The Great Oxidation Event some 2.4 – 2.2 billion years ago (Ga) is recorded in the BIF rock record by dramatic excursions in the abundances of certain redox-sensitive trace elements such as molybdenum, chromium, and copper. In this work we present data from new analyses of BIF as well as from an extensive literature compilation, all of which point towards profound changes in the supply of redox-sensitive trace elements coincident with the first accumulation of free oxygen in Earth’s atmosphere. Banded iron formations deposited prior to the Great Oxidation Event generally possess very low abundances of molybdenum and chromium, in accordance with the low mobility of these elements under anoxic or reducing conditions. Approximately concomitant with independent evidence for the first appearance of free oxygen circa 2.5 Ga, the abundance of these elements in BIF increases dramatically as they became increasingly mobile at Earth’s surface as the result of oxidation processes. The BIF record is not entirely straightforward, however; some non-redox-sensitive trace elements also show excursions at this time. Related proxies (e.g. black shales) should provide much needed additional insight into this enigmatic period of Earth’s history.

Mineral surfaces in prebiotic polymerization

J-F. LAMBERT Laboratoire de Réactivité de Surface, Univ Pierre et Marie

Curie, 4 Pl. Jussieu, 75252 PARIS CEDEX 05, France ([email protected]) The formation of biopolymers from preexisting small

biological molecules (e.g. peptides from amino acids, or RNA from nucleotides) is likely to have been one of the key steps in the emergence of life. Polymerization reactions, being thermodynamically unfavorable in aqueous solutions, cannot have taken place in a ‘primordial soup’. The most likely alternate scenarii include chemistry in hydrothermal fluids, chemistry in the adsorbed state or a combination of both.

Here we focus on amino acids (AAs) polymerization after adsorption on oxide minerals such as clays, silica, alumina or titania. Both the adsorption step and the subsequent polymerization can now be studied in detail by a combination of macroscopic and molecular-level information.

The analysis of AA adsorption isotherms, together with the application of in situ spectroscopic techniques, reveals that several different adsorption mechanisms must be envisaged accoridng to the system under consideration: in addition to straightforward electrostatic adsorption, which depends on the acido-basic speciation of the surface and the AA, instances of coordinative binding to surface cations, and of specific H-bonded adducts, are well documented.

Regarding polymerization, it has long been known empirically that wetting-and-drying cycles cause the formation of oligopeptides from adsorbed AAs in many systems, but only recently has this phenomenon been studied in molecular detail by TG, vibrational spectroscopies and solid-state NMR.

Most probably, the solution to the thermodynamic problem lies simply in the possibility of working under very low water activity during the drying step, since water is a product in the peptide bond formation reaction.

However the surface also plays a more specific role in controlling the kinetics of peptide bond formation. Here an application of Sabatier’s principle can be observed sinc the strength of the AA/surface interaction must be ‘just right’ for efficient surface catalysis to occur: this apparently involves the formation of well-defined H-bonding networks between the AA and surface groups such as silanols. Models of H-bonded structure have been proposed in recent DFT studies. Thus, our understanding of prebiotic polymerization processes is progressing and shows that a rich chemistry is operating in biomolecules/mineral surfaces systems.


Timing of metamorphism and extension in the western Himalaya:

Leo Pargil dome, NW India J. LANGILLE1*, M. JESSUP1, J. COTTLE2, G. LEDERER2

AND T. AHMAD3 1University of Tennessee, Knoxville, TN 37996, USA

(*correspondence: [email protected])

2University of California, Santa Barbara, CA 93106, USA

3University of Delhi, Delhi -110007, India The Himalayan orogen is the product of significant crustal

shortening and thickening that has occurred since the Eocene and has resulted in major fault systems, such as the Main Central thrust zone and South Tibetan detachment system which accommodated crustal shortening from the Eocene to middle Miocene. In contrast to these older structures, the Leo Pargil Dome, NW India, is a 30-km-wide, northeast-southwest trending antiformal structure bound by normal faults [1] that are interpreted to record the onset of orogen parallel extension in this convergent setting [2, 3].

The Leo Pargil dome is composed of amphibolite facies rocks intruded by multiple generations of variably deformed to undeformed leucogranite dikes and sills. In the deepest structural positions, the injection complex transitions into migmatitic gneiss. The northwest-dipping, 300-m-thick Leo Pargil shear zone records top-to-the-northwest normal-sense shear and separates footwall rocks on the western side of the dome from the low-grade Tethyan Sedimentary sequence in the hanging wall.

New pressure-temperature-time data from the Leo Pargil shear zone and the hanging wall were calculated using THERMOCALC. These data suggest that Barrovian metamorphism occured at ~640 °C and 0.7 GPa in staurolite grade hanging wall rocks. Syn-kinematic staurolite growth during top-to-the-northwest shear on the Leo Pargil shear zone occured at ~590 °C and 0.8 GPa. Monazite U-Th-Pb ages suggest Barrovian metamorphism occurred during the late Eocene to Early Oligocene. Staurolite growth during top-to-the-northwest shear on the Leo Pargil shear zone occured during the late Oligocene. This was followed by injection of multiple generations of leucogranite in the footwall during the early Miocene [4]. These data provide new constraints on the transition from crustal thickening to melting and exhumation in the NW Himalaya.

[1] Thiede et al. (2006) GSA Bulletin 118, 635"650. [2] Jessup et al. (2008) Geology 36, 587"590. [3] Murphy et al. (2002) GSA Bulletin 114, 428–447. [4] Lederer et al. (2010) Geochimica et Cosmochimica Acta, this volume.

Planetary evolution CHARLES H. LANGMUIR

Earth and Planetary Sciences, Harvard University, Cambridge MA 02138 ([email protected])

Planetary evoluton relates life, ocean, atmosphere and

planetary interior. One asepct is progressively increasing biological access to energy, which may provide a directionality to evolution. Earth began with reduced interior and exterior, and limited energy potential between reservoirs. Reduced external conditions were necessary for the origin of life. A series of energy revolutions changed the oxidation potential of the planet by generating oxidized and reduced reservoirs that form a ‘planetary fuel cell’ that powers modern life and surface processes. First autotrophy, then oxygenic photo-synthesis enhanced the productivity of the biosphere. Storage of organic matter led to gradual rise of oxygen, permitting aerobic respiration that increased energetic productivity by a factor of 18 and led to eukaryotic cells. Continued O2 production overcame the reduced sinks at the surface to create the global fuel cell with reduced reservoirs of Earth’s interior and organic carbon, and oxdized reservoirs in the ocean and atmosphere. Multicellular life evolved to take advantage of this energy potential. The rise of free O2 required lessening the oxygen sinks through progressive oxidation of reduced surface reservoirs. O2 in the atmosphere is trival compared to the vast reservoirs of oxidized Fe and S that have supplied most of the electrons to make organic matter. There is a mass balance problem that more oxidzed atoms than reduced carbon reside at the surface. From mass balance alone, the mantle cannot have become more oxidized over time because it would worsen the mass balance problem, and the mantle’s reduced Fe reservoir is too large. Subduction of reduced carbon is inevitable, particularly in the reduced ancient oceans, and may be the missing reduced reservoir. Today, more oxygen is subducted in the ocean crust than is formed by net organic matter burial. Change in the oxidation of ocean crust owing to the oxidation state of the deep ocean may provide a modern buffer for the oxyenated Earth.

The latest energy revolution is human civilization, which has enhanced energy access by 20-100 times relative to aerobic metabolism. The human energy revolution currently uses the stored solar energy in the planet’s fuel cell, and ultimately will access stellar energy directly through fusion. This is a new stage of planetary evolution equivalent to the invention of aerobic metabolism, and marks a new planetary era. As with other energy revolutions and era boundaries, catastrophe is possible. Only if planets are able to surmount such a crisis are there civilizations elsewhere in the galaxy.


A559

Binding of arsenic to natural organic matter in a minerotrophic peatland

P. LANGNER, C. MIKUTTA* AND R. KRETZSCHMAR Institute of Biogeochemistry and Pollutant Dynamics, ETH

Zurich, Switzerland (*[email protected]) In soils and sediments, arsenic (As) is known to be

effectively immobilized by metal-(hydr)oxides under oxidizing, and sulfide minerals under strongly reducing conditions. Recently, the binding of As to natural organic matter (NOM) has been proposed for organic soils depleted in metal-(hydr)oxides. However, direct spectroscopic evidence for this sequestration mechanism is still lacking. In order to investigate the role of NOM for As sequestration, we studied the speciation of As and iron (Fe) in a natural As-enriched peatland in southern Switzerland.

Sampled peat cores were shock-frozen in the field and kept anoxic in order to prevent speciation changes of redox-sensitive elements. The peat contained up to 950 g kg-1 NOM and 1.8 g kg-1 As (dry weight basis). Iron and sulfur (S) concentrations ranged between 3 to 60 and 0.03 to 40 g kg-1, respectively. Enrichments of As were found either within the top 0.2 m, or at depths between 1.5 and 2.8 m. The speciation of As and Fe was investigated by bulk As and Fe K-edge X-ray absorption spectroscopy at 77-80 K.

Based on linear combination fitting, we found significant differences in Fe and As speciation as a function of sampling depth. While in the upper parts Fe(III)-(hydr)oxides represented the major Fe species, the deeper peat layers were dominated by pyrite. Speciation analyses of As indicated that close to the peat surface, As was mainly present in the form of realgar, whereas in the lower part of the peat profiles, As(III) was predominantly coordinated to S atoms of NOM. The extended X-ray absorption fine structure of As in these samples closely resembled that of As(III) bound to cysteine residues in which As is coordinated to three S atoms at a distance of 2.20 to 2.25 Å [1-3]. This S-bound As fraction accounted for up to 88% of the total As in the peat.

Our results document that the sorption of As by particulate NOM can be regarded as a potent sequestration mechanism under sulfate reducing conditions. These observations represent a great step forward in our understandings of the potential mobility and toxicity of As in waterlogged environments enriched in NOM.

[1] Shi et al. (1996) Biol. Chem. 271, 9291–9297. [2] Bhattacharjee & Rosen (1996) Biol. Chem. 271, 24465–24470. [3] Martin et al. (2001) Structure 9, 1071–1081.

Prospects for nanoscale, hard x-ray studies of extraterrestrial materials A. LANZIROTTI1*, S.R. SUTTON1,2 AND G.J. FLYNN3

1Center for Advanced Radiation Sources, University of Chicago, Chicago Il 60637 USA (*correspondence: [email protected])

2Department of Geophysical Sciences, University of Chicago, Chicago, IL 60637 USA

3Department of Physics, SUNY-Plattsburgh, Plattsburgh, NY 12901 USA Analyses of the many primitive extraterrestrial materials

available are challenged by extreme heterogeneity at the smallest observable scales and limited sample masses. These materials include interplanetary dust particles (IDPs) harvested from the stratosphere and microparticles collected by the Stardust spacecraft during flyby of the Wild-2 comet. These particles range in size from a few tens of micrometers down to a few hundred nanometers and below. In the case of the Stardust cometary particles, the particles were largely aggregates of sub-micron components which gradually disintegrated upon penetrating the aerogel collection substrate.

Spatially-resolved x-ray analyses, such as x-ray fluorescence (XRF), x-ray absorption fine structure (XAFS), x-ray diffraction (XRD) and computed microtomography (CMT), are extremely valuable in studying such materials, providing chemical and physical state information in a largely non-destructive manner, leaving the samples available for additional study by complementary methods, such as spatially-resolved mass spectrometry (e.g. SIMS). Hard x-rays can also allow analyses with the samples still within their collection media, for example, in the case of the aerogel collected comet dust.

One challenge has been achieving appropriate spatial resolution with these x-ray methods. Soft x-ray (<1 keV) approaches, such as scanning transmission x-ray microscopy (STXM), routinely achieves tens of nanometers resolution allowing, for example, carbon speciation mapping. But, hard x-ray (>4 keV) approaches have generally been limited to the micrometer resolution. That situation is improving with more use being made of the few, currently existing higher resolution hard x-ray microprobes for this purpose. In addition, the advent of new x-ray sources and advances in x-ray optics will allow the spatial resolution of these hard x-ray instruments to be pushed to below the 100 nm regime. Higher spatial resolution is also advantageous for research on fine-grained, poly-mineralogic matrices that occur in larger meteorites.


Hybridized mantle sources of shergottites and ALH 84001

THOMAS J. LAPEN1 AND ALAN D. BRANDON2

1University of Houston, Houston, TX 77204-5007 ([email protected])

2University of Houston, Houston, TX 77204-5007 ([email protected]) Shergottite source 176Lu/177Hf and 147Sm/144Nd ratios span

a range of 0.028 – 0.052 and 0.18 – 0.28 [e.g. 1-5], respectively, reflecting variable mixtures of enriched and depleted mantle source components. Source 176Lu/177Hf and 147Sm/144Nd ratios of ALH 84001 (ALH), calculated for the measured Lu-Hf age of 4.091 Ga, are 0.018 and 0.172, respectively [2]. Although ALH is distinct both in age and lithology, it’s source is derived from a mixture of the same depleted and enriched components that produced the shergottites indicating that these same or similar mantle source materials produced magmas for nearly 4 billion years [2]. Furthermore, calculated source compositions of ALH indicate that it is derived from a source that has the highest proportion of the enriched component relative to recognized shergottites, thus better constraining the composition of this end-member.

To explain the formation of the mantle sources, we adopted a magma ocean crystallization model of [4]. The cumulate phases and trapped liquid in equilibrium with cumulate phases of the 200-750 km deep crystallizing section correspond to the depleted and enriched mantle components, respectively. This hybridized mantle source model does not require very late stage residual liquids after magma ocean crystallization (perhaps similar to lunar KREEP basalt sources) nor assimilated crustal components as an enriched end-member lithology.

Based on this magma ocean crystallization model and the 142Nd/144Nd – 143Nd/144Nd isotope systematics of shergottites and ALH [5], the average 147Sm/144Nd ratio of their integrated mantle source is ~0.225. It is important to note that this modeled mantle source represents only about 30% of the silicate portion of the planet making constraints on bulk-planet Sm/Nd ratios difficult. It is possible that primordial crust and uppermost mantle that developed during the last stages of magma ocean crystallization may account for the enriched component not sampled during partial melting of shergottite sources.

[1] Borg & Draper (2003) MAPS 38, 1713–1731. [2] Lapen et al. (In Review). [3] Borg L. et al. (2003) GCA 67, 3519–3536. [4] Debaille V. et al. (2008) EPSL 269, 186–199. [5] Debaille V. et al. (2007) Nature 22, 525–528.

Mechanisms influencing hydrate dissolution rates in undersaturated

systems: Lessons from field observations and laboratory results

L.L. LAPHAM1, R.M. WILSON1*, R.T. SHORT2, R. BELL3 AND J.P. CHANTON1

1Florida State University, Tallahassee, FL 32306 ([email protected], *correspondence: [email protected], [email protected])

2SRI International Marine Technology Program, St. Petersburg, FL 33701 ([email protected])

3University of South Florida, Tampa, Fl 33620 St. Petersburg, FL 33701 ([email protected]) Methane is a potent greenhouse gas, twenty times more

infrared-active than CO2, and an important energy source. For these reasons, methane hydrate, one of the largest potential reservoirs of methane on earth, is of considerable interest to scientists and industry alike. In particular, questions relating to the stability of methane hydrate are becoming more important as concern about the release of methane into overlying ocean (and eventually the atmosphere) and interest in the recovery of methane from this resource increase. Hydrates are stable under predictable temperature, pressure, and salinities under methane saturated conditions. When conditions are not favourable, methane hydrate should dissociate or dissolve into the surrounding water. Measurements made in situ of shallow buried hydrates indicate that surrounding waters are not methane-saturated. Although undersaturated conditions should favor rapid dissolution of the hydrate, observations indicate little apparent change in these formations over years. We are interested in examining the factors that contribute to hydrate stability in natural conditions allowing them to persist in undersaturated environments. We hypothesized that the presence of mixed-gas hydrates may be stabilizing these structures. To test this, we used laboratory measurements of methane concentration gradients near artificial hydrate to evaluate the dissolution rates of mixed-gas hydrate and pure methane hydrate. Our second hypothesis was that the presence of microbial biofilms or oil may be slowing methane hydrate dissolution in natural environments by increasing the boundary layer. We will present the results of our mixed-gas and methane hydrate dissolution rate observations and report on experiments examining the influence of protective oils on artificial hydrate stability.


A561

Ge-bearing minerals in rocks and ores of native iron from Dzhaltul

intrusion (Siberian platform) A.A. LAPKOVSKY* AND V.V. RYABOV

V.S. Sobolev Institute of Geology and Mineralogy SB RAS, Novosibirsk 630090, Russia (*correspondence: [email protected]) There are two types of native iron in the Dzhaltul

intrusion: ellipsoidal nodules in taxitic gabbro-dolerite, where native iron form sponges, and fine disseminations with graphite in dyke-like bodies of dolerite, which cut gabbro-dolerite [1, 2].

Ge is contained isomorfically into native iron, up to 0.15 wt.%. Ge content in tanite can reach 0.63 wt.% [1].

At the external contacts of dyke-like bodies of dolerite we found a unique association of tanite – wairauite (CoFe) - NiFeCo-alloy – cobaltpentlandite - orcelite (Ni4,77As2) – cabriite and determined; we also found that Ge content in tanite can vary from 1.02 to 1.15 wt.%, NiFeCo-alloy - from 0.58 to 1.28 wt.% and orcelite - from 0.89 to 1.03 wt.%. Grain sizes of these minerals range from 3 to 40 µm.

Also, in association with heazlewoodite we found a new phase of the following composition (wt. %): Ni – 65.44; Fe – 3.71; Cu – 5.03; Ge – 16.65; S – 8.8; Sb – 0.56. This mineral (Ni4,43Cu0,31Fe0,26)5 (S1,09Ge0,91)2 form an angular grain in pyroxene, size 16#27 µm. This phase is the first finding of high-Ni sulfogermanide, unlike the well known high-Cu minerals (renierite, germanite, maikainite et al.).

Our studies show that Ge content in native iron ores varies from 0.1 to 51.8 ppm. There is a direct correlation between native iron ores and As-Ge-Ni-PGE [2, 3]. The location of Ge-bearing minerals with graphite and other rare minerals allowed us to suggest that they formed as the result of dissociation of hetero-organic compounds (HOC). The dyke-like bodies were a channel for reduced fluids of complex composition. Volatile HOC dissociated at a geochemical barrier being host taxitic gabbro-dolerites.

This study was supported by RFBR Grant# 09-05-12015-Ofi_m.

[1] Oleinikov et al. (1985) Native iron formation in platform basic rocks (in Russian). [2] Ryabov et al. (2000) Magmatic formations of the Noril’sk region (in Russian). [3] Ryabov & Anoshin (1999) Geology & Geophysics 40.

Stable oxygen isotope measurements of arsenic and selenium oxyanions

P. LARESE-CASANOVA* AND R.E. BLAKE Department of Geology and Geophysics, Yale University,

P.O. Box 208109, New Haven, CT 06520 USA (*correspondence: [email protected]) Stable oxygen isotope ratios may be useful indicators of

aqueous metal and nonmetal oxyanion transformations because their oxidation, reduction, and exchange reactions involve bond-breaking and bond-forming between the central metal and peripheral oxygen atoms, leading to kinetic or equilibrium isotope effects. This study is evaluating whether stable oxygen isotopes within arsenic and selenium oxyanions are sensitive to physical, chemical, and microbial transformations and whether specific transformation processes produce unique isotopic signatures.

Analytical methods have been developed for measuring #18O values of oxygen within arsenic and selenium oxyanions. Aqueous arsenate, arsenite, selenate, and selenite oxyanions are precipitated as silver or barium salts and pyrolized at 1450 °C during TCEA-GC-IRMS analysis. Current precisions for barium salts of selenium are less than 0.2 ‰. #18O values are being monitored for O exchange reactions with water, oxyanion sorption to minerals, microbial respiration, and abiotic redox transformation. Our preliminary results confirm that arsenate exchanges O with H2O somewhat rapidly (half-life of <1 day), and this equilibrium process would likely override any kinetic isotope effect resulting from physical or chemical transformations.


Source rocks for sediment-hosted orogenic Gold deposits

R.R LARGE AND L.V. DANYUSHEVSKY CODES, University of Tasmania, Hobart, TAS, Australia

([email protected]) Currently accepted ore genesis models for orogenic gold

deposits consider that the gold is sourced from deep below the deposits, in the lower crust or mantle, and transported upwards, along major crustal fractures or shear zones, during metamorphism and deformation, to become concentrated in second order structures during the peak, or post-peak, of metamorphism. However, recent LA-ICPMS studies of pyrite in a number of gold provinces (Victoria Australia, Sukhoi Log Siberia and Carlin Nevada) supports a two-stage process of gold ore genesis in these districts. The first stage involves development of favourable source rocks, by pre-concentration of gold and arsenic during sedimentation and diagenesis in black mudstone facies of continental margin sedimentary basins. In the sediments, the gold is present as either, invisible gold trapped in diagenetic arsenian pyrite or, micro-nuggets (< 2 microns) of free gold associated with fine-grained clays and organic matter. These gold-bearing, organic-rich, sedimentary rocks are also enriched in a characteristic suite of elements, particularly V, As, Mo, Se, Te, Ni, Ag, Zn and Cu. Gold contents of these source rocks commonly range from 5 to 100 ppb, with arsenic from 10 to 100 ppm, and organic carbon from 0.2 to 2 wt %.

The second stage, of the two-stage process, occurs during late diagenesis and metamorphism of the sediments, associated with deformation, basin inversion and/or granite intrusion. Gold is released from the arsenian pyrite and from clay-organic matter intergrowths, associated with low-grade metamorphic reactions in the sediments. Progressive recrystallisation of sedimentary arsenian pyrite, releases not only gold, but other trace elements, in particular, Cu, Zn, Pb and Te. Conversion of gold-bearing arsenian pyrite to pyrrhotite at higher grades of metamorphism (lower-greenschist to upper-greenschist and amphibolite facies) is the ultimate process to release all the contained gold and arsenic to the metamorphic fluid. This late stage release may be responsible for the Au-As-rich rims on ore pyrites in some districts (e.g. Carlin and Bendigo). The H2S-CO2-CH4-bearing metamorphic fluid formed in this way, transports the gold and arsenic, through the permeable silt and sand facies sedimentary rocks, to become concentrated in zones of intense fluid flow and related pressure release, such as anticlinal fold axes, shear zones or dilatant quartz-vein reefs and stock-work zones, to form orogenic gold deposits.

Modeling horizontal gene transfer in porous media: Implications for contaminated ground waters

D. LAROWE1,2*, SHAFEI, B.1 AND P. VAN CAPPELLEN1,2

1School of Earth and Atmospheric Sciences, Georgia Institute of Technology (*[email protected])

2Department of Earth Sciences, Utrecht University Horizontal gene transfer (HGT), the process whereby one

organism acquires genetic material from another without being its offspring, is now recognized for its significant role in shaping the speciation, adaptation and diversification of microbial communities. Because the genes that are responsible for heavy metal resistance and xenobiotic degradation are among the most laterally mobile, HGT has great implications for the natural attenuation and bioremediation of contaminated soils and ground waters. However, the extent, frequency and regulation of HGT in the subsurface remains largely unexplored. Here, we present a reaction transport model (RTM) describing the coupled propagation of genetic information via HGT and pollutant degradation in subsurafce environments.

The RTM explicitly accounts for the kinetics of HGT by representing donor (B+) and recipient cells (B-), as well as cels that have recently received and donated the genes of interest (BT and BX, respectively). Transconjugant (BT) and exhausted (BX) states are included as state variables because of the observation that, following successful HGT events, both newly enabled microbes and the ones donating the mobile genetic element enter into a state in which neither can act as donor for a characteristic time period. For each biomass, conservation equations describe their distribution in time and space due to HGT, attachment to and detachment from solid phases, and advection plus dispersion.

The HGT-explicit RTM is applied as a sensitivity tool in the context of a virtual aquifer contaminated from a single point source. Microbes carrying genes that enable degradation of the pollutant of interest are released by the same point source. The model simulations illustrate the dependence of the spatio-temporal evolution of the contaminant plume on the HGT kinetics and the transport properties of the gene carriers, as these determine how fast the native biomass acquires the ability to degrade the pollutant. Overall, the results emphasize the need to recognize and quantify HGT in the risk assessment and remediation of contaminated aquifers.


A563

The geochemical signature of propylitic alteration in the Idaho

batholith PETER B. LARSON* AND CHAD PRITCHARD

School of Earth and Environmental Sciences, Washington State University, Pullman, WA, 99164-2812, USA (*correspondence: [email protected], [email protected]) Meteoric-hydrothermal systems, driven by shallow

granitic Eocene intrusions, have propylitically altered (the production of chlorite, illite, calcite, and albite) large volumes of the Cretaceous Idaho batholith. In many cases, the altered zones form annular rings around the Eocene plutons [1]. The oxygen isotope ratios of the rocks have been lowered by hydrothermal alteration to values near or less than zero per mil over broad areas. It has recently been suggested that these altered rocks serve as sources for the voluminous Miocene and younger low #18O rhyolite magmas in the Snake River Plain/Yellowstone (SRP/Y) volcanic province [2]. To test this hypothesis, a suite of samples have been collected across one of these altered areas in the Idaho batholith, the Sawtooth Ring Zone. The sample traverse comprises a 30km section across the alterred zone and went from fresh, through altered, and back into fresh rock. Major and trace element concentrations, oxygen isotope ratios, and Sr, Nd, and Pb isotope ratios have been measured on up to 10 samples.

Quartz-feldspar oxygen isotope fractionations increase with the amount of mineralogic alteration and can be used to moniter the degree of hydrothermal exchange. Loss on Ignition increases with alteration due to the development of hydrous minerals such as chlorite and illite, but major element concentrations do not change significantly. The major element ratios K2O/(K2O+Na2O), CaO/(CaO+Na2O), and MgO/(NgO+FeO) show no changes due to alteration. Sr, Nd, and Pb isotope ratios also show no variation as a function of alteration. Ba and Sr are slightly elevated in the altered rocks relative to the unaltered batholith, and are the only elements other than the O ratios and the increased hydration that show significant changes due to the hydrothermal water/rock exchange. The most pronounced geochemical signature in the altered rocks that correlates with the geochemistry of the SRP/Y rhyolites is the low #18O ratios.

[1] Criss & Taylor (1983) Bull. Geol. Soc. Am. 94, 640–663. [2] Boroughs et al. (2005) Geology 33, 821–824.

An integrated survey on mercury pollution and its impacts in Guizhou

Province, China THORJØRN LARSSEN*1, HUA ZHANG2 AND XINBIN FENG2 1Norwegian Institute for Water Research, Gaustadalléen 21,

0349 Oslo, Norway (*correspondence:[email protected])

2State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, P.R. China ([email protected]) With the high Hg emissions in China, there is an

increasing requirement to take appropriate abatement action. Better knowledge regarding Hg pollution in China is needed, related to emissions, transport, deposition, accumulation in the environment and its impacts. A large, Sino-Norwegian cooperation project (SINOMER) addresses problems related to mercury pollution in Guizhou province in southwestern China in an integrated fashion, by considering Hg releases to the environment, environmental impacts and Hg contamination in food products, as well as assessing impacts on the society and potential policy and mitigation options.

In Guizhou Province there are several considerable sources of Hg to the environment. The releases are both as direct discharge to water from mine tailings and industrial contaminated sites and to the atmosphere from coal combustion, metals smelting and other sources.

Concentrations of Hg in the environment, focusing in water, agricultural soils, rice and important vegetables have been measured in four different regions of the province. The surveys reveal that high concentrations are found in some highly contaminated areas (especially in the Wanshan Hg mining area), but show that in general Hg concentrations in water, soil and agricultural products are low. Exposure to Hg to the population from fish consumption is very low, contrary to the well-known problems in Europe and North-America, due to different environmental conditions, short aquatic food chains as well as generally very low fish consumption. Rice, on the contrary is the major pathway for methylmercury exposure.


Can studies of petroleum biodegradation help fossil fuel carbon

management STEVE LARTER1, IAN GATES1, JENNIFER ADAMS1,2,

THOMAS OLDENBURG1 AND IAN HEAD3 1Dept of Geosciences, University of Calgary, Canada

([email protected], [email protected]) 2Present address: ConocoPhillips, 600 N Dairy Ashford,

Houston, TX. ([email protected]) 3Newcastle University, Newcastle upon Tyne, UK

([email protected])

Recent studies of biodegrading oils from the organic

geochemical and biological perspective (MADCOR process-Jones et al, 2008) have resulted in significant advances. We review these and also look at routes to use this knowledge to decarbonise fossil fuel based energy systems. Popular carbon management strategies focus on removal of CO2 from flue gas streams or even from the atmosphere to subsurface storage. Here we present scoping studies for possible biogeochemical-engineering carbon management schemes suggested by observations from studies of biodegraded petroleum systems and fossil fuel energy recovery systems. We evaluate the feasibility of recovering hydrogen, instead of oil, directly from oilfields undergoing natural biodegradation processes and we also examine the feasibility of using a related process, biologically assisted carbon capture and conversion of CO2 to methane, via H2 + CO2 methanogenesis in the hydrogen-rich environments of weathering subsurface ultrabasic rocks, as a route to recycle carbon dioxide in flue gases as methane. We examine potential uses of refractory water soluble carbon compounds, analogues of compounds found in severely biodegraded oils, as inert carbon sequestration materials. We review advances in oil biodegradation systematics and look at some of the engineering, energy and geochemical barriers to the feasibility of these possible technology routes.

Biomineralization of halotrichite on bauxite ores

M. LASKOU, M. ECONOMOU-ELIOPOULOS,AND I. MITSIS Department of Geology and Geoenvironment, University of

Athens, Panepistimiopolis, GR-15784 Athens, Greece Yellow to gray-whitish bauxite ores of the Parnassos-

Ghiona bauxite deposits, are located at the uppermost part of the deposit, underlying thin layers of coal and U. Cretaceous limestone. Such an ore is characterized by the presence of abundant pyrite and fossilized micro-organisms, resulted the Fe-bioleaching and Al-enrichment (up to 70 wt% Al2O3). Present study was focused on the whitish material grown up, after two weeks, on the surface of polished sections of grey bauxite, exposed to air oxidation, in the room conditions (20-25°C) and low air humidity.

Figure 1: Back-scattered image from grey-yellow bauxite showing hydrous sulphates: needle-like halotrichite, [FeSO4.Al2(SO4)3.22H2O], and granular FeSO4.H2O.

Enzymes of bacteria are powerful catalysts. The protein

surfaces allow living bacteria to produce halotrichite and other sulphates on the thermodynamically unstable pyrite [1].

[1] Russell, M.J. Hall, A.J. Boyce, A.J. Fallick, A.E. (2005) Economic Geology, 100th Anniversary Special, 418–438.


A565

A thermochemical model for CO2-water interfacial tension

A. LASSIN1*, P. LEROY1, D. BROSETA2 AND M. AZAROUAL1

1BRGM, Water Division, BP 36009, 45060j Orléans cedex 2, France (*correspondence: [email protected], [email protected], [email protected])

2Laboratoire des fluides complexes, UMR 5150, Universite´ de Pau et des Pays de l’Adour, 64013 Pau-Cedex, France ([email protected]) Interfacial tension (IFT) of the CO2-brine systems is a key

parameter to study the fate of CO2 in the context of geological storage in deep aquifers. IFT contributes to the control of the repartition of the fluids in the host rock porosity, and then on the transport properties of the permeable medium, like the specific relative permeabilities. It also plays an important role on the risk of leakage through the cap rock and determines the quality of sealing.

In order to include this parameter in modeling studies concerning the short- and long-term behavior of a deep CO2 geological storage, a practical formulation of the CO2-water IFT has been developped in this study. With only one physical meaninful adjusted parameter, the model can describe the CO2-water IFT for temperatures and pressures ranging from 10 to 110°C and 0.1 to 40 MPa, respectively.

The model relies on the approach proposed by Rusanov and Prokhorov [1], where a number of required parameters can be calculated a priori from existing equations of state in the CO2-H2O system and geochemical equilibrium constraints. In the proposed model, focus was emphazised on the CO2 mole fraction at the interface in order to describe correctly CO2-water IFT data available in the literature [2, 3].

Depending on temperature, results suggest an important increase of the interfacial CO2 mole fraction as a function of CO2 fugacity up to a given value (> 5 MPa). For higher fugacities the interfacial CO2 mole fraction decreases and reaches a plateau. This behavior appears critical for the description of the CO2-water intefacial tension.

In combination with our previous work, [4], this new results will allow more comprehensive modeling of IFT of CO2-brines.

[1] Rusanov & Prokhorov (1996) Interfacial tensiometry, Elsevier. [2] Chiquet et al. (2007) Energy Conv. Manag. 48, 736–744. [3] Jho et al. (1978) J. Coll. Interf. Sci. 65, 141–154. [4] Leroy et al. (submitted to GCA)

Fracturing, cementation and feedback in a small-offset oblique slip

fault in sandstone S.E. LAUBACH*, M. ELLIS, P. HARGROVE AND

P. EICHHUBL Bureau of Economic Geology, The University of Texas at

Austin (*correspondence: [email protected]) Small oblique-slip faults that cut outcrops of low-porosity

marine and fluvial sandstones have associated fracture arrays that vary in spatial arrangement and porosity preservation depending on sandstone composition. Steeply dipping faults have displacements of ~ 1 m to tens of meters; in the subsurface these faults would likely be near or below seismic detection. Cement textures in fractures in Late Proterozoic Applecross Formation and Cambrian Eriboll Formation sandstones match those found in cores from producing tight gas sandstones, showing that the youngest fractures in these well exposed rocks are useful reservoir analogs. Faults have narrow cores of breccia surrounded by disseminated mostly opening-mode fractures. Older fluvial sandstone have halos of long, straight fractures that increase in length and abundance near fault cores. Halos are meters to tens of meters wide; width is fairly uniform along fault traces. In contrast, younger marine sandstones cut by the same faults have more abundant fractures that have a wider range of strikes and greater trace connectivity. Simple fracture halos are absent; instead, wide patches and irregular zones of high but fairly uniform fracture intensity are present along or between fault traces. Fracture arrays in both types of sandstone arise in part from development and evolution of subsidiary fractures at a range of scales. Applecross and Eriboll sandstones differ in composition (subarkose vs. quartzarenite) and, consequently, propensity for fractures to seal readily under the influence of the same thermal history. Although quartzose Eriboll sandstones contain more fractures, these are mostly narrower and are more likely to be quartz filled compared with those in the lithic and feldspar-rich Applecross, where quartz cement growth is impaired by the widespread presence of non-quartz substrate (feldspar, clay minerals) on fracture walls.


Laser ICP-MS study of trace element partitioning between olivine,

plagioclase and a basaltic melt M. LAUBIER1*, T.L. GROVE2 AND C.H. LANGMUIR1

1Harvard University, Cambridge, MA 02138, USA (*correspondence: [email protected])

2MIT, Cambridge, MA 02139, USA Trace element contents of minerals and co-existing melts

can be used to constrain corrections of melt compositions for fractionation and provide estimates of the redox state of magmas. Such application requires high precision, fO2 controlled measurements at low pressures and variable temperature of mineral-melt trace element partition coefficients. To address this need, 0.1 MPa experiments were performed over a temperature range of 1150-1175°C, at two oxygen fugacities (QFM and Ni-NiO) for ~70h. The starting material (MORB AII96-18-1, Mid-Atlantic Ridge [1]) was doped in 13 trace elements. Both isothermal and rapid cooling experiments were performed. In rapid cooling experiments, the samples were cooled very rapidly (~60 °C/min) from above liquidus (1230°C) to the target temperature. Trace elements in glass, olivine and plagioclase in the run products were analyzed by laser ICP-MS. Fe and Na loss in our experiments is low and unlikely to have significant effects on the liquidus temperature. The average olivine-liquid Fe-Mg KD is 0.28±0.01, the cpx-liquid Fe-Mg KD is 0.24±0.01, and the average plagioclase Ca-Na KD is 0.94±0.03. Rapid cooling has a major effect on phase stability since cpx is absent from rapid cooling experiments at 1165°C whereas isothermal runs contain 4% cpx. The proportions of phases and size of crystals also differ, with bigger and less abundant plagioclase (7% vs 16%) and olivine (4% vs 7%) crystals for rapid cooling. Furthermore mineral/melt partition coefficients are lower for compatible elements for rapid cooling experiments, and the opposite effect is observed for incompatible elements, consistent with boundary layer effects. For example in olivineD! s are higher for Sc, V and Yb and lower for Ni (19 vs 27) for rapid cooling. These results indicate that partitioning experiments should be performed isothermally.

Comparison of experiments from a non-doped or doped starting material shows good agreement for plagioclase/melt and olivine/melt partitioning. Our results show good negative correlations of the D values for Sr, Al, Ca, Na for plagioclase and Yb for olivine with temperature. Further work will focus on the effect of fO2 on the partitioning of elements with multiple valences such as Cr and Eu and cpx/melt partitioning using a basaltic andesite as starting material.

[1] Tormey et al. (1987) Contrib. Min. Pet. 96, 121–139

Carbonaceous asteroid sample return D.S. LAURETTA

Lunar and Planetary Laboratory, University of Arizona, Tucson AZ, 85721. ([email protected]) Asteroids are planetesimals that largely orbit between

Mars and Jupiter. Many asteroids are primitive, having escaped the high-temperature melting and differentiation that shaped the larger evolved asteroids and the terrestrial planets. The chemical and physical nature, distribution, formation, and evolution of primitive asteroids are fundamental to understanding Solar System evolution and planet formation. They offer a unique record of the complex chemical and physical evolution that occurred in the early solar nebula. Understanding the origin of organic compounds in early Solar System materials is central to astrobiology. Individual asteroids are ‘astrobiological time capsules’ that preserve a record of the evolution of volatiles and organics starting in the interstellar medium, through the birth and early evolution of the Solar System, to present-day space weathering at asteroid surfaces. Study of volatile-rich compounds and organic molecules in extraterrestrial materials are also of inherent interest to the study of Solar System formation.

An asteroid sample-return mission promises enormous scientific payoff. This mission concept has been extensively studied by independent, experienced teams in the U.S., Europe, and Japan and is very mature. All teams conclude that the highest value samples are pristine carbonaceous material from the early Solar System. Given our current technology and launch limitations, sample return from a carbonaceous near-Earth asteroid provides the highest science return with the lowest implementation risk.

An asteroid sample return mission must acquire samples with known geologic context. Finally, thorough contamination control and documentation is essential to achieving the objective of returning a pristine sample. Such a mission should have the following science objectives: 1) Characterize the asteroid physical properties. 2) Globally map the surface texture, spectral properties, and geochemistry of the target. 3) Characterize the regolith at the sampling site in situ with emphasis on the textural, mineralogical, and geochemical heterogeneity. 4) Return a sample to Earth in an amount sufficient for molecular, organic, isotopic, and mineralogical analyses and including documentation of all sources of contamination.


A567

Development of a new facility for dating old groundwaters and ice

cores based on 81Kr measurement B. LAVIELLE1*, E. GILABERT1 , B. THOMAS1

AND V. LAVASTRE2

1University of Bordeaux, CNAB, CNRS, Chemin du solarium, BP120, 33175 Gradignan CEDEX, France, (*correspondence : [email protected])

2University of Saint Etienne, LTL, 23 rue du Docteur Paul Michelon, 42 023 Saint Etienne CEDEX 2, France ([email protected]) Mainly produced on Earth by nuclear reactions induced

by cosmic rays in the atmosphere, the radionuclide 81Kr (t1/2=229, 000yr) is considered as the best tracer for absolute dating of old groundwater or ice core [1, 2]. Reliable residence times have been already determined by using AMS [3] and ATTA [4] techniques. Due to the extremely low concentra-tion of 81Kr in groundwater (<1200 atoms/L), dating requires large water samples (>2000L). CNAB has developed a set of instruments and lines designed for measuring 81Kr and 85Kr in 20L groundwater sample. Isotopic analysis of Kr is performed by using resonance ionization spectroscopy – time of flight mass spectrometry coupled with an atom buncher device [5, 6] operating at 20K in order to enhanced ionization efficiency and sensitivity, allowing precise measurement of a few thousands atoms of Kr [7]. In the case of Kr gas extracted from groundwater sample, a preliminary step performing a strong isotopic enrichment for 81Kr, 85Kr is necessary in order to decrease the abundance ratio Kr/81Kr by a factor of 106. For this purpose, a mass spectrometer based on a modified PT2 instrument from VG has been built, which includes a specially designed FEBIAD-type source capable to produced high Kr beam current (>50nA) with high transmission efficiency and a mass resolution of 240. Krypton-81 and 85Kr ions are collected by implantation on separate sapphires coated with a thin Al layer. Calibrations with air samples are currently in progress to optimize enrichment efficiency before processing groundwater samples.

The CNAB project was financially supported by ANDRA,

by the Région Aquitaine (France), by the ANR, by CNRS (GdR FORPRO, Chemistry and SDU-INSU Institutes), and by the University of Bordeaux.

[1] Thonnard N. et al. (1987) NIM B29, 398–406. [2] Lehmann B.E. et al. (1991) Appl. Geochem. 6, 419–423. [3] Collon P. et al. (2000) EPSL 103–113. [4] Sturchio N.C. et al. (2004) Geophys. Res. Lett. 31 L05503 (1-4). [5] Hurst G. S. et al. (1984) Journal of Applied Physics, 55, 1278–1284. [6] Gilmour, J.D. et al. (1994) Rev. Sci. Inst. 65, 617. [7] Lavielle B. et al. (2009) Met. Planet. Sci. 42, A92

Pressure induced redox reactions in FeCO3

BARBARA LAVINA1, PRZEMSLAW DERA2, EUNJA KIM1 AND ROBERT T. DOWNS3

1HiPSEC and Dept. of Physics, UNLV, Las Vegas, NV

2GSECARS, University of Chicago, Argonne, IL

3Geosciences, University of Arizona, Tucson, AZ Iron carbonate, FeCO3, decomposed at 35 GPa after

heating at lower than 1500K; the decomposition pressure could be lower as suggested by earlier shock compression studies [1, 2], since the inefficiency of laser heating before the breakdown might also have prevented an earlier reaction in the compression cycle. Iron phases were studied using synchrotron radiation with powder, multigrain and single crystal techniques according to the variable size of the crystallites obtained in the experiment. Fe3O4, in the high pressure orthorhombic structure, was detected as a breakdown product and we argue that the iron oxydation occurred through partial reduction of carbon. Upon decompression to 10 GPa and heating to 1800 K the redox reaction could be partially reverted.

Deep Earth major phases exhert a strong control on the iron speciation. Even though further studies are necessary to accurately define Fe-C-O redox exchanges in mantle assemblies, redox exhanges of this type are in agreement with the general considerations consensus on deep carbon speciation, but have not yet been clearly identified. The shifting of redox equlibria with pressure in the Fe-C-O system has remarkable implications. In particular it might define a boundary for the stability of carbonates and CO2, which can explain greater carbon subduction compared to hydrogen [3] and the development of C-O fluid phases from the uplifting of reduced carbon bearing rocks.

[1] Isambert et al. (2006) Earth & Planet Sc Lett 243, 820–827. [2] Bell (2007) Meteorit Planet Sci 42, 935–949. [3] Hirschmann & Dasgupta (2009) Chem Geol 262, 4–16.


Neptunium redox cycling – An XAS study

G.T.W. LAW 1, A. GEISSLER 2, J.R. LLOYD 2, I.T. BURKE 1, F.R. LIVENS 2, C. BOOTHMAN 2, M.A. DENECKE 3,

J. ROTHE 3 AND K. MORRIS 4*

1School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK

2Williamson Centre for Molecular Environmental Science, School of Earth, Atmospheric and Environmental Sciences, The University of Manchester, Manchester M13 9PL, UK

3Karlsruhe Institute for Technology, Institut für Nukleare Entsorgung, D-76021, Karlsruhe, Germany

4Research Centre for Radwaste disposal, School of Earth, Environmental and Atmosphereic Sciences, The University of Manchester, Manchester M13 9PL, UK (*[email protected]) Microbial mediated reactions in the geosphere can affect

the solubility of redox sensitive radionuclides and understanding these processes is essential for the safe management of radioactive wastes. Neptunium, an alpha emitting transuranic element, is of particular importance due to its long half-life, high radiotoxicity, and relatively high solubility as Np (V)O2

+ under oxic conditions. Here, we describe experiments where Np (V) was added to oxic sediment microcosms and anaerobically incubated. Enhanced Np removal to sediments occurred during development of microbially-mediated metal reduction and X-ray absorption spectroscopy showed this was due to reduction to poorly soluble Np (IV), with Np possibly associated with Mn/Fe bearing mineral phase (s). In subsequent reoxidation experiments with air and nitrate, sediment associated Np (IV) was found to be resistant to oxidative remobilization across a range of treatments. This study highlights the potential for indigenous microbial communities to critically control transuranic element solubility in environments relevant to the global nuclear legacy.

Toward a model framework for evaluating the long-term capacity of

soils to sequester carbon COREY LAWRENCE* AND JENNIFER HARDEN

US Geological Survey, 345 Middlefield Rd, Menlo Park, CA 94025 USA (*correspondence: [email protected]) Soil carbon (C) data that we have compiled from several

different chronosequences spanning a wide range of moisture conditions (MAP from 150 to 5000 mm yr-1) allow for a robust analysis of the relationship between soil state factors and temporal patterns of soil C storage. This analysis reveals a general pattern of steady increases in C storage during early stages of soil development to a maximum value at intermediate soil ages, followed by moderate declines in older soils. This temporal trajectory can be attributed to changes in organo-mineral interactions resulting from the initial weathering of primary minerals to meta-stable, poorly crystalline intermediates and, subsequently, to crystalline secondary minerals. This pattern highlights the importance of shifts in the dominant mechanisms of organo-mineral interactions over time, and suggests that soil water cycling may drive these changes because the flux of water through soils controls both the weathering of soil minerals and the input, transport, and loss of the organic matter. Therefore, we expect soil water flux to be an important parameter for simulating long-term soil C dynamics. To test this hypothesis, we explored the potential to use a reactive transport framework to simulate soil C storage over soil development timescales. Specifically, we incorporated several different mechanisms of organo-mineral stabilization into an existing reactive transport model. We then tested the ability of this model to reproduce soil C stocks measured in chronosequences from the western United States.


A569

Provenancing arsenic release and organic matter in shallow

groundwaters of South and South East Asia

M. LAWSON1*, C.J. BALLENTINE1, D.A. POLYA1, C.L. BRYANT2 AND A.J. BOYCE3

1SEAES University of Manchester M13 9PL, UK (*correspondence: [email protected])

2Radiocarbon Facility, East Kilbride G75 0QF, UK 3SUERC, East Kilbride, G75 0QF, UK

The release of arsenic (As) in the shallow reducing

groundwater extensively utilized as drinking waters in South and South East Asia has resulted in high levels of exposure to over 100 million people [1]. The As is mobilized through the microbially mediated reductive dissolution of Fe (III) bearing minerals coupled to the oxidation of organic matter (OM), which is therefore critically implicated in the process [2]. Currently there are several oustanding issues that limit our ability to predict distribution of groundwater As hazard both now and in the future, namely (1) the location of As release within the subsurface, (2) the source of OM driving these common biogeochemical processes, and (3) how the present As hazard will change in the coming years and decades.

We present here data collected from two As hotspots in West Bengal and Cambodia. In West Bengal, $18O, $D and tritium data of shallow groundwater suggest a contribution of modern evaporated surface waters to As rich groundwaters at depths of up to 80 m [3]. In Cambodia, preliminary 14C ages of dissolved inorganic and organic carbon within the aquifer sands show a depth dependent trend of increasing age along a flow path, with residence times of between 1000 and 4000 years at depths of 20 and 50 m respectively. Flow-path integrated rates of As release decrease with increasing depth, suggestive of a surface or near surface source of OM driving microbially mediated As release. The decreased As release rate at depth along a flow path suggests a potential role of abiotic desorption processes and groundwater flow regimes in controlling the spatial distribution of As within the subsurface. Comparisons between these two sites suggests that groundwater pumping practices may play a key role in contributing labile OM to the subsurface and in controlling the spatial distribution of As in this region.

[1] Ravenscroft et al. (2009) Arsenic Pollution, A Global Synthesis. Wiley-Blackwell. [2] Islam et al. (2004) Nature 430, 68–71. [3] Lawson et al. (2008) Min Mag 72(1) 441–444.

Experimental fractionation of Ni stable isotopes between metal and silicates at 500-950°C and 10 kbar

C. LAZAR*, E.D. YOUNG AND C.E. MANNING Department of Earth and Space Sciences, University of

California Los Angeles, CA 90095 (*correspondence: [email protected]) We determined the equilibrium nickel stable isotope

fractionation between metal and silicate phases at 500-950°C and 10 kbar, using piston-cylinder expeirments and the three isotope method [1, 2]. We combined NiO enriched in 58Ni with natural quartz, terrestrial Ni metal and H2O in sealed Au capsules, and held the experiments at P and T for different times. A final invariant assemblage of Ni metal, Ni talc, quartz and H2O was produced. BSE imaging revealed that metal and quartz were consumed to produce talc, consistent with the reaction: 3Ni°+4SiO2+H2O+1.5O2 % Ni3Si4O10 (OH)2. Our spiked starting NiO was isotopically shifted from the terrestrial mass fractionation line ($61Ni & $62Ni %& -28‰). Analysis by MC-ICPMS yielded &62Ni (metal-silicate) values of -0.76±0.01‰ at 500°C, -0.38±0.01 ‰ at 800°C, and -0.15±0.01 ‰ at 950°C. A best fit to the data gives &62Ni = 0.45±0.03 ' 106/T2.

Parallel quartz-free experiments containing similarly isotopically-spiked NiO and terrestrial metal did not react to a new assemblage and yielded no isotopic shifts between oxide and metal. This suggests that, despite the substantial isotopic gradient between phases, intergranular diffusion was not an important exchange mechanism in our experiments. We instead propose that recrystallization processes such as nucleation, growth and annealing caused the observed isotopic exchange. Such processes occur as a system chemically re-equilibrates to a stable mineral assemblage [1]. Our talc-bearing experiments began with a metastable assemblage, but the Ni-NiO experiments began at or near chemical equilibirum.

Our preliminary data, coupled with the similar Ni coordination environment among nickel silicates, suggests that there may be a measurable high-temperature metal-silicate fractionation of Ni isotopes. Core forming processes could lead to Ni isotopic fractionation on a planetary scale. Redistribution of Ni during metal growth attending serpentinization may also be accompanied by strong fractionation of stable Ni isotopes.

[1] Shahar, Young & Manning (2008) EPSL 268, 330–338. [2] Matsuhisa, Goldsmith & Clayton (1978) GCA 42, 173–182.


Geochemical assessment of geogenic Arsenic contamination in the

Floridan Aquifer O. LAZAREVA1*, G. DRUSCHEL2 AND T. PICHLER3

1Department of Geology, University of South Florida, 4202 East Fowler Ave., Tampa, FL, USA, (*correspondence: [email protected])

2Department of Geology, University of Vermont, Burlington, VT, USA, ([email protected])

3Geochemie und Hydrogeologie, FB Geowissenschaften, Universitat Bremen, Bremen, Germany, ([email protected]) During the past 30 years various occurrences of elevated

arsenic (As) in groundwater were reported. With a few exceptions the source of As was geogenic, i.e. naturally occurring in the aquifer matrix. The release of As from the aquifer matrix, however, is generally caused by anthropogenic perturbations of the physicochemical conditions.

Arsenic in the Floridan Aquifer, a very large limestone aquifer, is mostly associated with pyrite. Thus a change in redox conditions could cause the dissolution of pyrite and the release of As. This scenario is the current working hypotheses to explain elevated As observed during aquifer storage and recovery (ASR) operation in Florida, because the injected water is oxygenated. As a result, pyrite dissolves and As values in recovered water can be up to 130 µg/L. To test this hypothesis a set of leaching experiments were performed with three types of water: native Floridan groundwater, Tampa tap water and water from a wetland. Aquifer material was packed into PVC columns of 0.3 m lenth and water was percolated from the bottom up at 2 mL/min. Results form the column experiments were also compared to results obtained from 1D reactive transort modeling.

No As was released during the experiments using native Floridan groundwater. Tampa tap water, which closely resembles injection water used in ASR operation caused the release of As from the cloumns. Values were higher than the current drinking water standard. The experiments using wetland water showed highest release of As (up to 68 µg/L). This was unexpected because the wetland water was much less oxygenated than Tampa tap water and thus should be less aggressive. Results form the reactive transport model correlated well to those from the column experiments.

The experiments demonstrated that pertubations of native aquifer conditions cause the release of As from the aquifer matrix, although reaction may not be as simple as the dissolution of pyrite by oxygen, but governed by a complex set of factors including water redox potential, concentration of DO, SO4

2-/S2-, Fe3+/Fe2+, DOC and microbial activity.

Trace-element geochemical characterization of chalcopyrite using LA-ICP-MS – Possible application as

an ore deposit discriminator B. LAZICH, D.J. KONTAK AND T. ULRICH

Department of Earth Science, Laurentian Univeristy, Sudbury, Ontario, P3E 2C6 ([email protected], [email protected], [email protected]) Chalcopyrite is common in many sulphide-rich,

magmatic-hypogene mineralizing environments, and therefore, has potential to use its trace-element signature to characterize and discriminate amongst ore systems. Here we report the results of an exploratory study to investigate the suitability of chaclopyrite in this context using an extended list of 24 trace elements. 447 grains from 16 deposits were analyzed for 24 isotopes using LA-ICP-MS. Ore suites include magmatic Ni-Cu-PGE deposits (e.g. Noril’sk, Sudbury), high-T hydrothermal systems represented by porphyry Cu-Au (e.g. Grasberg), IOCG and granite-hosted Sn-Cu (e.g. East Kemptville, San Rafael) deposits, lower-T hydrothermal systems represented by volcanogenic massive sulphide (e.g. Kidd Creek), orogenic gold (e.g. Hollinger-McIntyre) as well as a syenite-associated Cu-Au (e.g. Upper Beaver). Results indicate a chemical uniformity for both intra-deposit and inter-deposit sampling of the same ore deposit type. However, there is a marked difference in the trace-element signature among different deposit types, thus offering the potential to use chalcopyrite to discriminate among different sulphide deposit types. Predictable enrichments of chalcophile and siderophile elements occur in certain deposit types, plus enrichment of some economically significant elements (e.g. up to 3000 ppm In and 15 ppm Au).


A571

Discrimination of emerald origins by chemical components

LE THI THU HUONG1, NGUYEN TRUNG CHI2, WOLFGANG HOFMEISTER2 AND TOBIAS HÄGER2

1Faculty of Geology, Hanoi University of Science, Hanoi, Vietnam

2Centre for Gemstone Research, Johannes Gutenberg-University, Mainz, Germany Laser ablation-inductively coupled plasma-mass

spectrometry (LA-ICP-MS) and Electron probe analysis (EMPA) were used to determine the concentration of 30 elements, i.e. Li, Be, B, Na, Mg, Al, Si, P, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Ga, Ge, Nb, Sr, Y, Zr, Nb, Mo, Cs, Ba, La and Ta in 36 emerald samples from various localities and different types of synthesis. The concentration of principle elements may allow us to specify wherether the sample is natural or synthetic in the first place. In addition, this approach can provide information regarding geographic origins of emeralds.

[1] Hänni, H.A. (1982) A contribution to the separability of natural & synthetic emeralds. Journal of Gemmology XVIII (2), 138 - 144. [2] Howthorne, F.C. & Cerny, P. (1977) The alkali-metal positions in Cs-Li Beryl. Canadian Mineralogist 15, 414–421. [3] Pearce, N.J.G. Perkins, W.T. Westgate, J.A. Gorton, M.P. Jackson, S.E. Neal, C.R. Chenery, S.P. (1997) A compilation of new & published major & trace element data for NIST SRM 610 & NIST SRM 612 glass reference materials. Geostandards Newsletter 21, 115–144. [4] Schrader, H.W. (1983) Contribution to the study of the distinction of natural & synthetic emeralds. Journal of Gemmology XVIII(6), 530–543. [5] Schmetzer, K. & Bernhard, H.J. (1994) Isomophic replacement of Al & Si in tetrahedral Be & Si sites of beryl from Torrington, NWS, Australia. Neues Jahrbuch für Mineralogie Monatshefte 3, 121–129. [6] Stockton, C.M. (1984) The chemical distinction of natural from synthetic emeralds. Gems & Gemmology 20(3), 141–145. [7] Shatskiy, V.S, Lebedev, A.S., Pavlyuchenko, V.S., Kovaleva, L.T., Kozmenko, O.A., Yudin, A.N., Belov, N.V. (1981) Conditions for entry of alkali cations into beryl. Translated from Geokhimia 3, 351-360. [8] Sherriff, B.L., Grundy, H.D., Hartman, J.S., Hawthorne, F.C., and (ern), P. (1991) The incorporation of alkalies in beryl: Multi-nuclear MAS NMR and crystal-structure study. Canadian Mineralogist 29, 271–285. [9] Stockton (1984) The chemical distinction of natural from synthetic emeralds. Gems & Gemmology 20(3), 141–145.

Arsenic and mercury enrichments in the sediments of the geothermal

springs of Playa Santispac, Concepcion Bay, Baja California

peninsula M.L. LEAL-ACOSTA1, E. SHUMILIN1, D. SAPOZHNIKOV2,

V. GORDEEV3 AND N. MIRLEAN4

1Centro Interdisciplinario de Ciencias Marinas, Avenida IPN S/N, Col. Playa Palo de Santa Rita, Apdo Postal. 592, La Paz, B.C.S., Mexico, C.P. 23096 ([email protected], *[email protected])

2V.I.Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, Moscow, Russia ([email protected])

3P.P. Shirshov Institute of Oceanology, Academy of Sciences, Moscow, Russia ([email protected])

4Instituto de Oceanografia, Fundação Universidade Federal do Rio Grande, Brasil ([email protected])

The fluids of the intertidal geothermal springs, found in the western coast of the Concepcion Bay of the Baja California peninsula, are enriched in some elements. The objective of this study is to characterize elemental composition of the surface sediments collected in the discharge points and adjacent area. The obtained results show that the sediments of three geothermal springs of the mangroves of the Playa Santispac are strongly enriched in Hg (0.55 - 25.16 mg kg-1). The concentration of this element decreases rapidly in the sediments of the mangroves lagoon (0.023-0.233 mg kg-1) and is in the range 0.006 - 0.060 mg kg-1 in the marine sediments collected in front of Playa Santispac. The arsenic displayed elevated contents in the sediments of the geothermal springs (13.4 - 111.2 mg kg-1), low levels in the sediments of the mangrove lagoon (0.7-2.6 mg kg-1) and in the marine sediments of a zone adjacent to Playa Santispac (1.4 ± 1.1 mg kg-1). The manganese, important component of the geothermal and hydrothermal discharges revealed the similar trend. Its elevated contents (9120 mg kg-1 and 2500 mg kg-1) were found in the sediments of the second and third geothermal spring, only 460 mg kg-1 in the first geothermal spring decreasing till 106-255 mg kg-1 in the sediments of the mangrove lagoon and smaller contents 31-125 mg kg-1 in the marine sediments, collected in front of Playa Santispac. The crust of the wall of the second geothermal spring of the mangroves of the Playa Santispac is characterized by very high contents of Mn (10.35 %) and of As (637 mg kg-1), comparing them with the sediments of the proper hot spring and of the surficial sediments of the study area. The enrichment of the sediments of the geothermal springs of the Playa Santispac could be the result of the fixing of the As and Hg in reduced, less soluble forms, such as sulfides and of the formation of the manganese minerals or coprecipitated with other insoluble carbonates or silica.


Temporal and spatial evolution of fluids related to hydrothermal

alteration and porphyry copper mineralization at Red Mountain, AZ

P. LECUMBERRI SANCHEZ1, R.J. BODNAR1 AND R. KAMILLI2

1Department of Geosciences. Virginia Polytechnic and State University. Blacksburg. VA 24061 USA ([email protected], [email protected])

2U.S. Geological Survey 520 North Park Avenue, Suite 355 Tucson, AZ 85719 ([email protected])

Alteration and mineralization characteristics of porphyry

copper deposits (PCDs) have been the focus of numerous field based, laboratory and theoretical studies, and it is widely recognized that fluids play a significant role in the genesis of PCDs. In this study, a three dimensional representation of mineralization, alteration and fluid inclusion characteristics of the porphyry copper system at Red Mountain, AZ, is being developed to evaluate the role of fluids in the temporal and spatial evolution of alteration and mineralization.

In most PCDs in the SW US, the shallow lithocap region has been removed by erosion. As a consequence, the thermal and chemical evolution in the upper part of the system has not been well characterized. In that context, the Red Mountain deposit, and its preserved lithocap, is an ideal location to study the evolution in space and time of alteration and mineralization in the upper part of a PCD.

At Red Mountain a low-grade (0.2 % Cu) enargite zone related to quartz-pyrite alteration overlies a higher grade chalcopyrite zone associated mainly with the deeper potassic alteration zone. The enargite-rich zone is frequently absent from porphyry copper deposits due to erosion, although it has been preserved in some other deposits with characteristics similar to those of Red Mountain (e.g. Sunnyside, El Salvador, Lepanto-Far Southeast, and Recsk). A near-surface chalcocite enrichment zone with grades between 0.4-1.1 % Cu lies above the main deep mineralization. The deep zone shows grades between 0.4- 0.8% in the copper ore shell, with grades of 1 to 1.2 % Cu at the margins of a breccia pipe located within the potassic alteration zone.

The occurrence of a high-sulfidation zone overlying more typical PCD mineralization represents the transition between the epithermal and porphyry environment. Fluid inclusions from the deeper parts of the system are characterized by coexisting halite-bearing and vapor-rich inclusions, whereas halite-bearing inclusions are less common in the more shallow parts of the system, consistent with the transition from the epithermal to porphyry environment.

Petrochronologic constraints on partial melting in the Leo Pargil

Dome, NW India G. LEDERER1*, J. COTTLE1, M. JESSUP2, J. LANGILLE2

AND T. AHMAD3 1University of California, Santa Barbara, CA 93106, USA

(*correspondence [email protected])

2University of Tennessee, Knoxville, TN 37996, USA

3University of Delhi, Delhi - 110007, India Evaluation of tectonic models for the Himalaya involving

ductile extrusion of mid-crustal material requires a thorough understanding of the processes of partial melting as a function of time. The Leo Pargil dome (LPD) in the northwestern Himalaya provides an ideal setting within which to study the systematics of melt generation, transport, and emplacement. The LPD consists of a high-grade metamorphic and anatectic core structurally separated from low-grade Tibetan metasedimentary rocks by the Leo Pargil shear zone (LPSZ), a complex low-angle, normal-sense detachment system. Understanding the metamorphic and exhumational history of the LPD within the context of competing geodynamic models depends upon detailed knowledge of the petrochronologic history of leucogranites preserved in the footwall and hanging wall of the LPSZ. Field observations and bulk rock isotopic data, supported by detailed U-Th-Pb and trace element analysis of accessory phase minerals from >30 leucogranite bodies, provide new data critical for a detailed understanding of the magmatic history of the LPD. Variably deformed dikes cross-cut and exhibit foliation, indicating syn-kinematic emplacement of leucogranite during top-to-the-northwest ductile deformation. Melting and emplacement of multiple generations of chemically and isotopically distinct intrusions occurred at the sub-million year time-scale at temperatures in excess of 700 °C between ~ 26 and 16 Ma. Phase equilibria modeling and geochronologic data from metamorphic rocks [1] support a model in which leucogranites are derived locally by minimum-temperature partial melting of Greater Himalayan Series rocks, rather than being derived distally and transported, as advocated by previous workers (e.g. [2]). Thus, geochemical and isotopic studies of LPD leucogranites place important constraints on the timing, duration, and source of melting within the NW Indian Himalaya.

[1] Langille et al. (2010) Geochimica et Cosmochimica Acta, this volume. [2] Leech (2008) Earth & Planetary Science Letters 276, 314–322.


A573

Effect of specific surface area on cube counting fractal dimension of 3D pore structures of model sands:

NMR micro-imaging study B.H. LEE* AND S.K. LEE

School of Earth and Environmental Scineces, Seoul National University, Seoul 151-742, Korea (*correspondence: [email protected], http://plaza.snu.ac.kr/~sungklee) Diverse macroscopic properties of earth materials and

porous media depend on their mircroscopic scale (from Å to mm) local structures [1, 2]. Fractal dimension of porous media allows us to link microscopic arrangements of constituent particles and their macroscopic properties such as permeability. As most of the studies for fractal dimension and the related properties of porous media have utilized 2D images (e.g. [3, 4]), despite the importance and applications, cube counting fractal dimensin (Dcc) of 3D pore structure and its relation with specific surface area in porous materials have not been systematically studied. Here, we explore the effect of specific surface area on 3D network and Dcc of pore structure of model sands composed of glass beads and silica gel using NMR micro-imaging to gain better insights into relationship among pore structure, fractal dimension, and the corresponding hydrologic properties.

Dcc analysis shows that even pore structures without self-similarity follow the power law within the upper and lower cutoff lengths, and Dcc increases from 2.5~2.6 to approximately 3.0 with increasing specific surface area from 2.5 to 9.6 mm2/mm3, with the data also showing that Dcc of pore network apparently increases with increasing porosity at constant specific surface area. The 3D micro-imaging data for the model porous networks show that the specific surface area increases from 2.5 to 9.6 mm2/mm3 with increasing porosity and permeability from 0.21 to 0.38, and from 11.6 to 892.3 D (Darcy), respectively. Those properties are relatively well explained with the Kozeny-Carman equation. The current results, together with analysis for natural sandstones with self-similarity show that Dcc is highly correlated with specific surface area, and thus, can be a controlling parameter of the permeability.

[1] Lee S.K. (2005) GCA 69, 3695–3710. [2] Lee S.K et al. (2008) PNAS 105, 7925–7929. [3] Yu & Li (2001) Fractals 9, 365–372. [4] Perfect (1997) Eng. Geol. 48, 185–198.

Conservative tracers of oxygen fugacity in basalts and their mantle

source regions CIN-TY LEE, PETER LUFFI, VERONIQUE LE ROUX

AND RAJDEEP DASGUPTA Dept. Earth Science, Rice University

Oxygen fugacity is an intensive parameter used to describe

the chemical activity of O2 in a given system and used as a proxy for the electrochemical redox potential between the different valence states of an element associated with a specific site in a given phase. Oxygen fugacity controls the speciation of redox-sensitive metals and volcanic gases and is hence important for understanding ore formation and the composition of the atmosphere. Arcs are the least understood tectonic environments in terms of fO2. This is where altered materials from the Earth’s surface are subducted back into the mantle and where magmas and volatiles are released back to the surface and atmosphere. Arc lavas are generally more oxidized than mid-ocean ridge basalts (MORBs) as evidenced by the higher Fe3+/FeT ratios of arc lavas (>0.1 and up to 0.6) compared to MORBs (0.1-0.2). Expressed in terms of log10 deviations from a reference buffer (fayalite-magnetite-quartz, ‘FMQ’) arc lavas have fO2s from FMQ to FMQ+4, whereas MORBs have fO2s of FMQ-1 to FMQ+1, that is, arc lavas are up to 4-5 orders of magnitude higher in fO2 than MORBs. The prevailing paradigm is that the high fO2 of arc lavas reflects an oxidized mantle. This view is driven by the perception that material being subducted is oxidized so that the mantle wedge also becomes oxidized due to infiltration of oxidized slab-derived fluids or melts.

However, debate still persists because the Fe oxidation states of primary arc magmas and sub-arc mantle have not yet been directly determined. Here, we show that Zn/FeT (FeT = Fe2+ + Fe3+) is a robust redox-sensitive element ratio that retains a memory of the valence state of Fe in primary arc basalts. During mantle melting, Fe2+ and homovalent Zn2+ behave identically, but because Fe3+ is more incompatible than Fe2+, melts generated at high oxygen fugacity have low Zn/FeT. Primitive island arc basalts are found to have identical Zn/FeT as mid-ocean ridge basalts, indicating that their Fe oxidation states are also similar. This, combined with studies of V/Sc, V/Ga, and Fe isotopes, implies that the oxygen fugacity of arc mantle is similar to the rest of the upper mantle hence, the higher oxidation states of arc lavas may be related to shallow-level differentiation processes. However, reconciling these observations with the apparent correlations between Fe oxidation state and water in arc lavas remains a challenge.


Hydrochemical and isotopic characteristics of shallow

groundwater in areas affected by the Norovirus

JEONG-HO LEE1, SEONG-TAEK YUN1*, SOON-OH KIM2, YONG SEOK JEONG3, BERNHARD MAYER4, KYOUNG-HO

KIM1, WEON-WHA JHEONG5 AND TAE SEUNG KIM5 1Department of Earth and Environmental Sciences, Korea

University, Seoul 136-701, Korea (*correspondence: [email protected])

2Department of Earth and Environmental Sciences, Gyeongsang National University, Jinju, Korea

3Department of Biology, KyungHee University, Seoul, Korea

4Department of Geoscience, University of Calgary, Canada T2N 1N4

5National Environmental Research Institute, Incheon, Korea Potential contamination of groundwater by the Norovirus

is a major concern in South Korea and elsewhere. In order to understand the occurrence, source (s), transport, and fate of the Norovirus in groundwater environments, hydrochemical (major ions and trace metals) and environmental isotopic analyses in addition to microbiological surveys focusing on total coliform, E.Coli, fecal bacteria and the Norovirus were performed for groundwater from 86 wells in four chosen areas with known Norovirus contamination in South Korea. Top soils of the study areas are permeable with moderately high hydraulic conductivities (10-4~10-5 cm/sec). Shallow groundwater samples tended to be rich in anthropogenic pollutants such as chloride, nitrate and sulfate. Large seasonal fluctuations of groundwater chemistry suggested that the studied groundwater systems are mostly susceptible to rapid recharge after large rainfall events. Cl versus Cl/Br plots suggested the origin of them and the potentially related Norovirus from septic effluents and animal wastes. The carbon isotopic compositions of dissolved inorganic carbon (DIC) (n=33) ranged from -8.4 to -18.6‰ (avg. -16.1‰), indicating that DIC was derived from soil organic matter and/or manure. The isotopic compositions of nitrate in 39 samples [#15N = 3.5 to 29.1‰ (avg. 13.4‰), #18O = -0.4 to 12.7‰ (avg. 4.4‰)] indicated that nitrate was derived predominantly from manure and/or sewage. Combined with field observations, we consider that leakage from latrines and sewage pipes as well as agricultural manure are likely the major sources of the Norovirus and related contaminants such as nitrate, chloride and sulfate.

Adsorption of amino acids on oxide surfaces as a function of

environmental conditions N. LEE1,2, C.M. JONSSON1,2, C.L. JONSSON1,2, S. OHARA2,

G.D. CODY2, K. KLOCHKO2, J.H. CLEAVES, D.A. SVERJENSKY1,2 AND R.M. HAZEN2

1Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, MD, 21218 ([email protected])

2Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Road NW, Washington D.C. 20015 A fundamental understanding of amino acid adsorption to

TiO2 can provide insight into biomolecular and biomaterial interactions and may have implications for prebiotic chemistry. Potentiometric titrations and batch adsorption experiments were used to study the adsorption of L-lysine on rutile (*-TiO2) over a range of environmental conditions such as pH, surface loading and the presence of another amino acid in the system. The maximum amount of lysine adsorbed was about 0.73 +mol per m2 at pH ~ 9 in water solutions containing glutamate. Theoretical surface complexation calculations suggest that lysine forms a rather weakly bound complex via coordination of the ,-NH3

+ group as an outer-sphere complex on the rutile surface, similar to previous studies of lysine adsorption on amorphous silica [2]. In addition, it is predicted that lysine adsorption will be enhanced when it is mixed with glutamate, which facilitates a favorable surface charge for lysine to attach. This study enables a better understanding of molecular level interactions between biological molecules and biomaterials such as titanium implants and may also be of importance for understanding the role of mineral-surface interactions in the origin of life [3].

[1] R.M. Hazen (2006) Mineral surfaces & the prebiotic selection & organization of biomolecules. Am. Miner. 91, 1715–1729. [2] Vlasova & Golovkova (2004) The adsorption of amino acids on the surface of highly dispersed silica. Colloid J. 66, 657–662.


A575

In situ observations of competitive adsorption of monovalent ions at the

muscovite (001)-water interface S.S. LEE1*, C. PARK1,3, N.C. STURCHIO2, K.L. NAGY2

AND P. FENTER1

1Chemical Sciences and Engineering, Argonne National Laboratory, Argonne, IL, 60439 (*correspondence: [email protected])

2Earth and Environmental Sciences, University of Illinois at Chicago, Chicago, IL 60607

3current address: HP-CAT, Geophysical Laboratory, Carnegie Institution of Washington, Argonne, IL 60439 Robust characterization of ion adsorption and desorption

processes is essential for assessing societal risks associated with the bioavailability of nutrients or toxic elements in soils and surface waters. In this study, we monitor the effect of a competing ion (Na+ or K+) on the distribution and adsorption thermodynamics of Rb+ at the muscovite (001)-water interface using in situ specular X-ray reflectivity combined with resonant anomalous X-ray reflectivity. Experiments were performed with aqueous solutions containing RbCl and either NaCl or KCl at a fixed ionic strength (3 mM).

These systematic measurements of competitive adsorption reveal insight into the adsorption of Rb+ and the competing ion. The variation of the average height of Rb+ with solution composition reveals that the relative proportions of inner-sphere (IS) and outer-sphere (OS) species of adsorbed Rb+ are not constant. Instead, Rb+ adsorbs mostly as an IS species in pure RbCl, or when competing with K+, but transforms to a distribution with equal proprotions of IS and OS when it competes with OS dominant Na+. The adsorption thermodynamics results show that the magnitude of the cation adsorption free energy decreases linearly with increasing magnitude of the cation hydration enthalpy. This indicates that cation hydration is an important factor in controlling the adsorption strengths as well as the IS/OS partitioning of these cations. Finally, we estimate the contribution of electrostatic attraction to the monovalent ions’ adsorption free energies as IS and OS species. The calculated energy difference between these two species (25-30 kJ/mol) is larger than that estimated (~10 kJ/mol) based on the difference in their adsorption heights (~4 Å) and the dielectric constant (~80) of bulk water. This large discrepancy suggests that a discrete interfacial hydration layer leads to a signficant reduction of the interfacial dielectric parameter.

La-Ce and Sm-Nd isotope geochemistry of Early Proterozoic

Imweon leucogranite, Korea SEUNG-GU LEE1*, YOSHIHIRO ASAHARA2,

TSUYOSHI TANAKA2, NAM HOON KIM3 AND YONG SUN SONG3

1Korea Institute of Geoscience and Mineral Resources, Daejeon 305-350, Korea ([email protected])

2Department of Earth and Environmental Sciences, Nagoya University, Nagoya 464-8601, Japan ([email protected], [email protected])

3Department of Environmental Sciences, Pukyeong National University, Pusan 608-737, Korea ([email protected]) La-Ce and Sm-Nd isotope systematics in the Precambrian

rocks provide a valuable information for the LREE pattern in the source material. The Imweon leucogranite in the northeastern Yeongnam Massif, Korea is stongly peraluminous and S-type granitic gneiss. The leucogranite granite was generated by partial melting of the metasediments, which consist of quartz+K-feldspar+plagioclase+biotite+ muscovite+sillimanite!garnet!tourmaline. Whole-rock Sm-Nd age suggests that the leucogranite should be formed by a magmatic episode at ca. 1.90Ga. One of the main geochemical characteristic of the leucogranite is that some of the granite shows ‘tetrad effect’ in the chondrite-normalized REE pattern. In this paper, we discuss La-Ce and Sm-Nd isotopic systematics for the Imweon leucogranite with REE tetrad effect to clarify whether the REE tetrad effect of the leocogranite was derived from the differentiation of the source magma or derived from the secondary processes such as metamorphism or hydrothermal alteration.

The present !Nd and !Ce values of the leucogranites with tetrad REE pattern are positive whereas the leucogranites without tetrad REE pattern have the negative !Nd and positive !Ce values. The initial !Ce values of the leucogranite are -2.5 < !Ce (t) < +21.7 whereas initial !Nd (t) values of the leucogranites are similar in the range of -8.71 < !Nd (t) < -4.31 regardless of the existence of tetrad REE pattern. This suggests that Ce isotopes of the source material should be heterogeneous whereas its Nd isotopes were relatively homogeneous. In addition, such La-Ce and Sm-Nd isotopic data reveal that the leucogranites should be derived from the same source material regardless the existance of the REE tetrad effect.


Changes of microbial diviersity and mineralogical composition during anoxic bioreduction of acid mine

drainage YURI LEE AND YUL ROH*

Dept. of Earth and Environmental Sciences, Chonnam National University, YongBong-dong, Buk-gu, Gwangju, Rep. of Korea (*correspondence: [email protected]) Microorganisms can aid or accelerate metal oxidation

reactions and cause precipitation of metal hydroxide and/or iron-oxyhydroxysulfate mineral at acid mine drainage (AMD) [1]. The objective of this study was to examine changes of microbial diversity and mineralogical composition during anoxic bioreduction of AMD.

AMD including precipitates were sampled at Jeonju Il mine, Wanju-gun, S. Korea. Glucose (10 mM) was innoculated into AMD to stimulate anoxic bioreduction of AMD using 2-L serum bottles closed with rubber stoppers. Changes of microbial diversity, geochemical and mineralogical characteristics were monitored by 16S rRNA, XRD, SEM-EDX, TEM-EDX, ICP-AES, and IC analyses.

Major elements of AMD and precipitates are Fe, Al, Mn, Na, and S (SO4). Mineralogical composition of precipitates at AMD are shcwertmannite [Fe8O8 (OH)8-2ｘ (SO4)ｘ·nH2O] and akaganeite (--FeOOH). 16S rRNA analysis showed that iron-oxidizing bacteria (e.g. Gallionella sp.) are dominant under oxic conditions, but iron-reducing bacteria (e.g. Geobacter sp.) are dominnant under anoxic environments. Geochemical and mineralogical analyses showed that schwertmannite and akaganeite transformed into iron sulfide (FeS) and siderite (FeCO3) within 3~4 days of the microbial growth stimulation under anoxic environments. Iron-reducing bacteria such as Geobacter sp. reduced Fe (III)-containing mienrals such as shcwertmannite and akaganeite into siderite under anoxic environments in AMD.

These results suggest that microorganisms can aid or accelerate precipitation of Fe (III)-containg minerals such as iron hydroxide and iron-oxyhydroxysulfate under oxic condituons and of Fe (II)-containing minerals such as FeS and siderite under anoxic environments at acid mine drainage (AMD).

[1] Johnson & Hallberg (2003) Research in Microbiology 154, 466–473.

CO2 clathrate formation and dissociation rates below 273K J.R. LEEMAN1 AND M.E. ELWOOD MADDEN2

1School of Geology and Geophysics, University of Oklahoma, Norman OK 73019, USA ([email protected])

2School of Geology and Geophysics, University of Oklahoma, Norman OK 73019, USA ([email protected]) CO2 clathrate hydrate is likely an important volatile phase

within permafrost and polar ice on Mars as well as icy moons and comets. In addition, CO2 hydrate may be useful on Earth as a solid phase for CO2 separation and sequestration in cold climates. However, we know very little about hydrate formation rates at temperatures below the freezing point of water ice, where hydrate forms from solid ice reacting with gas or liquid CO2. A device has been constructed to measure the rate of CO2 and CH4 clathrate formation and dissociation at temperatures below 273 K. A known surface area of ultrapure water ice is exposed to gas at temperatures and pressures within the hydrate stability field. Formation rates are determined by measuring the gas pressure decay within the headspace of the vessel, while dissociation rates are measured by monitoring the pressure increase as gas evolves. In both case, the gas flux in/out of the hydrate is calculated by applying the Van der Waal’s equation to high resolution temperature and pressure measurements. Initial formation rates averaged 1.57x10-4 molm-2s-1 at an average pressure of 7.45x10-1 MPa. Initial dissociation rates varied from 3.7 x10-4 molm-2s-1 to 3.5x10-4 molm-2s-1 at 4.46x10-1 MPa and 1.01x10-1 MPa respectively. These experiments took place at 250K. Following the initial reaction of the surface layer of ice (formation) or hydrate (dissociation), a thin layer forms and the process becomes diffusion limited. Determining the diffusion coefficient is non-trivial, as this is a moving boundary problem (similar to the Stefan problem) and several methods of solution are currently being investigated. These data have implications for modelling fluxes in both terrestrial and extra-terrestrial clathrate reservoir systems.


A577

Mercury isotopes in Illinois Basin coal: Organic and inorganic

constituents L. LEFTICARIU1*, J.D. BLUM2 AND J.D. GLEASON2

1Department of Geology, Southern Illinois University, 1259 Lincoln Dr., Carbondale, IL 62901, USA (*correspondence: [email protected])

2Department of Geological Sciences, University of Michigan, 1100 North University Ave, Ann Arbor, MI 48109, USA Mercury (Hg) is a metal of environmental concern in coal

due to its volatility, persistence, toxicity and tendency to bio-accumulate through the food chain [1]. Within coals, Hg has high affinities for both organic phases (i.e. organic-bound Hg) and inorganic phases (i.e. sulphide minerals). The occurrence and distribution of Hg in coal dictates its behaviour during coal processing and combustion, and its redistribution in combustion products.

We have investigated the Hg concentrations and Hg stable isotopic compositions of organic and inorganic constituents of the following coals from the Illinois Basin: Herrin No. 6 and Springfield No. 5 of the Carbondale Formation and Murphysboro and Mount Rorah of the Spoon Formation. Our results show that the concentration of Hg is highly variable among these coals and significantly below the average for U.S. coals (170 ppb, U.S. Geological Survey COALQUAL database). Hg concentrations measured in samples of fracture-filling pyrite were two orders of magnitude higher than that measured in coal samples. Thus, Hg is dominantly associated with sulfides in Illinois coal.

Distinct Hg isotopic ratios were measured in organic and inorganic constituents of Illinois coals. The pyrite samples were isotopically unfractionated relative to the NIST 3133 Hg isotope standard. The Hg isotopic signatures of coals from the Illinois Basin overlap those of other coal samples worldwide [2] and include some of the lowest #2°2Hg values measured for coals (-2.7 ‰ #2°2Hg). Unexpectedly, each coal seam exhibits a unique range of #2°2Hg values. Additionally, Herrin No. 6 and Mount Rorah coals display negative mass independent fractionation (&199Hg and &2°1Hg down to -0.2‰).

These results indicate that Hg isotopes can be used to (1) fingerprint individual coal seams from Illinois Basin and (2) trace the depositional and post-depositional contributions of Hg to coals.

[1] Diehl et al. (2004) Int. J. Coal. Geol. 59, 193–208. [2] Biswas et al. (2008) ES&T 42, 8303–8309.

Cs sequestration into a microporous gallosilicate framework

K.M. LEFTWICH AND A.J. CELESTIAN* Western Kentucky University, Bowling Green, KY 42101,

USA (*correspondence: [email protected]) A gallium silicate microporous framework with the zeolite

CGS topology is being tested as an ion exhanger for targeted removal of Cs+ from aqueous solutions. The CGS framework may be an ideal structure for sequestering large ionic radii cations due to elliptical and branching 10 and 8 member-rings (MR). Elliptical channels in zeolitic matierals have enhanced ion selectivity [1, 2] for cations that do not fit initially in the ellipitcal channels, and therefore must distort to accommodate the ingong cation. However, it is not know what drives the spontaneous structural transformations to accomodate these large ionic radii species.

In the as-synthesized K+ form of the CGS structure (K-CGS), the elliptical channels cannot accommodate Cs+ due to unacceptable short Cs-O bond distances to the framework. Therefore, the structure must distort to accommodate the guest species. This process has been observed from time-resolved X-ray diffraction ion exchange studies at NSLS Beamline X7B using 10mM CsCl at a flow rate of 0.2 mL/min. Elliptical channels in K-CGS distort and expand as Cs+ exchanges for K+. Exchange was completed within 10 minutes. Ion exchange seems to have involved two steps as measured from preliminary unit cell refinements: 1) unit cell expansion as Cs enters the structure, and 2) unit cell contraction as Cs may enter the branching conduits. The branching channels in CGS may also enhance ion conductivity by providing storage space away from the center of the channels so that ions are free to move in and out of the structure. This two-step ion exchange process is similar to other zeolitic materials, such as the titanosilicate CST [1], TsG-1 [2], and bernisite [3], where ion exchange was enhanced by structural distortions.

[1] Celestian et al. (2008) J. Am. Chem. Soc. 130, 11689–11694. [2] Lee et al. (1999) Chem. Mater. 11, 879–881. [3] Lopano et al. (2009) Am. Min. 94, 816–826.


Influence of vegetation type and climate on native selenium

distribution and speciation in soils I. LE HECHO1, J. TOLU1,2*, M. BUENO1, Y. THIRY2

AND M. POTIN-GAUTIER1

1University of Pau & Pays de l’Adour, LCABIE/CNRS UMR 5254, Pau, 64000, France (* [email protected])

2ANDRA Institute, Châtenay- Malabry, 92298 Cedex, France

Context and objective The long-lived radioisotope 79Se is found in high level

nuclear wastes for which a geological disposal in deep clay formations is considered to be a safe option [1]. The safety assessment of such waste disposal involves the understanding of Se transfert in soil. Se mobility and bio-availibility are strongly dependent on its speciation and binding to soil fractions [2]. The inorganic species become increasingly mobile in the order Se (-II)<Se (0)<SeIV<Se (VI) (Fig. 1).

Figure 1: Biogeochemistry of selenium in soil [2]

The aim of this study is to assess the impact of two environmental factors on native Se species distribution in soils: i) the vegetation type (grassland, forest and culture) and induced organic matter modification (content and nature); ii) the climate (montain; oceanic temperate; warm, cold and temperate continental) where soils were developped.

Analytical methodology

To determine trace Se species distribution in the studied natural soils, our methodology, previously developed, was based on extraction by selective reagents and on sensitive analytical method. Results of total Se distribution among the operationnally defined fractions were compared to literature studies [3, 4]. This study originality resides in Se speciation determination in each soil fraction.

[1] ANDRA, (2007) Phys. Chem. Earth. 32, 1–537. [2] Séby et al. (1997) Sci. Total Environ. 207, 81–90. [3] Coppin et al. (2006) Biol. Fertil. Soils 42, 379–386. [4] Tan et al. (2002) Sci. Total Environ. 284, 227–235.

EarthChem: Next generation of data services in geochemistry

KERSTIN LEHNERT1, DOUGLAS WALKER2, CELINE CHAN1 AND JASON ASH2

1Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY, 10964 (*correspondence: [email protected])

2University of Kansas, Lawrence, KS ([email protected]) Geochemical online databases such as PetDB, SedDB,

NAVDAT, and GEOROC have created digital data services that give researchers easy access to comprehensive, thematically focused compilations of analytical data for igneous, metamorphic, or sedimentary rocks, and that allow them to extract from these compilations within minutes new synthesis data sets as defined by their own criteria. The next level of data services was developed by EarthChem, offering a central access point to geochemical data in federated geochemical databases, with tools to search, filter, retrieve, and visualize the data, in order to integrate data access across systems, further data discovery and support data analysis.

EarthChem has now started to develop its next generation of data services, responding to the growing demands for user-based data contributions, long-term data archiving, interoperability, and expanded data coverage. Large emphasis is placed on the development of tools that help investigators organize and manage their data in a way that minimizes their efforts to submit data and metadata to EarthChem, and that also supports quality control of user contributions to the EarthChem Repository.

The new EarthChem Repository will provide data storage and stewardship for the widest range of geochemical data sets and data collections, with a data publication service that will allow users to obtain Digital Object Identifier for Scientific Primary Data (STD-DOI) to make their submitted data citable as publications.

The new EarthChem data services are meant to encourage data contributions by investigators to ensure more efficient and timely growth of the data collections, to help researchers comply with existing and emerging requirements for data publication and data reporting by publishers and funding agencies, and to improve data quality.

A new service-oriented architecture will be developed for the EarthChem Data Engine as the next generation portal that will offer a superior range of options and possibilities for interaction and data exchange with other systems. In addition, EarthChem will create new digital content, expand partnerships, and continue to promote the implementation of more open and standardized data reporting in geochemistry.


A579

The application of Multi-purpose geochemical analysis in south of Chifeng, Inner Mongolia, China

WANSHAN LEI1* AND DEBO LOU2

1College of Earth Science and Resources, Chang'an University, Xian 710054, China (*correspondence: [email protected])

2Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China The southern Chifeng is located in the connecting zone

between northern margin of the North China Platform and the Tianshan-Xingmeng orogenic belt. The unique tectonic environment enhance the complexity of geochemical condition. Based on statistics, this study evaluates whether the research of geochemistry can offer assist in delineating the prospective area.

In this study, concentrations of 14 elements were measured using atomic absorptioin spectroscopy in 3771 samples from the south of Chifeng.The multivariate statistical analyses were applied in the study area, which include R-cluster analysis, factor analysis and the correlation analysis. The comprehensive analyses classifies the ore-forming elements into four groups: the first group of Mo and W which indicates the high-temperature hydrothermal mineralization; the second group of Cu, Ni, Mn and Zn indicating the middle-temperature hydrothermal mineralization; the third group of Ag, Bi, Au, Sn, As and Sb indicating the midhigh-temperature hydrothermal mineralization; the last group of Hg and Pb which indicates the low-temperature hydrothermal mineralization.The multipurpose geochemical analysis suggests that the multi-stage mineralization, multi-period mineralization and the superposed mineralization can exist simultaneously in the study area.Furthermore, combining with the means of spectral analysis (S-A) and concentration area (C-A) which can delineate anomalies caused by mineralization, we can propose prospecting areas for some specific hydrothermal mineralization polymetallic deposits.

Fractionation of Li isotopes during mineral dissolution of granite

E. LEMARCHAND1,2*, B.C. REYNOLDS2, R. KRETZSCHMAR1 AND B. BOURDON2

1Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Switzerland (*[email protected])

2Institute of Geochemistry and Petrology, ETH Zurich, Switzerland During the last decade, numerous studies have explored

the use of Li isotopes as potential tracers for silicate weathering. Li isotope fractionation occurs during water/rock interactions and typically leads to a heavier isotopic composition of natural waters compared to the corresponding source rocks. This makes Li isotopes a good candidate to trace weathering in soils or at catchment scale but the exact processes governing the isotopic variations observed in surface waters are still not fully understood. It has been suggested that a preferential incorporation of light Li (6Li) in secondary phases is responsible for the heavy Li isotope signature of surface waters. It has also been suggested that a preferential leaching of heavy Li (7Li) during rock minerals dissolution could yield heavy isotopic composition in surface waters. Experimental studies confirmed the first hypothesis [1, 2], but the second one was not yet explored in detail.

In this study, we conducted dissolution experiments with crushed granite in fluid-flow reactors. The crushed granite (100-200µm) was leached for one month at pH values ranging from 2.5 to 5.5 with two different acids: HCl (proton promoted dissolution) and oxalic acid (proton and ligand promoted dissolution). The chemical composition of the effluent was analyzed by ICP-OES and quadrupole-ICPMS, and the Li isotopic composition was determined using a Nu Plasma 1700 MC-ICPMS. Fe, Mn, Mg and Li were released into solution at higher relative rates than Si, Al, K and Na, suggesting preferential dissolution of phyllosilicates such as biotite. Despite this preferential dissolution, only a small isotopic fractionation was observed (~1‰), with 6Li being released preferentially into solution.

Our results imply that the heavy Li isotopic composition observed in surface waters cannot be explained by a preferential release of 7Li into solution during granite dissolution. Secondary processes, such as precipitation of secondary phases, may be a more likely explanation for the observed isotopic variations in surface waters.

[1] Pistiner & Henderson (2003) Earth. Plannet. Sci. Lett. 214, 327–339. [2] Vigier, Decarreau, Millot, Carignan & France-Lanord (2008) Geochim. Cosmochim. Acta. 72, 780–792.


FT-ICR/MS and quantum chemical study of the aqueous microsolvation

of cadmium chloride complexes KONO H. LEMKE1, SEYED A. SADJADI1 AND

TERRY M. SEWARD2 1Department of Earth Sciences, University of Hong Kong,

Pokfulam Road, Hong Kong, SAR ([email protected])

2Institute for Mineralogy and Petrology, ETH Zürich, CH-8092, Zürich, Switzerland Quantum chemical and mass spectrometric studies of

hydrogen bonded complexes are of fundamental importance in shaping our understanding of molecular interactions in the bulk liquid phase. The gas phase solvation of Cadmium chloride species according to X·(H2O)n + H2O= X·(H2O)n+1, X=[CdClm]2-m, provides a suitable model for such studies and, can as such provide insight into the stability and abundance of ionic water clusters in high temperature low density aqueous fluids [1] as well as serve as a model system for ionic dissolution and precipitation reaction in water clusters [2]. The work here presents new results for the stability, structure and abundance of hydrated [CdClm]2-m complexes via MP2/CBS and CCSD (T)/CBS calculations with cc-pVXZ-PP basis sets (X=D, T, Q) in combination with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR/MS). Gas phase ion-molecule experiments were conducted on a modified 7 Tesla FT-ICR/MS equipped with electro spray ionization (ESI) source and IRMPD laser for ion fragmentation. A preliminary analysis of results from this study indicates that i) Cd2+ prefers to coordinate six first shell water molecules rather than seven [3, Fig.], ii) the stepwise attachment of Cl- onto hydrated [CdClm]2-m yields a suite of energetically similar isomers and iii) FT-ICR/MS experiments currently underway, will provide additional insight concerning the stability of these clusters. Implications for metal-halide transport in high temperature vapor will be discussed.

[1] Likholyot et al. (2007) GCA 71, 2436. [2] Niedner-Schatteburg et al. (2000) Chem. Rev. 100, 4059. [3] Chillemi et al. (2005) J. Phys. Chem. B 109, 9186.

Mineralogical niches shape microbial populations responsible for Fe(III) reduction on a diverse set of Fe(III)

(hydr)oxides CHRISTOPHER J. LENTINI* AND COLLEEN M. HANSEL

School of Engineering and Applied Sciences, Harvard University, Cambridge, MA USA (*correspondence: [email protected]) Iron oxides are ubiquitous in nature. Central to an

understanding of the iron geochemical cycle are dissimilatory Fe (III) reducing microorganisms (DIRMs), which serve as catalysts for environmentally significant redox reactions. Although well studied, there is considerable disagreement on whether these microorganisms can use highly crystalline forms of Fe (III) oxides as terminal electron acceptors in the environment. However, the reduction of these highly crystalline phases (goethite, hematite, magnetite) has been observed in the laboratory, under column flow experiments and in natural soils. Yet, current model DIRMs in culture show diminished abilities to reduce these more crystalline phases, only reducing a small fraction of the potentially available Fe (III).

Given the large range in the properties of Fe (III) oxides, we predicted that different groups of bacteria may specialize in the reduction of the various phases. We systematically tested this hypothesis through Fe-enrichment studies. In total, enrichments included: 4 Fe (III) (hydr)oxides (ferrihydrite, lepidocrocite, goethite and hematite) including a no iron control to test for fermentative organisms, 3 carbon sources (glucose, lactate, acetate) plus an equal mix of the 3, and 5 dilutions done in duplicate, leading to 200 enrichments. After enrichment, microbial communities were analyzed by T-RFLP and 16S clone libraries. Iron reduction was monitored by measuring Fe (II) production, while iron mineralogy was analyzed with EXAFS and XRD.

Data from two experiments, including this enrichment and an initial smaller study, support our mineralogical niche hypothesis. T-RFLP and 16S based phylogenetic analysis illustrates different and novel metal-reducing communities enrich on various Fe (III) (hydro)oxides. Fe (II) and EXAFS studies indicate the reduction of crystalline Fe oxides in specific enrichments.

These findings suggest that differences in the Fe (III) (hydr)oxides are important factors in shaping the community composition in iron reducing environments. It also suggest that the role of model DIRMs may be minor in the reduction of more recalcitrant Fe (III) oxide phases while the role of other organisms needs further investigation.


A581

The ‘bio’ in biominerals — Identification of proteins associated to microbially produced selenium

particles M. LENZ1, B. KOLVENBACH1, B. GYGAX2, S. MOES3

AND P.F.X. CORVINI1

1University of Applied Sciences Northwestern Switzerland (FHNW), Institute for Ecopreneurship, Gründenstrasse 40, 4132 Muttenz, Switzerland

2 University of Applied Sciences Northwestern Switzerland (FHNW), Institute of Chemistry and Bioanalytics, Gründenstrasse 40, 4132 Muttenz, Switzerland

3 Biozentrum of the University of Basel, Department of Biochemistry, Klingelbergstrasse 50-70, 4056 Basel, Switzerland Selenium oxyanions are frequently encountered in surface

waters as result of anthropogenic activities and natural weathering processes, representing a serious ecotoxicological risk due to their high toxicity and bioaccumulation potential. Different microbial groups can reduce water soluble, mobile and toxic selenium forms to elemental selenium, considered less toxic. Such biogenic elemental selenium, however, does not crystallize to large particles and remains dispersed in solution as a colloidal suspension of nanoparticles [1, 2], thus being subject to re-oxidation, uptake and assimilation by biota. The probable reason for the tendency of biogenic selenium to remain suspended in solution is an organic layer modifying the surface, preventing crystallization and conferring the selenium core with physico-chemical properties different from particles without such a layer. Extracellular proteins have been previously shown to determine aggregation and thus dispersal of biogenic chalcogen nanoparticles in the environment [3]. By using Electrospray Ionization (ESI) Mass-Spectrometry we studied biogenic selenium particles formed by phylogenetically different microorganisms (e.g. Bacillus selenatarsenatis, Sulfurospirillum barnesii, Rhodospirillum rubrum), demonstrating that proteins appear to be strongly associated with biogenic selenium nanoparticles of different origin.

[1] Zhang et al. (2004) JEQ 33, 559–564 [2] Lenz et al. (2008) JEQ,37, 1691–1700 [3] Moreau et al. (2007) Science, 5831, 1600–1603

Global biogeochemical cycle of silicon: sources and fluxes

ABRAHAM LERMAN AND DARCY DAN LI Department of Earth and Planetary Sciences, Northwestern

University, Evanston, IL 60208, USA ([email protected] ([email protected])) The main sources of silicon in its global biogeochemical

cycle are very large, as it is the second most abundant element, after oxygen, in the sedimentary and crystalline crust (Figure 1). Si in solution, mostly in the form of Si (OH)4, is utilized by the land plants and aquatic taxa that incorporate Si in their cell structure and secrete silicate skeletons. Estimates of global primary production show that Si accounts for ~1.5% molar mass of terrestrial primary production and ~4.5% of marine primary production, where it is coupled to the other major nutrient cycles of C, N, and P.

Mean concentration of dissolved SiO2 in world rivers (10.4 mg SiO2/L) and river runoff represent a SiO2 release rate per 1 m2 of land drainage area of the crustal sources of 0.065 mol SiO2 m-2 yr-1 or 1.8 g Si m-2 yr-1. In comparison to the extensively studied dissolution rates of common silicate minerals in sediments and crystalline crust, this release rate corresponds to reactive mineral weathering surface areas of an order of 102 m2. Studies of the interconnected rock porosity, its surface area, and pore size help determine the weathering layer thickness.

Biological fixation of Si is the main mechanism of its removal from water and storage in sediments, where diagenesis of detrital minerals and neoformation of clays also contribute to the balance.

Figure 1: Composition of an average sediment (mass

g) by rock types and their SiO2 content. Modified from Lerman and Wu (2008).


First series transition metals (Zn, Fe, Mn, Co, Sc, V) as tracers of

mineralogic heterogeneities in the mantle

V. LE ROUX, R. DASGUPTA AND C.T.A. LEE Department of Earth Sciences, Rice University, 6100 Main

Street, Houston TX 77005 USA Major element heterogeneities in the Earth’s mantle may

be inferred from peridotite samples, oceanic basalts and seismological data. It is widely believed that the Earth’s mantle holds heterogeneities, because subduction transfers eclogitic material back into the mantle, lithosphere delaminates, and melt percolation affects the modal mineralogy of the peridotitic mantle. Melt-rock reaction products may range from dunite to pyroxenite, depending, for example, on whether the percolating melt is saturated or undersaturated in olivine, respectively. Oceanic basalts are also characterized by large isotopic and trace element variability that is hard to reconcile with partial melting of a pyrolite-like mantle alone.

Here we use first series transition metals, Zn, Mn, V, Sc, Co, and Fe systematics in mafic and ultramafic systems to detect mineralogical and lithological heterogeneities that deviate from pyrolite-like peridotitic mantle dominated by olivine and orthopyroxene. We suggest that those moderately incompatible elements are more robust indicators of mineralogic heterogeneities than highly incompatible elements. Exchange partition coefficients (KD) between peridotite and melt have been estimated (1) theoretically, through mineral/mineral elemental partitioning on natural samples using LA-ICPMS combined with experimental database and (2) experimentally, by conducting mineral (olivine, orthopyroxene and clinopyroxene) /melt partitioning experiments using a piston-cylinder apparatus at temperatures and pressures relevant for the Earth’s upper mantle. Particularly, we suggest that Zn/Fe is minimally fractionated during partial melting of peridotite and differentiation of primitive basalts, but highly fractionated if garnet and/or clinopyroxene are the dominant phases in the source during melting. We propose that the Zn/Fe ratios of primitive ocean island basalts (OIB) and mid ocean ridges basalts (MORB) could trace the major element and mineralogic heterogeneities of their mantle source region. The high Zn/Fe ratios of some OIB require in their source the presence of high Zn/Fe lithologies or lithologies that have bulk Zn/Fe exchange coefficients <<1. All garnet and clinopyroxene-bearing lithologies, such as eclogites and pyroxenites fit the latter requirement.

Boron isotopic geochemistry of the McMurdo Dry Valleys, Antarctica

DEBORAH LESLIE1,2*, NATHANIEL WARNER3, AVNER VENGOSH3, JOHN OLESIK2, KATHLEEN WELCH1

AND W. BERRY LYONS1,2 1Byrd Polar Research Center, The Ohio State University,

Columbus, OH 43210, USA (*correspondence: [email protected])

2School of Earth Sciences, The Ohio State University, Columbus, OH 43210, USA

3Nicholas School of the Environment and Earth Sciences, Duke University, Durham, NC 27708, USA The boron isotopic geochemistry was investigated in the

ice-covered lakes and glacial meltwater streams within Taylor and Wright Valley of McMurdo Dry Valleys (MCM), Antarctica, in order to achieve a greater understanding of the origin of solutes. MCM is the largest ice-free region in Antarctica, and has mean annual temperature of ~-20°C and annual precipitation of <5 cm per year. Even under this extremely arid climate, hydrological connectivity exists throughout the austral summer during which time ephemeral streams form from glacial meltwater and flow into ice-covered, closed basin lakes. The source of boron and the geochemical evolution of these water bodies are reconstructed by using #11B, B/Cl, and Na/Cl ratios. Concentration of B and its isotopic composition were measured by inductively coupled plasma mass spectrometry and negative thermal-ionization mass spectrometry techniques, respectively. In Taylor Valley, B/Cl ratios suggest two sources of boron to the lakes, a terrestrial weathering source and a marine source. These ratios also indicate the depletion of boron by adsorption within the higher rock-water aquatic systems of Wright Valley. #11B values span the range of 12.3‰ to 51.4‰, with the heaviest value in the hypolimnion of a highly evaporated hypersaline lake. Depending on the landscape position and history of each lake, two isotopic mixing regimes exist: marine with terrestrial-influenced meltwater and ancient evaporated seawater with marine-influenced lake water.


A583

Neutrophilic, Fe(II)-oxidizing organism isolated from 1.4 km-depth

in Cu/Zn Mine, Canada K. LESLIE1, C. IHLENFELD2, C. OATES2

AND D.A. FOWLE1 1Department of Geology, University of Kansas, Lawrence, KS

66049, USA ([email protected])

2Geochemistry Division, Anglo American plc, 20 Carlton House Terrace, London, SW1Y 5AN, United Kingdom The existence of a diverse biosphere in the deep terrestrial

subsurface has long been established. Recent investigations have expanded our understanding of the microbial ecology, the feedbacks between geochemistry and microbial metabolism, and energtics/diversity/adaptation of microbial metabolisms [1, 2]. Environments that were considered void of life (extreme physical conditions, lack of photosynthetically derived substrates) have been shown to contain diverse communties with unique and sustainable metabolisms [3].

Here we investigated a unique biofilm community located at 1.4 km depth, in the Triple 7 Cu/Zn mine (Flin Flon, Canada). We studied this community (including borehole fluids and the associated Fe-precipitate and biofilm) using molecular and cultivation techniques. The groundwater geochemistry is oxic, circumneutral, saline (4.7%) and metal rich. 16S gene sequencing identified two organisms, similar to Flexibacter tractuosus and Marinobacter spp. (typically marine organisms) present in the borehole fluids; while only Marinobacter spp. was detected in the biofilm. Isolates of the neutrophilic, halophilic Marinobacter spp. were obtained, and it was demonstrated to be capable of organotrophic growth (anaerobically and aerobically) and lithotrophic growth on Fe (II) with O2 in gradient tubes [4].

To examine the biogeochemical Fe- and trace metal- cycling in this deep subsurface setting, incubation experiments were carried out with the Fe (II)-oxidizing Marinobacter isolate and pyritic (non-metal) and mineralized (metal-containing ore) material in batch and column flow-through settings. The activity of the Marinobacter isolate resulted in an increase in the mobilization of Fe, S and trace metals (Cu, Zn) from all materials. These results indicate that microbial activity in the subsurface affects the mobilization of Fe and trace elements, and that Fe (II)-oxidation may be an important biogeochemical process in the deep subsurface.

[1] MacLean et al. (2007) Geomicrobiol J 24, 491–504. [2] Sahl et al. (2008) Appl. Environ. Microbiol. 74, 143–152. [3] Lin et al. (2006) Science 314, 479–482. [4] Emerson & Moyer (1997) Appl. Environ. Microbiol. 63, 4784–4792.

Metatranscriptomic insights into the geomicrobiology of deep-sea

hydrothermal plumes R.A. LESNIEWSKI, K. ANANTHARAMAN AND G.J. DICK* Dept. of Geological Sciences, University of Michigan, Ann

Arbor, MI 48109, USA (*correspondence: [email protected]) Geomicrobiological processes within deep-sea

hydrothermal plumes mediate the fate of hydrothermal inputs in the oceans, but little is known about the microorganisms underpinning these reactions. Recent results from Guaymas Basin (GB) show enhanced microbially-mediated Mn (II) oxidation rates in plumes [1], but microbial diversity that is indistinguishable from surrounding ambient seawater [2]. Enhanced microbial activity in the plumes is also reflected by RNA concentrations that are ~four times higher than background.

Here we report metagenomic and metatranscriptomic analyses of microbial communities in GB plumes versus background deep-sea waters. Of ~3 million 454 Titanium pyrosequencing metatranscriptomics reads, 85% were rRNAs, providing deep views into the relative activity of specific taxa. Analysis of 16S rRNA gene transcripts at coarse phylogenetic levels revealed no major differences between plume and background. In constrast, large differences in protein-coding genes were observed, including overexpression in the plume of genes for sulfur oxidation, electron transport proteins, and a multicopper oxidase potentially involved in Mn (II) oxidation. Transcripts of genes for ammonium uptake and ammonia oxidation were prevalent in both plume and background.

Assembly of ~2 million metagenomic sequence reads produced near-complete genomes of dominant populations including SUP05-like Gammaproteobacteria, Crenarchaeota, and SAR324 Deltaproteobacteria. Comparative genomic analyses are underway to assess the metabolic potential of these plume poppulations relative to genomes retrieved from other marine environments.

Overall, our results suggest that microorganisms active in GB hydrothermal plumes are indigenous to the ambient deep sea. Shifts in their physiological state, manifested by shifts in gene expression, appear to underpin enhanced geomicrobiological activity observed in deep-sea hydrothermal plumes.

[1] Dick et al. (2009) GCA 73, 6517–6530. [2] Dick et al. (in press) Environ. Microbiol.


Elucidating the bimodal acid-base behavior of the water-silica interface

from first principles KEVIN LEUNG1*, IDA M.B. NIELSEN2*

AND LOUISE CRISCENTI3 1([email protected])

2([email protected])

3([email protected]) Understanding the acid-base behavior of silica surfaces is

critical for many nanoscience and bio-nano interface applications. Silanol groups (SiOH) on silica surfaces exhibit two acidity constants—one as acidic as vinegar—but their structural basis remains controversial. The atomic details of the more acidic silanol site govern not just the overall surface charge density at near neutral solution pH, but also how ions and bio-molecules interacts with and bind to silica immersed in water. Using ab initio molecular dynamics simulations and multiple representative crystalline silica surfaces, we determine the deprotonation free energies of silanol groups with different structural motifs. We show that previously proposed motifs related to chemical connectivity or inter-silanol hydrogen bonds do not yield high acidity. Instead, a plausible candiate for pKa=4.5 silanol groups may be found in locally strained or defected regions with sparse silanol coverage. In the process, irreversible ring-opening reactions of strained silica trimer rings in contact with liquid water are observed.

Sulfidation of silver nanoparticles CLÉMENT LEVARD1,2*, MARC MICHEL1,3

AND GORDON E. BROWN, JR.1,2,3 1Department of Geological & Environmental Sciences,

Stanford University, Stanford, CA 94305-2115, USA (*correspondence: [email protected])

2Center for Environmental Implications of NanoTechnology (CEINT), P.O. Box 90287, Duke University, Durham, NC 27708-0287, USA

3Department of Photon Science and Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, MS 69, 2575 Sand Hill Road, Menlo Park, CA 94025, USA

The focus of this study is on understanding the behavior of

coated Ag nanoparticles (Np) under varying environmental conditions (Eh, pH, different solution components and concentrations). A significant effort has been made to characterize corrosion product formation prior to solubility measurements and reactivity studies and in particular the sulfidation process, which is the most likely corrosion phenomenon that might happen in the environment.

Therefore, three sizes of Ag Np coated with PVP (polyvinyl pyrrolidone) were produced using the polyol process (7 ± 1 nm; 25 ± 4 nm and 55 ± 9 nm). The Ag NP samples were reacted with a Na2S solution with different concentrations so the sulfidation process could be studied step-wise for each particle size. Corrosion products were characterized (SEM, XPS, XRD, surface charge, etc.) after 24 hours of reaction

Based on SEM results, we infer that the sulfidation process is the result of dissolution-precipitation. Moreover, we found that: (i) acanthite (Ag2S) is formed as a corrosion product; (ii) Ag Np aggregation increased with sulfidation rate; (iii) pHPZC increases with the sulfidation rate; and (iv) the solubility of corroded, sulfidated Ag Np appears to be lower than that of fresh Ag Np.

These results are important to consider in predicting the behavior of Ag Np in natural ecosystems. The aggregation caused by sulfidation may seriously limit their transport in porous media such as soils. Modification of the surface charge during the sulfidation process may have an important impact on electrostatic interactions between the Ag Np and charged phases in soils such as natural organic matter. Finally, the observed decrease in solubility of Ag Np after sulfidation may strongly impact the toxicity of silver since it is well known that Ag+ has a greater toxicity than metallic Ag. Sulfidation of Ag Np may limit their transport and toxicity in soils.


A585

17O anomalies in sedimentary silica and oxides

N.E. LEVIN1,2*, T.D. RAUB2, N. DAUPHAS3 AND J.M. EILER2

1Johns Hopkins University (*correspondence: [email protected])

2California Institute of Technology ([email protected], [email protected])

3The University of Chicago ([email protected]) Recent oxygen isotope measurements demonstrate small

but significant deviations from a single mass dependent fractionation line among terrestrial materials [1, 2]. These anomalies confirm theoretical expectations of variation in the #17O-#18O relationship for equilibrium and kinetic isotope fractionations such that kinetic processes result in a relatively shallow slope (0.513) and equilibrium procesess result in a steeper slope (0.529) [3]. Here we present $17O data for sedimentary silica and oxides, including cherts and banded iron formation (BIF) materials. We report $17O relative to a reference line (#’17O-#’18O), slope 0.530 ± 0.003 (95% conf, MSWD = 1.07 [4]), that we produced from analysis of igneous and high-grade meta-igneous garnet, albite, pyroxene, olivine and quartz. This slope is higher than slopes previously generated for garnets (0.527 ± 0.001) and quartz (0.524 ± 0.001) in other laboratories [2], but within error of the slope predicted for equilibrium fractionation (0.529).

Archean cherts yield average #18O values of 21.6 ± 0.3‰ (SMOW) and $17O values of -0.13 ± 0.01‰. #18O and $17O values of Phanerozoic cherts average 31.8 ± 2.0‰ and -0.16 ± 0.01‰, respectively. BIFs from Greenland yield #18O of 10.8 ± 1.7‰ and $17O of -0.04 ± <0.01‰. Slopes needed to produce these results by fractionation with respect to seawater (assuming #18O is 0‰ SMOW) average 0.523, 0.524 and 0.526 (std. err. <0.001) for Archean cherts, Phanerozoic cherts and BIFs, respectively. If initial water #18O is varied by ± 5‰ the calculated slopes all remain less than 0.527.

These $17O results demonstrate detectable 17O anomalies in sedimentary silica and oxides. Negative $17O values in Phanerozoic cherts indicate that such anomalies can be produced in marine authigenic minerals within an oxygenated atmosphere; i.e. they are not likely connected to photochemical 17O anomalies. We hypothesize that these compositions result from mass dependent, kinetic fractionations associated with silica precipitation from seawater.

[1] Barkan & Luz (2005) Rap. Comm. Mass. Spectr. 19 3737–3742. [21] Rumble et al. (2007) GCA 71, 3592–3600. [3] Young et al. (2002) GCA 66, 1095–1104. [4] Ludwig (2003) http,//www.bgc.org/isoplot_etc/software.html.

Water intermittent dynamics over a colloidal interface:

Probing adsorption and relocation statistics in confinement

P. LEVITZ PMC, Ecole Polytechnique-CNRS, Palaiseau, 91128 France,

([email protected]) Water confined in the vicinity of mineral surfaces is a

ubiquitous situation encountered in geological, physical, biological, and industrial systems.�As a result, much research effort has been devoted to understand the effect of confinement and surface forces on water dynamics. A coarse grain picture of this dynamics over a surface can be considered as an intermittence of adsorption steps and bulk relocations from one point to another point of the interface. Adsorption statistics such as the adsorption time distribution and its first moment reflect the degree of interaction of the molecule with the colloidal interface. The relocation statistics strongly depends on the shape of the colloidal particle, the surface forces and the bulk confinement [1-3]. In this talk, a theoretical analysis of the intermittent dynamics (ID) is first proposed for different interfacial geometries [2-3]. Direct comparisons with recent Molecular Dynamics simulations are discussed [4]. In the second part, we present an experimental investigation of the ID, using NMR relaxometry for various colloidal systems (flat colloidal clay particles [4], imogolite strands [5], plaster pastes [6]). Comparison with analytical derivations is discussed. Evaluation of the fluid-surface interaction in term of ‘nano-wettability’ is emphasized.

[1] Levitz (2005) J. Phys. Condens. Matt. 17, S4059. [2] Levitz, Grebenkov, Zinsmeister, Kolwankar & Sapoval (2006) Phys. Rev. Lett. 96, 180601. [3] Levitz, Zinsmeister, Davidson, Constantin & Poncelet (2008) Phys. Rev. E 78, 030102 (R). [4] Bonnaud, Coasne & Pellenq (2010) J. Phys.Chem., in press. [5] Levitz & Korb (2005) Europhysics Letters 70, 684. [6] Korb & Levitz (2008) Proceedings of MRPM 9.


Does the Chelex resin in DGT devices really act as a perfect planar sink for metals? Kinetic limitations of DGT

measurements J. LEVY1*, H. ZHANG1, W. DAVISON1, J. PUY2

AND J. GALCERAN2 1Lancaster Environment Centre, Lancaster University,

Bailrigg, United Kingdom, LA14DF (*correspondence: [email protected], [email protected], [email protected])

2Department de Química, Universitat de Lleida, Rovira Roure 191, 25198, Lleida, Spain ([email protected], [email protected]) Diffusive gradient in thin films (DGT) is a dynamic

technique that can measure metal speciation in situ, and has been widely applied to waters, sediments and soils. Like any analytical technique it relies on a number of assumptions, a major one being that the gel-integrated binding phase will bind trace metals irreversibly and near instantaneously. However, the Chelex beads (or another iminodiacetate based resin, SPR-IDA) in a typical DGT device for trace metal measurements is not a perfect planar sink. Multiple resin gel layers were used to enable analysis of different depths of a DGT binding phase. At pH 7, when no fulvic acid was present, metal penetration to the back layer was low and similar for all metals. However, at lower pH up to 42% of an individual metal accumulated by the DGT was in back resin layers. This was most noticeable for Mn at pH 4 and 5, but was also found for Cd and Co at pH 4. These metals have predicted lower affinity for Chelex when compared to other metals. This suggests that binding to Chelex may sometimes be kinetically limited, particularly for Mn. For all metals, more metal was found in back layers when fulvic acid was present. Metal penetration to back layers also increased with decreasing pH. A model was developed to determine the distance that metals may penetrate into DGT resin layers.

Production of primary particles at the sea surface that can function as

cloud condensation nuclei ERNIE R. LEWIS

Atmospheric Sciences Division, Environmental Sciences Department, Building 815E, Brookhaven National Laboratory, Upton, NY, USA 11973 ([email protected]) As the oceans cover the vast majority of Earth’s surface,

marine clouds are an important contributor to Earth’s radiative balance. The formation and microphysics of these clouds depends on the sizes and numbers of aerosol particles present upon which cloud drops can form. In marine environments particles that are directly produced at the sea surface provide the dominant contribution to aerosol mass concentration, but their relative contribution to aerosol number concentration is not well quantified. Knowledge of the size-dependent production flux and its dependence on parameters such as wind speed, is necessary to understand and accurately model cloud formation in the marine atmosphere. Until recently it has been thought that primary aerosol particles produced at the sea surface were not abundant relative to other aerosol particles in the radius range of several tens of nanometers, those sizes thought to be most important for cloud drop formation, but several recent formulations have been presented for the flux of these particles that suggest that they may be produced in large numbers. However, the number of particles that would be produced according to these formulations seems unrealistically high, and failure of many previous investigations to detect particles of these sizes causes concerns as to the extent to which the formulations are applicable to oceanic particle production. Here the production flux of particles with radii at formation less than a few tenths of a micrometer is discussed, with older investigations reviewed and newer formulations examined.


A587

Submarine magmatic-hydrothermal systems at the Monowai Volcanic

Centre, Kermadec Arc M.I. LEYBOURNE1*, C.E.J. DE RONDE1, E.T. BAKER2,

KEVIN FAURE1 S.L. WALKER2, J. RESING2 AND G.J. MASSOTH1

1GNS Science, P.O. Box 30-368, Lower Hutt, New Zealand (*correspondence: [email protected])

2PMEL, National Oceanic and Atmospheric Administration, 7600 Sand Point Way, Seattle, WA 98115-6349, U.S.A The Monowai volcanic centre (MVC), located mid-point

along the ~2530 km long Tofua-Kermadec arc system, is comprised of a large elongate caldera (7.9 x 5.7 km; 35 km2; floor depth = 1590 m), formed within an older caldera (84 km2). Associated is a large active stratovolcano, which rises to within ~ 100 m of the sea surface. Atypical of arc caldera volcanoes, mafic rocks dominate the MVC, with only rare andesites. Volcanic rocks are typical arc tholeiites, derived from partial melting of highly depleted mantle fluxed with fluids from the subducting Pacific Plate; there is little evidence for contribution from subducted sediment.

Plume mapping shows at least four hydrothermal systems with venting from the summit of Monowai cone and on its northern flank. Monowai caldera has a major hydrothermal vent system associated with the southwest wall of the caldera. The cone summit plume is gas-rich and acidic with &pH = -2.0, H2S . 32 µM and CH4 . 900 nM, and total dissolvable Fe (TDFe) to 4200 nM, TDMn to 412 nM, and TDFe/TDMn (up to 20.4). By contrast, Monowai caldera plumes have lower TDFe, but range to higher TDMn concentrations, and are relatively gas-poor (no H2S detected, &pH = -0.6 pH units, CH4 to 26 nM). Elevated TDMn and lower TDFe/TDMn for Monowai caldera plumes compared to Monowai cone likely reflects significant precipitation of Fe-sulfides in the subsurface, raising the distinct possibility for the occurrence of buried massive sulfide mineralization at Monowai.

Particulate samples are enriched in Al, Ti, Ca, Mg, Si, and S, with the cone summit plume particularly enriched in K, As, W and Cu, Pb, Zn. The elevated Ti and Al suggest acidic water-rock reactions and intense high-sulfidation alteration of the host volcanic rocks. Monowai caldera has numerous vents (< 60°C) and a large biomass of vent-associated fauna, including the mussel Bathymodiolus sp. and the tubeworm Lamellibrachia sp.

Monowai cone shows evidence of significant magmatic volatile ± metal contributions to its hydrothermal system. By contrast, Monowai caldera is dominated by hydrothermal water-rock reactions.

Sequential leaching methods for strontium isotope stratigraphy: Analysis of marine authigenic

carbonates and phosphates DA LI1*, GRAHAM SHIELDS2, HONGFEI LING1*

AND MATTHEW THIRLWALL3 1Dept. Earth Sciences, Nanjing University, 210093, Nanjing,

China (*correspondence: [email protected])

2Dept. Earth Sciences, UCL, London, WC1E 6BT, UK

3Dept. Earth Sciences, Royal Holloway, TW20 OEX, UK Strontium isotope stratigraphy (SIS) involves the

correlation of geographically separated strata using their Sr isotope signatures. The use of SIS is based on evidence that seawater is generally homogeneous with regard to its Sr isotope composition - this is because the residence time of Sr in the ocean (~>2 Ma) is >1000 times longer than its ocean circulation time (~1500 a) - and assumes that marine authigenic sedimentary components preserve the original Sr isotopic ratio of ancient seawater. Marine Sr isotope data derive mainly from calcitic and apatitic fossils, and more rarely limestones, which together have been used to reconstruct secular trends in seawater 87Sr/86Sr (eg. [1]). However, the extent to which other marine authigenic minerals may provide primary information about ocean composition has been less well studied, and inappropriate leaching methods often applied. Bailey et al. [2] revealed that Sr from non-target phases may substantially contaminate the 87Sr/86Sr of a limestone sample and must be avoided when analysing bulk limestones for SIS. Here we widen the scope of those experiments to dolostone and phosphorite as well as limestone samples. The samples were collected from the Xiaotan section on China’s Yangtze Platform which spans the late Neoproterozoic to basal Cambrian. These samples contain micrite, francolite (phosphate) and dolomite. Micrites and dolostones were leached using 0.3% acetic acid to dissolve 30% and 40% of the carbonate fraction, respectively. Phosphorites were first leached by 0.3% acetic acid to dissolve all the carbonate fraction and then attacked using 0.05M nitric acid to dissolve the phosphate phase. The Sr released after each leaching step was analysed isotopically using TIMS at Royal Holloway, University of London.

Our data show that the second leachate yielded significantly lower 87Sr/86Sr ratios than the first leachate by up to 0.0006 in 15 out of 19 micrite and by up to 0.0037 in 9 out of 11 dolostone samples (only two second leachates had significantly higher values by up to 0.0011). The phosphate phase yielded similar 87Sr/86Sr ratio as the carbonate leachate of the same sample (within ±0.0002 in all 5 phosphorite samples) and these ratios fell in the stratigraphic trend.

Based on our and previous studies, we give out a simple guideline for future use of authigenic sediments for SIS. [1] Veizer et al. (1999) Chem. Geol. 161, 59– 88. [2] Bailey et al. (2000) Chem. Geol. 167, 313–319.


Global biogeochemical cycle of silicon: New model

DARCY DAN LI AND ABRAHAM LERMAN Department of Earth and Planetary Sciences, Northwestern

University, Evanston, IL 60208, USA ([email protected], [email protected]) Silicon, as the second abundant element in soil and earth’s

crust, is geochemically important both in inorganic and organic regimes. Silicate weathering due to tectonic uplifting is great associated with long-term CO2 consumption and consequently climate change. Rough estimations of global primary production show that Si accounts for ~1.5% molar mass of terrestrial primary production while ~4.5% of marine primary production is contributed by Si. Furthermore, the coupling of Si cycle with other major nutrient cycles of C, N, P, and S can be used as forcings to investigate the role of Si in fields of earth, biology, and ecology sciences.

Thus, a model of the global biogeochemical cycle of Si was developed to explore the incorporation of all these geochemical and biological processes and to quantify the changes of each geochemical reservoirs and fluxes under perturbations. Three domains, terrestrial, coastal ocean, and Open Ocean are established. Terrestrial domain deals with processes occurring on land and freshwater environments, including mineral weathering and other geochemical processes, primary production of land biota (Si:C ratio taken as 0.02, compared to 0.15 for that of marine diatoms), as well as that of freshwater diatom. Open ocean domain contributes ~80% of all marine primary production. Coastal ocean domain is the linkage between those two domains; distinct water chemistry changes and subsequent biological transformations makes it a critical place of global changes.

Sensitivity tests of temperature-dependent perturbations, e.g. weathering and primary production are put forward as of an evaluation of the model’s robustness on a timescale of 10000 yrs.

Figure 1: A simplified model of biogeochemical cycle of Si.

Cultivation practices affect heavy metal migration between soil and

Vicia faba FEILI LI, LIJIA NI, JIN YUAN, G. DANIEL SHENG*

College of Biol. & Environ. Engineering, Zhejiang Univ. of Tech., Hangzhou 310032, China ([email protected])

Introduction Pot-test experiments were conducted to study the

influences of mulching and fertilizing on the migration of heavy metals from soil to vicia faba (broad bean). Semi-transparent film was used to mulch soil. Swine manure compost was mixed with soil at a rate of 50 mg kg-1 as fertilizer. Broad bean was grown for several months until fruits were formed. Soils and bean parts were sampled to analyze and fractionate heavy metals. Results and Discussions

Mulching promoted an obvious growth of broad bean [1]. Fertilizing decreased soil pH and increased SOM content [2]. Mulching reduced the exchangeable metal fractions by 5% to 52%. Fertilizing, in contrast, increased the exchangeable fractions of most of the metals except Fe and Pb by 20% to 295%. While the two cultivations increased obviously metal concentrations in bean laminas as compared to unmulched and unfertilized controls, the levels of most of the metals except Pb decreased in bean fruits.

Calculated bioconcentration factors (BCF) and transfer factors (TF) indicate that the cultivations had little influences on the metal enrichments in roots, but promoted their migration from roots to laminas [3]. In particular, mulching greatly promoted the absorption and translocation of Fe, while fertilizing enhanced the bean fruit uptake of Pb [4, 5].

Figure 1: Influence of cultivation practices on BCF and TF of metals *1: no mulching and no fertilizing (control); 2: mulching only; 3: fertilizing only; 4: joint mulching and fertilizing.

[1] Ehlken Kirchner (2002) Journal of Environmental Radioactivity 58, 97–112. [2] Bulluck et al. (2002) Appl. Soil Ecol. 19, 147–160. [3] Liaoyan (2003) 197–206. [4] Queirolo et al. (2000) Sci. Total Environ. 255, 75–84. [5] Tommasini et al. (2000) Appl. Geochem. 15, 891–900.


A589

Geochemistry and environmental impact of cadmium in cadmium-rich

Pb–Zn mine wastes of Southwest China

H. LI1,2,3*, T. XIAO1, D. LI2,3, Z. ZHU2,3 AND Z. NING1 1State Key Laboratory of Environmental Geochemistry,

Institute of Geochemistry, Chinese Academy of Science, Guanshui Road 46, Guiyang 550002, China (*correspondence: [email protected])

2Chongqing Institute of Geology & Mineral Resources, Chongqing 400042, China

3Chongqing Research Center of State Key Laboratory of Coal Resources and Safe Mining, Chongqing 400042, China Much attention has been paid to the environmental impact

of cadmium (Cd) in the Pb'Zn mineral processing wastes [1, 2]. In order to identify the potential environmental risks of Cd, we studied the geochemical behaviours of Cd in the mine wastes from the China’s largest Jinding Pb-Zn deposit located in southwest China. The result showed that the oxidized ores have the lower Zn/Cd ratios [3], suggesting that Cd tends to become enriched in the secondary minerals during the weathering processes. Based on the results of X-ray diffraction and scanning electron microscope studies combined with energy-dispersive spectrometry, Cd is also incorporated into secondary mineral smithsonite. Leaching test indicated that Cd was easily released from the oxidized ores, and the abundance of smithsonite was the main carrier to control the leaching processes [3]. Sequential extraction suggested that high Cd levels in the weak-acid extracted fraction have significant mobility and bioavailability into the ambient environment [1, 4]. Therefore, cadmium in the mine wastes from Cd-rich Pb–Zn mine areas appears to pose high potential for environmental risk, especially in the aquatic ecosystems [2].

[1] Li et al. (2007) Geochimica 36, 612'620. [2] Schmitt et al. (2007) Ecotox. Environ. Saf. 67, 31'47. [3] LI et al. (2008) Chinese J. of Geochem. 27(1), 21–27. [4] Lottermoser et al. (2008) Appl. Geochem. 23, 723'742.

Partial melting processes during exhumation of the subducted

continental crust in the Sulu UHP terrane, China

HONGYAN LI1* KAI YE2 JINGBO LIU2 DONG WANG1

1Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China (*correspondence: [email protected])

2Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China During the continental deep subduction process, it was

deduced that no significant dehydration occurs, and syn-collisional magmatism is generally absent. However, some field observations, together with U-Pb dating, REE and Hf isotope analysis results of zircons, will be presented here, to disclose obvious fluid/melt activities and partial melting processes during the early stage of exhumation of the subducted continental crust in the Sulu UHP terrane.

In the southern Sulu UHP terrane, some zoisite-kyanite-paragonite quartz noddles occur in epidote-bearing eclogite in the Donghai area. Zircons from a noddle give a SHRIMP U-Pb age of 219±9Ma. The cores and rims of the zircons from the country gneiss of the epidote-bearing eclogite show irregular patch structures and oscillatory zonings, respectively. They have different Hf isotopic values, but they give a consistent age of 218±5 Ma. These indicate that an aqueous fluid activity and a partial melting process of granitic gneiss occur at 218-219Ma.

In the northern Sulu UHP terrane, widespread migmatization domains can be observed. In the field, dark gneiss and pale gneiss show structures similar to magma mingling. Leucogranite veins locally occur in the UHP unit. (1) In the Rongcheng area, both dark gneiss and pale gneiss in a migmatite domain have protolith ages of ca 780Ma. The mantles and rims of the pale gneiss show CL features of metamorphism and partial melting origin, respectively. Their ages of 242±9 Ma and 220±4 Ma are regarded as the time of peak metamorphism and partial melting of the pale gneiss. (2) In the Weihai area, zircons from a pegmatite vein within gneiss, with clear oscillatory zonings, gave two ages of 221±7Ma and 199±Ma. Zircons from the country gneiss show a core-mantle-rim structure, the cores and rims show magmatic zircon characteristics and yield ages of 772±7 Ma and 195±4 Ma, respectively. Uniform zircon Hf isotopic values are observed in the pegmatite and the rims of the country gneiss. Thus, we interpret the age of 221 Ma as the time of pegmatite crystallization and 199 Ma as the timing of remelting of the country gneiss intruded by the pegmatite.


Hydrogen isotope geochemistry of giant gas field in Ordos Basin

JIAN LIN1,2* ZHISHENG LI1,2 DONGLIANG WANG1,2 AND JIN LI1,2

1Research Institute of Petroleum Exploration and Development (Langfang Branch), Petrochina, 065007 P.O. Box 44, Langfang, HeBei, China

2The Key Laboratory of Gas Formation and Development, Petrochina, 065007 P. O. Box 44, Langfang, HeBei, China (*correspondence: [email protected]) The Ordos Basin is located in north-central China, is

China's second-largest sedimentary basin, which contains the largest amount of gas fields with proved geological reserves over 100 b m3 in China. 60 natural gases are sampled in Sulige, Yulin and Zizhou gas fields, and hydrogen analysis is carried out for all the natural gas samples. Our research results have shown that the gases in this basin are generally coal related gases with heavy hydrogen isotopic compositions [1-4]. However, the hydrogen isotopic distribution is different from each gas fields. In Sulige gas field, the $DCH4 value of natural gas is -180‰!-167‰, $DC2H6 value ranges from -165‰ to -149‰, and $DC3H8 ranges from -166‰ to -146‰; The $DCH4, $DC2H6, $DC3H8 values of natural gas in Yulin gas field are -174~-168‰, -160~-143‰, -152~-132‰, respectively; The $DCH4, $DC2H6, $DC3H8 values of natural gas in Zizhou gas field are -169~-160‰, -158~-137‰, -152~-129‰, respectively. Hydrogen isotope values become heavier from east to west (Sulige -Yulin - Zizhou), namely the maturity of the natural gas increased gradually, and is consistent with that the maturity of Carboniferous-Permian source rocks become higher from east to west. This fully reflect the ralationship between hydrogen isotope values and the maturity of the natural gas.

From the aspect of hydrogen isotope series of CH4, C2H6, C3H8 ralationships, the study shown that the hydrogen isotope series of Yulin and Zizhou gas fields increased gradually, the $DC2-1 values and $DC3-2 values greater than 5‰, exhibited a positive sequence; The $DCH4, $DC2H6 of Sulige gas field exhibited a positive sequence, however, majority of gases showed a reverse sequence with $DC2H6, $DC3H8 values, the $DC3-2 values lessr than -5‰, consistent with the C2H6, C3H8 carbon isotope series. This indicates that the natural gas of Sulige gas field is mixed with different maturity natural gas.

In summary, the hydrogen and carbon isotopic characteristics all showed that the natural gas in Ordos Basin is coal related gas, the hydrogen isotopic values can well reflect the maturity of natural gas.

[1] Dai J.X. et al. (2005) Acta Petrolei Sinica 26(1) 18–26. [2] Li J. et al. (2008) Marine & Petroleum Geology 25, 401–415. [3] Dai J.X. et al. (2003) Large Gas Fields in China & their Genesis. Science Press, Beijing, pp.93-136. [4] Dai J.X. et al. (1992) The Geology of Natural Gas in China (Vol.1) Petroleum Industry Press, Beijing, pp.1-220.

Industrial bio-heap leaching of uranium ores in a uranium mine

LI JIANG1 *, LIU YAJIE2, RAO JUN1, SUN ZHANXUE2, WANG XUEGANG2, LI XUELI2 AND SHI WEIJUN2

1East China Institute of Technology, School of Chemistry Biology and Material, Fuzhou City, Jiangxi Province, P.R. Chnia, 344000 (*correspondence: [email protected])

2East China Institute of Technology, School of Civil and Envrionmental Engineering, Fuzhou City, Jiangxi Province, P.R. Chnia, 344000 Bioleaching have been widely thought as a commercial

and environment friendly technique to recover metals from the low grade ores [1]. Through bio-leaching, uranium leaching yields can be increased, acid consumption can be reduced, and the leaching period can be shorten, as a result, lowering the production costs and raising the economic efficiency. In recent years, with the low grade uranium ores increasing in China, it is difficult and low efficiency to extract uranium from this kind of ores by traditional techniques. Therefore, bio-leaching, as a prospected technique which can lower down the production costs greatly, has been favoured by some of the Uranium Mines. Especially at the moment of energy crisis, it is very important to develop bio-leaching to the industrial production for the low grade uranium ores.

In this study, a 4, 315 tons of uranium minerals heap was biult in a Uranium Mine in southern China. The average chemical uranium grade of the minerals is 0.186%, mineral particle size is -6mm. A consortia with ferrous and sulfur oxidized acidiphiles was used to irrigate the heap after 30 days acidified with sulfuric acid solution. After 120 days, the leaching rate of 92.63% was obtained. Comparing to the conventional heap, leaching rate of the test heap increased about 3%, leaching period shortened 30-40 days and the acid consumption reduced about 2%. After the bio-heap leaching, the uranium content of slag is 0.0137%, which is lower than the conventional heap. Consequently, this industrial test of bio-heap leaching can be applied in this Uranium Mine and other Uranium Mines.

Thanks for the supports of Jiangxi Provincial Department of Education Project (GJJ09008), National Natural Science Foundation of China Project (50974043) [1] Brierley & Brierley (2001) Hydrometallurgy. 59, 233–239.


A591

Migrations of sediment redox boundaries as indicators of change in

oligotrophic systems JIYING LI1, SEAN A. CROWE2, DAVID MIKLESH3,

DONALD E. CANFIELD2, SERGEI KATSEV1,3*

1Large Lakes Observatory, University of Minnesota Duluth (*correspondence: [email protected], [email protected])

2NordCEE, University of Southern Denmark ([email protected], [email protected])

3Dept. of Physics, University of Minnesota Duluth ([email protected]) In oligotrophic environments, such as the deep Arctic

Ocean, the depth of oxygen penetration (OPD) into sediments is deep and highly sensitive to the supplies of oxygen and organic matter from the overlying water [1]. Recorded in the distribution of redox-sensitive metals, changes in the OPD may reveal temporal trends in trophic conditions. In sediments recovered from the deep basins of Lake Superior, oxygen penetrated below diagenetic layers of iron and manganese by 3 cm or more in both June and October. This suggests either a long-term decrease in the productivity of the lake or large seasonal changes. The latter may result from changes in the bottom water oxygen levels, which fluctuate by about 10%. These large OPD migrations would strongly affect sediment effluxes of nutrients, such as nitrate. Herein we discuss challenges in detecting the temporal variations in sediment redox balance, in determining their time scale and time lags, and accounting for the effects of strong lateral heterogeneity in sediment properties. Based on our diagenetic studies, we place new constraints on nutrient budgets in Lake Superior.

[1] Katsev et al. (2006) Limnol. Oceanogr. 51, 1581–1593.

Nitrogen in the Canadian Shield: Resolving abiotic contributions and

biological cycling L. LI1*, B. SHERWOOD LOLLAR1,

G. LACRAMPE-COULOUME1, J. MORAN2 AND G.F. SLATER2

1Dept. of Geology, University of Toronto, Toronto, ON Canada M5S 3B1 ([email protected], [email protected], [email protected])

2School of Geography and Earth Sci., McMaster University, Hamilton, ON, Canada L8S 2G4 ([email protected], [email protected]) There is increasing interest in understanding the Earth's

geological nitrogen budget and reservoirs - a topic important not only for understanding greenhouse warming on the early Earth [1], but for understanding the environment in which life arose. While hydrocarbon gases and H2 have been investigated in the > 2 Ga rocks of the Canadian Shield - to date little research has been undertaken on the substantial quantities of molecular nitrogen (N2) also found in these subsurface environments.

The results of gas content (by gas chromatography) and nitrogen isotope (by GC-IRMS) analyses show a clear positive relationship between N2/O2 and $15NN2 for samples with N2/O2 < 20, indicating the low $15NN2 values are attributable to air contamination. However, samples with N2/O2 > 20 show a narrow range of 7-9‰ in $15NN2, with a few samples as enriched as +17.5‰. The $15NN2 values seem to be quite uniform compared to the hydrocarbon and H2 gas geochemistry and isotopic signatures - which have been shown to vary significantly from one site to another based on the relative dominance of microbial processes, versus abiotic water-rock reactions, such as H2-producing radiolysis and/or serpentinization coupled to hydrocarbon formation via Fischer-Tropsch synthesis and polymerization.

The kinetic isotope effect associated with thermal decomposition of NH3 is large (17‰). Generally, denitrification and ammonia oxidation are also associated with large kinetic fractionation effects (>10‰) with only a few small fractionation effects (<3‰) observed for microbial denitrification. The $15NN2 values may be relatively constant if equilibrium isotope fractionation between N2 and its source species can be reached, although equilibration is unlikely at temperatures <300°C. Ongoing investigation of $15N of ammonium and nitrate in the hosting saline ground waters and rocks will help to further evalute the sources and sinks of N2 in this setting.

[1] Goldblatt et al. (2009) Nature Geoscience 2, 891–896.


High salinity CO2-rich magmatic fluids: Features of the East Qinling-

Dabie porphyry Mo belt, China NUO LI

School of Earth and Space Sciences, Peking University, China ([email protected]) Porphyry deposits are most commonly discovered in

continental and oceanic arcs, and generally contain coexisting high-salinity brine and low salinity aqueous vapor [1, 2]. The East Qinling-Dabie orogenic belt contains several Yanshanian Mo deposits that developed after the continental collision between the North China Craton and the Yangtze Craton at Meozoic [3, 4]. Most of these Mo deposits occur as porphyry, porphyry-skarn and skarn types, with Mo metal reserves of ~ 6 000 000 tonnes. Previous works have focused on their geological, geochemical and geochronological features, but characters of the ore-forming fluids are still open issues. In this contribution, we provide the first systematic constraints of the ore-forming fluids, and propose that high-salinity CO2-rich fluids can be regarded as a criterion for distinguishing between porphyry deposits in continental collsion setting and magmatic arc setting.

Four types of fluid inclusions have been recognized in these deposits, namely pure carbonic inclusions, carbon dioxide–aqueous inclusions, aqueous inclusions and polyphase daughter mineral-bearing inclusions. Obtained homogenization temperatures are basically higher than 300°C, and salinities can reach up to 67.2 wt%NaCl. eqv. It seems that the porphyry-mineralizing fluids in the East Qinling-Dabie belt are typified by high temperature, high salinity and CO2-rich.

Considering that porphyry systems in island arcs commonly contain early coexisting high-salinity brine and low salinity aqueous vapor [1, 2], with no appreciable CO2, we speculate that hypothermal brine appears to be indicative of magmatic-derived fluids, whereas high abundance of CO2 can be regarded as a criterion between magmatic fluids in continental collision setting and island arcs. [1] Cline, J.S. Bodnar, R.J. (1991) J. Geophys. Res. 96, 8113–8126. [2] Phillips, G.N. Zhou, T. (1999) Society of Econ. Geol. Newsl. 37, 6. [3] Chen, Y.J, Fu, S.G. (1992) Gold mineralization in Western Henan, China. Beijing, Seismological Press, 234. [4] Chen, Y.J, Li, C. Zhang, J. Li, Z. Wang, H.H. (2000) Sci China Ser D 43, 82–94.

Geochemistry and petrogenesis of volcanic rocks from the Sanlangpu

Formation and the Dashigou Formation in Qinling Mountains,

China PING LI1, XUE-YI XU1, JUN-LU CHEN1

AND HONG-LIANG WANG1,2

1Xi’an Center of Geological Survey(Xi’an Institute of Geology and Mineral Resource), CGS, Xi’an, Shaanxi 710054, China

2State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi’an, Shaanxi 710069, China) We present a detailed geochemistry study, new age dating

for The Sanlangpu Formation and the Dashigou Formation volcanic rocks form the Xixiang Group, which provides significant insights into the petrogenesis of the volcanic rocks. The Sanlangpu Formation volcanic rocks, consisting of basalt and rhyolite which can be considered as bimodal magma suite, lie uncomfortably with the Sunjiahe Formation. The Dashigou Formation volcanic rocks are composed of basalt, andesite and rhyolite, lie up comfortably with the Sanlangpu Formation. A combined field, geochronological, and geochemical study of the volcanic rocks is reported here. This study provides the first reliable LA-ICPMS zriron U-Pb dating for rhyolite sample collected form the Gangchang village in Nanzhen County gave a weighted mean 2°6Pb/238U age of 803.0±5.3Ma, which documented report of Neoproterozoic magmatism in Xixiang area. All the volcanic rocks belong to subalkali magma and erupted within plate. Trace element ratio partial melting composition model suggest basalts form the Sanlangpu Formation are derived from primary garnet lherzolite with a partial melting degree of 7%. According to the similarity of the trace element ratios and patterns, we also suggest an impossible source of the Baimianxia Formation basalts for rhyolites, and the rhyolite magma might undergone strong crystallization of plagioclase during its evolution. On the other hand, the basalt, andesite, and rhyolite in the Danshigou formation have the same trace element ratios, ! (t) and TDM, suggesting a same parent magma. Basalts in Danshigou Formation are possible derived from primary garnet lherzolite with the partial melting degree of 10%, and andesite derived when the residual magma approach to 70% during crystallization, and rhyolites occurred when the residual magma approach from 20% to 30%. The basaltic parent magma underwent strong crystallization of plagioclase and Fe-Ti oxides. It is inferred that the Sanlangpu Formation and the Dashigou Formation volcanic rocks also be attributed to the products of Neoproterozoic continental berak-up in northern margin of the Yangze Plate.

This study was supported by the National Natural Science

Foundation of China (Grant No. 40872061, 40772137 and 40972150).


A593

Features and significance of boiling oil inclusion in Ordos Basin, China

RONGXI LI*, LIU XIAOJIE AND LIU JIANCHAO Key Lab of Mineral Resources & Geology Engineering,

Education Ministry of China, Chang’an University, Xi’an, 710054, China (*correspondence: [email protected]) Ordos Basin, the second largest oil/gas production basin in

China, is located in center of north China. Upper Triassic Yanchang Formation, the most important commercial oil-producing bed, consisted of fine grain calcareous sandstone with low-permeability [1]. Drilling cores show that upright micro-fractures, cut through oil sandstone beds, were frequently filled by small calcite veins with several milimiters wide. Microscope observation indicates that large numbers of boiling oil inclusions contained in carbonate cements and calcite veins of sandstone. Oil inclusions, with bright yellow fluorescence under reflected blue light, occurred along growth zones or as clusters in the host calcite crystals (Fig.1-1). Two-phase inclusion with liquid (L) and vapour (V) (Fig.1 -2, 3) and three-phase inclusion with liquid (L), vapour (V) and small dots of black solid bitumen (Fig.1-4) were coeval and they concentrated in growth zone of calcite crystal (Fig.1-1). Gas/liquid ratio of oil inclusion was highly variable from about 5%(Fig.1-2) to nearly 70% (Fig.1-3). Homogenization temperature of all kinds of inclusion narrowed in a range from 74 to 11 with the peak of 101

Figure 1: Photomicrograph of boiling oil inclusions. Intergrowth between oil inclusions of different types and

texture of calcite indicates that gas-rich and liquid-rich oil inclusions appeared to have been trapped simultaneously. Coexisting of oil inclusions of different types strongly suggests that oil boiling occurred during the period of calcite cementating of sandstone and calcite vein filling. Features of oil inclusions represent a case of heterogeneous migrating and trapping of liquid oil during boiling process because of cracking of sandstone due to over presure.

[1] Yongtai Y. et al. (2005) AAPG Bull. 89, 255–269.

Partial melting during continental subduction-zone metamorphism: Evidence from multiphase solid

inclusions within minerals of UHP felsic vein and host eclogite in the

Dabie orogen SHU-NING LI AND YONG-FEI ZHENG

School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China ([email protected]) Multiphase solid (MS) inclusions, with regular shapes and

radial fractures, are found within metamorphic minerals such as garnet, kyanite and epidote in felsic vein and host eclogite at Sanzusi in the Dabie orogen. Coesite pseudomorphs are found in epidote of both felsic vein and eclogite, indicating significant fluid activity under UHP metamorphic conditions. The common paragenesis of the MS inclusions is quartz + K-feldspar ± silicate, suggesting that they are daughter minerals precipitated from hydrous silicate melts. Because of their constant volume ratios, a constraint is placed on the chemical composition of metamorphic melt: 0.12wt.% Na2O, 7.49wt.% K2O, 0.34wt.% FeO, 0.07wt.% MgO, 0.10wt.% CaO, 7.84wt.% Al2O3, 0.24wt.% TiO2, 83.74wt.% SiO2 and 0.05wt.% NiO. Such a composition suggests that the MS inclusions were crystallized from ultrapotassic and silica-oversaturated melts, providing an insight into the material transfer within the deeply subducted continental crust.

The occurrence of felsic MS inclusions in the UHP eclogite-facies minerals demonstrates that hydrous melts are rich in K2O and SiO2. They were probably produced by partial melting of the eclogite itself due to the dehydration reaction of phengite. This process may take place during the ‘hot’ exhumation at HP eclogite-facie subsequent to the peak UHP metamorphism. Although the chemical composition and paragenesis of these MS inclusions may be partially reset during amphibolite-facies retrogression, they are still an effective tool to investigate the nature and composition of metamorphic melt in the continental subduction zone. The existence of hydrous melts in the UHP metamorphic minerals is clearly evidence for partial melting of UHP rocks at the deep subduction zone. This would greatly influence the rheology of deeply subducted continental crust and thus contribute to the rapid exhumation of the UHP slab. It also has bearing on element mobility in association with fluid/melt flow during the exhumation.


Mantle-like magnesium isotopic composition of orogenic eclogites from the Dabie-Sulu UHPM belt,

China W.-Y. LI1,2*, F.-Z. TENG2, Y. XIAO1 AND J. HUANG1

1School of Earth & Space Sciences, University of Science & Technology of China, Hefei, 230026, P. R. China (*correspondence: [email protected])

2Department of Geosciences & Arkansas Center for Space and Planetary Sciences, University of Arkansas, Fayetteville, AR 72701, USA To date, little is known about the behaviour of Mg

isotopes during metamorphic dehydration. Orogenic eclogites are eclogite-facies metamorphosed subducted oceanic crust or mafic continental materials. Studies of orogenic eclogites can therefore help to constrain Mg isotope geochemistry during high-grade metamorphism and understand subduction processes. Here, we reported high-precision Mg isotopic data for a suite of orogenic eclogites from Bixiling in the Dabie-Sulu ultrahigh-pressure metamorphic (UHPM) belt, China.

The Dabie-Sulu UHPM belt of east-central China was formed by deep subduction of continental crust. The Bixiling eclogitic body is one of the well-studied eclogitic bodies in the Dabie area. The protolith of the Bixiling eclogite has been suggested to be gabbro cumulates derived from fractionation of basaltic magma at the deep crust, which subsequently experienced continental crust subduction, metamorphism and fast exhumation [1, 2]. Fresh eclogite samples were collected along a road section across the Bixiling eclogitic body. Samples are characterized by low SiO2 content (44.4 to 53.0%), variable MgO content (5.1 to 10.5%), and positive Eu anomalies ($Eu of 1.1 to 1.4).

Regardless of the variable MgO contents and different degrees of olivine crystallization, Mg isotopic compositions of the Bixiling eclogites are relatively homogeneous, with $26Mg ranging from -0.44 to -0.26, and fall within the range of terrestrial basalts and mantle peridotites. The mantle-like Mg isotopic signature of the Bixiling eclogites seems to record that of their protoliths, i.e. mantle-derived gabbro cumulates. This observation agrees with the absence of Mg isotope fractionation during basalt differentiation [4] and suggests limited Mg isotope fractionation during metamorphism, up to eclogite-facies, for mafic rocks. Consequently, Mg isotopes could be potentially used as tracers of source materials of metamorphic rocks.

[1] Zhang et al. (1995) J. Petrol. 36, 1011–1037. [2] Chavagnac & Jahn (1996) Chem. Geol. 133, 29–51. [3] Xiao et al. (2000) Contrib. Mineral. Petrol. 139, 1–16. [4] Teng et al. (2007) Earth Planet. Sci. Lett. 261, 84–92.

Mg isotope exchange rate and fractionation factor between epsomite and aqueous solution constrained by

three isotope method WEIQIANG LI1,2* BRIAN L. BEARD1,2

AND CLARK M. JOHNSON1,2 1Univ. Wisconsin-Madison


2NASA Astrobiology Institute Sulfates are considered as one of the major reservoirs for

water on the Martian surface [1] and Mg-sulfate is the most abundant Martian sulfate [2]. Mg-sulfates are also common minerals in the Phanerozoic evaporites on Earth. Use of the Mg isotope composition of Mg-sulfates as a recorder of the hydrological histories of Mars and Earth requires well constrained Mg isotope fractionation factors between the Mg-bearing solid and aqeous phases.

Re-crystallization experiments of two batches of fine epsomite grains (average size: 5 +m vs. 15 +m) in saturated MgSO4 solution were carried out at 7°C and 20°C. The three isotope method was applied to monitor the degree of isotope exchange between the solid and aqueous phases using a 25Mg spike and to determine the equilibrium isotope fractionation factor between epsomite and aqueous Mg. Each experiment was duplicated and XRD analyses confirmed that all the mineral reactants and products were epsomite.

The isotope exchange rate is faster at 20°C than 7°C but all experiments show near complete isotope exchange (Figure 1). Additionally, at a given temperature, isotope exchange is more rapid in the finer grained epsomite (Figure 1). The Mg isotope fractionation factors between epsomite and aqueous Mg at 7°C and 20°C are indistinguishable. At 20°C, &26/24Mgeps-sol = 0.53±0.22‰, while at 7°C, &26/24Mgeps-sol = 0.53±0.12‰.

Figure 1: Rate of Mg isotope exchange in epsomite recrystallization experiments (error bars show the 2sigma variation from duplicate experiments).

[1] Wang et al. (2008) JGR 113, 1–35. [2] Clark et al. (2005) EPSL 240, 73–94.


A595

The experimental study on the uranium migration process of

sandstone-type uranium mineralization

LI WENJUAN* AND ZHANG WEN East China Institute of Technology, Fuzhou, Jiangxi 344000,

China (*correspondence: [email protected]) A test device on long-distance uranium migration for the

simulation of the uranium migration process in sandstone uranium deposits has been designed [1].

The organic tube with 35mm internal diameter and 300cm long was used in the test device. The test device artificially tilted angle is 13.7° due to ore deposits angle is about 10°.The water-head is about 3m and the flow rate is 100ml/d in the device.

The sample mouthes were set at 40, 60, 130, 200, 250cm respectively. The researchers have studied the hydrodynamic conditions of uranium and the changes of the hydrology chemical parameters (Eh, Ph, U, Fe, etc.) through analyzed the samples chemical composition respectively, furthermore, concluded the regularities of uranium mineralization.

The experimental water samples come from a slope plot springs near the 377 orebody in Yili Basin, Xinjiang. The total water samples is 5000ml, which uranium content reached 0.276mg/l.

Then the test device was filled into sand-sample with purified water immersion, so as to determine the initial Eh value and the dispersion parameter.

The experimental study on uranium migration with the water samples has been on. The results shows that uranium was precipitated when the uranium content in water samples down to 0.002mg / l.

All the uranium at the 30cm point was restored after 9h, and at the 60cm was restored but at 130cm is not restored after 11h.. The result is 0.58m when the data was bring into the model-generation, however, there are some errors compared to the test results. The main reason is that the parameters of flow control is few, boundary and initial conditions is simplistic.

This study is financially supported by the China ‘973’ Project under Project No. 2002CB211704.

[1] Li W.J. et al. (2009) Goldschmidt Conference Abstracts 46.

A LA-ICP-MS chronological and tectonic environment study of the

ore-bearing volcanics in Baiyin orefield

XIANG-MIN LI, ZHONG-PING MA, JI-MING SUN AND JIYU-AN YU

Xi’an Center of Geological Survey (Xi’an Institute of Geology and Mineral Resource), CGS, Xi’an, Shaanxi 710054, China The Northern Qilian orogenic zone is one of the most

important massive sulfide deposit provinces in China and the world, especially, the Baiyin mine field which located at its east is a representative massive sulfide deposit. After the porphyroclastic lava extruding and the quartz albitophyre intruding which belong to the later acidic volcanic, The Baiyin mine field began mineralization, and ends at a relatively quiet period before a large-scale basic volcanism. Therefore, there is an important meaning to research the age and tectonic environment about the acid volcanic and the basic volcanic. In this paper, by using LA-ICP- MS zircon U-Pb isotope dating techniques we were determine the age of the basic volcanic in Baiyin orefield, the formation time of the basic volcanic in Baiyin orefield is 465.0±3.7Ma, this age should be belonging to Middle Ordovician"Researched by predecessors and with the same method, the age of acid volcanic in Baiyin orefield is 467.3±2.9 Ma, So we think the age of the rocks and the mineralization of the Baiyin orefield shoud be appertaining the later Middle Ordovician. All the discovered industrial deposits were produced in marine bimodal volcanic rocks, the marine bimodal volcanic rocks are composition of quartz keratophyre、spilite and a small amount of keratophyre, Chondrite-normalized trace element distribution patterns display that there is a negative anomalies for the Nb, Ta and Ti, combined with tectonic evolution of the North Qilian Mountains, and the ore-bearing volcanic rocks of the Baiyin mine should be formed in the island arc--rift environment in the later Middle Ordovician. The results of the study has a very important significance for tectono-magmatic evolution of the Qilian orogenic belt and also for the guiding the regional geological prospecting.

This study is supported by National scientific and

technological support projects (No. 2006BAB07B03-02) and China Geological Survey survey project (No. 1212010818090)


Self-sealing effect of CO2-hydrate in the sediment storage concept of CO2

XIAOCHUN LI1 AND TAKASHI OHSUMI2* 1Chinese Academy of Sciences, Wuhan 430071, PR China

([email protected])

2CRIEPI, Abiko, Chiba 270-1194, Japan (*correspondence: [email protected]) Based on the laboratory measurements of the induction

time (formation time) of CO2 hydrate, the time period of liquid CO2 travelling in the pore space before clogging was estimated.

The simulated pore space passage in laboratory was devised with a pair of grated silica glass plates, which gives network paths with the size of 200 micrometer in width and 20 micrometer in depth. At 5 degree C, the continuous flow regime was observed for 3 hours with the experimental breakthrough pressure of 0.4 MPa.

As an evaluation of the dymamic self-sealing capability during the upward leakage of the stored liquid CO2 within the sediment layers, the hydraulic model analysis was made whether or not the buoyant liquid CO2 reaches to the seabed. The calculation results showed that the clogging within an overlying sediment layers with total thickness of 171 m and with the permeability of 1 darcy, will take place before the front of the injected CO2 reaches to the seabed.

Inside the Exclusive Economic Zone of Japan, the sea area covered with the sediment layers thicker than 1000 m, and with a water depth greater than 500 m, and with a bottom seawater temperature lower than 5 degree C is estimated to be 150, 000 km2, which corresponds to the estimated sediment storage potential of 480 billion tonne of CO2, based on the assumption that the effective thickness of storage layers is 200 m, the effective porocity is 20 % and the effective sweep efficiency of the injected liquid CO2 with the density of of 800 kg/m3 is 10%.

The work was conducted when the authors were engaged

in Research Institute of Innovative Technology for the Earth, and was financially supported by Minstry of Economy. Trade and Industry, Japan.

S and O isotopes to identify the source of sulfate in the Jialing River, a headwater tributary of the Yangtze

X.D. LI1*, C.Q. LIU1, X.L. LIU1,2, N. AN1 AND L.R. BAO1,2

1Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, Guizhou, PR China (*correspondence: [email protected])

2Graduate University of Chinese Academy of Sciences, Beijing, PR China This study analyzed the chemical (Ca2+, Mg2+, Na+, K+,

HCO3", Cl", NO3

", SO42") and isotopic (#34SSO4 and #18OSO4)

compositions of 23 samples uniformly distributed and collected along the Jialing River. The chemical composition of the river water is characterized by high concentrations of Ca2+ and HCO3

", followed by Mg2+ and SO42", which account for

more than 90% of total ion concentration. Analyses of the stoichiometry of the river water show that the water chemistry is controlled by carbonate dissolution not only by carbonic but also by sulfuric acid, and indicate that sulfuric acid plays an important role in carbonate weathering. The river waters studied here are rich in sulfate ion. The co-variation of #34SSO4 and #18OSO4 is used to interpret the origin of sulfate (Figure 1).

Figure 1: #34SSO4 versus #18OSO4, along with ranges for potential sources.

The sources of SO4

2" are considered to be most likely the high sulfur-content coal combustion and oxidation of sulfide minerals during weathering of coal containing strata in the Jialing River catchment.

[1] Yoon et al. (2008) Aquat Geochem 14, 147–170. [2] Xu & Liu (2007) Chem Geol 239, 83–95. [3] Chen & Chu (1988) Chem Geol 72, 155–161. [4] Goldberg et al. (2005) Precambrian Res 137, 223–241. [5] Li et al. (2006) J Geochem Explor 89, 227–230.


A597

Hydrothermal contributions to oceanic anoxic event 2?

Evidence from trace metals X.N. LI1*, S. SEVERMANN1, J. OWENS2 AND

B.B. SAGEMAN3,

1Institute of Marine and Coastal Sciences, Rutgers University, New Brunswick, NJ, 08901, USA (*correspondence: [email protected], [email protected])

2Dept of Earth Sciences, University of California–Riverside, Riverside, CA 92521 ([email protected])

3Earth and Planetary Sciences, Northwestern University, Evanston, IL, 60208 ([email protected]) Different mechanisms have been put forward to explain

the observed increase in organic carbon burial during the Cretaceous ocean anoxic event 2 (Cenomanian-Turonian). Increased hydrothermal activity associated with large scale submarine magmatic events has been proposed to play an important role to deplete the deep water oxygen and supply trace metals such as Fe to the surface water to enhance primary productivity [1]. We will test this idea by examining several sites throughout the Western Interior Seaway (WIS). Here a gradient in trace metal enrichments has previously been ascribed to a hydrothermal source that likely originated from the Caribbean Large Igenous Province [2]. In this study, we will present a detailed geochemical dataset (including Fe redox proxies, trace metal and Rare Earth Element concentrations) from sediments deposited during the C/T transition in the WIS and the Proto North Atlantic Ocean to constrain potential hydrothermal contributions. Further, we will compare the trace metal abundances with Fe isotope compositions to test the suitability of this novel isotope sytem as a direct tracer for hydrothermally derived Fe.

[1] Kerr (1998) Journal of the Geological Society 155, 619–626. [2] Orth et al. (1993) Earth Planetary Science Letter 117, 189–204.

Isotopic signatures in Cedar Butte lavas: An indication of thermal

diffusion? X-X. LI1, C.C. LUNDSTROM1, Z-F ZHANG1,

M. MCCURRY2 AND C. HOLMDEN3

1Dept. of Geology, Univ. of Illinois Urbana Champaign, Urbana, IL 61801 ([email protected])

2Dept. of Geology, Idaho State Univ. Twin Falls ID 83303

3Dept. of Geology, SIL, Saskatchewan, Canada Cedar Butte, a volcanic complex which lies in the

volcanically active Snake River Plain (SRP), erupted a compositional progression of lavas from initial high silica rhyolite to final basaltic trachyandesite in the late Pleistocene (~0.4 Ma). The curved array on a MgO vs SiO2 diagram is consistent with fractional crystallization from a tholeiitic basaltic parent, ruling out a primary role for mixing in producing this compositional sequence (McCurry et al, 2008).

To gain insight into how magma differentiation from basalt to rhyolite might occur, we analyzed Fe isotope ratios in a suite of Cedar Butte lavas (ranging from 56 wt% to 75 wt% SiO2) as well as a high silica rhyolite from nearby Big Southern Butte by high resolution MC-ICPMS. Results show a progressive increase in #56Fe with SiO2 with the most silicic samples having #56Fe of ~0.40 ‰. This upwardly curving progression of #56FeIRMM-17 with increasing SiO2 is opposite to the predicted sense of #56Fe occurring during magnetite removal. Given that the predicted magnitude of fractionation of iron isotopes at inferred magmatic temperatures is also smaller than observed, this trend is unlikely to simply reflect fractional crystallization. An alternative mechanism for producing the compositional zoning and isotopic signature is a top down crystallization-reaction process involving a downward moving temperature gradient zone (Lundstrom, GCA, 2009). Such a process differentiates the magma by a moving thermal migration zone while thermal diffusion isotopic fractionation leads to heavy isotope enrichment at the cold end of the gradient (in the most silicic material). Ultimately, basaltic magmas may melt the compositionally zoned mush formed by this process, leading to eruption.

The hypothesis is testable through analyses of other isotopic systems. Double spike 238U/235U analysis of 3 samples (two compositional endmembers) found no significant fractionation; however, significant fractionation was unlikely to be found. Calcium isotopic analysis of Cedar Butte samples is in progress and we will report these results. Finally, piston cylinder T gradient experiments are in progress to gain further constraint on whether this alternative differentiation process could form Cedar Butte lavas.


Ge isotope fractionation during adsorption processes onto the surface

of Fe oxy(hydro)oxides XUEFANG LI AND YUN LIU*

State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China (*correspondence: [email protected]) Fe oxides and oxyhydroxides, such as goethite, hematite,

ferrihydrite and so on, are ubiquitous in forms of secondary minerals in soils and sediments, and also are major components of ferromanganese crusts and nodules in oxic ocean environments. Because of their strong adsorption characteristics, Ge and Ge isotope distributions in natural environments are partly controlled by such adsorption processes [1, 2]. However, molecular level mechanisms of these processes are elusive so far. This study investigates Ge isotope equilibrium fractionation during the surface adsorption processes by using high-level quantum chemistry methods.

The possible adsorbed Ge complexes on Fe (III)-oxyhydroxides surfaces are carefully verified by comparing their energies and geometries with known experimental evidences. The Bigeleisen-Mayer formalism has been used to calculate the Ge isotope fractionation factors. The e!"#$%&'(#)*$%+#$+%"*),'-) .%"/+"'#("*)&.) $0")1")*2"#("*),%")&3$,('"-),$)B3LYP/6-311+G (d, p) level.

Our results show that the Ge adsorption structures onto Fe (III) ferrihydrite mainly are bidentate corner-sharing type, e.g. tetrahedral Ge is bonded to two corners of two adjacent octahedral Fe atoms. The fractionation between the bidentate corner-sharing complex and Ge (OH)4, which is dominant species in natural waters, is around -1.7‰, light Ge isotopes prefer to be adsorbed. This fractionation will profoundly affect the Ge isotope compositions of rivers, groundwater and hydrothermal fluids, even is responsible for the enrichment of heavy Ge isotopes in seawater.

[1] Galy et al. (2002) GCA 66, A259. [2] Pokrovsky et al.(2006) GCA 70, 3325–3341.

Authigenic and biogenic minerals in volcanic hot springs of Kamchatka,

Russia YILIANG LI* AND SANYUAN ZHU

Department of Earth Sciences, the University of Hong Kong (*correspondence: [email protected]) The volcanic hot spring deposits from Kamchatka, Russia

were examined by scanning electron microscopy and transmission electron microscopy equipped with energy dispersive spectroscopy. Those hot springs include Burlyashii, Oil pool, Zavarzin, Thermophile and Jen’s vents, which were previously reported for microbial ecology and mineralogy. Opal A spheroids are common in all hot spring sediments with particle size from <20 nm to 50 nm. Euhedral single quartz nanoparticles of ~700 nm crystallized from Opal-A can be observed scattered on the surface of anhedral sediments. Anthigenic kaolinite of sharp faces can be observed in all hot springs with Si, Al and O as major compositions and having flaky- and scale-like structures. Iron sulfides are common with a wide spectrum of crystal sizes and morphologies. Small pyritic iron sulfides have octahedral shape with crystal size around ~20-80 nm; while pyrite crystals of ~200 nm to 500 nm and these >1 µm have cubic structure. The small pyrite crystals are also observed assembled to bigger cubic shapes, showing an ostwald ripening process. There are also spheriod shaped, ~1 µm size pyritic aggregates with rough surface which showed a sulfate-reducing bacteria mediated formation of iron-sulfides. Fibrous and tabular gypsum crystals can be observed coexisting with sulfides, indicating local oxidation condition. Euhedral crystals of element sulfur of ~30 µm can also be observed. Magnetic minerals are abundant in Jen’s vents, however, no magnetite can be detected, implying the existence of magnetic iron sulfides though thermophilic iron-reducing bacteria were isolated from some springs. Detrital quartz and silicates of larger sizes can be observed in some hot spring, showing water-rock interaction induced corrosion structures. The high abundance of iron sulfide minerals and the high percentage of menaquinones in sinter deposits indicated highly reduced conditions. The common existences of submicro- to nano-meter authigenic minerals, the abundant bacteria filaments, biofilms and diatoms indicate microbial mediation is a significant factor in the mineralization of those minerals in the hot springs.


A599

Potential ecological risk assessment model for heavy metal contamination

of agricultural soils Z.Q. LI1,3*, W. LIU3, D.P. LU2 AND J.Z. WANG2

1Department of Geochemistry, Chengdu University of Technology, Chengdu, Sichuan 610059, China (*correspondence: [email protected])

2Provincial Key Lab. of Neuclear Technology in Geoscience, Chengdu University of Technology, Chengdu, Sichuan 610059, China

3State Key Lab. of Geohazard Provention & Geoenvironment Protection, Chengdu University of Technology, Chengdu, Sichuan 610059, China This work (was to develop a new potential ecological risk

assessment model to be used as a diagnostic tool for heavy metals contaminated agricultural soil control purposes. The main-road for ecological risk of heavy metals contaminated soil is soil-vegetation-man. Using environmental bioavailability explains the heavy metals contamination degree of the soil. The model is Ei

r = Cfi (Te

i. Eir = Potential

ecological risk index for the metal (i); Cfi= Degree of

contamination for the metal (i). Cfi= (Ci

bio/Coi)1/2, Ci

bio= soluble fraction + exchangeable fraction [1] of the metal in soil for the samples, which is defined as environmental bioavailability of the metal (i) in soil. Co

i= safe content of the metal (i) in vegetation issued by the national government. Te

i = the element toxic-response factor for the given substance: Zn=1, Pb=5, Cd=15, Cu=2, Cr=11, Ni=3. Based on the 14 soil samples and 14 sweet potato samples correspondingly from contaminated agricultural soil in the vicinity of a Pb-Zn mining district, SW Sichuan Province, table 1 shows correlations between the contents of Cu, Pb, Cd and Zn in sweet potato and Pi (Contamination Degree), Ii (Geoaccumlation index), Er

i for Cu, Pb, Cd and Zn, respectively. It is very clear that Er

i by the new model has higher coloration coefcient than both Pi and Ii. This demonstrates that the new model is more accurte to response the ecological risk level of heavy metal contaminated agricultural soil.

Cu Pb Cd Zn PCu 0.36 PPb 0.4

PCd 0.13 PZn 0.49

ICu 0.40 IPb 0.2

ICd 0.18 IZn 0.51 Er

Cu 0.60 ErP

0.7

ErC

0.71 Er

Zn 0.87 Table 1: Correlations between PTEs contents of sweet potato & Pi, Ii, Er

i

Support by State Key Lab. of Environmental

Geochemistry, China (SKLEG5010).

[1] Tessier et al. (1979) AC. 51, 844–850.

Helium isotope composition and its geological significance of the eclogites

in the Lasha Terrane, Tibet ZHAOLI LI, JINGSUI YANG, ZHIQIN XU, TIANFU LI,

XIANGZHEN XU AND YUFENG REN

Key Laboratory for Continental Dynamics of MLR, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China A new occurrence of eclogites has been discovered in the

Lhasa terrane, northeast of Lhasa, Tibet. It is extended along the northern margin of the Gangdese magmatic arc. Different from most formerly found eclogites, which are associated with the subduction of the continental slab, the newly discovered eclogites are associated with the subduction of the oceanic slab. As a result, Lasha eclogites will play an important role in the research of ultrahigh pressure metamorphism and have distinct geological significance.

We use helium isotope tracing technique in this research. Helium composition of Lasha eclogites, isotopic ratios and abundance was present in the paper. The 3He abundance of omphacite and garnet are varied in the range of 2.41 10-

12cm3STP/g ~ 9.37 10-12cm3STP/g. The 4He abundance of them are varied in the range of 0.11 10-6cm3STP/g ~ 4.93 10-6cm3STP/g. Compared to the garnet selected from the same sample, the omphacite has relatively higher 3He and 4He abundance than that of the garnet. It suggests that the omphacite and the garnet in the eclogites might have different catching and holding capability for helium isotope.

The 3He/4He ratios of the omphacite and the garnet of the Lasha eclogites are varied in the range of 1.15 ~ 25.48 Ra. They are lower than that of the mantle, and higher than that of the crust. It might indicate a mixed crust-mantle source. This conclusion is in accordance with the results of major elements, trace elements, rare earth elements and Sr-Nd isotopic compositions. It suggests that the newly discovered eclogites should be derived from the depleted mantle, or there must be some mantle-source substance in the diagenesis of the Lasha eclogites.


Pursuing the “original” composition of bone mineral

ZHEN LI* AND JILL PASTERIS Department of Earth and Planetary Sciences, Washington

University in St. Louis, St Louis MO 63130, USA (*correspondence: [email protected]) Fossil bones and teeth have been widely studied to

reconstruct the paleoenvironment and paleoclimate. Appropriate interpretation of the trace-element and isotopic chemistry of fossils requires studies of unaltered material, i.e. what is the relation between the original carbonated hydroxylapatite of bones/teeth and the fossil mineralized material? Bones with a high degree of mineralization would be the best material from which to establish the chemical and physical features of original bone mineral. We chose to study the rostrum of the Blainville’s beaked whale, Mesoplodon densirostris (family Ziphiidae), which is the densest bone so far recorded [1, 2]. Raman microprobe analyses show that typical areas in the rostrum contain >96 wt.% apatite. Quantitative electron microprobe (EMP) analyses of the apatite, assuming substitution of carbonate for phosphate, translate into the formula:

(Ca8.54Mg0.25Na0.38)[(PO4) 4.99 (CO3) 1.01](OH)0.99 This formula indicates ~6.7 wt.% carbonate in the bioapatite

of the rostrum, which is approximately what our Raman analyses show. EMP also reveals minor (F) and trace elements (S, Cl, K) in the bone apatite.

Elemental maps (EM) show compositional variations, typically < 1 wt.% abs for each element. For example, EM show elevated S concentration in a concentric pattern around vascular holes (Fig. 1a). Typical areas within the longitudinal section of the rostrum also display banded distribution of S (Fig. 1b). We are exploring whether the S resides dominantly in organic matter or is incorporated into the biologically precipitated mineral. In fossil material, it is important to know if such trace elements were part of the original bone mineral.

Figure 1: Sulfur maps around the vascular holes (see arrow) in the transverse (a) and longitudinal (b) sections of the rostrum.

Partially funded by NIH grant 1R21AR055184-01A2.

[1] Rogers et al. (1999) J. Mater. Sci. Lett. 18, 651–654. [2] Zylberberg et al. (1998) Bone 23, 241–247.

The lithium isotopic characteristics of the Jiajika rare-metal deposit in

Sichuan, China LI ZHENZHEN1,2, TIAN SHIHONG2,3, HOU ZENGQIAN4,

SU AINA2,5, LI JIANKANG2 AND YANG ZHUSEN2

1Kunming University of Science and Technology, Kunming 650093, P.R. China ([email protected])

2Institute of Mineral Resources, CAGS, Beijing 100037, P.R. China ([email protected])

3Key Laboratory of Metallogeny and Mineral Assessment, MLR, Beijing 100037, P.R. China

4Institute of Geology, CAGS, Beijing 100037, P.R. China

5East China Institute of Technology, Fuzhou 344000, China The eastern part of the Qinghai-Xizang plateau (Tibet

plateau) is an important area of pegmatite and its importance is next only to that of the Altay area in Xinjiang. It is also an important concentration area of rare-metal resources, where the Jiajika rare-metal deposit is the largest pegmatite-type Li-polymetallic deposit in China. Nevertheless, few researches have been carried out in the area because of its remote location at high mountains and extremely unconventional traffic. Ar-Ar plateau ages and isochron ages, which indicate that the deposit formed within the period from the Indo-China movement of plate-collision-style to the Yanshanian movement of continental orogeny, are similar to many pegmatite-type rare-metal deposits in China and other countries.

Lithium is a useful trace element for solving controversies such as crust-mantle material recycling, magmatism and fluid (hydrothermal) activity. Samples from Jiajika rare-metal deposit were analysed by MC-ICP-MS in the University of Maryland. Two samples of spodumene contain 33592 and 34264 ppm Li and have $7Li values of –0.6 and –0.4. One sample of biotite in granite contains 7350 ppm Li and has $7Li value of +0.6. They are consistent in the uncertainty range. Therefore, following interpretations of published data of C, H and O isotopes and fluid inclusions, we consider that spodumenes in the rare-metal deposit may have originated from the granite, suggesting that ore-forming fluids were also derived from the granite.

This work was supported by grants (Contracts No. K0802,

12120108160, 40973013, 40603012, 2009-SYS-06, 13-7-5 and 081206). We thank L.R. Roberta, W.F. McDonough and Qiu L. for their help with MC-ICP-MS measurements.


A601

Fe isotope composition of BIF from NE China and its paleographic

implications Z.H. LI, X.K. ZHU AND S.H. TANG

Lab Isotope Geol., MLR, Inst. Geol., CAGS, Beijing, China ([email protected], [email protected]) Fe is the most abundant element engaging in redox

chemistry, and is one of the element has been used biologically at very early stage. Thus understand the geochemical cycling of Fe has great implications for the development of an oxygenated atmosphere and the origin of life. Banded iron formations (BIFs) are chemical deposits from oceans. They have potential to preserve paleoceanographic signitures. Here we report the results of an iron isotope study on BIFs from North China Craton.

The BIFs studied were formed at the Archean–Proterozoic transition period (2.5 Ga), and subjected to ampiblite-facies metamorphism. They consist of finely layered alternating beds dominated by magnetite and quartz respectively, with minor amounts of pyrite and hematite. The minerals of magnetite, hematite and pyrite were separated, and the bulk rocks were powdered. After purification using anion exchange chromatography, Fe isotope ratios of both bulk samples and mineral separates were measured using a Nu Plasma HR MC-ICPMS at hi-res mode. The results are expressed as deviations in permil relative to the same isotope ratios of the reference material IRMM-14. The results show some important features: 1) the overall variation in Fe isotope compositions ranges from 0.11 to 2.09‰ in �57Fe values, significantly heavier than the bulk silicate Earth; 2) Fe isotope compositions of bulk samples are negatively correlated with both Fe (III)/Fe (II) ratios and Fe contents.

The average Fe isotope compositions obtained from BIFs in this study for pyrite and magnetite are unusually high relative to the bulk silicate Earth, other BIFs in Transvall and Greenland, and MOR hydrothermal fluids. This suggests that only a small fraction of Fe (II) in sea water has been oxidised to Fe (III) to form the BIFs in Anshan area, which implies an atmosphere with low O2 contents at the time. Alteratively, this may imply that some fraction of Fe (II) has been precipitated as iron sulfide or carbonate, resulting relative enrichment of heavy isotopes in seawater, prior to the precipitation of BIF. Indeed, some archean pyrite deposites in North China exhibit very light Fe isotope signature.

Stable sulfur isotope analysis and its application on hydrogen sulfide

origin identification in Sichuan Basin ZHISHENG LI1,2* DONGLIANG WANG1,2 JIN LI1,2

1Research Institute of Petroleum Exploration and Development-Langfang Branch, Petrochina. 065007 P.O. Box 44, Langfang, HeBei, China

2The Key Laboratory of Natural Gas Accumulation and Development, Petrochina. 065007 P.O. Box 44, Wanzhuang, Langfang (*correspondence: [email protected])

The Delta S elemental analysis, continuous flow interface,

isotope mass spectrometer (EA / ConFlow / IRMS) were adopted in this study, and have established a mature on-line method to get sulfur isotope value of H2S of natural gas. Taking Sichuan Basin as the research object in this paper.

The H2S in the Feixianguan Formation of Lower Triassic in Sichuan basin was thought to originate from thermochemical sulphate reduction (TSR) [1], however, Some scholars believe that the source rocks with high FeS2 can generate H2S directly [2, 3].

The natural gas of Puguang Gas Field is considered as the highest content of H2S and an average H2S content of about 16%, and those in other regions, which is mostly concentrated between 1% and 8%. The H2S sulfur isotope of natural gas in Moxi Gas Field is the lightest, between 9 ‰ and 12 ‰; those are more similar in Zhongba, Wubaiti, Puguang and Huanglong-chang gas fields, distributed between 12 ‰ and 20 ‰; the sulfur isotope value of H2S of natural gas in Wolonghe Gas Field is the heaviest, closing to 30 ‰.

In conclusion, the hydrogen sulfide of Puguang, Wubaiti, Zhongba, and Moxi Gas Field come from thermal sulfate reduction reaction.

[1] Guangyou Zhu, et al. (2005) Isotopic evidence of TSR origin for natural gas bearing high H2S contents within the Feixianguan Formation of the northeastern Sichuan Basin, southwestern China [J]. Science in China (SeriesD) 35(11) 1037–1046. [2] Jian Li, et al. (2005) Geochemistry & origin of sour gas accumulations in the northeastern Sichuan Basin, SW China. Organic Geochemistry, 36 (12) 1703–1716. [3] Zengye Xie, et al. (2008) Genesis on Hydrogen Sulfide of Feixianguan Formation in Sichuan Basin. Acta Sedimentologica Sinica, 26(2) 314–323.


Chemical basis of microbe-carbonate interactions

BIN LIAN1 AND H. HENRY TENG2

1Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China

2Department of Chemistry, the George Washington University, Washington, DC, 20052, USA ([email protected]) The interplay of microbes and carbonate minerals at near-

surface conditions is extensive and plays a critical role in regulating water chemistry and atmospheric compostion. It is widely accepted that microbe-carbonate interactions are biologically induced processes; however the participating chemical agents are largely unidentified. Here we study the interactions of selected microorganisms and carbonate minerals to evaluate the chemistry involved. We first examined the effect of a soil bacterium on calcite crystallization and found that the mineralization process was affected by the culture composition. Results show that the crystal size, quantity, as well as morphology differ depending upon whether nitrogen is present in the cultural media. Fewer crystals are seen in the absence of N, but the grains tend to be large and morphologically less affected. Further analyses indicate that N affects the extent of capsule formation and the activity of metabolic carbonic anhydrase (CA). Under N stress conditions, the bacteria secrete large amount of extracellular polymeric substances (EPS) and consequently grow a thick capsule; however, CA produced by the metabolic process has a low activity. These observations suggest that both EPS and CA may be actively involved in the mineralization processes. Additional carbonate dissolution experiments reveal that Ca release does not respond to microbially induced pH change in the experimental solutions, but show a strong correlation with the activity of carbonic anhydrase from different microorganisms, implying that metabolic products, not acidity, may be the governing factor for microbe-calcite interaction. These results suggest that microbial mineralization and dissolution are multifaceted processes that may include substrate effect, enzymatic catalysis, as well as acid and ligand promoted surface and solution chemistry.

Release of toxic elements from air-exposed coal of Guizhou, China

HANDONG LIANG1*,3, JOSEPH A. GARDELLA2 AND BRETT YATZOR2

1State Key Lab of Coal Resources and Safe Mining, China University of Mining and Technology, Beijing 100083, PR China (*correspondence: [email protected])

2University of Buffalo of SUNY, New York 142602, USA

3Chizhou University, Anhui, 247000, PR China Long-term air-exposure of coal presents potential

environmental and human health hazards [1, 2]. Confined by limited reseach approaches, the chemical mechanisms of the release of toxic elements in coal remains largely unkown. Our research focuses on outcrop coal which prevails in Guizhou province of China and is often collected for local residential use in remote area with a long history, which is believed to be a potential source for some serious endemic diseases [2-4].

Outcrop coal samples from Guizhou were analyzed by means of time-of-flight secondary ion mass spectrometry (TOF-SIMS) with high mass and spatial resolutions. In previous study, evidence of elemental sulfur (S8) in organic maceral of high sulfur coal from Guizhou were presented [5].

Hundreds of ion images obtained from our study with high mass spectra explicitly explain the spatial segregation and speciation relationships between elements and organic and inorganic molecular species (see Fig. 1). This information enhances previous studies which note the presence of species. The activations and releases of both siderophile and lithophile elements are largely attributed to natural oxidation of sulfur in coal. Also, two states of clay were observed in organic maceral and inorganic phases.

Figure 1: Negative ion images to illustrate correlation of distribution of organic and inorganic specie in air-exposed coal from Puding area of Guizhou.

In addition, our results show direct evidence that fluorine

(F) does exist in the syngenetic clay of the coal rather than organic macerals.

Support provided by State Scholarship Fund of China

(No.2007106398) and US National Science Foundation.

[1] Finkelman et al. (2004) Int. J Coal Geol. 59, 19–24. [2] Finkelman et al. (2002) Int. J Coal Geol. 50, 425– 443. [3] Zheng et al. (2006) Goldschmidt Conf. Abs. A744. [4] Dai et al. (2007) Appl. Geochem. 22, 1017–1024. [5] Liang (1999) Chinese Sci. Bull. 44, 1242–1245.


A603

Geochemistry and tectonic setting of the Cretaceous alkaline complex in

the South-western margin of the Ordos Basin, North China Craton

JI-WEI LIANG1,2 AND RONG-XI LI1

1Open Laboratory of Mineralization and Dynamics, Chang’an University, Xi'an 710054, China

2State Key Laboratory of Continental Dynamics, Northwest University, Xi'an 710069, China The alkaline complex is located at the junction zone

between two fold belts, i.e. thrust belt in the western edge of the Ordos Basin and the Qinling Orogenic Belt, Central China. It was emplaced along a narrow linear W-E Mesozoic deep fault belt across southern margin of the North China Craton. Seismic exploration revealed the complex includes at least nine separate intrusions distributed in an area of more than 70 km2. Drilling cores reveal the multilayered complex intrusion occurs from 1961 m to 3710 m, embedded in the sedimentary rocks of various ages, from Proterozoic- Triassic. The complex is composed of nepheline syenite, monzonite diorite, alkali-feldspar trachyte, garnet syenite, aegirine-augite syenite from top to bottom. All types of rocks of this complex show high REE contents (/REE185.58-499.80), high LREE/HREE ratios (14.02-31.39), as well as high (La/Yb)N ratios (63.97-21.13), without significant $Eu anomalies. Chondrite normalized REE patterns of rock samples show LREE segments steep rightward against HREE curve segments basic level. Major element compositions of the complex show high K2O+Na2O (6.48-12.32% wt), low SiO2 (48.86-62.70% wt). while trace element compositions reflect high Sr/Y (67.04-102.64), Zr/Hf (43.10-65.76) and Nb/Ta (18.04-19.93) values, while low Y/Nb (0.533-0.791) values. It is enrichment in LILE (e.g. Rb, Sr, Ba, Th, etc.) and depletion in HFSE (e.g. Nb, Ta, Ti, P). LA-ICP-MS zircon U–Pb analyses indicate that the complex was emplaced at the time of 114±1.1Ma. Intrusion occurred in the early Cretaceous. It is proposed that the complex formed in the extension tectonic setting. The parental magmas probably derived from partial melting of an enriched metasomatic mantle. It is closely related to the geodynamic background of North China craton lithospheric thinning, magmatic underplating and tectonic conversion.

[1] Gao, S. et al. (2004) Nature 342, 892–897.

The impacts of mariculture on mercury distribution in sediments

and cultured fish P. LIANG1, D.D. SHAO1, H.S. WANG1, S.C. WU1,

J.B. SHI2 AND M.H. WONG1* 1Croucher Institue of Environmental Science, Hong Kong

Baptist University, Hong Kong, China

2Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China (*correspondence: [email protected]) To study the impact of mariculture on mercury speciation

and distribution in sediments and cultured fish around Hong Kong coastlines, samples were collected from six mariculture sites and corresponding reference sites.

Total mercury (THg) concentrations in the surface sediments of mariculture sites were significantly higher (P<0.01) than corresponding reference sites. However, methylmercury (MeHg) concentrations and the ratio of MeHg to THg in mariculture sediments were lower (P<0.05) than corresponding reference sites. The ratio of MeHg to THg in sediments was inversely related (r=-0.579, P<0.05) with organic matter content across the sites, indicating that organic matter affected Hg methylation in surface sediments.

Total mercury and MeHg in muscles of three cultured fish species were analyzed. The average MeHg concentration in muscle was 75ng/g, below the WHO limit of 500ng/g [1].

Mariculture activities increased THg loading in sediments by the input of unconsumed fish feeds and fish excretions. However, the complexation of Hg with ligands in the organic matter beneath the floating cages reducd Hg bioavailability to methylation bacteria, and thereby inhibited MeHg production [2]. Accordingly, changes in allochthonous organic inputs could affect the production of MeHg by altering the bioavailability of mercury buried in the sediments [3].

In general, there was a significant decrease in fish muscle MeHg and THg concentrations with fish length and weight for red snapper (Lutjanus campechanus) and snubnose pompano (Trachinotus blochii), which may be related to the dilution effect on mercury concentration according to fish growth.

[1] WHO (2003) JECFA 61st Meeting, 18. [2] Ullrich et al. (2001) Crit. Rev. Env. Sci. Technol. 31, 241–293. [3] Hammerschmidt et al. (2008) Mar. Chem. 109, 165–182.


Geochemistry characters of Cenozoic Tuoyun alkaline basalts, southwest

Tian Shan, northwest China T. LIANG, Z.H. LUO AND R. LU

State Key Laboratory of Geologic Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China ([email protected]) Cenozoic Tuoyun alkaline basalt lolcates in Southwest

Tian Shan, northwestern China. There are seven volcanoes in Tuoyun basin and form a series of volcanic apparatus included calderas, volcanic necks and cone sheets hosted megacryst of pyroxene, anorthoclase as well as kaersutite, and deep-seated mantle xenoliths such as augite and peridotite [1]. The SHRIMP dating of the sample collected in basaltic cone sheet is 48.1Ma which suggested magma activity in Tuoyun basin are only one stage rather than two periods in previous studying, 100-120Ma and 67-46Ma [2]. Tuoyun volcanic rocks are classified as alkali basalts comprised of tephrite-basanite, phonotephrite, trachybasalt and basalt series. Mg-numbers vary from 52 to 72, and the samples hosted peridotite xenoliths have higher Mg-number.

Strong positive Nb-Ta anomalies for Tuoyun basalts in spider disgram. The characters of LREE enrichment and smoothed REE pattern without Eu anomaly were shown. The samples hosted peridotite xenoliths show higher LREE enrichment [(La/Yb)N=16–28] than other basaltic samples [(La/Yb)N = 8–16]. Nd isotopic compositions are relatively homogeneous with 143Nd/144Nd ratios ranging from 0.512701 to 0.512886. Sr isotopic compositions are relatively wide variation with 87Sr/86Sr ratios ranging from 0.703690 to 0.705455. The ratios of 2°6Pb/2°4Pb, 2°7Pb/2°4Pb and 2°8Pb/2°4Pb are in the range 18.2402-18.4900, 15.4961-15.6147 and 38.1662-38.5564, respectively.

On the basis of combination on geochemistry characters, complex SHRIMP age sprerum of single zircon [3-4] and the depth range of partial melting in mantle source [5], the formation of Tuoyun basalt is a production of lithosphere delamination, rather than small mantle plume [2].

[1] Liang et al. (2005) Xinjiang Geology 23, 105–110. [2] Edward & Nicolas (2000) Lithos 50, 191–215. [3] Liang et al. (2007) Acta Petrogica Sinica 23, 1381–1391. [4]-Liang et al. (2010) Earth Science Frontier 17, 24–48. [5] Liang et al. (2008) Acta Petrogica Sinica 24, 2820–2838

Grain growth and dissolution during crystal-melt interaction

YAN LIANG1, YINHUA XIA2 AND PAUL BONS3 1Department of Geological Sciences, Brown University,

Providence, RI 02912 ([email protected])

2Division of Applied Mathematics, Brown University

3Mineralogy and Geodynamics, Institute for Geosciences, Eberhard Karls University Tübingen Grain growth or dissolution arises in a crystal-melt

aggregrate when there is a difference in chemical potential between the crystals and the melt. The kinetics of grain growth and dissolution in 1-D and 2-D mono-mineralic and bio-mineralic systems is examined using numerical methods. Diffusion equations for the independent components in the melt and crystals were solved numerically in using finite difference and finite element methods. The input parameters are the liquidi and solidi of the crystals, initial crystal and melt proportions and distributions, and diffusion coefficients of the components in the melt and crystals.

The kinetics of crystal-melt interaction in 1-D setup is relatively well understood. It is characterized by dissolution and reprecipitation [1]. Dissolution-reprecipitation arises because the rate of diffusion in the melt is much faster than that in the solid. If the melt is initially under-saturated with respect to the crystals, the crystals dissolve and the bulk melt composition quickly evolves to the local liquidus or liquidi of the dissolving crystals. Since the interiors of the crystals are still over-saturated with respect to the melt, dissolution reverses to precipitation that is rate-limited by diffusion in the crystal. Under 2-D settings, the size and distribution of the crystals are also important in re-distributing the dissolved materials between the melt and the solid. Smaller crystals may be completely consumed by the melting or dissolution reaction on a diffusion-in-melt limited time scale, whereas larger crystals are preferentially preserved. Reprecipation happens primarily around undissolved larger crystals. The averaging size of the dissolving crystal (s) therefore may increase (rather than decrease) during crystal-melt interaction. Depending on deformation mechanism, the presence of a stress field may hinder grain growth during melt-rock interaction, though the relationship between diffusion-limited grain growth and deformation is still not well understood.

An important consequence of dissolution-reprecipitation is the acceleration of crystal-melt re-equilibration in partially molten silicates, though selective preservation of large grains may lead to exceptions. Animations showing the effects of dissolution-reprecipitation on element distribution during partial melting and crystal-melt interaction under 1-D and 2-D settings will be presented.

[1] Liang Y. (2003) G3, doi, 10.1029/2002GC000375.


A605

Sorption of Np, Pu, Tc, and I to saltstone and cement formulations

under oxidizing and reducing conditions

MICHAEL S. LILLEY1, BRIAN A. POWELL1 AND DANIEL I. KAPLAN2

1Department of Environmental Engineering and Earth Sciences, Clemson University, Clemson, SC

2Savannah River National Laboratory, Aiken, SC Plutonium, neptunium, technetium, and iodine present

appreciable risks at sites around the world due to their potential mobility. Sorption of each of these radionuclides is profoundly influenced by oxidation/ reduction reactions. Therefore, the mobility of each radionuclide may be greatly influenced by redox speciation. The primary focus of this study was to determine distribution coefficients (Kd) for each radionuclide for engineered saltstone systems with varying amounts of reducing slag. Sorption experiments were performed under oxidizing and reducing conditions using Np(V), Pu(IV), Tc(VII), and I(I). Np and Pu both exhibited strong affinity for concrete and saltstones under both oxidizing and reducing conditions. Distribution coefficient (Kd) values of >105 were calculated for all Np and Pu systems under oxidizing and reduction conditions. Experimental conditions had a far greater effect on Tc sorption. Under oxidizing conditions, Tc showed similar affinity for concrete and saltstone despite the presence of reducing slag and Kd values remained around 10. However, under reducing conditions, Tc sorption increased relative to the oxidizing conditions and the Kd values increased with increasing reducing slag concentration in the solid. This behavior is consistent with reduction of Tc(VII) to Tc(IV). Similar reduction of Tc(VII) in the presence of saltstone was observed by Lukens et al. [1]. The rate of Tc sorption, from which reduction was infered, increased with increasing reducing slag content. It was determined there is a second order dependence on slag concentration and a steady state is reached around 3 weeks. Under oxidizing conditions, the iodide exhibited similar behavior to Tc and had Kd values significantly lower than Np and Pu. However, unlike the Tc systems, increased sorption was not observed under reducing conditions thus indicating that the majority of iodine remains as the initially amended iodide in both systems.

[1] Lukens et al. (2005) Environmental Science & Technology 39, 8064–8070.

Reduction of Hg(II) to Hg(0) by nitrate enrichment cultures derived

from subsurface sediments CHU-CHING LIN1*, YANPING WANG1,

HEATHER WIATROWSKI2, NATHAN YEE1AND TAMAR BARKAY1

1Rutgers University, New Brunswick, NJ, USA (*correspondence: [email protected])

2Clark University, Worcester, MA, USA Although microbial mercury (Hg) reduction has been well

documented in aerobic resistant prokaryotes carrying mer operons that are capable of reducing Hg(II) to Hg(0), little work has been undertaken to investigat mer activities among anaerobes and in anoxic zones. In this study, we conducted laboratory experiments to explore the mechanisms of Hg(II) transformaiton by denitrifying enrichments, as nitrate is often present as a co-pollutant in many heavy metal contaminated sites.

Enrichments were established with subsurface sediments from Oak Ridge, TN, and an oligotrophic growth medium that simulated in situ groundwater chemistry. Ten (or 20) mM acetate and 5 (or 10) mM nitrate were chosen as the electron donor and terminal electron acceptor, respectively. Data from Hg toxicity experiments showed that Hg inhibited denitrifying activities at concentrations higher than 10 +M. Under this threshold, the enrichments detoxified Hg by reducing Hg(II) to Hg(0), as indicated by the formation of Hg(0) trapped in a solution consisting of strong acids (i.e. nitric acid and sulfuric acid) and oxidants (i.e. permanganate and persulfate). Surprisingly, denitrification and an increase in cell biomass did not follow Hg(II) reduction; rather, Hg(0) was oxidized to Hg(II) upon onset of growth in the enrichments. The nature of these interesting observations is currently investigated.

Two bacterial strains isolated from the enrichments and identified as Ralstonia sp. and Bradyrhizobium sp. (99% identity, based on 16S rRNA gene sequencing) reduced Hg(II). Using degenerate PCR primers, merA, the gene encoding for mercuric reductase, was detected in both isolates. Taken together, these results suggest that Hg redox cycling, including detoxifying processes that result from the activity of Hg-resistant denitrifiers, could affect Hg speciation and hence Hg mobility in anoxic environments. A better understanding of the processes mediated by anaerobic microbial consortia that control the mobility of Hg in groundwater aquifers is crucial for future environmental management and remediation efforts.


Mechanism of electron transfer during dissimilatory Mn(IV)

reduction by Shewanella oneidensis MR-1

H. LIN1, J.L. BURNS2, T.J. DICHRISTINA2 AND M. TAILLEFERT1*

1School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, 30332-0340, United States

2School of Biology, Georgia Institute of Technology, Atlanta, GA, 30332-0230, United States

The mechanism of dissimilatory Mn (IV) reduction by S.

oneidensis MR-1 remains poorly understood. In a recent study, we provided complementary genetic and chemical evidence that S. oneidensis reduces Mn (IV) through two successive transfers of one electron with Mn (III) as a transient intermediate and that the Mn (III) (but not Mn (IV)) reduction step is linked to energy generation and growth. Here, the mechanism of each reduction step was examined with a suite of known S. oneidensis deletion mutant strains fed either Mn (IV) oxides or soluble Mn (III)-pyrophosphate as terminal electron acceptor. The results indicate that MtrB, a --barrel protein embedded in the outer membrane, and MtrC, a c-type cytochrome peripherally attached to the cell surface, play important roles in each electron transfer step. In turn, OmcA, another decaheme c-type cytochrome found on the cell surface, does not participate in the reduction of Mn (IV) or Mn (III). Finally, the Type II secretion system of S. oneidensis plays a crucial role in each reduction step, most likely by translocating MtrC to the cell surface. These findings indicate that the mechanism of dissimilatory Mn (IV) reduction involves a complex electron transfer pathway that is different than that of Fe (III) reduction.

The application of hydrosialite method to protect hydrocarbon

reservior SHIGUO LIN1,2*, ZHENGWEN LI2, ZONGLI WANG2

AND JUN LI2 1School of Energy Resources, China University of

Geosciences, Beijing, China 10083, China. 2Research Institute of Petroleum Exploration and

Development-Langfang Branch, PetroChina Ltd, Langfang, Hebei, 065007, China (*correspondence: [email protected]) Hydrosialite method is used very widely in stratigraghic

classification, depositional environment analysis and reservior protection [1, 2].

Hydrocarbon reservoir sensitivity experiment

The main Hydrosialite of Upper Triassic Xujiahe formation are andreattite, chlorite and kaolinite. Choose 4 block specimen which the content of chlorite and the permeability are high to do the reservoir sensitivity experiment. Our results are showned in the tables below.

Table 1: Clay mineral sensitivity experiment result.

Discussion results

Clay mineral is the most significant reason of hydrocarbon reservoir damage. Include three aspects below. Draw up the difference steps to aim at different damage.

1. Atomy emigration. Illite-smectite and kaolinite make the velocity sensitivity damage. The resolve way is to control the velocity of fluid to go into reservior, below 4.11m/d.

2. Acid treat generate chemical precipitate. Chlorite make acid sensitivity damage. There are two ways to resolve, one is to use clear water to substitute formation water before acid, then flowback acidizing fluid. Another is to add chelant and oxygen scavenger.

3. Water sensitivity damages the reservoir. When the smectite touch the operating fluid (like fresh water)-the salinity is below formation water, may cause swell and genertate damage. The way to take precaution against water sensitivity is that the salinity of operating fluid is higher than threshold salinity. This is higher than 37500mg/L.

[1] Wilson (1999) Clay Minerals 34(1), 7–25. [2] Jian Li et al. (2005) Organic Geochemistry 36, 1703–1716.


A607

Contribution of methane seeps to the post-Marinoan cap carbonate?

Evidence from carbon isotope and petrology in Yangtze Gorges area,

South China Z. LIN1,2, D. FENG1, Q. LIU1,2 AND D.F. CHEN1*

1CAS Key Laboratory of Marginal Sea Geology, Guangzhou Institute of Geochemistry, CAS, Guangzhou 510640, China (*correspondence: [email protected])

2Graduate University of Chinese Academy of Sciences, Beijing 100049, China Extremely negative methane-derived $13Ccarb values from

the Ediacaran Doushantuo cap carbonate (ca. 635 Ma) in the Yangtze Gorges area, South China, were taken as direct evidence for the hypothesis of methane hydrate destabilization. However, the methane-derived $13Ccarb signatures were reported only from specific strata of the cap carbonate in three locations in the Yangtze Gorges area, South China. Here we report $13Ccarb values as low as -44.36‰ (VPDB) in the calcitized structures in two strata from the Jiulongwan cap carbonate section in the Yangtze Gorges area, South China. These extremely negative $13Ccarb values were obtained only from calcite components, while the dolomite components of cap carbonate usually showed relatively heavier $13Ccarb values from -7.00‰ to 1.43‰. Petrographic data show that the calcites with extremely negative $13Ccarb value occur as blocky cements, veins, and usually replaced former precipitated dolomite at early diagenesis, suggesting that during or after the precipitation of cap dolomite, the methane hydrate destabilization and subsequent methane oxidation resulted dedolomitization of cap carbonate, leaved behind stratigraphically restricted distribution of calcite components with extremely negative $13Ccarb values. Extremely negative carbon isotope values certify the destabilization of methane hydrate in post-Marinoan ocean, but stratigraphically and limitedly occurrence imply that the link between the formation of cap carbonate, mainly consisting of dolomite, and the destabilization of methane hydrate in postglacial ocean is still not clear.

This study was partially supported by the NSF of China

(Grants, 40872079, 40725011) & by Guangzhou Institute of Geochemistry, Chinese Academy of Sciences (Grants, GIGCX-07-13)

Microbial mineral carbonation in anaerobic fermentations

R.E.F. LINDEBOOM1*, J. WEIJMA1 AND J.B. VAN LIER2 1Environmental Technology, Wageningen University, 6700

EV The Netherlands (*correspondence: [email protected])

2CITG, TU Delft, The Netherlands

Mineral carbonation and Anaerobic fermentation In anaerobic digesters organic waste is converted into

biogas (65% CH4) by micro-organisms according to the following simplified equations [1]:

(1) C6H12O6 ) 2 CH3COOH + 2CO2 + 2H2 (2) 2CH3COOH + 2H2O ) 2CO2 + 2CH4

Thus, production of CO2 dilutes the caloric value of the biogas. Furthermore, production of acetic acid acidifies the reactor broth. Below a pH of 5.5 production of CH4-rich biogas is strongly inhibited [2].

Mineral carbonation reactions (with olivine and wollastonite) were used to prevent pH drop and directly sequestrate CO2, according to the following reaction equations [3]:

(3) CaSiO3 (s) + 2H+ (aq) )Ca2+ (aq) + SiO2 (s) + H2O (l) (4) Ca2+ (aq) + CO3

2- (aq) ) CaCO3 (s)

Discussion of results

Reaction rates of respectively 0.44, 0.21 and 0.12 gCOD-CH4/g VSS/day were obtained for phosphate, wollastonite and olivine buffer. Addition of wollastonite and olivine resulted in the dissolution of Ca2+ and Mg2+ and the precipitation of carbonate mineral according to reaction (4). Also significantly improved biogas composition (>95% CH4) was measured. Wollastonite showed to be more reactive. Details on the experiment will be elaborated.

[1] Stams & Plugge (2009) Nature Review Microbiology 7, 568–577. [2] Lettinga et al. (2000) Biological wastewater treatment-part 1 Wageningen University p. 200. [3] Kodama (2008) Energy 33, 776–784.


Assessing freshwater aquifer contamination from Carbon Capture

and Storage CO2 leak M.G. LITTLE1 AND R.B. JACKSON2

1GSA/USGS/AAAS Congressional Science and Technology Policy Fellow, 2170 Rayburn, Washington, DC, 20515, USA (*correspondence: [email protected])

2Department of Biology and Nicholas School of the Environment and Earth Sciences, Duke University, Durham, North Carolina 27708-0340, USA ([email protected]) Carbon Capture and Storage (CCS) refers to a suite of

technologies used to separate, compress, transport and store CO2 produced from large, stationary emissions like coal-fired power plants. If undertaken on a large scale, only very small CO2 leaks (<0.1%/yr) will be acceptable to achieve the goal of mitigating rising atmospheric CO2 concentrations. However small, such leaks will be inevitable and may pose a risk to shallow, drinking-water if a significant pH change results. Here, we seek to characterize this risk. We first identify fresh groundwater resources that are geographically coincident over the most likely CCS sites, i.e. deep saline aquifers. The presence of moderate concentrations of naturally occurring aqueous trace metals in some of these aquifers suggests that the host aquifer sediment has a potential for additional release in the presence of CO2. We thus narrowed our selection to drinking-water aquifers with reported concentrations of toxic metals to be 10 to 100% of maximum contaminant loads (MCL). We then collected aquifer sediment samples from these locations and subjected subsamples to continuous incubation in water supersaturated with CO2 for more than 200 days and to a control incubation without CO2. Our samples are from the following aquifers: Mahomet (Illinois), Ogallala (Texas), Columbia (Virginia), and Aquia (Maryland). Simulated groundwater samples were regularly analysed. For the pH range reached in our experiments (~4.5 to 5.5), (1) As concentrations generally decreased in comparison to the control; (2) Cd and U both increase significantly in the Mahomet and Ogalalla; and (3) most major element cations increase, including Fe and Ca. In conclusion, given the appropriate lithology, CO2 leaks may pose a risk for release of U and Cd into drinking water; however, additional As releases are probably low. Additionally, a suite of easily detectable elements—Mn in particular—may be suitable for monitoring purposes. The experiment is on-going and ultimately we will extrapolate our analysis of our laboratory incubations to predict locations most susceptible to toxic metal release due to CO2 leakage from CCS.

Copper isotope fractionation in seawater: The role of scavenging by

ferromanganese crusts S.H. LITTLE1*, D. VANCE1, D.M. SHERMAN1

AND J.R. HEIN2

1Department of Earth Sciences, University of Bristol, Bristol BS8 1RJ UK (*correspondence: [email protected])

2US Geological Survey, Menlo Park CA Dissolved Cu in seawater has a heavy isotopic

composition (#65Cu = +0.9-1.5‰) relative to both rocks (~0‰) and the riverine input (at around +0.7‰). Vance et al. [1] suggest that this is a result of partitioning of Cu isotopes between a heavy dissolved phase, where Cu is bound to organic ligands, and a light particulate phase, dominated by Fe-Mn oxides. However, no data exist for the isotopic composition of Fe-Mn precipitates from seawater with which to test this view.

Here we report #65Cu in Fe-Mn crusts from the three major ocean basins. A Pacific crust (D11) shows no variation in Cu isotopes (#65Cu = 0.54±0.06‰) over the past 17 Ma. The Atlantic crust (Lesser Antilles, TR079) shows an increase in #65Cu from 0.11‰ to 0.36‰ from 3 Ma to the present. In the Indian Ocean crust (109D-C), #65Cu values decrease from ~0.3‰ to ~0.12‰ between 11 and 6 Ma, and then remain constant at ~0.12‰ from 6 Ma to present.

µ-XRF element maps and EXAFS of TR079 show that Cu and Zn are predominantly sorbed to the Mn-oxide phase, #-MnO2. Sherman et al. [2] have shown that #-MnO2 (birnessite) preferentially sorbs the light Cu isotope from simple aqueous solutions, with a $65Cu (diss-sorb) of ~+0.5‰. Thus the direction of fractionation between dissolved Cu in seawater and the Fe-Mn crusts is consistent with an equilibrium fractionation for Cu isotopes between these two phases.

[1] Vance D et al. (2008) EPSL 274, 204–213. [2] Sherman et al. (2009) GCA 73, A1208.


A609

Lithium isotope composition of the dissolved and suspended loads of the

Changjiang River CONG-QIANG LIU, QILIAN WANG, ZHI-QI ZHAO

AND BENJAMIN CHETELAT State Key Laboratory of Environmental Geochemistry,

Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550002 China ([email protected], [email protected], [email protected],

[email protected])

The stable isotopes of lithium provide information on

chemical weathering processes and the balance of primary silicate rock dissolution to secondary mineral formation. We surveyed lithium isotopic compositions of dissolved and suspended loads of Changjiang River and its main tributaries, with purposes of better understanding lithium isotope behavior during weathering process, and deciphering the effects of weathering intensity and rock types on Li content and isotopic composition of river water.

The Li contents and isotope compositions ("7Li) of the studied river waters rang from 150nmol/L to 4570nmol/L and from +7.6‰ to +28.1‰, respectively. The "7Li values are comparable with, while the Li contents of the Changjiang River water are signigicantly higher than those of the world rivers, such as Congo, Amazon, Mississppi and Himalayan rivers. The Li contents of river water decrease, while the "7Li values increase from upper to lower reaches of Changjiang River. The variations of Li content and "7Li value of the river water can be mainly described in terms of mixing of two componeants originated from evaporate dissolution and silicate weathering.

The "7Li values of the suspended matter are relatively constant, ranging from -4.7‰ to +0.7‰, as ompared with the change of the "7Li values of the dissolved load. The fractionation of Li isotope composition between the dissolved and susppended loads increases from the upper to lower reaches of Changjiang River, and with increasing of "7Li values of the river water. The isotopic fractionation of lithium between the dissolved and suspended loads is mainly controlled by the weathering of bedrocks, and also affected by other factors such as absorption of secondary minerals.

This work is financially supported by National Natural

Science Foundation of China (40721002, 90610037).

Ailaoshan Ophiolite Belt, Yunnan Province, southwestern China:

SSZ type or MORS type? CUI LIU, JINFU DENG, JUNLAI LIU, SHANGGUO SU,

YUE CHEN AND WEIQIONG KONG

State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing, 100083, China The Ailaoshan Ophiolite Belt (AOB) is located within the

Ailaoshan Fault belt, Yunnan province, SW China. Previous studies have suggested that the AOB is MORS type (Zhang et al. 2008). However, this traditional view fails to account for the data reported here.

In Shuanggou, Maoheshan, Laojinshan and westert Mojiang, we recognized for the first time the HMAs (boninites), which include dominant basaltic andesites and minor andesites. Geochemically, the AOB HMAs are sub-alkaline,, with Mg numbers >0.6, FeO*/MgO: 0.66-1.18 (total Fe), MgO = 8-15 wt% (only one is 7.42), are low-Fe calc-alkaline, and LT-, MT-HMAs, similar to those of the present-day HMAs from Chichijima, Japan. Apart from the HMAs, we also identify the characters of plagioclase granites within the AOB. These rocks are silica-rich (SiO2 > 73 wt%), sub-alkaline. With higher Mg number of 0.39-0.66, lower K2O, low FeO*/MgO, and belonging to low-K CA and low-Fe CA series rather than TH series of mid-oceanic ridge. Importantly, these plagioclase granites are C series of SSZ rather than A or AC series of mid-ocean ridge in SiO2-(Na2O+K2O-CaO) diagram showing Peacock’s alkali-lime index (Pearce, 1984).

Taken together, the existence of HMAs and the characters of plagioclase granites suggest that the AOB is likely formed in a SSZ setting rather than a mid-ocean ridge setting.

Supported by NSFC (40802020), CGS (1212010661311,

1212010911028)


!"#$%&'#((#)*'%+&,"%-,$*.+&/$CO2, CH4 and N2O of soil profile in Karst

areas, southwest China F. LIU1,2, C. LIU1*, S. WANG1 AND Z. ZHU3

1The State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China (*correspondence: [email protected])

2Department of Chemistry and Life Science, Baise University, Baise 533000, China

3Chongqing Institute of Geology and Mineral Resources, Chongqing 400042, China Carbon dioxide (CO2), methane (CH4) and nitrous oxide

(N2O) are the three most important greenhouse gases (GHG) which contribute to global warming. Soil is the major biological sink or source for atmospheric GHG. Concentrations of GHG in the soil can provide some valuable information about production, consumption and transportation of gases through the subsurface. Although there are many researches on spatial variations of GHG in soil profile, few quantitative analyses on their interrelationships. Here, The monthly concentrations of CO2, N2O and CH4 along with soil depth were measured for a year in karstic region, southwest China. The objective of this research was to better understand the interrelationships among CO2, N2O and CH4 in soil. The results indicated that subsurface concentrations of CO2, N2O and CH4 varied in 0.35~35.3mL·L-1, 0.31~5.31+L·L-1 and 0.1~4.7+L·L-1, respectively. With the increment of soil depth, CO2 and N2O concentration increased firstly and then decreased or tended to be stable at 30~40cm depth, while CH4 had an inverse trend. The variations in CO2 along with soil depth was significantly positive correlated with that in N2O (p<0.05~0.01) and negative correlated with that in CH4 (p<0.01). The significant negative correlation between CH4 and N2O just was observed in some study sites (p<0.01). Such interrelationships among GHG in soil suggest that there may be some relationships between soil N and Soil C dynamics in soil, and some research in future would be deserved.

Multi-phase reactive flow and transport modeling of CO2

sequestration in the Mt. Simon sandstone formation, Midwest USA

FAYE LIU1*, PENG LU1, YITIAN XIAO2 AND CHEN ZHU1

1Indiana University, Department of Geological Sciences, Bloomington, IN 47408 (*correspondence: [email protected])

2ExxonMobil Upstream Research Company, Houston, TX 77027 Multi-phase reactive flow and transport modeling is an

effective tool for monitoring, verification, and accounting of CO2 sequestration in deep geological formations. In the current study, modeling is performed to simulate large scale CO2 injection (one million tons per year for 100 years) into Mt. Simon sandstone, a major deep saline reservoir in the Midwest of USA. The long-term fate of CO2 was simulated by extending the modeling period to 10, 000 years. The results indicate that most of the injected CO2 remains within a radius of 3300 m lateral distribution. Four major trapping mechanisms and their spatial and temporal variations are evaluated in our simulations: hydrodynamic, solubility, residual, and mineral trapping. A strongly acidified zone (pH 3-5) forms in the areas affected by the injected CO2 (0 – 3300 m), and consequently causes extensive mineral precipitation and dissolution reactions. The predicted long-term fate of CO2 is closely linked to the geochemical reactions conceptualized in the models. In our model, the replenishing water continues to dissolve CO2 long after the injection, which results in total dissolution of hydrodynamically trapped CO2 at the end of 10, 000 years. In contrast, most previous models neglected the regional flow after injection and hence artificially limited the extent of geochemical reactions as if in a batch system. Consequently, a supercritical CO2 plume (hydrodynamic trapping) would persist after 10, 000 years. The continued supply of acidified water from interaction between replenishing water and CO2 also results in extensive dissolution of feldspars and precipitation of secondary clay minerals, to a much more extent than what predicted in models without including regional flow. However, the prediction of complete dissolution of feldspars in 10, 000 years can also result from the artifact that Transition State Theory (linear) rate laws are used in our model (as well as all previous work), which overestimates the rates of feldspar dissolution near equilibrium [1].

[1] Zhu, C. (2009) Geochemical modeling of reaction paths & geochemical reaction networks. In Thermodynamics & kinetics of water-rock interaction (eds Oelkers, E.H. & Schott, J.) vol. 70, pp.533-569, Mineralogical Society of America.


A611

Zircon as an unique window for the tectonic evolution of UHP

metamorphic terrane: Mineral inclusions and U-Pb SHRIMP age

FULAI LIU1 AND JUHNGUANG LIOU2 1Institute of Geology, Chinese Academy of Geological

Sciences, Beijing, 100037, China, ([email protected])

2Department of Geological and Environmental Sciences, Stanford University, Stanford, California, 94305, USA, ([email protected])

Zircons from Sulu-Dabie UHP rocks, including outcrop and cores from drill holes contain abundant mineral inclusions of protolith, prograde, UHP and retrograde minerals in different domains. Systematic studies on inclusions in zircons indicate that the Sulu-Dabie UHP terrane extends for > 2000 km and is about 50 km wide with 5 km in depth at least, probably the largest UHP terrane recognized thus far. Igneous mineral inclusions are common in the inherited zircon cores. In contrast, quartz eclogite-facies inclusions occur in prograde domains, coesite eclogite-facies inclusions are preserved in UHP domains, and amphibolite-facies inclusions are enclosed in outmost retrograde rims. Parageneses and compositions of inclusion minerals preserved in distinct zircon domains constrain prograde metamorphism at 570-690 °C and 1.7-2.1 GPa, and UHP metamorphism at 750-850 °C and 3.4-4.0 GPa, following by rapid decompression to amphibolite-facies retrograde metamorphism at 550-650 °C and 0.7-1.05 GPa. U-Pb SHRIMP analyses of the zoned zircons show four meaningful ages of the Sulu-Dabie metamorphic evolution: (1) Neoproterozoic protolith ages (800-750 Ma); (2) 246-244 Ma for early-stage prograde metamorphism; (3) 234-225 Ma for UHP metamorphism; (4) 215-208 Ma for late-stage retrogression. This indicates that Neoproterozoic voluminous bimodal igneous rocks in response to the breakup of Rodinia supercontinent, together with various sedimentary rocks, and minor ultramafic rocks, were subjected to coeval Triassic subduction to mantle depths and exhumation during the collision between the Yangtz and Sino-Korean cratons. The related subduction and exhumation rates for the Sulu-Dabie UHP rocks would be up to 4.7-9.3 km Myr-1 and 5.0-11.3 km Myr-1, respectively. The zonal distribution of mineral inclusions and the preservation of index UHP minerals such as coesite imply that zircon is the best mineral container for each metamorphic stage. Similar conclusions have been documented elsewhere for other UHP terranes.

The constraint of abyssal crustal and mantle structures to abiogenetic gas

in Songliao basin LIU HONGLIN1*, WANG JIANMIN2, ZHUO SHENGGUANG3,

WANG XIANBIN4 AND TUO JINCAI4 1Daqing Petroleum Institute, Daqing, Hei Longjiang, 163318,

China (*correspondence: [email protected] )

2Daqing Drilling & Exploration Engineering Co., Daqing, Hei Longjiang, China ([email protected])

3North East University at Qinhuangdao, Qinhuangdao, Hebei, 066004, China ([email protected])

4Key Lab of Petrol Resources Research, CAS, Lanzhou (xbwang@lzb. ac. cn) The features of abyssal crust and mantle structures and

geologic process. We have found that the alkane carbon isotope $13C of natural gas in more than 30 wells around Xujia area in the Songliao Basin, with abiogenetic characteristics [1, 2]. Studies revealed that abiogenetic gas was constrained by abyssal crustal and mantle structures. It was found that Low velocity-High conductivity layers developed in upper and lower middle crusts, and we infer that both layers are composed of mantle fluid, which is closely related to abiogenetic gas, indicated by the polyspectrum characteristics of deep seismic reflection analysis. Under Xujia fault depression, where abiogenetic gas was found, thermal diapirs developed, which was the result of abyssal crustal and mantle geological processes. The resulted pressure (P) and temperature (T) made Fe group elements segregate out and accelerated the Fischer-Tropsch synthesis [3]. The lithosphere structures [4] and deep faults are major controlling factors for migration and distribution of abiogenetic gas. Most of the abiogenetic gas pay wells are distributed along the deep faults constructing an intricate conducting system for abiogenetic gas migration, and thick volcanic layer together with weathered basement formatted reservoir bed at the bottom of Xujia fault depression.

Specific crustal and mantle structures and intricate abyssal geological processes formatted a delicate abiogenetic gas generation, migration, accumulation match around Xujia fault depression in Songliao Basin.

[1] Wang Xianbin et al. (2009) Science China Earth Science (Series D) 39(5), 602–614. [2] Wang Xianbin et al. (2006) China Basic Science 4, 12–20. [3] Lu Gongxuan et al. (2004) Natural Gas Geoscience 17(1), 125–130. [4] Yang Baojun et al. (2003) Science In China (Series D) 33(2), 170–176.


The Middle and Upper Ordovician !13C excursions in South China:

Implication for paleoceanographic change

JIANBO LIU1*, ZI GUI2 AND JUNJUN WEN1

1Department of Geology, Peking University, Beijing 100871, China (*correspondence: [email protected])

2University of Nebraska-Lincoln, Department of Geosciences, Lincoln, NE 68588-0340, United States

Several significant positive $13C excursions before the

Hirnantian have been recognized in the Mid and Late Ordovician, which seems to be global signs. The early Katian Guttenberg excursion (GICE) have been well documented from a number of localities in North America, northern Europe, and Asia, and might reflects global cooling resulting from enhenced marine organic carbon burial and a drawdown of pCO2. However, the origin of the GICE and other carbon isotopic excursions is still a topic of debate, and need further studies to constrain its origin and relationship with paleoceanographic changes.

A complete carbonate succession of the Darriwilian to lower Katian stages is well exposed near Xingshan County town, the northwestern Hubei Province of South China. The Mid and Upper Ordovician strata in the section consist of the Kuniutan and Pagoda formations, characterized by nodular argillaceous limestone with polygonal cracks, primarily deposited in a deep subtidal setting. Values of $13Ccarb begin at + 0.2‰ in the lowermost Kuniutan Formation and keep in the range of 0.6‰ ± 0.1‰ in the formation with a positive excursion (up to +1.2‰) occurring in the upper Kuniutan Formation, which is possible coeval to the Mid-Darriwilian positive excursion documented in Baltoscandia. A rapid rise in $13C values from +0.5‰ in the uppermost Kuniutan Formation through the Datianba Formation to the GICE value of +2.0‰ in the lower Pagoda Formation of the Katian Stage. $13Ccarb values shift back to +1‰ in the upper Formation.

Two positive excursions in $13Ccarb of the Middle and Upper Ordovician at Xingshan show an identical trends in Baltoscandia and North America, representing a global positive shifts in carbon isotopic composition of the Ordovician oceans. The driving forces causing the main late Ordovician shifts in the carbon isotope trend should be global. The GICE interval in Xingshan is characterized by purple skeletal wackestone, deposited under a distinctive paleoceanographic condition. Global cooling and conseqent strongly upwelling on shelf might be responsible for the rapid increases in carbon isotopic composition of the Mid and Late Ordovician oceans.

Geochemistry and origin of dissolved methane and helium gas in

geothermal water, Weihe Basin, China

L. JIANCHAO1,2, L. RONGXI1,2* AND L. XIAOJIE1,2 1Key Lab of Mineral Resources & Geology Engineering,

Education Ministry of China, Chang’an University, Xi’an, 710054, China (*correspondence: [email protected])

2School of Geosciences & Mineral Resources, Chang an University, Xi’an, 710054, China Weihe Basin is a Cenozoic graben basin located between

Qinling Orogen Belt and North China Block [1]. Geothermal water from big faults across the basin contains abundant soluble hydrocarbon gas in which methane accounts for from 10% to 24% with the highest of 82.44% and helium gas for from 0.15% to 0.3% with the highest of 3.95%. Value of 13C of hydrocarbon gas increases with carbon number. Dissovled methane in center area of the Cenozoic deposition of Weihe Basin was biological gas featured with 13C1 less than -55‰ while methane from other area was pyrolysis gas with 13C1 of -38.7‰ ! -27.2‰. Zhang Jiapo Formation, a set of Paleogene lacustrine deposition in Weihe Basin with higher abundance of mixed type I and II organic material, was believed to be source rock of biological gas. Palaeozoic carbonate and coal series under Cenozoic sediments were probably the source rocks of pyrolysis gas.

Helium isotope analysis of helium gas released from geothermal water shows that 3He / 4He values are between 7.80±0.23'10-7-4.7±0.24'10-8. R/Ra valus of helium gas are less than 1.0. Combined with 4He / 2°Ne ratios from 220 to 1985, it indicates that helium gas dissolved in geothermal water derived from crust mixed with trace of mantle sourced helium. Regional geological data analysis shows that granite abundant in radioactive uranium, exposed in Qinling Orogen Belt and buried in large areas under Cenozoic sediments in south area of Weihe Basin is the main source rock of soluble helium in geothermal water.

[1] Liu, S. (1998) Journal of Asian Earth Sciences 16, 369–383.


A613

Os isotope evidence for diachronous formation of lithospheric mantle beneath the Trans-North China

Orogen, North China Craton J. LIU1*, R.L. RUDNICK1, R.J. WALKER1, S. GAO2

F.Y. WU3, W.L. XU4 AND Y.G. XU5

1Dept. of Geology, University of Maryland, College Park MD 20742 USA (*correspondence: [email protected])

2China University of Geosciences, Wuhan 430074, China

3IGG, Chinese Academy of Sciences, Beijing 100029, China

4College of Earth Sciences, Jilin University, Changchun 130061, China

5GIG, Chinese Academy of Sciences, Guangzhou 510640, China The north-south trending Trans-North China Orogen

(TNCO) formed as a result of the collision of the Eastern and Western blocks of the North China Craton ca. 1.85 Ga [1]. While the crust of the TNCO originally formed during the Archean, the age of the underlying lithospheric mantle is in dispute. Osmium model ages for xenolithic peridotites from localities in the northern TNCO are reported to be either ~1.9 Ga [2] or ~2.5 Ga [3, 4]. If the Proterozoic ages are correct, they may suggest that the mantle lithosphere was replaced during the orogeny. In the southern TNCO, limited Archean Os model ages for sulfides from peridotite xenoliths suggest the presence of Archean lithospheric mantle there [5]. It, thus, remains unclear whether or how the lithospheric mantle was influenced by the orogeny. To address these issues, we analyzed the Os isotopic compositions and HSE contents of 76 peridotite xenoliths from five localities within the TNCO: three in the north (Hannuoba, Yangyuan, and Fansi), two in the south (Fushan and Hebi), as well as one locality (Jining) in the Western block, which lies only ~100 km to the west of Hannuoba and Yangyuan. We also re-analyzed samples from previous investigations [3, 4] that yielded Early Proterozoic to Archean model ages. We find no evidence for Archean lithospheric mantle beneath Hannuoba, Yangyuan and Jining. Instead, ~2 Ga model ages dominate. In contrast, Early Proterozoic to Late Archean lithosphere is found in the more southerly localities (Hebi, Fushan, and Fansi). Proterozoic mantle lithosphere coincides with the extension of the nearly east-west trending ~1.95 Ga khondalite belt in the Western block (Jining is located in this belt). Thus, the khondalite belt may represent a collision zone that crosscuts the TNCO [6] and disrupted the lithosphere there. Elsewhere within the TNCO, we find no evidence for lithospheric replacement following its original formation in the Archean.

[1] Zhao et al. 2005. Precambrian Research 136, 177–202. [2] Gao et al. 2002. EPSL 198, 307–322. [3] Xu et al. 2008. Lithos 102, 25–42. [4] Zhang et al. 2009. JSC, London, 166, 249–259. [5] Zheng et al. 2007. GCA 71, 5203–5225. [6] Xu et al. 2010. Precambrian Research 177, 266–276.

Evolution of fluid chlorinity indicated by Cl-bearing minerals in the processes of subduction and

exhumation of UHP eclogites of Yangkou from the Sulu ultrahigh

pressure metamorphic terrane, China JINGBO LIU*, LINGMIN ZHANG, QIAN MAO AND KAI YE

State Key Laboratory of Lithosphere Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029, China (*correspondence: [email protected]) The apatites preserved in subduction process from coronal

metagabbro, coronal eclogite and coesite-bearing eclogite at Yangkou have been studied in this paper. The apatites in coronal metagabbro and coronal eclogite show low Cl contents with the same compositions. However, some of apatites in coesite-bearing eclogite, with increasing Cl zoning from core to rim, show evident enrichment of Cl, which reflects a development of Cl enrichment in fluids along the prograde metamorphic process. During the exhumation process, Cl-rich amphibole and apatite occur in the quartz-phengite vein, and as coronas and in the symplectite after omphacite [1]. All types of amphiboles and apatites have large variations of chlorine contents, and are zoned with decreasing Cl contents from core to rim. It can be determined that the fluids were evolved along decreasing chlorine content from early to late stages.

The development of Cl enrichment in fluids along the prograde metamorphic process is inferred to be related to hydration reactions of phengite formation and more accommodation of water in the nominally anhydrous minerals in country gneisses. Oppositely, the water release by the decomposition of phengite and the nominally anhydrous minerals in country gneisses results in decreasing chlorinity of fluids during the exhumation process of UHP terrane.

[1] Liu et al. (2009) Eur. J. Mineral. 21, 1265.


Suitable hydrogeochemical conditions for in situ uranium leaching in the

Shihongtan deposit J. LIU1,2, Y. ZHOU1, Z. SUN1,2 AND B. HU1,2

1Key Laboratory of Nuclear Resources and Environment (East China Institute of Technology), Ministry of Education, Nanchang, Jiangxi 330013, China (*correspondence: [email protected])

2Laboratory of National Defence Key Discipline of Radioactive Geology and Exploration Techniques (East China Institute of Technology), Fuzhou, Jiangxi 344000, China The Shihongtan uranium deposit is one of the largest

sandstone-type uranium deposits in China. Because the total dissolved solids of groundwater is high up to 8-12g/L in this deposit, it is difficult to extract uranium by alkaline in situ leaching which can produce calcite precipitation and result in chemical plugging.

Based on investigation of hydrogeological conditions of in situ leaching, geochemical modeling and laboratory experiments, the suitable hydrogeochemical conditions for alkaline in situ leaching were obtained as follows: The activity product of [Ca2+]*[ CO3

2-] should be less than 3.39'10-9 when the pH value of ground water is less than 6.9 in natural conditions. During the in situ leaching process, the dissolution-precipitation of calcium carbonate is influenced by the concentration of HCO3

-, Ca2+ and pH value of ground water. Higher concentration of HCO3

- is favorable for uranium leaching. To keep the saturated index of calcium carbonate be less than 0, the concentration of Ca2+ or pH value must be reduced if the concentration of HCO3

- is increased. It is necessary to control suitable pH and the lowest Ca2+ concentration in order to keep high concentration of HCO3

-. The alkaline in situ leaching is suitable for uranium extraction from this deposit if the conditions of Ca2+, pH and HCO3

- are under well control.

This work was supported by the Basic Science Research

Project (A3420060142) from China National Defense Science and Technology Industry Bureau, and China National Natural Science Foundation (No. 40872165).

Inter-comparison of methods to detect Methylmercury in porewater

of rice paddy JINLING LIU1,2, XINBIN FENG1*, LIHAI SHANG1, GUANLE QIU1, HAIYUYAN1 AND HENGYAO1,2

1State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550002, China (*correspondence: [email protected])

2Graduate University of Chinese Academy of Sciences, Beijing, 100049, China ([email protected]) Understanding the mechanisms of the transport of

dissolved Methylmercury (MeHg) from rice paddy soil into the water column is very important to better reveal the processes of bio-accumulation of MeHg by rice plants. The detailed information on MeHg distribution in porewater of rice paddy soil is also important to understand the processes of MeHg bioaccumulation in rice. Three methods are currently used for porewater sampling: the dialysis device (peeper), sediment core sectioning (core) and the diffusive gradient in thin films (DGT). However, none of these methods are considered as a standard method. Field inter-comparison were performed at rice paddy near Wanshan mercury mined area in Guizhou, China to test if these methods could give comparable results. Even the discrepancies of MeHg concentrations obtained from different methods were significant; all three methods reported a similar trend of MeHg distribution in soil profile. Based on different principles, these methods reflect different states of MeHg in porewater. Flux, equilibrium concentration and instantaneous concentration of MeHg in porewater are detected by DGT, peeper and core sectioning methods, respectively. Considering the repeatability and accuracy of MeHg concentrations in soil porewater, the DGT technique was considered as the best method.


A615

Reduction of contaminant Tc(VII) by magnetite (Fe3O4) and

titanomagnetite (Fe3-xTixO4) nanoparticles

J. LIU*,1, C.I. PEARCE1, O. QAFOKU1, E. ARENHOLZ2, S. HEALD3, T. PERETYAZHKO1 AND K.M. ROSSO1

1Pacific Northwest National Laboratory, Richland, WA 99354 USA (* Correspondence: [email protected])

2Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA

3Argonne National Laboratory, Argonne, IL 60439, USA The radionuclide technetium is an important subsurface

contaminant at many nuclear reprocessing sites, such as the Hanford site, Washington, USA. This research investigated reduction kinetics of the highly soluble pertechnetate anion [Tc (VII)O4

-] to sparingly soluble [Tc (IV)O2·H2O] by nanoscale mixed valent iron oxides. Magnetite (Fe3O4) and Ti-substituted magnetite (TixFe3-xO4) are common minerals in Hanford sediments. Nanoparticle forms with varying Ti content (0 < x . 0.5) were synthesized using an aqueous solution protocol. The resulting magnetite (x = 0) were ~12 nm spherical nanoparticles, and titanomagnetite (0 < x . 0.5), formed ~10 nm spherical nanoparticles. X-ray diffraction (XRD) patterns show that the cell parameter increases with increasing Ti-doping up to x = 0.35, which indicates that, when present, titanium ions replaced iron ions in the crystal structure up to this amount. The distribution and ratio of Fe2+ and Fe3+ cations were studied by X-ray absorption spectrospcopy (XAS) and X-ray magnetic circular dichroism (XMCD). Lattice Fe (II) concentration increases systematically with increasing Ti doping when 0 < x . 0.35, consistent with substitution as Ti (IV).

Tc (VII) reduction rates by the magnetite and titanomagnetite nanoparticles were measured in HEPES buffer solution at pH = 8. Titanomagnetite shows significantly higher reactivity than magnetite, and the higher levels of Ti-substitution yields a higher reduction rate and extent. No crystalline secondary phases were detected in the reaction products. The smaller cell parameters of the residual nanoparticle solids indicates that the structural Fe (II) was oxidized by Tc (VII). The collective measurements point to a picture of condition-sensitive dynamic exchange of reducing equivalents between bulk lattice Fe (II), more accessible surface-associated Fe (II), and solubilized Fe (II) that is dictated by the chemical potential of Fe (II) built into the solid, a property that in turn depends on the nature and content of aliovalent metal substitution impurities.

Ore-forming fluid characteristics of the Hukeng tungsten deposit, Jiangxi

Province, South China JUN LIU1, HUISHOU YE2, GUIQING XIE2

AND WEI ZHANG3 1The Civil Engineering School, Anhui University of

Architecture, P.R. China ([email protected])

2Institute of Mineral Resources, Chinese Academy of Geological Sciences, P.R. China

3Geoscience and Resource School, China University of Geoscience, P.R. China Hukeng tungsten deposit, located in Wugongshan

metallogenic belt in central part of Jiangxi Province, South China, is one large scale quartz vein type wolframite deposit, which is in the south margin of Hukeng granite intrusion, covering the area of 6 km2. The deposit can be divided into quartz-wolframite, quartz-fluorite-wolframite and quartz-pyrite-sphalerite-wolframite three metallogenic stages [1].

There are three dominant types of fluid inclusions related to metallogenesis in the Hukeng quartz vein wolframite deposit: liquid-rich inclusion, gas-rich inclusion and liquid-gas two-phase inclusion, in which liquid-gas two-phase inclusion occupies more than 90% of the whole.

The homogenization temperatures of fluid inclusions from quartz in three metallogenic stages vary from 200 to 3000, with peak values between 220 and 2400; and the salinities are from 0 to 10 wt%NaCleq., with peak values between 6 and 8 wt%NaCleq.; and the corresponding densities range from 0.7 to 1 g/cm3, with peak values between 0.8 and 0.9 g/cm3. These features represent that the fluids are medium temperature, low density and low salinity in the ore-forming fluids in the Hukeng tungsten deposit.

The analytic results get by Laser Laman Spectroscopy, indicate the fluids in different metallogenic stages of the deposit belong to Na+-K+- Cl--SO4

2- type, suggesting the fluids formed under relative reducing environment.

The H-O isotopic values show that the ore-forming fluids are predominated by magmatic water, mixed with minor amount of meteoric water. Moreover, the ore-forming fluids took place hydrogen and oxygen isotopic exchange with water from metamorphic rocks.

This research was financially supported by the National

Key Basic Science Research Project of China (973 Program, 2007CB411407). [1] Liu. (2008) doctoral dissertation, China University of Geoscience, P.R. China, 76–78.


Modeling heat transfer from convecting, crystallizing, replenished

andesitic magmas at oceanic spreading centers

L. LIU1* AND R.P. LOWELL2 1School of Earth and Atmospheric Sciences, Georgia Tech

Atlanta, GA 30332 USA (*correspondence: [email protected])

2Department of Geosciences, Virginia Tech, Blacksburg, VA 24061 USA ([email protected]) Although most hydrothermal systems at oceanic spreading

centers are driven by basaltic sub-axial magma chambers, some hydrothermal fields (e.g. at the 9°N overlapper on the EPR and at Eastern Lau Spreading Center and Manus Basin) are underlain by high-silica andesite and dacite magmas. The kinematic viscosity of these magmas differ significantly from one another. Mid-ocean ridge basalt magmas are very dry, hence viscosity depends mainly on the crystal content and to a lesser degree on temperature whereas the viscosity of high-silica magmas is also affected by water content. As a result of their higher silica content and lower liquidus and solidus temperatures, these magmas have a greater viscosity than basaltic magmas.

We have incorporated an equation for the viscosity of andesitic magma [1] as a function of temperature, crystallinity and water content into our earlier model of magma convection [2] in order to determine the convective heat flux magmas having a range of silica and H2O contents.. Simulations comparing dry basalt, 0.1 wt.% H2O andesite and 3 wt.% H2O andesite show that higher viscosity andesitic magmas convect less vigorously than their basaltic counterparts, which results in both lower initial heat flux and in a slower rate of decline of the heat flux. Heat flux data are not available for hydrothermal systems driven by andesitic magmas at oceanic spreading centers, but the initial simulated heat flux of ~ 100 W/m2 is still likely to be sufficient to drive observed hydrothermal venting. The slower rate of decay suggests that hydrothermal systems driven by andesite could have longer lifetimes than those driven by basalt. Because magma replenishment is needed to maintain hydrothermal temperatures, however, the higher viscosity, andesitic magmas may undergo slower rates of replenishment. Hydrothermal activity of andesite-hosted systems may exhibit greater temporal variability related to magmatic heat flux than those underlain by basaltic magma.

[1] Vetere et al. (2006) Chem. Geol. 228, 233–245. [2] Liu & Lowell (2009) J. Geophys. Res. 114, B02102.

Dating of multi-stage metamorphism events: Constraints on episodic zircon growth from retrograded eclogites of

the South Altyn Tagh, China L. LIU1*, D.L. CHEN1, C. WANG1,2, Y.T. CAO1,

L. KANG1, W.Q. YANG1, X.H. ZHU1

1State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi’an 710069, P R China (*correspondence: [email protected])

2Xi’an Center of Geological Survey, China Geological Survey, Xi’an 710054, P R China The South Altyn Tagh is an ~ 250 km HP-UHP

metamorphic belt in the northwestern of China. In the Jianggalesayi, the western of the South Altyn Tagh, coesite pseudomorphs in garnet and omphacite and abundant exsolution needles of quartz in omphacite are founded [1]. Recently, Liu et al. [2] discovered evidence of former stishovite in metamorphosed sediments, and the minimum metamorphic pressure was estimated to exceed 12 GPa.

Although many U–Pb zircon age studies have been performed on these HP/UHP rocks, the geochronological of peak or retrograde metamorphism is still oversimplified. Based on mineral inclusion, cathodoluminescencent (CL) images, trace element analyses, and high precise U–Pb age obtained from distinct zircon domains of the Jianggalesayi retrograded eclogites, three discrete and meaningful age groups have been identified. Proterozoic ages of 727 and 715 Ma for dusty inherited zircon cores indicate that the protolith age of eclogite. The group of 499±5 Ma ages for grey-white luminescent zircon mantles is consistent the timing of a UHP metamorphic event studied by previous [3, 4]. The weighted means of 451 ± 4 Ma obtained from dark grey luminescent overgrowth rims represents the age of retrograde eclogite-facies metamorphism. These multi-stage metamorphism age records the information of zircon overgrowth during subduction and exhumation of the South Altyn Tagh UHP terrane, and provide the clue to constraint the exhumation rate.

[1] Zhang et al. (2002) CSB 47, 751–755. [2] Liu et al. (2007) EPSl, 263, 180–191. [3] Zhang et al. (1999) CSB 44, 1109–1112. [4] Liu et al. (2004) JAES 35, 232–244.


A617

Prominent half-precessional signal of East Asian Winter Monsoon in

Chinese Loess Sequence LIANWEN LIU, JUN CHEN AND JUNFENG JI

Department of Earth Sciences, Nanjing University, Nanjing 210093, China, ([email protected]) The history of East Asian Winter Monsoon (EAWM) was

reconstructed based on geochemical record from the loess deposit at the Weinan section in the southeastern Loess Plateau. The section contains 26 m of loess–palaeosol sequences with base age of around 250 ka and can be divided into seven sub-layers downwards, which correspond to the seven marine oxygen isotopic stages (MIS1-7) of the last two glacial-interglacial cycles. Multi-paleoclimate proxies, such as magnetic susceptibility (MS), Zr/Rb ratio and grain size, were determined. The Zr/Rb ratio pattern shows two features. Firstly, similar to the variation of MS and mean grain size (MGS), the Zr/Rb ratio generally correlates well with stratigraphic marker and shows very strong 100kyr cycles. Samples from the loess layers deposited in the glacial periods are characterized by a high Zr/Rb ratio, whereas for samples taken from the paleosol layers deposited in the interglacial periods usually displayed a low Zr/Rb ratio. Secondly, different from the MS and GMS record, Zr/Rb ratio shows remarkable half-precessional cycles in the Weinan section. For example, there are significant six, four and six cycles in the Zr/Rb record during MIS 5 (S1), MIS 6 (L2) and MIS 7 (S2) respectively. Although the precise time control point is absent, the temporal pattern of reconstructed EAWM suggests an obvious presence of half-precessional (around 11kyr) climate variability in the Loess Plateau during the last 250 ka, especially during the period between 60 ka and 250 ka. Because the half -precessional cycle is peculiarly appeared in the tropical region, our result suggests a low latitude influence on the EAWM regime over the past 250 ka.

This work was funded by the NSF of China through

Grants 40973063.

Sedimentary and geochemical evidence for methane seep from a

dolomite chemoherm in the Nantuo (Marinoan) glacial deposit, Zunyi

area, SW China Q. LIU1,2, Z, LIN1,2, D. FENG1 AND D.F. CHEN1*

1CAS Key Laboratory of Marginal Sea Geology, Guangzhou Institute of Geochemistry, CAS, Guangzhou 510640, China (*correspondence: [email protected])

2Graduate University of Chinese Academy of Sciences, Beijing 100049, China A dolomite chemoherm, 1.6 m high and 3.6 m wide,

occurs in the upper part of the Nantuo Formation, and outcrops along the roadside near Jinhe village, south of Songlin town, Guizhou Province, SW China,. The massive dolomite of chemoherm mainly consists of microcrystalline dolomite with minor pyrite, and detrital quartz and feldspar. The upper part of chemoherm contains an ice-rafting igneous gravel. Botryoidal structure, oolitic structure, pyrite framboid, and barite crystal fans occurred in the chemoherm, that are frequently observed in modern seep sediments.

In the lower part (from 0 cm to 122 cm) of the chemoherm section, the $13C values are from "4.65‰ to "3.94‰, the Ce/Ce* ratios are from 0.61 to 0.98, and the Ba contents are from 307 ppm to 10, 529 ppm. The $13C, Ce/Ce* and Ba contents show a synchronous variation. The $13C decreases to "4.65‰ at 41 cm height and the Ce/Ce* and the Ba increases to a peak value, and then drops to a normal level.

The $13C values are from "6.36‰ to "5.51‰ in the upper part (123-160 cm), lower than that of the lower part of the chemoherm. The Ce/Ce* ratio increases from 0.86 at the 131 cm height to 1.82 at the 158 cm height. Ba contents all are higher in the upper part, and there are two extremely high values, 2.63!104 ppm at the 131 cm and 2.93!104 ppm at the 149 cm height, where barites occurred.

These sharply and significantly negative $13C excursions, positive Ce anomalies, extremely high Ba contents in the dolomite chemoherm, all are similar to seep carbonates, suggested that the late Neoproterozoic deglaciation might be related to methane release.

This study was partially supported by Guangzhou Institute

of Geochemistry, Chinese Academy of Sciences (Grants: GIGCX-07-13), and by the NSF of China (Grants: 40872079, 40725011).


The investigation of magnesium isotope fractionation during granite

differentiation S.-A. LIU1*,2, F.-Z. TENG2, S.-G. LI1, Y.-S. HE1

AND S. KE2,3

1School of Earth & Space Science, University of Science & Technology of China, Hefei, 230026, P. R China (*correspondence: [email protected])

2Isotope Laboratory, Department of Geosciences & Arkansas Center for Space and Planetary Sciences, University of Arkansas, Fayetteville, AR 72701, USA

3School of Earth Science and Mineral Resources, China University of Geosciences, Beijing100083, China Magnesium isotope fractionation during differentiation of

basaltic magmas is insignificant, based on studies of global oceanic basalts [1, 2]. It is however uncertain whether or not resolvable Mg isotope fractionation may occur during differentiation of granites, which generally occurs at lower temperatures. To address this issue, here, we report high-precision Mg isotopic data for a suite of well-studied I-type granitoids and associated hornblende and biotite minerals from the Dabie Orogen, central China.

Although these granitoids formed through various degrees of partial melting and fractional crystallization, their $26Mg values show a limited range from -0.26 to -0.15, indistinguishable within our external analytical precision (± 0.07‰; 2SD). Coexisting hornblendes and biotites display similar $26Mg values that are identical to those of their hosting granitoids. The limited inter-mineral isotope fractionation agrees with theoretical predictions. Overall, the data from granitoid whole rocks and mineral separates suggest that Mg isotopes do not significantly fractionate during granite differentiation.

Magnesium isotopic compositions of the Dabie granitoids are similar to those of previously studied I-type granitoids and terrestrial basalts and peridotites [1-5], further confirming that magma processes do not significantly fractionate Mg isotopes. The deep continental crust, as sampled by I-type granitoids, has a mantle-like Mg isotopic composition. Given that Mg isotopes significantly fractionate during surface weathering processes, Mg isotopes can thus potentially be used for tracing recycling of surface materials.

[1] Teng et al. (2007) EPSL. 261, 84–92. [2] Teng et al. (2010) Lunar & Planetary Science Conference, 41, #2019. (2009) PNAS. 106, 20652–20657. [3] Li et al. (2009) AGU Abstract. [4] Handler et al. (2009) EPSL 282, 306–313. [5] Yang et al. (2009) EPSL. 288, 475–482.

Performance assessment for Beishan HLW repository site based on the

preliminary FEP analysis LIU SHUAI1,2 WANG JU1 LIU XIAODONG2 AND

CHEN WEIMING1 1Beijing Research Institute of Uranium Geology, Beijing,

100039, China ([email protected])

2East China Institute of Technology, Fuzhou, 344000, Jiangxi, China The preliminary FEP analysis for the Beishan HLW

Repository Site of China is very important currently. China began nuclear research and development about several decades. China now has an ambitious plan to develop nuclear power generation in order to meet rapid economic development and mitigate global warming effect by reducing fissile fuel dependence. At the same time, China will generate a considerable amount of HLW. For protecting the environment, China has selected Beishan area in Gansu Province as the geological disposal of HLW.

However, during HLW disposal, performance assessment is necessary. Currently, China scientists began the first performance assessment (PA) to Beishan repository site, In this large and systematic research and development process, preliminary FEP analysis for Chinese Beishan site is the first, and important, step. Features, Events and Processes (FEP) are adopted in safety and performance evaluation of radioactive waste repository systems. There are several FEP catalogues publicly available, like the NEA (Nuclear Energy Agency) FEP database and SKB FEP database. Among these databases, the SKB’s database is best fit the Chinese program because of similarities disposal concept and host rock. As a preliminary analysis, note that not all the included FEPs must be included in PA is important. The iterations of screening and auditing are needed to determine the importance levels of the included FEPs. This will involves experts of different fields or subsystems to provide in-depth technical basis and reach consensus on whether a FEP should be modeled, treated as a parameter.


A619

A synchrotron XAS study of speciation and thermodynamic

properties for aqueous cobalt chloride complexes at 600 bar

and 35-500°°C W. LIU1, S. BORG1,3, D. TESTEMALE4,5, B. ETSCHMANN2,,

J-L HAZEMANN4,5 AND JOËL BRUGGER2 1CSIRO Earth Science and Resource Engineering, Australia


2South Australian Museum and The University of Adelaide, Australia.

3CODES, The University of Tasmania, Australia

4Institut Néel, Département MCMF, France. 5ESRF, Polygone Scientifique, 6 rue Jules Horowitz, 38043

Grenoble, France Aqueous Co (II) chloride complexes play a crucial role in

cobalt transport and deposition in ore-forming hydrothermal systems, ore processing plants, and in corrosion of special Co-bearing alloys. Numerical modelling of reactive transport of cobalt in hydrothermal fluids relies on the availability of thermodynamic properties for Co complexes under wide range of T, P and salinity.

We used synchrotron X-ray absorption spectroscopy techniques to determine the speciation of cobalt (II) in 0-5 m chloride solutions at 35-440°C and 600 bar. The qualitative analysis of XANES spectra shows that octahedral species predominate in the solutions at 35°C, while tetrahedral species become increasingly important with increasing temperature, with the tetrahedral CoCl4

2- complex predominating at high chloride concentrations and high temperatures. Ab initio XANES calculations confirmed this structural evolution, and the EXAFS analysis reveals the structure parameter for these models. Finally, the XANES spectra have been used to derive the thermodynamic properties of the CoCl4

2- complex, which enable the thermodynamic modelling of cobalt transport in hydrothermal fluids. Solubility calculations show that tetrahedral CoCl4

2- is responsible for transport of cobalt in hydrothermal solutions with moderate Cl concentration (~2 m NaCl) at and above 250°C, and decreasing temperature and dilution can cause deposition of cobalt from hydrothermal fluids.

Application of laser ablation-ICP-MS in environmental fate and transport

studies X.G. LIU1 AND Q.H. HU2*

1School of Environmental Studies, China University of Geosciences, Wuhan, 430074, P.R. China ([email protected])

2Department of Earth and Environmental Science, The University of Texas at Arlington, Arlington, TX 76010, USA (*correspondence: [email protected]) In studies supporting environmental remediation, nuclear

waste disposal, or the decontamination of radionuclides accidentally or deliberately dispersed in an urban environment, it may be necessary to determine the micro-scale contaminant distribution within solid samples, as a prerequisite to an understanding of the processes controlling contaminant transport. This paper discusses the utility of using a micro-scale sensitive analytical approach, laser ablation coupled with inductively-coupled plasma-mass spectrometry (ICP-MS), for profiling contaminant concentration directly on solids. The approach is discussed in the context of three cases or applications: (1) 3-D imaging of the uranium distribution in sediment grains from the Hanford site; (2) fracture-matrix interaction in unsaturated fractured rock in a potential high-level nuclear waste repository; and (3) cesium deposition and migration in concrete after a mock detonation of a radiological dispersal device. It is shown that the application of laser ablation-ICP-MS can help investigators understand and quantify interacting unsaturated transport processes (imbibition, diffusion, and sorption), as well as factors (water saturation, sample size, and pore connectivity) affecting contaminant transport in unsaturated geological media.


Two episodes of eclogite-facies HP metamorphism in Huwan shear zone and its implication for evolution of the western Dabie orogen, central

China XIAO-CHI LIU, YUAN-BAO WU* AND LAI-SHI ZHAO

State Key Laboratory of Geological Processes and Mineral Resources, Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China (*correspondence: [email protected]) The Huwan shear zone in the western Dabie orogen is a

key area to investigate the evolution the Qinling-Dabie-Sulu orogenic belt. However, its evolution history has not been well constrained. In this study, we present U-Pb age, trace element and Hf isotope compositions of zircons from HP rocks from the Huwan shear zone. The results are used to constrain the timing and sequence of subduction and exhumation of the Huwan HP rocks and also have implications for the exhumation processes of the whole western Dabie HP-UHP metamophic terrain.

Two eclogite samples (08HW51 and 07XX10) contain magmatic zircons with formation ages of 411 ± 4 and 700 ± 14 Ma, and !Hf (t) values of +6.4 to +14.7 and –0.7 to +7.7. Their protoliths might be derived from the Paleotethyan oceanic crust and Neoproterozoic juvenile continental crust, respectively. They also have metamorphic zircons with ages of 306 ± 7 and 310 ± 2 Ma. The metamorphic zircons show trace element characteristics of eclogite-facies metamorphic zircons, indicating couple subduction of oceanic and continental rocks during the Carboniferous.

Metamorphic zircons in a quartz vein 08HW05 within schist and an amphibolite 08HW52 yield weighted mean ages of 241 ± 1 and 243 ± 4 Ma, respectively. All of metamorphic zircon domains are characterized by low Th/U ratios, relatively flat HREE patterns, weak negative Eu anomalies, and low 176Lu/177Hf ratios. These features suggest that the metamorphic zircons formed under eclogite-facies conditions. This indicates that some rocks in the Huwan shear zone also have experienced a second eclogite-facies metamorphism event at ca. 243 Ma. Available geochronological data suggest HP metamorphism occurred at ca. 227 Ma in the Xinxian UHP zone.

Therefore, the Huwan HP shear zone might have suffered multiple burial-exhumation cycles related to orogen-scale alterations. And the whole western Dabie orogen has experienced diachronous subduction and exhumation during the Triassic.

Diachronous subduction and exhumation of the Tongbai-Dabie-Sulu HP/UHP metamorphic belt in

central China X. LIU1,2*, B.-M. JAHN2, J. CUI1 AND Y. LOU1

1Institute of Geomechanics, CAGS, Beijing 100081, China (*correspondence: [email protected])

2Institute of Earth Sciences, Academia Sinica, Taipei 11529, Taiwan Geochronological data suggest diachronous subduction

and exhumation of different HP/UHP slices in the Tongbai-Dabie-Sulu orogen. In the Tongbai terrane, retrograded eclogites and their country gneisses from the Tongbai Complex were metamorphosed at ca. 230-220 Ma [1], whereas eclogites from the two HP eclogite zones on both sides of the Tongbai Complex have the peak metamorphic age of ca. 255 Ma and cooling age of ca. 238 Ma [2]. Similarly, in the western Dabie terrane, the UHP slice occurring in the core of the Xinxian antiform were metamorphosed at ca. 227 Ma and cooled at c. 213 Ma [3, 4], whereas the HP slice represented by the Huwan and Hong’an HP eclogite zones on the two limbs of the Xinxian antiform recorded the metamorphic age of ca. 240 Ma and cooling age of ca. 230 Ma [4-6]. In fact, the recent dating has distinguished three and two UHP slices of different ages in the eastern Dabie [7] and Sulu terranes [8], respectively, suggesting that the UHP terrane is also not a single coherent slice. Therefore, diachronous subduction and exhumation might be a major mechanism for the formation and uplifting of the HP/UHP rocks in the Tongbai-Dabie-Sulu orogen. The ca. 255 Ma eclogite zones in the Tongbai terrane should represent an earliest subducted and exhumed HP slice in the orogen.

[1] Liu X et al. (in review) Lithos. [2] Liu X et al. (2008) Lithos 105, 301–318. [3] Wu et al. (2008) CMP 155, 123–133. [4] Liu X et al. (2004) Tectonophysics 394, 171–192. [5] Eide et al. (1994) Geology 22, 601–604. [6] Cheng et al. (2009) AGU Fall Meeting. [7] Liu Y et al. (2007) Lithos 96, 170–185. [8] Liu F et al. (2009) JMG 27, 805–825.


A621

Tectonic controlled oil generation of source rock and exploration in west

margin of Ordos Basin, China L. XIAOJIE1,2, L. RONGXI1,2( AND L. JIANCHAO1,2

1Key Lab of Mineral Resources & Geology Engineering, Education Ministry of China, Chang’an University, Xi’an, 710054, China (*correspondence: [email protected])

2School of Geosciences & Mineral Resources, Chang an University, Xi’an,710054, China Ordos Basin, lies in the western margin of the north

Chinese Block, is a wide asymmetry Mesozoic depression basin. From later Triassic to later Cretaceous, west margin of the basin alternatively experienced tectonic subsidences to form thousands meters of fluvial-delta-lake sediments and tectonic uplifts to form thrusts and folds which were intensified by Himalayan tectonic movements. Upper Triassic oil shale and black mudstone of Chang 7 section of Yanchang Formtion were confirmed to the best qualified oil source rock of Ordos basin [1].

On the basis of analysis to geological evolution, history of hydrocarbon generation of Chang 7 source rocks in west margin of Ordos Basin were studied. The buried depth of Chang 7 source rocks at present was variable in the area because of different degree of uplifting after Tertiary. However, recovery studies to thermal and hydrocarbon generation history indicate that Chang 7 source rocks experienced two times of hydrocarbon generation. The first time of hydrocarbon generation took place at later Jurassic when thermal degree of Chang7 source rocks reached to VRo of 0.71% due to sudden subsidence of the area. But oil produced during this period was escaped completely because of tectonic uplift and erosion at later Jurassic. The second time of hydrocarbon generation took place at early Cretaceous when thermal degree of Chang 7 source rocks got to VRo of 0.89% because of extensive subsidence again. Oil generated at this time was the most important oil resources which were very essential to reservoir formation.

There was best reservoir formation condition for oil generated at the second time. Oil reservoirs related with thrust and folds structure at later Cretaceous would be the valuable targets for exploration in the area.

[1] Li Rongxi et al. (2008) Russian Geology & Geophysics 49, 23–27.

Proterozoic crustal evolution of Yangtze Craton revealed by detrital zircons from Shenlongjia area, South

China XIAOMING LIU1*, WENLI LING2 AND SHAN GAO2

1State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi’an 710069, China (*correspondence: [email protected])

2State Key Laboratory of Geological Processes and Mineral Resources, Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China ([email protected], [email protected]) Integrated U-Pb dating, Hf-isotope and O-isotope analysis

of detrital zircons from Shenlongjia sandstone in the northern part of the Yangtz Craton has been used to identify the province of the clastic sediments and to provide some clues on Proterozoic crustal evolution of Yangtze Craton.

The zircons from interbedded andesite of Zhengjiaya group, the buttom of Shenglongjia formation, were dated to 1153±24 Ma, which indicates that the Shenglongjia formation was deposited in the late of Meso-proterozoic. The detrital zircons from the sandstone of Zhengjiaya group show three concordia U-Pb age populations, 1.5-1.7Ga, 1.9-2.1Ga and 2.85-2.95Ga. The detrital zircons from sandstone of Liangfengya group which overlain Kuangshishan group (the top group of Shenglongjia formation) show three concordia U-Pb age populations, 1.5-1.7Ga, 1.8-1.9Ga and 1.9-2.1Ga. The age population difference between Zhengjiaya and Liangfengya groups indicates the changes of source area. The Hf-isotope data suggest that the recycling of ca. 3.2 Ga crust materials of Yangtze Craton took place in the time intervals 1.8-1.9Ga and 1.9-2.1Ga, and the important juvenile crust growth occurred at 1.5-1.7Ga, which also suggested by some 1.5-1.7Ga zircons with $18O values in the range of 5.41-5.67

Supported by National Natural Sicence Foundation of

China (Grant No. 40673057) and National Basic Research Program of China (Grant No. 2009CB825003)


Low ##7Li regolith produced during basalt weathering: A case study from

the Columbia River Basalts XIAO-MING LIU1*, ROBERTA L. RUDNICK1,

WILLIAM F. MCDONOUGH1 AND MICHAEL CUMMINGS2 1Department of Geology, University of Maryland, College

Park, MD 20742, USA (*correspondence: [email protected])

2Department of Geology, 1Portland State University1, Portland, OR 97207, USA Chemical weathering may influence the bulk composition

of the continental crust [1, and references therein]. Because Li isotopes fractionate significantly during continental weathering, they may provide a useful tool for evaluating the influence of weathering on crust composition and secular changes in continental weathering intensitites and processes.

Li isotopes were analyzed on two ~10 m deep drill cores through bauxites developed on Columbia River Basalts in Oregon and Washington, west of the Cascade Mtns. Both profiles are strongly depleted in Li (normalized to immobile Hf) relative to fresh basalt, consistent with Li loss via leaching during weathering. However, contrary to simple leaching, Li concentrations increase upwards in the profiles, with the most intensively weathered bauxites at the tops of the profiles having higher Li than lower sections of the profiles. In addition, #7Li values decrease systematically towards the surface, reaching values that are 6 to 8‰ lower than those of the fresh basalt. These results cannot be explained by Li loss via equilibrium Rayleigh distillation, as this would produce a positive correlation between Li concentration and #7Li, and the opposite is observed. These findings are remarkably similar to those for a 50 m laterite profile developed on the Deccan basalts [2], which suggests a global similarity in process. Although the latter results were attributed to mixing with an unusually isotopically light (-5‰) aeolian component, we suggest instead that the mixing occurs between Li-rich secondary minerals (e.g. clays that preferentially incorporate 6Li into their structure) and leached basalt deeper in the profile. This study confirms that chemical weathering of basalts, which may be the main building blocks of the continents, produces large fractionation of Li isotopes and an isotopically light regolith.

[1] Lee et al. (2008) Proc. Natl. Acad. Sci. U.S.A. 105, 4981–4986. [2] Kisakurek et al. (2004) Chem. Geol. 212, 27–44.

The Dupal isotope anomaly in the Paleo-Asian sub-oceanic mantle: Nd-Sr-Pb isotope evidence from

ophiolites in Northern China X.J. LIU1,2,3*, P.R. CASTILLO2, J.F .XU1 AND Q.Y. HOU1

1Key Laboratory of Isotope Geochronology and Geochemistry, Guangzhou Institute of Geochemistry, CAS, Guangzhou 510640, China (*correspondence: [email protected])

2Scripps Institution of Oceanography, UCSD, La Jolla, CA, 92093, USA

3Graduate School of CAS, Beijing 10039, China It has been suggested [1] that the Dupal isotope anomaly

[2] can be traced in the Paleozoic ophiolites from the Paleo-Asian Ocean (PAO), which was formed during the break up of the Rodinia Supercontinent between 1000 and 300 Ma [3]. New Sr, Nd and high-precision Pb isotope data for basalts, gabbros and plagioclase separates from the ophiolites in the E and W Junggar blocks and central Tianshan tectonic zone in the southern PAO combined with published data suggest that the PAO crust and related arc magmas indeed have a Dupal-like isotope signature. In detail, the Pb isotopic compositions of the plagioclases are more tightly clustered than those of the whole rocks, indicating that the Pb isotopic composition of the mafic rocks from the PAO ophiolites may have been compromised by alteration. Nevertheless, all samples have high 2°8Pb/2°4Pb for given 2°6Pb/2°4Pb ratios (i.e. positive $8/4 values), similar to Indian Ocean MORB. The trace element signatures of the mafic rocks from the W Junggar and central Tianshan ophiolites are similar to those of normal- and enriched-MORB whereas those of the E Junggar ophiolites are transitional between MORB and arc basalt. The new southern PAO samples have higher $8/4 than the early-Paleozoic (570Ma) ophiolites from Agardagh Tes-Chem in the northern PAO [4] and these indicate that the Dupal isotope anomaly became stronger with time and from north to south. Finally, the PAO mantle is isotopically heterogeneous and lends support to the idea that the Dupal isotope anomaly existed prior to the opening of the Indian Ocean [5]. Such a long period of existence and large-scale distribution indicate that the Dupal isotope anomaly may not simply be an attribute of certain mantle domain, but a reflection of a mantle process as well.

[1] Dupre & Allegre (1980) Nature 286, 17–22. [2] Hart (1984) Nature 309, 753–757. [2] Dobrestove et al. (1995) International Geology Review 37, 335–360. [3] Pfänder et al. (2002) Contributions to Mineralogy & Petrology 143, 154–174. [4] Xu & Castillo (2004) Tectonophysics 393, 9–27.


A623

A combined AFM and FTIR study of EPS-coated goethite

XINRAN LIU*, KAI UWE TOTSCHE AND KARIN EUSTERHUES

LS Hydrogeology, Institute of Earth science, Friedrich Schiller University Jena, 07749 Jena, Germany (*correspondence: [email protected]) Goethite is an important geosorbent in soils and aquifers

of temperate climate. Adsorption of extracellular polymeric substances (EPS) to minerals is of environmental concern as the coverage of mineral surfaces by EPS will change interface properties and reactivity. EPS were extracted from Bacillus subtilis and Pseudomonas fluorescens separately and used for adsorption to goethite. Fourier transform infrared spectroscopy showed structural differences between cell-bound and free EPS. Atomic force microscopy was used to study the interaction between EPS and goethite. Employing phase-shift-imaging we found that up to 60% of the exposed goethite surface was covered by EPS (Fig. 1). Force volume study in air revealed that adhesion changed after EPS adsorption to goethite (Fig. 2). This change of surface property will affect the reactivity and mobility of goethite as a geosorbent.

Figure 1: AFM Phase-shift images of pure goethite (left) and of EPS-coated goethite (right). Figure 2: AFM force image (left) and adhesion map of 2#2 µm (right) of EPS-coated goethite. Compared to pure goethite (data not shown), the adhesion force of tip-sample decreased after EPS adsorption to goethite. Further study in liquid is ongoing.

Analysis of microorganisms community composition for column

bioleaching test of uranium ores LIU YAJIE*, LI JIANG, XU LINGLING, LIU JINHUI, LI

XUELI, SHI WEIJUN AND WU WEIRONG East China Institute of Technology, School of Civil and

Envrionmental Engineering, Fuzhou City, Jiangxi Province, P.R. Chnia, 344000 (*correspondence: [email protected])

Introduction

Acidophilic microorganisms play an important role in both environmental and industrial systems, such as the environmental problems of acid mine drainage (AMD) and bioprocessing termed bioleaching [1]. Most of the microorganisms functioned in bioleaching systems are chemolithotrophic, some of them are heterotrophic and mixtrophic acidophiles. For the composition of microorganisms community in a given bioleaching system has important correlation to the mineral recovery, analysis of the composition give us new insight into the bioleaching processes, as a result to guide the industrial operation.

In this study, both methods were applied to analysis the microorganisms composition.

Results

Two group samples took from the test bioleaching columns of uranium minerals. The first group samples were taken from the stage of uranium concentration in the leachates more than 400mg/l, when the temperature was 25-300; the second ones from the latter stage of bioleaching, when the temperature was 35-400and uranium concentration in the leachates less than 20mg/l. Samples were analysed by double layers plates and t-RFLP methods. Results showed the predominant bacteria were Athidithiobacillus. ferrooxidans (more than 65%) in the first group samples and Leptospirillium ferriphilum (about 50%) and Athidithiobacillus caldus (35%) in the second group samples; the minor ones were heterotrophs Acidiphillum sp. and Acidobacterium sp. in the first group, as well as fungus, Acidomyces richmondensis, when the leaching yields were low. The interplay between the microorganisms composition and leaching system indicated that in a given bioleaching system, the microorganisms composition were varied with the temperature and environment of leaching, in the other hand, the varied leaching environment can change the microorganisms composition.

Thanks for the supports of Jiangxi Provincial Department of Education Project (GJJ08309), Chinese National 863 Project (2007AA06Z120) and National Natrual Science Foudation (50974043).

[1] Schippers, Kock, Schwartz & Böttcher et al. (2007) Journal of Geochemical Exploration 92, 151–158.


Effects of water in lunar basalts YANG LIU AND LAWRENCE A. TAYLOR

Planetary Geoscience Institute, Deptartment of Earth & Planetary Sciences, University of Tennessee, Knoxville, TN 37996, USA ([email protected]) Volatiles play important roles in phase equilibrium,

magma genesis and transport. Owing to the previous concept of a ‘bone-dry’ moon, contrasting models are proposed for high-Ti basalt genesis, namely re-melting of ilmenite-rich cumulate by overturning versus assimilation by low-Ti melt. The debate between these two models is largely arisen because of the experimentally determined negative buoyancy of the dry high-Ti melt (e.g. [1]). Recently, significant water was discovered in the lunar glass beads and apatite [2-5], which transfers to existence of water in the lunar mantle. This would suggest a re-evaluation of lunar magma genesis and the density of high-Ti melt. Using the estimated initial water in very-low-Ti glass beads (primitive low-Ti melt) from Saal et al. [3], the mantle source rocks for these beads may contain 26-48 ppm H2O if 10% partial melting is assumed. As ilmenite-rich cumulate forms after 95% crystallization of the LMO [7], the ilmenite-rich cumulate would have 520-960 ppm water. Assuming 10% melting, the high-Ti melt from the ilmenite-rich layer likely contains 0.5-1 wt% H2O. This amount of water can decrease the density of high-Ti melt to a density (3240 kg/m3) less than that for olivine (3300 kg/m3) at 1500°C and 2 GPa, the solidus of high-Ti basalts. It is clear that the above calculation provides a promising first approximation on the initial H2O content in high-Ti melts. Here, we review recent results of water in lunar samples and evaluate its effects on various aspects of lunar basalts.

[1] Circone & Agee (1996) Geochimica Et Cosmochimica Acta 60, 2709–2720. [2] Elkins Tanton, L. T. et al.. (2002) EPSL 196, 239–249. [3] Saal, A. et al. (2008) Nature 454, 192–196. [4] Liu et al. (2010) LPSC 41s, #2649. [5] Greenwood et al. (2010) LPSC 41st, 2439. [6] McCubbin et al. (2010) LPSC 41st, 2468. [7] Snyder, Taylor, & Neal (1992) Geochimica Et Cosmochimica Acta 56, 3809–3823.

Geology and C, H and O isotopic geochemistry of Dongmozhazhua Pb-

Zn ore deposit, Qinghai, China YINGCHAO LIU1, ZENGQIAN HOU2, ZHUSEN YANG1

AND SHIHONG TIAN1

1Institute of Mineral Resources, CAGS, Beijing 100037,China ([email protected])

2Institute of Geology, CAGS, Beijing 100037, China) The Dongmozhazhua Pb-Zn ore deposit, located in the

north of ‘Three River’ Pb-Zn-Cu-Ag metallogenic belt in Northeast Tibetan plateau, is controlled by the regional NW-SE thrust system. Ore bodies, hosted in limestone rocks of Late Triassic Bolila Formation and Early-Middle Permian Jiushidaoban Formation, are stratabound with colloform and xenomorphic grain textures and dissemination and breccia structures. Ores mainly consisted of sphalerite, galena, pyrite, calcite, dolomite and barite. The alteration types are strong dolomitization and weak silicification.

The H-O isotopic data of fluid inclusions in calcites (Fig.1a) indicate the fluid were mainly derived from pent-up water in the basin and partly from hydrothermal fluid. The C-O isotopic data of calcites and host limestone rocks (Fig.1b) indicate the dissolution of carbonate rocks have occurred during the ore-forming process. Therefore the fluid may have moved long distance in the basin after derived and got lots of ore-forming materials such as metals.

The geology and C-H-O isotopes of this deposit are

similar to MVT deposits in the world [3], therefore the authors consider this deposit as a MVT-like Pb-Zn deposit controlled by the thrust systerm in the orogenic belt.

This work was supported by grants (Contract No.

2006BAB01A08, 2009CB421008 and 2009CB421007). [1] Lu H Z et al. (2004) Beijing, Science Press, 19~20. [2] Liu J M et al. (1997) Acta Mineralogical Sinica 17, 448~456. [3] Leach et al. (2005) Economic Geology 100th Anniversary Volume, 561–607.


A625

An experimental study on the autotrophic denitrification with

sulphur electron donor in groundwater

Y. LIU1, J.Z. QIAN2*, Z. CHEN2 AND J.F. WU3

1School of Biotechnology and Food Engineering, Hefei University of Technology, Hefei 230009, China ([email protected])

2School of Resources and Environmental Engineering, Hefei University of Technology, Hefei 230009, China (*correspondence: [email protected])

3Department of Hydrosciences, Nanjing University, Nanjing 210093, China ([email protected]) An understanding rate of nitrate removed in groundwater

is vital for groundwater risk management associated with nitrate pollution, and to safeguard groundwater supplies and groundwater-dependent surface waters. In order to provide nitrate pollution bioremediation in groundwater with technical data by means of the autotrophic denitrification reaction nature, sulfur-contaminated soil sample from near a coal pile in Hefei city was collected. Thiobacillus denitrificans were isolated and incubated from the soil in enrichment culture medium (Na2S2O3·5H2O 5.0g, K2HPO4 2.0g, KNO3 2.0g, NaHCO3 1.0 g, MgSO4·7H2O 0.6g, NH4Cl 0.5g, FeSO4·7H2O 0.01g, in 1000 ml of deionized water, pH7.0-7.6) at 28 for 5 days, which was used to remove nitrate from groundwater with sulfur as electron donor, and adding some CaCO3 to adjust alkalinity under anaerobic condition. The results show that: (1) The concentration of NO3

--N was decreased to the value less than 10 mg/L at the hydraulic residence timeHRT) of 15 d, while the initial nitrate concentration was 100

mg/L, keeping S/N quality ratio of 3 (for S2O32- to NO3

-) and the initial turbidity at 660 nm of the culture after inoculation was adjusted to 0.10. (2) In general, the initial concentration of NO3

-N has a negative effect on the rate of NO3-N removed.

The optimal initial concentration of NO3-N is 40 mg/L with

75.5% removal rate. (3) Under the invariable HRT, completely denitrification dealing with the highest nitrate concentration is relate to sulfur grain diameter, the smaller the sulfur grain diameter, the larger the maximum volumetric loading rate of NO3

-N, and the main component of the tail gas is nitrogen. The results provide new experimental supporting for the nitrate contamination remediation in groundwater and protecting the groundwater-dependent surface waters.

This study was supported by the Program for New

Century Excellent Talents in University (No. NCET-06-0541) and the National Natural Science Foundation of China (No.40872166; 40672154).

Compilations of cratonic peridotite xenoliths: Constraints on continental

lithospheric mantle compositions YONGSHENG LIU1* AND PETER B KELEMEN2

1State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China (*correspondence: [email protected])

2Dept. of Earth & Environmental Sciences, Columbia University, NY 10964-8000, USA ([email protected]) Low temperature Kaapvaal and some Siberian xenoliths

from kimberlite are characterized by opx-enrichment coupled with high Mg# olivine, and have been accepted as typical feature of Archaean cratonic mantle. Keleman et al. [1] suggest that opx-rich mantle with high Mg# olivine could be produced by reaction between SiO2-rich liquids (e.g. small degree melts of subducted eclogite) and previously depleted, low-opx peridotites. The later could be formed by Archean mantle melting to the exhaustion of orthopyroxene [2]. In this work, data of peridotite xenoliths from the worldwide major continents were compiled to investigate the distribution of mantle xenoliths with opx-enrichment coupled with high-Mg# olivine and evaluate the refertilization of depleted Archaean mantle by SiO2-rich melt percolation. The database indicates that, (1) although ‘Archean’ mantles are generally not opx-rich, mantle with oilvine Fo>92 and opx-rich peridotite is almost exclusively Archean, (2) xenoliths from Greenland are generally characterized by high-Mg# olivine and opx-rich trend, (3) some xenoliths from Siberian craton show also opx-enrichment coupled with high Mg# olivine, (4) some xenoliths from Slave craton show high Mg# olivine, but cpx-enrichment, (5) slight opx-enrichment coupled with high Mg# olivine are also observed in a few Wyoming and Tanzania xenoliths, (6) xenoliths from Australia and North China show generally low Mg# olivine.

[1] Bernstein, Kelemen & Hanghøj (2007) Consistent olivine Mg# in cratonic mantle reflects Archean mantle melting to the exhaustion of orthopyroxene. Geology 35(5), 459–462. [2] Kelemen P.B. Hart S.R. & Bernstein S. (1998) Silica enrichment in the continental upper mantle via melt/rock reaction. Earth & Planetary Science Letters 164(1-2), 387–406.


The theoretical estimation of mass-dependent fractionation line (MDFL)

positions of oxygen isotopes YUN LIU* AND XIAOBIN CAO

State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China (*correspondence: [email protected]) Small mass-independent processes have been paid more

and more attentions as potential new proxies of environment change. Angert et al. (2004) proposed that 17O-excess in ice could indicate the variations in oceanic humidity and was confirmed by Landais et al. (2008). This kind of small mass-independent process studies require not only high precision analytical techniques, but also a high precision MDFL slope position in terms of 2 values (i.e. 0.528 vs. 0.52) and the temperature dependence of 2. Here, we study the 2 values of many important O isotope systems and try to establish a simple way of estimating unknown 2 value if it is needed.

Based on the logarithm-type expression for small delta (#), we calculated many 2' values by using high-level quantum chemistry methods. We find: 1) although anharmonicity affects the reduced partition function ratios (RPFR) for some molecules, it has little effect on the MDFL position due to large cancelation. 2) Crossover relates to the frequencies shifts (i.e. &,) and also the frequencies shift factors (i.e. &,/,). Crossover usually occurs at relative low temperatures. 3) The 2' values are varied at different temperatures but are almost constant within a small temperature range, such as from -50°C to 50°C, which is a temperature range many studies focused on. 4) Because the number of actual 2' values is numerous, the work of producing these 2' values will be extremely demanding. Alternatively, we propose a simple way to predict the 2' values approximately. We find that the difference of 2' values between similar chemical structure units is small (often to the fourth digit after zero point). This finding enable us to estimate almost all 2' values if we have provided the beta values of the most typical O isotope systems.

[1] Angert et al. (2004) GCA, 68, 3487–3495. [2] Landais et al. (2008) GeoPhys. Res. Lett. 35, L02709.

Oil sources analysis in Northern Qaidam Basin, China

ZHAOQIAN LIU1,2* AND LIANFU MEI1 1Key Laboratory of Tectonics and Petroleum Resources

(China University of Geosciences Wuhan), Ministry of Education, Wuhan, 430074, China ([email protected]) (*correspondence: [email protected])

2Department of Geological & Enviromental Sciences, Stanford University, CA 94305, USA Three GC/MS analyzed oil-bearing sand core samples

whose depths were 135m, 158m and 319m respectively, all produced from Middle Jurassic in Mahaigaxiu anticline of Northern Qaidam Basin in China, show interesting different biomarker features. The two samples from shallower layer are mature oil and contain lacustrine and terrigenous organic matter preserved under oxic conditions. The sample from the deepest layer indicates lacustrine organic matter preserved suboxic and higher salinity conditions and is the only one which underwent biodegradation and immature oil. Oil-oil correlation between the three samples and other oil samples from surrounding area Yuqia and Mabei oil field indicates that the samples from shallower and deeper layers have very similar biomarker features with Yuqia oil and Mabei oil, respectively. Based on oil-oil correlation and thermal history analysis of source rocks, we consider that the mature oil in shallower layer came from the Middle Jurassic source rock in Yuqia depression which reached and maintained in the oil window in the early Cretaceous and the immature oil in the deeper layer migrated from the Middle Jurassic source rock in Gaxi depression which subsided in connection with the tectonic movement in Paleogene and reached the oil window and oil generation peak in late Paleogene..

With the help of seismic cross section analysis, fission track dating evidences and modelled time-temperature thermal history, we consider that this interesting event of immature oil and mature oil accumulated in deeper and shallower layers respectively was closely bound up with two tectonic movements in Cenozoic. In Paleogene, the immature oil from Yuqia depression migrated to Mahaigaxiu anticline which was formed by compression from South Qilian Mountains in the same period. In Neogene, the eastern end of mahaigaxiu anticline upwarped and the western end pitched because of the uplift of Lvliang Mountain which located in the western end of Mahaigaxiu. In the same period, many NE strike slip faults were formed and cut the Mahaigaxiu anticline. Mature oil from Gaxi depression migrated to the eastern end of the anticline and migrated vertically to the shallower layer when the oil met cutting faults.


A627

Mn in welding fume: Characterization and exposure

biomarkers KENNETH JT LIVI1, JULIE RICHMAN2 AND

ALISON S GEYH2 1Integrated Imaging Center, Johns Hopkins University,

Baltimore, MD 21218, USA

2Dept. Environmental Healt Sciences, Johns Hopkins School of Public Health, Baltimore, MD 21205 USA The association between exposure to airborne Mn and

neurotoxic outcomes is well understood. However, the association between airborne Mn exposure and Mn uptake from the pulmonary system remains unclear. Toxicological research indicates that the chemical and physical form of Mn in exposures are determinants of the time course of Mn uptake.

Welding fume was selected as the source of Mn inhalation exposure. The goal of this human exposure assessment study was to: 1) fully characterize the weld fume, and 2) identify the time course of uptake and clearance of metals in the pulmonary system following inhalation exposure. Scanning transmission electron microscopy spectrum imaging, employing energy-dispersive X-ray spectroscopy and electron energy-loss spectroscopy, was used to determine the size and composition of fume nanoparticles. Mn in exhaled breath condensate (EBC) and blood Mn were selected as biomarkers of exposure. Two measures of exposure were developed and characterized for incorporation in the study: primary particle count median diameter (CMD) and Mn composition by size. In addition, a method for the collection and analysis of EBC was characterized and incorporated in study measures.

The average Mn concentration in welding fume was 375 µg/m3 (range 8-1800 µg/m3). Fume nanoparticles crystallized with the spinel structure (hausmannite and magnetite). The average primary particle CMD was 6.9 nm (range 3.2-14.5 nm). There was an overall positive correlation between Mn content and particle size. In addition, the smallest size fraction (<10 nm) exhibited a lowering of Mn content consistent with a ‘self cleansing’ mechanism observed in semiconductor materials. The average mean valence state of Mn was +2.15.

No trend in uptake of Mn due to welding was measured in blood. Nine exposed subjects had a significant EBC Mn peak concentration following welding. Among subjects with an EBC-Mn peak, the primary particle CMD and the Mn composition by particle size slope were associated with the timing and concentration level of the maximum EBC Mn peak. Our findings suggest that an understanding of the particle size and composition is important when characterizing the impact of inhalation exposure to Mn.

New strategies for precise & accurate isotope ratio determination from very

small analyte quantities using the NEPTUNE Plus MC-ICP-MS

N.S. LLOYD*, J.B. SCHWIETERS AND C. BOUMAN

Thermo Fisher Scientific, Hanna-Kuanth-Str. 11, 28199 Bremen, Germany (*correspondence: [email protected]) The Thermo Scientific NEPTUNE Plus with Jet Interface

offers unparalleled MC-ICP-MS sensitivity for heavy isotopes. An ion yield of c. 4% has previously been reported for uranium [1]. Sensitivity enhancements have been achieved through a combination of a dry high-capacity (100 m3/h) interface pump, X-cone, Jet cone, and the Cetac Aridus II desolvating nebuliser system.

The sensitivity of the Jet Interface for small spot size (< 10 µm diameter) LA-MC-ICP-MS was trialled for natural uraninite, NBL U030 & U500 certified reference materials, using a New Wave Research UP-213 laser ablation system.

For applications where very small absolute quantities of analyte are available in solution, improved sample introduction strategies are desirable. For example, in nuclear forensics, 1 – 2 µm diameter uranium oxide particles comprise less than 40 pg of total uranium. Traditionally these are analysed using TIMS. MC-ICP-MS offers greater productivity, and large datasets can yield more information [2]. This analytically challenging application is used to illustrate new capabilities for isotope ratio measurement from very small analyte quantities.

A combination of ESI SC-2 DX microFAST injection autosampler, Apex IR FAST nebuliser and SpiroX heated membrane desolvator were trialled as a sample introduction system for MC-ICP-MS. This combination allows the automated rapid injection of solution micro-samples. Reagent blank levels can be minimised and wash-out is rapid. The efficiency of sample introduction is significantly increased, and therefore the signal to noise ratio is improved.

[1] Bouman et al. (2009) Geochim. Cosmochim. Acta. 73(13, Supplement 1). [2] Lloyd et al. (2009) J. Anal. At. Spectrom. 24(6), 752–758.


Evaluation of some feldspar specimens as candidates to be

characterized as Reference Materials for their minor and trace element

contents M. AMELIA V. LOGAN

Smithsonian Institution, Department of Mineral Sciences, P.O. Box 37102, NHB-119 Washington DC, 20013, USA ([email protected]) Four feldspar specimens from the Smithsonian Microbeam

Reference Materials Collection (Jarosewich et al. 1980) are being evaluated for their suitability as candidates to be characterized as RMs for their trace element contents: Lake County plagioclase, Ab33 An66Or1 (NMNH 115900); Kakanui anorthoclase, New Zealand, Ab71 An5Or24 (NMNH 133868); Great Sitkin anorthite, Ab5 An95 (NMNH 137041); and microcline from an unknown locality, Ab12 An0Or88 (NMNH 143966). Preliminary results of Ti, Fe and Sr contents by electron microprobe (20 kV, 200 nA, 20 +m) are reported in table 1 as ppm ± 3; n = grains; N = analyses. Table 1 NMNH N N Ti Fe Sr 115900 15 30 250±10 3300

± 100

250±50

133868 4 80 b.d.l. 1100± 100

2000±300

137041 4 80 60± 10 3500± 90

360±40

XRF analysis on 1.5 g of NMNH 133868 indicated

1900±50 ppm Sr. Ti, Fe and Sr contents in microcline (NMNH 143966) were below the detection limit of the electron microprobe. These results indicate that Lake County plagioclase (NMNH 115900), Great Sitkin anorthite (NMNH 137041) and Kakanui anorthoclase (NMNH 133868) are good candidates for further characterization by other microbeam techniques.

[1] Jarosewich, Nelen & Norberg (1980) Reference samples for electron microprobe analysis. Geostandards Newsletters 4, 43–47.

REE fractionation during low-temperature water-mineral

interaction A. LOGES1*, S. GÖB1, D.E. JACOB2, M. BAU3,

T. WAGNER4 AND G. MARKL1

1Institut für Geowissenschaften, Tübingen University, D-72070 Tübingen, Germany, (*correspondence: [email protected])

2Institut für Geowissenschaften, Universität Mainz, D-55099 Mainz, Germany

3Earth & Space Sciences Program, Jacobs University, D-28725 Bremen, Germany

4Institute of Geochemistry and Petrology, ETH Zurich CH-8902 Zurich, Switzerland We have investigated the factors that control REE

redistribution during low-temperature water-mineral interaction, using the Clara fluorite-barite mineral deposit (Schwarzwald, Germany) as a case study. In this deposit, fracture hosted secondary minerals (secondary fluorite, goethite, and Mn oxides) were formed during water-mineral interaction and remobilization of the primary mineral assemblage (fluorite, barite). The trace element and REE distribution (including Y) of a representative set of mineral and water samples have been analyzed by LA-ICP-MS and solution ICP-MS.

Prominent Y anomalies and Y-Ho fractionation have been found in many samples in addition to redox sensitive anomalies like Ce and Eu. There is good correlation between La, Gd, and Y anomalies in our goethites and Mn oxides, where REE incorporation is controlled by sorption. La and Gd anomalies can be used as a quantitative expression for the tetrad effect and Y-Ho fractionation is related to the (usually weaker) tetrad effect, as it is known from other geochemical systems. In primary and secondary fluorites these anomalies show no correlation. This suggests that sorption on oxides and hydroxides has large influence on the REE behaviour during low-temperature mineral-water interaction and remobilization even if they are only minor phases. Conversely, secondary fluorites apparently have REE patterns closer to those of the waters they have precipitated from. Combined with apparent distribution coefficients calculated from co-genetic mineral pairs, this allows a better reconstruction of the chemical composition of waters from mineral REE patterns and improves understanding the impact of different parameters that control REE incorporation in complex natural systems.


A629

Characterization of biominerals associated with the Rio Tinto River,

Spain L.M. LOISELLE* AND G. SOUTHAM

Department of Earth Sciences, University of Western Ontario, London, ON N6A 5B7, Canada (*correspondence: [email protected]) Acidophilic, aerobic iron and sulfur oxidizing bacteria

thrive in the waters of the Rio Tinto River in Spain, a Martian terrestrial analogue due to the presence of jarosite and other sulphate minerals [1]. The objective of this study is to document the influence of these acidophilic microbial communities on the iron oxides from this analogue environment in conjuction to characterizing the advantages and limitations of analytical techniques currently used in astrobiological research.

Iron hydroxy sulfate (jarosite) containing sediments were collected from the Rio Tinto River, near Nerva, Spain. Acidophilic Fe and S oxidizing bacteria were cultured in a ferrous sulfate medium resulting in the formation of jarosite (XRD). Bacteria were difficult to observe within the iron oxides using phase contrast light microscopy. However, when stained with SYTO 9 dye and propidium iodide, cells were easily distinguished amongst the oxide matrix. Light micrographs of synthetic jarosite [2] were comparable to those of the biogenic system. However, the synthetic and biogenic oxides were easily distinguished from one another when examined using scanning electron microscopy. In addition to the presence of bacterial cells, which were clearly visible at high resolution, the synthetic and biogenic jarosite minerals possessed distinctly different morphologies. The precipitation of jarosite in Rio Tinto appears to be directly influenced by biology, beyond simply promoting the oxidation of reduced iron and sulfur compounds associated with the formation of these acid ecosystems.

[1] Fernández-Remolar et al. (2005) Earth & Planet. Sci. Lett. 240, 149–167. [2] Basciano & Peterson (2007) Mineral. Mag. 71, 427–441.

Assessing landscape response to land-use change using sediment-chemical chronologies and backcast modeling

DAVID T. LONG1*, CATHERINE H. YANSA2, BRYAN C. PIJANOWSKI3 AND MATTHEW J. PARSONS4

1Geological Sciences, Michigan State University, East Lansing, MI, USA. ([email protected])

2Geography, Michgian State University, East Lansing, MI, USA. ([email protected])

3Forestry and Natural Resources, Purdue University, West Lafayette, USA. ([email protected])

3Geological Sciences, Michgia State University, East Lansing, MI, USA. ([email protected]) Understanding the impact of land-use change (e.g.

urbanization, deforestation) on the flows of mass and energy in watersheds has been complicated by the lack of metrics to learn from the past. Recently, an innovative Backcast Model, which is a modification of an artificial neural network and GIS-based forward casting Land Transformation Model has been developed. In this paper we compare temporal chemical trends from lake sediments in Michigan, U.S.A. to past changes in land use based on the results of the Backcast Model. The hypothesis is that when land-use change is stabilized, the flow of mass and energy across a watershed will come into balance (equilibrium/steady state) with watershed physical, chemical, and biological processes.

Sediment cores were sectioned immediately after collection. Pore water was collected by whole core squeezing. Chemicals were analyzed via ICP-MS. Historic land-use change was modelled in a 500 meter buffer around each lake. Chemicals examined included proxies for pollution (e.g. Pb), in-lake processes (e.g. Ca), and watershed export (e.g. Al).

The following questions were addressed 1) do temporal changes in chemical proxies correlate with land use change, 2) can periods of balance be recognized from the temporal patterns of the chemical proxies, 3) do periods of balance correlate with periods of minimal use change and 4) can regime shifts be identified, 5) is there a lag time between land-use change and proxy response? System stability was recognized by symmetrical temporal patterns among and within proxy groups. The results are positive for questions 1 through 4. There were not enough data to answer question 5, however. These results are interpreted to support the hypothesis, but more work is needed to better understand the feedbacks between land-use change and the flows of mass and energy in watersheds.


Mantle flow in subduction zones and implications for material transport

and mixing in the mantle MAUREEN D. LONG

Department of Geology and Geophysics, Yale University, PO Box 208109, New Haven, CT, 06520. ([email protected]) The character of the mantle flow field in subduction

systems and the dynamic interaction between slabs and the ambient mantle remain poorly understood, despite their importance for our understanding of subduction processes and of the geometry and dynamics of mantle convection. In order to identify subduction processes that make first-order contributions to the global pattern of mantle flow in subduction zones, we have compiled shear wave splitting measurements from subduction zones worldwide. We have estimated average splitting parameters for the wedge and sub-slab region and compared them to other subduction parameters. We tested for relationships between sub-slab and wedge splitting and other parameters such as trench migration velocity, convergence velocity, and the age, dip, and morphology of the subducting slab. The global splitting dataset supports a model in which the mantle beneath subducting slabs is dominated by three-dimensional flow induced by trench migration, while in the wedge there is an interaction between the two-dimensional corner flow induced by the downdip motion of the slab and the three-dimensional flow field associated with the migration of the trench. Our model suggests that downgoing slabs entrain little, if any, of the surrounding ambient mantle when (or if) they penetrate the transition zone and enter the lower mantle; this has significant implications for the material flux between the upper and lower mantle reservoirs and the extent of mantle mixing. In the wedge, our model implies that trench-parallel flow is important in many (though not all) mantle wedge systems with significant implications for melt generation and material transport in the wedge.

Better lighting through geochem-history

BRIAN B. LOONEY* AND MILES E. DENHAM Savannah River National Laboratory, Aiken, SC 29803, USA

(*correspondence: [email protected]) In describing subsurface processes, Paul Johnson of the

University of Arizona famously observed: ‘It’s dark down there.’ This ‘darkness’ is a central challenge for contaminant geochemists as they study the complexity of subsurface systems, environments in which numerous and interrelated process control the mobility, toxicity and overall character of contaminants. Characterization, via solid and fluid samples collected from boreholes and using geophysical methods, dimly illuminate isolated portions of the subsurface for observation but leave many unanswered questions. Thus, geochemists use other strategies to assist in identifying key transformation and transport processes and in quantifying these processes to support environmental management decisions. Historically, a central front for lighting up the subsurface has been a stepwise process: carefully controlled laboratory studies of isolated individual reactions followed by thermodynamic/kinetic geochemical models to composite the many contributing bits and build up a virtual world. The Department of Energy Office of Science – Biological and Environmental Research Division – recently advocated supplementing the traditional ‘bottom-up’ paradigm described above with research that approaches subsurface challenges from a ‘top-down’ or complex systems perspective. Simple historical examples from real-world sites illustrate the potential usefulness of a systems approach in which site history is synergistically combined with intermediate- and field-scale observation of physical conditions, emergent biogeochemical impacts, and temporal changes. In particular, some stark geochemical lessons can be identified by comparing and contrasting the various attempts to establish facilities for high-level nuclear waste disposal around the world. The journey from shallow groundwater, to Yucca Mountain, to the Boom Clay suggests that supplementing the standard paradigm with the emerging systems approach will be both a challenge and an opportunity. Geochemists who embrace the challenge will have a more diverse and powerful toolbox to illuminate the subsurface and to improve the future of environmental management.


A631

The melting curve of FeSi to 150 GPa: Implications for D"

O.T. LORD1*, M.J. WALTER1, D.P. DOBSON2, L. ARMSTRONG1, S.M. CLARK3 AND A. KLEPPE4

1Department of Earth Sciences, University of Bristol, UK

2Department of Earth Sciences, University College London, London, UK

3Advanced Light Source, Lawrence Berkeley National Lab., Berkeley, CA, USA

4Diamond Light Source Ltd., Harwell Science and Innovation Campus, Didcot, Oxfordshire, UK FeSi has been suggested as a possible constituent of the

Earth’s D$ layer as a reaction product between the (Mg, Fe)SiO3 perovskite or post-perovskite of the lower mantle and the Fe alloy of the outer core [1]. FeSi may also occur as a result of exsolution from the outer core during secular cooling [2].

We have measured the melting curve of FeSi up to 150 GPa using the LH-DAC and standard methods described elsewhere [3]. We utilize discontinuities in the laser power vs. temperature function as our primary melting criterion, and have sucessfully coroborated our melting curve with multi-anvil experiments at 12 GPa.

The resulting melting curve reaches 4000K at the CMB (see figure below). Based on a simple estimate of the adiabat throughout the D$ layer, this result suggests that FeSi might be solid in the upper part of the D$ layer, but is likely to be molten toward the base. Such melts are likely to have a density intermediate between the mantle and core, and would therefore pond at the CMB. Molten FeSi is expected to have seismic wave velocities significantly lower than PREM at these depths, making it a plausible component of the deep melts thought to result in the Ultra-Low Velocity Zones [4].

[1] Knittle & Jeanloz (1991) Science 251, 1438–1443. [2] Buffet, Garnero & Jeanloz (2000) Science 290, 1338–1342. [3] Lord, O. T. et al. (2010) J. Geophys. Res., in press. [4] Caracas & Wentzcovitch (2004) Geophys. Res. Lett. 31, L20603.

Carbonation of forsterite exposed to water-saturated supercritical carbon

dioxide J.S. LORING1, Z. WANG, C.J. THOMPSON, A.G. JOLY,

D.S. SKLAREW, K.M. ROSSO AND A.R. FELMY

1Pacific Northwest National Laboratory, Richland, WA 99352, [email protected] One of the strategies for combating global warming is to

sequester vast quantities of CO2 by hydrodynamically trapping it as a supercritical fluid (scCO2) in unusable saline aquifers in deep geological formations. The buoyant scCO2 plume held in place by low permeability caprock will initially be out of equilibrium with host and caprock minerals and residual trapped formation fluids. Mineral transformations are expected to play an important role in determining long-term caprock performance by affecting porosity and the capillary entry pressure of scCO2 into caprock fractures. We developed an in situ spectroscopic method for studying reactions between minerals and scCO2 at geologically relevant formation temperatures and pressures. We present results for the transformation of forsterite (Mg2SiO4), a model magnesium silicate, to magnesium carbonate, emphasizing fluid compositions between neat and water-saturated scCO2 as the long-term dominant fluid phase.

Experiments were performed using a flow-through system and a high-pressure transmission mid-infrared cell. One ZnSe window of this cell was coated with a thin overlayer of a synthetic forsterite. Absorbance spectra were recorded as a function of time after exposing the forsterite to single-phase water-saturated scCO2 at 50 °C and 180 atm. The water concentration in the scCO2 was quantified using the HOH bending mode of monomeric H2O at 1608 cm-1, and compared for consistency with literature values. The forsterite was reacted for a 24 hour period, and any transformation to magnesium carbonate was monitored by following changes and the growth of specific bands in the spectra. The above experiment was compared to a modified scenario where small amounts of immiscible bulk liquid water were allowed to condense and coat forsterite surfaces in simultaneous contact with the scCO2 fluid. The presence of the liquid water was evidenced by a broad OH stretching band at 3200 cm-1. The forsterite was allowed to react for another 24 hours.

Preliminary results demonstrate marked differences in the metal carbonation rates in the two scenarios. The presence of a thin liquid water film coating the mineral surfaces dramatically increases carbonation rates even though water is available in both scenarios. This finding has important implications for long-term CO2 storage.


Towards !11B external reproductibility of 0.1‰ (2") for MC-

ICP-MS measurements with direct injection as introduction system

P. LOUVAT*, G. PARIS, J. BOUCHEZ, J. GAILLARDET AND J. MOUREAU

Géochimie-Cosmochimie, Institut de Physique du Globe de Paris (UMR CNRS 7154), Université Paris Diderot, 4 place Jussieu, 75252 Paris Cedex 05, France (*correspondence: [email protected]) Recent development of the d-DIHEN [1] (demountable

direct injection high efficiency nebulizer) has permitted faster and more precise determination of boron isotope ratio by MC-ICP-MS [2].

With direct injection, the whole volume of sample introduced through the d-DIHEN ends up in the plasma, thus theoretically increasing the sensitivity, compared to other classical introduction systems (spray chambers and desolvation systems such as APEX and Aridus). However, the ionisation yield is not as good as expected due to still large water droplet size. Direct injection systems are interesting for ‘sticky’ elements, for which wash times are hard to reduce with the classical introduction systems, and for volatile elements, whose sensitivity cannot be enhanced by desolvation. Boron belongs to both categories.

With d-DIHEN on a Neptune MC-ICP-MS, boron sensitivity reaches 10V/ppm for an uptake rate of 30 µl/min and wash times are of only 2 to 3 minutes. We are able to measure sample/standard every 6 to 7 minutes. The actual external reproducibility is 0.25‰ based on 3 to 5 replicate measurements of a sample solution, over different days. Using a bracketing sequence of 3 successive standard – sample measurements for each sample at a boron concentration of 200 ppb, we can achieve an external reproducibility of 0.15‰ (23) over the 11B/10B isotope ratio of most seawater and carbonate samples. Automation of the sample introduction (SC-DIN) is expected to enhance the reproducibility. The chemical separation might become a limitation for such precise determination.

[1] Westphal, Kahen, Rutkowski, Acon & Montaser (2004) Spectrochimica Acta 59, 353–368. [2] Louvat, Bouchez & Paris (in press) Geostandards & Geoanalytical Research.

Zr mobilization and complexation in subduction zone fluids

M. LOUVEL1, C. SANCHEZ-VALLE1, W.J. MALFAIT1, D. TESTEMALE2 AND J-L. HAZEMANN2

1Institute for Mineralogy and Petrology, ETH Zurich, CH-8092 - Zurich, Switzerland ([email protected])

2Institut Neel, CNRS-Grenoble, F-38042 - Grenoble, France The distinctive depletion in HFSE observed in arc magmas

has been a matter of debate in the study of trace-element recycling in subduction zones. Recently, several studies proposed that HFSE could be efficiently mobilized by alkali SiO2-rich fluids and fluorine-rich melts [1, 2]. In order to investigate the behavior of HFSE in subduction zone fluids, the speciation and partitioning of Zr were determined in situ using X-ray Absorption Fine Structure (XAFS) and Synchrotron X-ray fluorescence (SXRF) spectroscopy up to 800 °C – 1.5 (1) GPa. Experiments were conducted in a hydrothermal diamond-anvil cell (HDAC)[3] at BM30B FAME beamline at the ESRF (Grenoble, France). Zr fluid-melt partition coefficients were determined in the haplogranite-H2O system, while Zr speciation was investigated over a wide range of compositions, including 5000ppm Zr standard solutions (in 2.5 wt% HCl), Na2Si2O5 and haplogranite glasses and melts, and alkali–SiO2 aqueous fluids (20-30 wt% NS2). In addition, the influence of fluorine on Zr speciation and partition was also investigated.

The results of SXRF experiments show that Zr preferentially partitions into the melt phase at any investigated P-T. The partition coefficients DZr

fluid/melt increase with increasing temperature and with the addition of fluorine, suggesting the efficient mobilization of Zr (and HFSE) by fluids enriched in alkali-Al-Si dissolved components, possibly due to changes in Zr complexation. High-resolution XANES spectra of Zr in glasses, melts and alkali-SiO2 fluids display distinct features compared to Zr in HCl, but bear a strong resemblance to spectra in vlasovite (Na2ZrSi4O11), providing evidence for octahedrally coordinated Zr [4]. However, the similarities observed between Zr XAFS spectra in F-free and F-bearing melts may indicate the absence of Zr-F complexation in hydrous silicate melts. Further modelling of XANES and EXAFS spectra is in progress to better constrain the complexation of Zr in subduction zone fluids. The implications of this results for Zr and HFSE recycling in subduction zones will be discussed.

[1] Manning et al. (2008) Earth Planet. Sci. Lett. 272, 730–737. [2] Farges (1996) Chem. Geol. 127, 253–268. [3] Bassett et al. (1993) Rev. Sci. Inst. 64, 2340–2345. [4] Sokolova E. et al. (2006) Can. Mineral. 44, 1349–1356.


A633

Preliminary model of hydrothermal circulation at East Pacific Rise 9°°50**N constrained by thermal,

chemical, and seismic data R.P. LOWELL1 *, A. FAROUGH1

AND L.N. GERMANOVICH2 1Department of Geosciences, Virginia Tech, Blacksburg, VA

24061 (*correspondence: [email protected], [email protected])

2School of Civil and Environmental Engineering, Georgia Tech, Atlanta, GA 30332 ([email protected] The East Pacific Rise 9°50* N area has been a subject of

intense multidisciplinary study for two decades. Currently, numerous data sets provide strong constraints on magmatic activity, on the depth and flow geometry of hydrothermal circulation, on the thermal and chemical evolution of vent fluids, and on the evolution of biological communities. These data together provide strong constraints on acceptable mathematical models of the magma-hydrothermal system.

Using a combination of thermal, geochemical and seismic data as constraints [1, 2, 3], we develop a preliminary model hydrothermal circulation along approximately 2 km of ridge axis from TWP to the Bio9 vent complex. We first use a single-pass model [4] together with a heat flux estimate of 160MW and average vent temperature of 370°C to obtain a mass flux of + 80 kg/s, a conductive boundary layer thickness of + 25 m, and a permeability of the discharge zone ranging between 3 x10-12 and 3 x 10-13 m2. Secondly, we use a two-limb single-pass model using the observed partitioning of heat flow between focused and diffuse discharge [5] and vent chemistry [2] to show that at least 80% of the total heat flow comes from magma sources. As a result of these analyses, we find that the sub-axial magma chamber must be actively replenished on a decadal time scale, which is consistent with recent petrological data. Finally, the preliminary model suggests that the seismically inferred recharge zone may not be large enough to carry all the flow without clogging as a result of anhydrite precipitation. Further analysis of this issue will require numerical modeling.

[1] Ramondenc et al. (2006) EPSL 245, 487–497. [2] Von Damm & Lilley (2004) Geophys. Monogr. 144, 245–268. [3] Tolstoy et al. (2008) Nature 451, 181–184. [4] Lowell & Germaonvich (2004) Geophys. Monogr. 148, 219–244. [5] Germanovich et al. (2010) J. Geophys. Res. (in press)

Sulfate reduction in peatlands – Does a rare keystone microorganism

drive a process that mitigates global warming?

ALEXANDER LOY

Department of Microbial Ecology, University of Vienna, Austria, ([email protected]) Methane emission from peatlands contributes substantially

to global warming but is significantly reduced by sulfate reduction, which is fuelled by globally increasing aerial sulfur pollution. However, the biology behind sulfate reduction in terrestrial ecosystems is not well understood and the key players for this process as well as their abundance remained unidentified. At a model peatland site, we monitored long-term temporal and spatial changes in the diversity of the marker genes dsrAB using microarray and quantitative PCR techniques. These genes encode subunits of dissimilatory (bi)sulfite reductase and are generally characteristic for microorganisms that reduce sulfate, sulfite or some organosulfonates for energy conservation, but can also be present in anaerobic syntrophs. Members of novel, uncultivated dsrAB lineages (approximately representing species-level groups) (i) dominated a temporally stable but spatially diverse dsrAB community and (ii) represented relatively abundant ‘core’ members of the autochthonous microbial community. A biogeography survey showed that several of these novel dsrAB-carrying microorganisms are widespread in different peatlands from various geographic locations (distance ~1-400 km). Surprisingly, comparative 16S rRNA gene stable isotope probing in the presence and absence of sulfate indicated that a Desulfosporosinus species, which constitutes only 0.006% of the total microbial community, is the major sulfate reducer in the model peatland. Parallel stable isotope probing of dsrAB confirmed that no other microorganisms contributed substantially to sulfate reduction. For the identified Desulfosporosinus species a high cell-specific sulfate reduction rate of 341 fmol SO4

2– cell–1 day–1 was determined. Thus, the small Desulfosporosinus population has the potential to reduce sulfate in situ at a rate of up to 18.5 nmol (g soil w. wt.)–1 day–1, sufficient to account for the bulk of sulfate reduction in the peat soil. These data show that the identified Desulfosporosinus species, despite being a member of the 'rare biosphere', can drive an important biogeochemical process that diverts the carbon flow in peatlands from methane to CO2 and, thus, alters their contribution to global warming.


Structure and vibrational spectroscopy of hydrogen clusters in

hydrogen clathrate hydrate by molecular dynamics simulation and

first-principles calculation H.L. LU1, J.W. WANG2* AND U. BECKER2

1National Research Council Canada, Ottawa, Ontario K1A 0R6, Canada ([email protected])

2Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan, 48109, USA (*correspondence: [email protected], [email protected]) Molecular modeling techniques are applied to elucidate

the vibrational spectroscopy, and the molecular and electronic structure of encaged hydrogen molecules in hydrogen hydrate. Molecular-dynamics simulations, using empirical potentials, are performed to generate collections of the clathrate water cages of different hydrogen occupancies. The first-principles calculations, using Density Functional Theory with B3LYP hybrid density functionals for exchange and correlation, are carried out to optimize the structures and to calculate the Raman shift and activity. The Raman spectra of encaged hydrogen molecules are computed by a weighted moving average over a number of different structural configurations for each type of hydrogen occupancies. The results show that experimentally observed Raman peaks around 4120~4125 cm-

1 are from the hydrogen molecule singly occupied in the small cages, and those around 4125~4150 cm-1 from those in the large cages with one to four hydrogen molecules. The Raman peaks of H2 molecules in the doubly occupied small cages are expected to be around or above 4155 cm-1, which has not observed in experiment. This result could inspire new experiments for synthesizing hydrogen clathrate with higher hydrogen occupancy [1]. Additional molecular structural analysis shows that the hydrogen molecule singly-occupied in the small cages and those in the large cages are loosely encaged, while hydrogen molecules doubly-occupied in the small cage are tightly confined in the cages. Normal mode analysis shows that there is limited vibrational coupling for H2 molecules in L1-4 while a strong vibrational coupling is observed in S2. The isovalue maps of total electron density and electrostatic potential suggest significant electron sharing between H2 molecules and water molecules, and important interaction between hydrogen and water oxygen atoms.

[1] Wang, Lu & Ripmeester (2009) Journal of American Chemical Society 131, 14132–14133.

Effect of brine on the TSR and generation of H2S revealed by gold-

tube simulation experiments HONG LU*, TENGSHUI CHEN AND PING’AN PENG

State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 (*correspondence: [email protected]) In MgSO4-nC24 TSR system, compared to that in blank

series, the H2S yield was slightly increased with addition of montmonllite (1.48 mg), and much more H2S was available with addition of minor elemental sulfur (only 0.19 mg) which was consistent with previous studies [1]. Meanwhile, yield of H2S was largerly enhanced with addition of NaCl (3.0 mg). The MgSO4-nC24 TSR experiment with addition of different weight of NaCl furtherly illustrated that yield of H2S was continuously increased even with addition of 6 mg NaCl.

Figure 1: Gas yields in the gold-tube simulation experiment of magnesium sulfate and nC24 under 420 oC and 50 MPa.

A very low solubility of CaSO4 relative to higher solubility

of Na2SO4 and MgSO4 in pure water at room temperature, together with a sharply decreased trend of the solubility of CaSO4 with increased temperature under 100 °C, may limited the imagination of anhydrite as an effective reactant for participation in TSR. However, most saline formation fluids are brine [2] and composed dominantly of Na, Ca and Cl and slightly enriched in Mg [3]. Moreover, at 100, 150 and 200 °C, the CaSO4 solubility in NaCl solution (0.005~0.035 mol/kg H2O) increased with increasing salinity at high NaCl concentrations up to halite saturation, and apparently larger than that in Na2SO4 (0.002~0.009 mol/kg H2O) and K2SO4 (0.001~0.009 mol/kg H2O) solution [4]. This indicates that solubility of anhydrite or gypsum can be greatly enlarged in brine solution in the real subsurface, thus, the possibility and rate of TSR from anhydrite under practical geological conditions can be greatly enhanced.

[1] Goldhaber & Orr (1995) J. Am. Chem. Soc. 412–425. [2] Carpenter, 1978. Geol. Surv. Circular 79, 60–77. [3] Posey & Kyle (1988) Chem. Geol. 74, 1–24. [4] Freyer & Voigt (2004) GCA 68, 307–318.


A635

Environmental geochemistry of the Second Songhua River in

Northeast China J.L. LU1, L.B. HAO1*, Y.Y. ZHAO1, R.J.BAI2,

X.Y. ZHAO1 AND B. CAI3

1College of GeoExploration Science and Technology, Jilin University, Changchun 130026, China (*correspondence: [email protected])

2Jilin Geological Survey Institute, Changchun 130026, China ([email protected])

3Changchun Monitoring Station, National Urban Water-supply Water Quality Monitoring Net, Changchun 130041, China Water environment has attracted people's attention due to

its close relationship with the people's life and environmetal investigation and evaluation of the many large river have been carried out in the world. As a tributary of the Songhua River in Northeast China, the Second Songhua River is the largest river in Jilin province and water environment is essential for local residents. In order to investigate the water environment of Second Songhua River, water, sediments and suspended matter were sampled and many heavy metals (As, Cd, Cr, Cu, Hg, Pb, and Zn) and some organic pollutants (polycyclic aromatic hydrocarbons, phthalic acid esters and BTEX) were analyzed.

The results indicated that the content of heavy metals and organic pollutants of water were relatively low, while those of sediment were relatively high. Levels of contaminants in suspended matters were changed greatly. The content of heavy metals and organic pollutants tend to increase first and then decrease along the main river and this variation was influenced mainly by the industrial and agricultural activities in the drainage area.

The applications of photogrammetric technology in the deformation

measurement based on CCD camera LÜ KAIYUN AND ZOU SHILIN

East China Institute of Technology, Fuzhou, Jiangxi Province, 344000, China ([email protected], [email protected])

Optical three-dimensional measurement method is a non-

contact, high precision, convenient and quick measurement method. The main topic is to research the applications of the technical architecture of digital close-range photogrammetry in the deformation measurement. There are two main aspects of deformation analysis, one is the monitoring data and information collation, analysis and interpretation, including gross errors excluding, monitoring data de-noising, etc.; the other is the structure of the security and stability of the state of assessment, prediction and forecasting to ensure the structural safety in construction and operation process.In this area, in addition to traditional statistical analysis methods, there are many methods based on fuzzy mathematics, gray theory, artificial neural networks, time series theory and so on. The subjects using the widely used CCD camera as a tool, according to the classical principles of photogrammetry and the latest research results of image processing and computer vision, study the three-dimensional measurement theory of not calibrating CCD camera under the control of nothing, or lacking material conditions, and provide a set of feasible three-dimensional measurement method. Take the displacement measurement in civil trials for example, using Matlab as tools develope a practical calculation procedures.

This work was supported by the Jiangxi Province Natural

Science Foundation of China (Grant No: 2009GQS0001) and Key Laboratory of Geospace Environment & Geodesy ministry of Education. China (Grant No:08-01-04)


Experiments of CO2-brine-feldspar/sandstone/shale interactions:

Implications for geological carbon sequestration

PENG LU1, FAYE LIU1, SHEILA HEDGES2, CRAIG GRIFFITH2, YEE SOONG2 AND CHEN ZHU1

1Department of Geological Sciences, Indiana University, Bloomington, IN 47405 (*correspondence: [email protected])

2U.S. DOE, National Energy Technology Laboratory, P.O. Box 10940, Pittsburgh, PA A series of feldspar/sandstone/shale-brine-CO2

hydrothermal experiments have been performed in the laboratory. Navajo Sandstone samples (target formation for CCS in the US west), shale chips from the basal Eau Claire Formation in south western Indiana (caprock for storage in the Midwest), and alkali feldspar samples were reacted with CO2 and brine at 200 °C and 200 – 300 bars. The evolution of brine chemistry during the experiments was monitored and the solid reaction products were analyzed with XRD, SEM, and TEM.

The Navajo Sandstones after experiment show dissolution textures, the formation of carbonate minerals, and precipitation of allophane and illite/smectite cements. There is no evidence that suggests the removal of clay coating due to chemical reactions. For the CO2-brine-shale system, only minor dissolution of K-feldspar and anhydrite was observed. However, precipitation of pore-filling and pore-bridging illite and/or smectite, carbonates may reduce the permeability and tend to locally enhancing the integrity of the repository.

The feldspar-CO2-brine experiments allowed us to examine how the dissolution of feldsapr and precipitation of secondary mienrals are coupled. Experimental evidence shows that product mineral precipitation is a slow kinetic process and partial equilibria between aqueous solution and product minerals were not held. In contrast, the experimental evidences are consistent with our new hypothesis that slow clay precipitation kientics partly explains the well known field – lab rate discrepancy [1].

This work is supported by the U.S. DOE. Any opinions,

findings, and conclusions or recommendations expressed in this material, however, are those of the authors and do not necessarily reflect the views of the United States Government or any agency thereof. Also acknowledge collaboration on experimental work with Bill Seyfriedn and Qi Fu. [1] Zhu, C. 2009. Geochemical Modeling of Reaction Paths & Geochemical Reaction Networks. In, Oelkers, E. H. & Schott, J. (eds) Thermodynamics & kinetics of water-rock interaction. vol. 70, pp.533-569, Mineralogical Society of America.

Taking the iron snow shuttle to the microbial iron cycle

in acidic lake sediments S. LU1*, M. REICHE1, T. NEU2, S. GISCHKAT1

AND K. KÜSEL1 1Friedrich Schiller University Jena, 07743 Jena, Germany


2Helmholtz Centre for Environmental Research – UFZ, 39114 Magdeburg, Germany Acidic coal mine lakes are characterized by low pH, high

concentrations of Fe (II) and sulfate and high Fe (III) solubility. In Lake 77, Germany, microbial oxidation of dissolved Fe (II) forms iron-rich macroscopic aggregates (iron snow) that precipitate to anoxic sediments. This iron snow provides an important input of Fe (III)-oxides for microbial reduction. Currently, we have only a marginal understanding of the microorganisms involved in this iron cycle at pH 3 to 5. This study aimed to (i) explore the diversity of microbial communities in iron snow and sediments of an acidic coal mine lake and (ii) elucidate the mechanisms of iron reduction at acidic pH using isolates from lake sediments. Microorganisms in iron snow were found to co-existed with iron minerals, mainly schwertmannite, using confocal laser scanning microscopy. The dominant phylogenetic group in the iron snow was ,-Proteobacteria (96% of 16S rDNA clones), and included two major genera Acidocella (63%) and Acidiphilium (22%), which are known Fe (III) reducers. Differences were observed in the composition of microbial communities in upper acidic (pH 2.8; zone I) and lower, slightly acidic (pH 5.3; zone IV) sediments. Zone I was dominated by Actinobacteria (37%), !-proteobacteria (16%) and Acidobacteria (12%), while zone IV was dominated by Acidobacteria (24%) and #-Proteobacteria (19%). The abundance of !-proteobacteria was lower in zone I compared to the iron snow and only small portion were detected in zone IV. Acidobacteria, --Proteobacteria and Firmicutes were found in both zones suggesting that those taxa can cope with both acidic and slightly acidic conditions. A total of 37 acidophilic and acido-tolerant isolates were obtained using an overlay plate technique. A number of isolates were capable of either oxidizing or reducing iron, whereas, some strains showed both iron-oxidation and -reduction abilities. The ability to oxidize and reduce iron varied with different iron sources and availablilty of O2. Our data indicates a link between microbial communities present in iron snow and lake sediment. However, further work is needed to understand the role of ,-Proteobacteria in iron snow and the mechanisms of Fe (III)-reduction at low pH.


A637

Petrological and geochemical evidence for the “hot” exhumation of

UHP metamorphic rocks in continental subduction zones

X.-N. LU, Q.-X. XIA, Z.-F. ZHAO AND Y.-F. ZHENG School of Earth and Space Sciences, University of Science

and Technology of China, Hefei 230026, China ([email protected]) Variable temperatures of 400 to 900°C have been

frequently obtained from Fe-Mg partition thermometry for coexisting garnet and omphacite from UHP eclogites in the Dabie-Sulu orogenic belt. This is inconsistent with petrological, geochronological and geochemical constraints on P-T paths of UHP slabs during subduction and exhumation of continental crust. A potential problem with the Fe-Mg partition thermometry is retrograde reset of element partition after peak UHP metamorphism that is defined at the climax of metamorphic pressures. However, continental subduction-zone metamorphism is characterized by a peak pressure at lower temperatures and a peak temperature at lower pressures, corresponding to the ‘hot’ exhumation at HP eclogite facies. This is indicated by compositional gradients across garnet from UHP granitic gneiss in the Dabie-Sulu orogenic belt, with the highest Ca content in cores for the maximum pressure but the lowest Fe/Mg ratios in rims for the maximum temperatures. This generalization holds regardless of the differences in P-T paths between different UHP slabs (i.e. low-T/UHP, mid-T/UHP and high-T/UHP units)

The realization of ‘hot’ exhumation in the continental subduction zone has important implications for metamorphic dehydration, partial melting and element mobility of UHP rocks. Many hydrous minerals were metastable at the peak pressures but became decomposed with increasing temperature during the ‘hot’ exhumation. The pressure decrease also causes exsolution of structural hydroxyl and molecular water from nominally anhydrous minerals. This is capable of forming local sinks of aqueous fluid within the UHP slabs, and eventually leads to partial melting at appropriate P-T conditions. Dehydration melting has been found to occur in low-T/UHP granitic gneiss, mid-T/UHP eclogite and eclogite-gneiss contact, and high-T/UHP gneiss and gneiss-eclogite contact. Local sinks of hydrous melts form felsic veins at different scales, from veinlets on thin sections via microveins in hand specimen to veins on field outcrops. LA-ICPMS U-Pb dating on melt-grown zircons (having steep HREE patterns) from the UHP rocks and enclosed veins gave concordant ages that are consistently 10-20 Myr younger than the UHP metamorphic event. Therefore, the ‘hot’ exhumation is a characteristic feature of continental subduction-zone metamorphism.

LA-ICPMS zircon in situ analysis of magmatism and mineralization in the Jinchang gold ore-field, Heilongjiang

Province, China Y-H. LU*, Y. ZHANG AND Y. LAI

Key Laboratory of Orogenic Belt and Crustal Evolution, Peking University, Beijing 100871, China (*correspondence: [email protected]) There has been a growing recognition that the various

mineral deposit types have a heterogeneous temporal distribution, with characteristic peaks in their abundance at specific times in Earth history [1]. It has been proved that ore-systems can serve as an ideal geodynamic probe as well [2]. To bracket the mineralization time and to understand tectonic setting of the Jinchang gold deposit, which is a large intrusion-related hydrothermal ore-system developed in the eastern end of the huge Central Asia Orogenic Belt, precise U-Pb ages, REE concentrations and Lu-Hf isotopes of ore-hosting granite and ore-forming diorite intrusions are obtained on single zircon grain using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS).

All zircon grains have natural growth-zoning texture, with the Th/U ratio ranging mainly from 0.5 to 1.5, showing the nature of zircon grains of magmatic origin. The weighted average 2°6Pb/238U ages of zircon grains from granite and diorite are 202.1±3.0 Ma and 111.5±1.2 Ma, respectively, representing the times of two magmatic-hydrothermal mineralization events. The age of 198.0±3.9 Ma for the altered ore-hosting granite in northern Banjiegou circular structure system possibly reflects a late hydrothermal modification event which causes the 202-Ma granite yields younger age. Hence it is the overprinting and combination of two magmatic-hydrothermal mineralization events in the same position resulted in formation of the Jinchang large gold deposit. The earlier event at about 202 Ma originated from granite magmatism occurred in continental collision regime after the closure of Paleo-Asia Ocean. The later magmatic-hydrothermal event at about 111 Ma occurred in magmatic arc or back-arc extensional setting related to northwestward subduction of paleo-Pacific oceanic plate. The characteristics of host magma are shown by REE and Lu-Hf analysis, which indicates the mantle material addition.

[1] Goldfarb et al. (2001) Ore Geology Reviews 18, 1–75. [2] Chen et al. (2008) Geology in China 35(6) 1059–1073 (in Chinese with English abstract)


I/Ca ratios in marine carbonate as a palaeo-redox proxy during oceanic

anoxic events ZUNLI LU1, HUGH C. JENKYNS1 AND ROSALIND E.M. RICKABY1

1Department of Earth Sciences, University of Oxford, Parks Road, Oxford, OX1 3PR, UK, [email protected] Periods of globally distributed extreme oxygen depletion,

so-called Oceanic Anoxic Events (OAEs), have been recognized in the Mesozoic geological record and appear characteristic of episodes of extreme warmth. Here we explore the application of iodine to calcium ratios (I/Ca) in marine carbonate as a new geochemical proxy to constrain seawater redox change, and provide additional insights into the response of ocean chemistry to ancient climatic warming. Iodine has long been known as a redox-sensitive and biophilic element, mainly present as iodate and iodide in seawater, with the former converting to the latter under anoxic conditions. Laboratory experiments growing carbonate crystals from solutions spiked with iodate show that this is the ionic species incorporated into the carbonate structure, likely substituting for the CO32- ion. A fall in the I/Ca ratio measured in carbonates formed in shallow water by marine calcifiers during the Early Toarcian and Cenomanian–Turonian OAEs is interpreted both as a response to a decrease in the iodate:iodide ratio in ocean waters and the drawdown of the global iodine inventory under conditions of accelerated organic-matter burial. The results suggest that I/Ca ratios in carbonates may be used to monitor seawater oxidation levels throughout Earth history.

Bioreduction of nitrobenzene, natural organic matter and hematite by Shewanella putrefaciens CN32

F. LUAN AND W. BURGOS*

Dept. Civil Environ. Eng., Penn State Univ., University Park, PA 16802, USA ([email protected], *correspondence: [email protected]) We examined the reduction of nitrobenzene by S.

putrefaciens CN32 in the presence of natural organic matter (NOM) and hematite. Bioreduction experiments were conducted with combinations and varied concentrations of nitrobenzene, soil humic acid, Georgetown NOM, hematite, and CN32. Abiotic experiments were conducted to quantify nitrobenzene reduction by biogenic Fe (II) and by bioreduced NOMs. We show that CN32 can directly reduce nitrobenzene. Both NOMs enhanced nitrobenzene reduction and the degree of enhancement depended on properties of the NOMs. Hematite enhanced nitrobenzene reduction by indirect reaction with biogenic-Fe (II), however, enhancement was dependent on the availability of excess electron donor. Under electron donor-limiting conditions, reducing equivalents diverted to hematite were not all transferred to nitrobenzene. In systems that contained both NOM and hematite we conclude that NOM-mediated reduction of nitrobenzene was more important than Fe (II)-mediated reduction. Our conclusion agrees and contrasts with related studies. Hofstetter et al. (1) concluded that TNT reduction by solid-associated Fe (II) was more important than by reduced quinones, while Zhang and Weber (2) concluded that CNAAzB reduction occurred through a solution phase pathway via reduced NOM, and Kwon and Finneran (3) concluded that RDX reduction occurred concurrently by both solid-associated Fe (II) and reduced quinones. Differing conclusions drawn from these studies highlight the difficulty in generalizing contaminant behavior in increasingly complex systems but also highlight the need for additional research in this area.

[1] Hofstetter et al. (1999) Environ. Sci. Technol. 33, 1479–1487. [2] Zhang & Weber (2009) Environ. Sci. Technol. 43, 1042–1048. [3] Kwon & Finneran (2009) Environ. Eng. Sci. 26, 961–971.


A639

Insights on the evolution of the lithospheric mantle underneath the Gibeon Kimberlite field, Namibia TIMO LUCHS*, GERHARD BREY AND AXEL GERDES

Institut für Geowissenschaften, Goethe Universität, Frankfurt am Main (*correspondence: [email protected]) The kimberlitic volcanism in the Gibeon Province in

Namibia about 70 - 80 Ma ago brought garnet peridotite xenoliths, clinopyroxene and garnet megacrysts and occasionally crustal xenoliths to the surface (e.g. [1]). The province is situated within the Namaqua-Natal belt in the Rehoboth terrane which gives mixed ages between 0.9 – 2.0 Ga. Re-Os isotope measurements on the garnet peridotites range up to only 2.5 Ga [3], indicating a Proterozoic mantle age. However, on the basis of high modal abundances of orthopyroxene in some of the Gibeon xenoliths, similar to those known from the Archaean Kaapvaal craton, Franz et al. (1996) suggested that they represent slivers of the subcontinental lower lithosphere of the Kaapvaal Craton which were transported underneath the Namaqua-Natal belt during jurassic and cretaceous continental breakup.

In order to constrain the nature of depletion and possible enrichment processes, we determined trace elements of the constituent minerals of 19 garnet peridotite xenoliths from several localities in the Gibeon province by laser ablation single collector ICP MS.

The REE patterns in most garnets are LREE depleted as it is typical for mantle xenoliths from off craton (Proterozoic) areas and in cratonic mantle that has been melt-modified. In contrast, two garnets show sigmoidal patterns characteristic for garnet peridotites from Archean cratons. Hence, these samples may represent relic cratonic areas, in accord with the findings of Franz et al. (1996), whereas most of the mantle beneath Gibeon is younger or has later been refertilised.

Analysis of the Sm-Nd- and Lu-Hf-isotope systematics by solution multicollector ICP MS is in progress. We anticipate that the Sm-Nd isotope system will reflect LREE-enrichment accompanying younger mantle metasomatism whereas the Lu-Hf system may yield actual formation ages.

[1] Davies & Spriggs et al. (2001) Journal of Petrology 42(1), 159–172. [2] Franz & Brey et al. (1996) Contributions to Mineralogy & Petrology 126(1-2), 181–198. [3] Pearson, Carlson, Shirey, Boyd & Nixon (1995) Earth & Planetary Science Letters 134, 341–357.

Carbon isotopic and noble gas compositions of quartz-hosted

gas-rich fluid inclusions from the Lower Saxony Basin (Germany)

V, LÜDERS, B. PLESSEN AND S. NIEDERMANN Helmholtz Centre Potsdam GFZ, Telegrafenberg, 14473

Potsdam, Germany ([email protected]) The southern part of the Lower Saxony Basin (LSB) in

NW Germany is characterized by local magnetic and positive gravity anomalies as well as high maturity of organic matter in sedimentary rocks (up to 6% Rr). The origin of these thermal anomalies is discussed controversially. It is either attributed to deep-seated intrusions of igneous rocks in Early Creatceous times or by an increased amount of burial with subsequent tectonic inversion. However, the presence of abundant quartz veins and fracture-fills in Upper Carboniferous to Lower Cretaceous host rocks reveals evidence for high fluid-flow in this part of the LSB.

The salinity in the range between 0.5 and 25 wt.% NaCl eq. and homogenization temperatures between 130 and 265°C of quartz-hosted inclusions are highly variable. Migration of CH4-CO2 (±N2) gas mixtures along fissures and veins occurred along with the migration of fluids as indicated by abundant gas-rich inclusions in quartz. The carbon isotopic compositions of gas inclusions in quartz differ significantly: inclusions in quartz from fracture-fills hosted by Upper Carboniferous rocks show $13C of about -30‰ for CH4 and -10‰ for CO2. This gas is most likely derived from coal seams within the Upper Carboniferous strata. In the eastern part of the study area CH4 inclusions in quartz hosted by Mesozoic rocks show considerably lower $13C values of about -42‰ suggesting marine shales as most likely source rocks.

Fluid inclusions show general noble gas signatures indicative of typical crustal fluids, such as radiogenic He (3He/4He < 3!10–8), moderately nucleogenic Ne (2°Ne/22Ne close to atmospheric, 21Ne/22Ne < 0.07) and radiogenic Ar (4°Ar/36Ar < 1300). Only a few samples show increased 3He/4He ratios in the range of several 10–7 up to a maximum of (4.1±2.0)!10–6, or 2.9 times the atmospheric value of 1.4!10–6. Such high ratios can only be explained by a contribution from mantle-derived fluids, which is also supported by a slightly higher-than-atmospheric 2°Ne/22Ne ratio (10.08 ± 0.07) in one sample. In addition, those samples showing mantle influence are also characterized by the highest 4°Ar/36Ar ratios found in the sample suite (up to 6100). This mantle input may be related to supposed magmatic intrusion (s) in Lower Cretaceous times.


Sr isotopes in Banded Iron Formation carbonates: Disequilibrium with

ancient seawater J.M. LUDOIS, 1 A. HEIMANN, 2 C.M. JOHNSON1, B.L. BEARD, 1 J.W. VALLEY, 1 E.E. RODEN, 1

M.J. SPICUZZA, 1 AND N.J. BEUKES3 1University of Wisconsin, Department of Geoscience, 1215 W.

Dayton Street, Madison, WI 53706, USA

2East Carolina University, Department of Geological Sciences, Greenville NC 27858, USA

3University of Johannesburg, Department of Geology, Johannesburg, South Africa

Introduction Constraining the isotopic composition of ancient seawater

can give insight into past geologic and oceanic processes. Here we analyzed Rb-Sr isotopes on the same samples previously analyzed for Fe, C, and O isotope compositions by Heimann et al. 2010 [1] of banded iron formation (BIF) carbonates (siderite/ ankerite) from the Kuruman Iron Formation and underlying platform carbonates (calcite/dolomite) from the Gamohaan Formation, Transvall Craton, SA.

Isotopic Results and Interpretations

Isotopic analysis revealed large Fe isotope variability (!56Fe=+1 to -1‰), low !13C values (-12 to -1‰), and !18O values of ~21‰ [1]. Sr isotope analysis revealed a large range of initial 87Sr/86Sr ratios, with calcite at or near the 87Sr/86Sr ratio of ~2.5 Ga seawater (~0.705) [2], whereas the iron-rich carbonates have initial 87Sr/86Sr ratios that range from at or near seawater to very high ratios of ~0.745. Combining the initial 87Sr/86Sr with the !13C shows Fe-poor carbonates (calcite and dolomite) have both Sr and C isotopic composition close to or at sea water composition, whereas the Fe-rich carbonates (siderite and ankerite) are farther from equilibrium with seawater. Because these Fe-rich carbonates are bounded by shale layers, the radiogenic 87Sr/86Sr ratios likely reflect small-scale fluid interaction during authigenic mineral formation in the soft sediments during microbial iron reduction.

[1] Heimann et al. (2010) EPSL in press. [2] Veizer (1989) Ann. Rev. Earth Planet. Sci. 17, 141–167.

Marine-terrestrial linkages associated with Early Cretaceous (Aptian-

Albian) global change G.A. LUDVIGSON1*, L.A. GONZALEZ2,

E. GULBRANSON3, E.T. RASBURY4, G. HUNT5, R.M. JOECKEL6, L. MURPHY1 AND J.I. KIRKLAND7

1Kansas Geological Survey, Univ. Kansas, Lawrence, KS 66047, USA (*correspondence: [email protected])

2Geology Dept. Univ. Kansas, Lawrence, KS 66045 3Dept. Geology, Univ. California Davis, CA 95616 4Dept. Geosciences, Stony Brook Univ., NY 11794 5Dept. Geol. Sciences, New Mexico St. Univ., Las Cruces,

NM 88003

6School of Nat. Res., Univ. of Nebraska, Lincoln, NE 68583

7Utah Geol. Survey, Salt Lake City, UT84114 A calcrete succession from the Cedar Mountain Formation

(CMF) of Utah is calibrated by detrital zircon U-Pb dates spanning from ~ 131 to 105 Ma, overlapping Oceanic Anoxic Events OAE1a and OAE1b. Coupled chemostratigraphic profiles of calcite & organic carbon #13C data show parallel structure, and capture records of the early Aptian Ap7 and late Aptian-early Albian Ap12-Al1 features [1] in long-ranging positive Carbon Isotope Excursions (CIEs). CIEs are expressed in profiles with background calcrete #13C values of ~-6‰ VPDB (#13Corg values of ~ -30‰), and peak calcrete #13C values of ~ -3‰ VPDB (#13Corg values of ~ -27‰). The Ap7 peak is calibrated by a 119.4±2.6 Ma U-Pb date on calcrete. Coordinated #13C data show Aptian-Albian CIEs coincide with atmospheric pCO2 changes following conventional methodology [2]. Moreover, the Ap7 and Ap12-Al1 CIEs coincide with changes in calcrete #18O values, ranging from ~ -8‰ VPDB in background positions up to -4 to -3‰ at the peaks of the Ap7 & Ap12-Al1 CIEs. Diagenetic studies of selected calcretes in the CMF consistently yield Meteoric Calcite Line values with #18O of -8‰ VPDB, showing that #18O of zonal paleoprecipitation changed little over time. Some components in CIE calcretes show evidence for evaporative enrichments of early diagenetic porewater #18O values by 4 4‰. Along with dramatically-reddened siliciclastic mudstone strata from the Ap7 & Ap12-Al1 intervals, diagenetic studies suggest that the CIEs were episodes of continental aridification.

[1] Herrle et al. (2004) Earth & Planet. Sci. Letters 218, 149–161. [2] Ekart et al. (1999) Amer. Jour. Sci. 299, 805–827.


A641

Trophic transfer of methylmercury in a simple food chain

A.C. LUENGEN1,3*, N.S. FISHER1 AND B.A. BERGAMASCHI2

1SOMAS, Stony Brook Univerisity, Stony Brook, New York 11794-5000

2USGS Water Science Center, Sacramento, CA 95819-6129 3Present Address: Environmental Sciences Department,

University of San Francisco, San Francisco, CA 94117 (*correspondence: [email protected]) In previous laboratory experiments assessing the influence

of naturally occurring dissolved organic matter (DOM) from the San Francisco Bay Delta on methylmercury (MeHg) bioavailability, we found that phytoplankton accumulation of MeHg was inversely proportional to the DOM concentration over a natural range of DOM concentrations. The goal of this experiment was to determine if the differences in MeHg concentrations in phytoplankton would be passed on to amphipods (Hyalella azteca) consuming those phytoplankton. We exposed the diatom Cyclotella meneghiniana to MeHg for 24 hours in water with (10 mg L-1) or without organic matter from Mandeville Tip in the Delta. Radiolabeled cells were then resuspended into unlabeled fresh water (to minimize potential for amphipods to take up MeHg from the dissolved phase). Amphipods were fed radiolabeled cells for 35 minutes and then fed unlabeled algae during depuration. We followed the depuration of MeHg from the amphipods for 96 hours. Amphipods feeding on phytoplankton from the high DOM treatments initially accumulated less MeHg than amphipods feeding on phytoplankton from the no DOM treatment. However, assimilation efficiencies of ingested MeHg in the amphipods were around 65-70% for both treatments and MeHg retention in amphipods was unaffected by DOM. The results suggest that DOM decreases the amount of MeHg that can be accumulated in aquatic food chains by influencing the amount taken up from water by phytoplankton but not by influencing the trophic transfer process itself.

Redistribution of elements and isotopes in silicates by diffusion of

dissolved water in a T gradient C.C. LUNDSTROM1 AND I. BINDEMAN2

1Dept. of Geology, Univ. of Illinois Urbana Champaign, Urbana, IL 61801 ([email protected])

2Dept. of Geology, Univ. of Oregon, Eugene, OR 97403 The formation mechanisms of differentiated igneous rocks

and continental crust remain debated. While partial melting and fractional crystallization clearly play a role, are they the whole story? Recent experiments (all at 0.5 GPa) examining the behavior of wet silicates in a temperature gradient suggest another important mechanism for forming silicic materials: diffusive transport of silica through water rich but undersaturated melts in a temperature gradient.

Huang et al. (GCA, 73, 729–749 2009) showed that AGV-1 andesite with 4% H2O in a large temperature gradient from 950 to 350°C evolved to a crystalline granitic composition at the cold end of the gradient. New experiments have been performed on RGM-1 (rhyolite) and BCR-1 (basalt) compositions. RGM-1 contained 4 wt% water in a welded double capsule and lasted 25 days. The run product consisted of an all glass upper third, a prominent plagioclase only layer in the middle and a bottom third consisting of mostly quartz plus muscovite. In contrast, two BCR-1 experiments had no water added (run in graphite capsules) and were run for variable times (7 and 45 days). Although mineral layering (of OPX, GT and CPX) occurred in the 45 d experiment, its lower third had little compositional change nor enrichment in silica. We attribute the differences in silica enrichment at the cold ends of these experiments to reflect the transport of components through a hydrous melt in a temperature gradient.

The AGV-1, RGM-1 and one of the BCR-1 charges were analyzed for #18O and D/H by new methods developed at Oregon. Despite almost entirely crystalline cold ends, the AGV-1 and RGM-1 charges show dramatic changes in #18O and D/H consistent with thermal diffusion isotopic fractionation occurring as water diffused through the charge. #18O steadily increases down temperature in each charge with total offsets between the cold and hot ends of 18‰ (AGV) and 28‰ (RGM). The isotopic sensitivity for the AGV charge is the same as found in previous Soret experiments. In contrast, the short BCR experiment shows no significant variation in #18O. These dramatic differences in isotopic behavior reflect the ability of molecular water dissolved in a silicate melt and subject to a T gradient to move through and rapidly exchange isotopes with coexisting mineral grains.


Impact of provenance and diagenesis on sandstone reservoir quality of the Middle Permian in northern Ordos

basin, Chian JING-LAN LUO1*, XIN-SHAN WEI2 AND XIN-SHE LIU2

1State Key Laboratory of Continental Dynamics, Northwest University, Xi’an, 710069, China (*correspondence: [email protected])

2Research Institute of Exploration and Development, Changqing Oil Field, Petrochina, Xi’an, 710021, China The rock types and mineral components of the Permian He

8 sandstones in the northern Ordos basin is controlled by provenance and diagenesis, based on study of LA-ICPMS dating for detrital zircons, mineral assemblages of sandstones, diagenesis and diagenetic evolution of mineral components and pore structures. Parent rocks determined types, component maturity, primary skeleton of sandstones, influenced diagenetic paths, authigenic minerals in sandstones, which resulted in diversity of pores and pore throats, thus varied reservoir qualities. The quartzarenite mainly located in the west area of the Ordos basin derived from the Khondalite (1.8-2.3Ga) and the TTG gneiss, granulites and granites (2.4-2.6Ga) outcropped to the north and northwest margin of the Ordos basin. In addition to the above parent rocks, lithicarenite distributed in the east part is mainly derived from the Archean metamorphic rocks (>2.6Ga) and the Devonian-Carbonniferous granite and volcanic materials (400-300Ma). While the provenance of lithic quartzarenite predominated in the middle part is from the both sources. Average porosity lost caused by compaction for the quartzarenite, lithicarenite and lithic quartzarenite is 17.2%, 18.5% and 18.3%, respectively, and caused by cementation is 15.0%, 14.7% and 15.8%, respectively. Three types of the sandstone are of different quality due to diversities in components and cements. The quartzarenite is the best gas-bearing reservoir which is of the highest primary porosity (av. 35.1%) and excellent reservoir quality with av. porosity and permeability of 9.7% and 2.7mD, respectively. The lithic quatzarenite is in the second place with av. primary porosity of 34.2%, av. porosity and permeability of 10.9% and 0.87mD, respectively. The lithicarenite is unfavorable reservoir which is of relatively low primary porosity (av. 33.6%) and inferior quality with av. porosity and permeability of 9.6% and 0.5mD, respectively.

This study is supported by the National Natural Science

Foundation of China (Grant No. 40872083).

The scavenging behavior of 230Th and 231Pa in the ocean: A model prediction

SHANGDE LUO

Department of Earth Sciences, National Cheng-Kung University, Tainan, 701, Taiwan, ROC ([email protected]) 230Th and 231Pa are two important radionuclides in the

uranium decay series which have been widely used to undertsand the past and present oceanic processes. To quantitatively constrain the oceanic behavior of these two radionuclides, a model analysis is conducted based on the observational data on particle-solution distribution coefficient (Kd) of 230Th and 231Pa collected from various parts of the world oceans. Our analysis indicates that it is the nature of particles which scavenge thorium and protactinium from seawater, rather than ocean circulation, that plays an important role in determining the 231Pa/230Th ratio in ocean sediments. The nature of particles affects the scavenging of 230Th and 231Pa by exerting an important control on the particle-solution distribution of 230Th and 231Pa in the ocean. This study shows that while ocean circulations are quite different in the world oceans, a simple scavenging model can be established to characterize the behavior of these radionuclides based solely on particle compositions.

It is estimated based on the data from Arabian Sea that Kd (Th) in lithogenics is (2.2'3.0) !107 g/g, about one order of magnitude higher than that in both carbonate and organics or two orders of magnitude higher than in opal, suggesting that the lithogenics dominates the scavenging of 230Th in the Arabian Sea. In contrast, Kd (Pa) is estimated to be on the order of ~106 g/g in lithogenics, comparable to that in opal and organics but about one order of magnitude higher than in carbonate. The results imply that the fractionation between Th and Pa is controlled mainly by the lithogenic-to-opal ratio in marine particulates, consistent with the results from the open equatorial Pacific and Southern Oceans even though both Kd (Pa) and Kd (Th) of lithogenics in the Arabian Sea are about one order of magnitude lower. From this study, we also found that the affinity of carbonate for Th and opal for Pa is significantly higher in the deep ocean (at ~3000 m) than in the thermocline (~500 to 1000 m), opposed to that of lithogenics for Th and Pa showing significant decreases with the water depth from < 1000 m to ~3000 m. It appears that changes of particle’s properties during its transit from the surface to deep oceans may exert an important control on the scavenging and fractionation of radionuclides in the ocean.


A643

The formation of shallow biogas of Songliao Basin, China

X. LUO, Y. ZHANG AND J.LI Research Institute of Petroleum Exploration & Development,

Beijing 100083, China ([email protected], [email protected], [email protected]) Gases appearing with different grade in over 10, 000 wells

in Changyuan structure of Daqing show that shallow biogases widespread distribute in Songliao Basin. Biogases mainly distribute from several dozen meters to 1600 meters and from Nengjiang formation to Qingshankou formation of Cretaceous vertically and mainly distribute the medium and the west of basin. Gases are mainly biogases such as Aonan, Alaxin and Honggang gas pools. The contents of methane and ethane in biogas pools are between 92% and 94% and between 0% and 0.3 respectively. The contents of nitrogen and dioxide are between 3% and 15% and 0.5% and 1.7% respectively. The ratio of total hydrocarbon divided by methane is more than 0.99. The isotope compositions of methane and ethane are between -51.9‰ and -55.9‰ and between -42.7‰ and -37.3‰.

The research indicates that there has good geological environment of forming biogas in shallow layer of Songliao Basin. Firstly, during the period from Qingshankou formation to Nengjiang formation of Cretaceous, the sedimentary environment had being anaerobism. Thousands of types of organism in palaolake with area up to 200, 000 km2 are suitable for Methanobacteria living. Secondly, most of these rocks are immature with vitrinite reflectance are lower than 0.5% now. The temperature is relative low. Methanobacteria likes to live in here. Thirdly, relatively low contents of sulphate and salinity (mainly from 2000 to 3000ppm) are suitable for Methanobacteria living. Fourthly, there are kinds of bacteria determined in present rocks. Methanobacteria have detected from 25 rock samples in 33 rock samples. Better organic type of rocks, Methanobacteria is more easily to be detected. Fifthly, rocks from Qingshankou formation to Nengjiang formation of Cretaceous are easily to be degraded by anaerobic bacteria. The degree of degradation of rock is related with type of organic matter and living environment of bacteria. The better of type, the more easily to be degrade, while, it is no connection with formation and vitrinite reflectance of rocks.

Comparison study on the extraction ability of heavy metals availability in

contaminated soils by different extraction techniques X.M. LUO, D.D.LIU AND F. LIU*

Beijing Key Laboratory of Water Resources & Environmental Engineering, China University of Geosciences(Beijing), Beijing, 100083, PRC (*correspondence: [email protected])

The environmental risks of heavy metals depend on its speciation distribution in contaminated soils. The chemical speciation analysis was one of the hot topics in environmental sciences. In this paper, four soil samples with different pH values were collected. The Tessier, BCR and TCLP extraction techniques were employed to extract heavy metals available fraction.

Extraction ratio (%)

Samples Extraction techniques As Cu Ni Pb Zn

Tessier 18.90 78.71 91.79 88.54 91.32

BCR 15.32 76.77 90.52 76.69 90.61 S1 pH=3.61

TCLP 12.56 75.02 90.11 67.19 90.14

Tessier 0.46 78.63 85.72 80.33 89.37

BCR 0.39 73.63 82.24 58.43 86.19 S2 pH=4.16

TCLP 0.44 70.39 80.85 48.90 83.32

Tessier 35.56 73.17 62.41 81.40 61.37

BCR 26.96 33.94 35.74 28.96 49.73 S3 pH=5.91

TCLP 23.24 32.00 30.339 20.18 46.20

Tessier 17.19 47.04 43.70 53.39 51.33

BCR 14.56 23.04 40.22 10.51 39.07 S4 pH=7.01

TCLP 13.57 19.18 39.58 8.42 37.27 Table 1: Availability fraction extraction ratios by three extraction techniques.

The results illustrated the Availability fraction extraction

ratios by three extraction techniques. In order to extract heavy metals available fraction in soils correctly, different sequential extraction procedures should be employed for soils with different properties.

[1] Tessier, Campbell & Bisson (1979) Sequential extraction procedure for the speciation of particulate trace metals [J]. Analytical Chemistry 51(7), 844–851.


Crystal chemistry of Uranium and Thorium in apatites

YUN LUO1*, JOHN RAKOVAN2 AND JOHN M. HUGHES3 1Department of Earth and Plantery Sciences, Washington

Unviersity in St. Louis, St. Louis, MO 63130, USA (*correspondence: [email protected])

2Department of Geology, Miami University, Oxford, OH 45056, USA ([email protected])

3Department of Geology, University of Vermont, Burlington, Vermont 05405, USA ([email protected]) Understanding the crystal chemistry of actinides in the

apatite structure is critical for the evaluation of its potential use and stability as a radionuclide sequestration and remediation agent. Because of its common occurrence and its high affinity for many radionuclides (i.e. U, Th, REE, 9°Sr, 9°Y, etc), apatite has been used in geochronological and petrogenetic studies for decades. Those studies provide important information for the performance and properties of actinide containing apatites in specific natural environments over geologic periods, which cannot be duplicated purely by laboratory studies. However, little is known about the mechanism of incorporation and structure response of apatite to substituent actinides. It is therefore fundamentally important to understand the substitution mechanisms and other intrinsic and external factors that control the chemical composition and structural variation in actinide containing apatites.

In this study, U and Th substituions into fluor- and chlor-apatites were examined by the complementary use of diffraction and spectroscopy techniques. Results from single crystal X-ray diffraction indicate that U and Th show a marked perfence for Ca2 site in fluorapatite, whereas they favor both Ca1 and Ca2 sites in chlorapatite. Extended X-ray Absorption Fine Structure (EXAFS) is used to obtain quantitative information about the local structure distortions around U and Th in both natural and synthetic apatites. The EXAFS fitting results show that U and Th partitions into the Ca2 site in fluorapatite and yielded a ~0.05 – 0.08Å decrease of average Ca2-O bond distances associated with local structure distortions which extend over the first O shell to the second P shell. The substitution of U/Th in the Ca2 site of fluorapatite causes an overtall shrinkage of the Ca2 site and potentially rotations of the PO4 polyhedra that are linked with Ca2 site. We speculate that the preference of Ca2 site over Ca1 site in fluorapatite is to minimize distortion of the Ca1-PO4 framework of the fluorapatite structure. U/Th is chlorapatite is currently under EXAFS investigation in which case different approaches are taken to model one absober in two structure sites.

Quantitative assessment of the bioavailability and toxicity of nanometal particles in aquatic

environments: New methodologies SAMUEL N. LUOMA3,2,1, MARIE-NÖELE CROTEAU1, AGNES DYBOWSKA3, SUPERB MISRA3, TING GUO2, PHILIP S. RAINBOW3 AND EVA VALSAMI-JONES3

1U. S. Geological Survey, Menlo Park, CA, USA

2John Muir Inst.of theEnvironment and Dept. Chemistry, University of California, Davis, USA

3Depts. Zoology and Mineralogy, The Natural History Museum, London, UK Understanding bioavailability is a pre-requisites for

understanding toxicity of nanomaterials in the aquatic environment. Yet only a few studies have begun to quantitatively address these processes. Bioavailability is defined by uptake rates from food and water, as well as loss rates from an organism. Knowledge of those rates for a species of animal will allow comparisons of nanomaterial formulations and modeling of potential for bioaccumulation at environmentally realistic concentrations. Quantifying the rates is possible in simple experiments that require a tracer. Here we show that metal nanomaterials can be synthesized with a unique stable isotope ratios then employed in such experiments. Recent results comparing Ag nanomaterials with different caps, ZnO nanoparticles and Ni nanoparticles in an aluminium oxide matrix, show that the biology of the organism, the characteristics of the nanomaterial and the interaction of the nanomaterial in the environment all combine to affect bioavailability and resultant toxicity, sometimes in unanticipated ways.


A645

A physical model for a chemical flux: An attempt to integrate Ganga and Brahmaputra particle composition

M. LUPKER1*, C. FRANCE-LANORD1, J. LAVÉ1 AND J. BOUCHEZ2

1CRPG-CNRS, 15 rue Notre-Dame-des-Pauvres, 54501 Vandoeuvre-les-Nancy, France (*correspondence: [email protected])

2GFZ, Telegrafenberg, D-14473 Potsdam, Germany Large rivers are powerful integrators of geochemical and

physical processes at work in their catchment area. They are also central in global biogeochemical cycles as they redistribute mass and elements accross the earth surface. While river solute fluxes provide insights into chemical weathering fluxes and rates, suspended sediments are also of prime interest as they provide a record of the processes sediments undergo from source to sink in terms of erosion, weathering and biological activity. Evaluating the chemical composition of the material that is transported by rivers is thus a key point in our understanding of large scale Earth surface processes and mass transfer. Any of these attempts raises the problem of integrating sampled sediments both spatially and temporally through a river section. It has long been recognized that sediment composition is not uniform through the water column as a result of hydrodynamic mineral sorting and flow conditions of the river. These effects have to be accounted for in order to derive realisitic sediment compositions.

This work focuses on the Ganga and Brahmaputra (G&B) rivers that transport the products of Himalayan erosion to the Bay of Bengal. Depth samplings of sediments where performed on these two rivers in Bangladesh at different water levels along with Accoustic Doppler Current Profilling (ADCP) of the river sections to record water velocities and fluxes. The data was used to fit a Rousean suspended sediment model to predict the grain size distributions of the river sections. These grain size distributions are then used to derive chemical compositions of the river sediments as a strong correlation exists between grain size parameters and chemical compositions. By extrapolating these instantaneous fluxes through the monsoon hydrological cycle we attempted to estimate the chemical average composition of the G&B sediments. These chemical compositions are compared to the average Himalayan crust composition, and using a chemical mass balance approach we infer total erosional fluxes of the two Himalayan basins.

Kink site reaction kinetics: A new model unifies crystal dissolution and

growth theory ANDREAS LUTTGE* AND ROLF S. ARVIDSON

Department of Earth Science MS-126, Rice University, 6100 South Main Street, Houston TX 77005 USA (*correspondence: [email protected]) It has been long recognized that crystal growth and

dissolution processes are mainly governed by kink site reaction kinetics (Fig. 1). Traditionally, it has been assumed that equilibrium is achieved if arrival and departure rates of lattice-building molecules are equal. New considerations, however, raise significant doubt that this simple model is correct. A detailed analysis of the processes that occur at kink sites during the overall dissolution reaction leads to the initially surprising result that the probability is always in favor of lattice destruction – this result is in agreement with the thermodynamic rule of increasing entropy.

The destructive processes are eventually countered by the arrival of molecules at the kink sites. This model scenario can explain a number of critical experimental observations and predicts that the reaction rate as function of distance from equilibrium must be continuous at equilibrium, i.e. $G = 0. Ultimately, our model allows us to unify crystal dissolution and growth theories.

Figure 1: Schematic rendering of kink site at step edge.


Protolytic equilibria at ‘inert’ — electrolyte interfaces

JOHANNES LÜTZENKIRCHEN1, NIKOLA KALLAY2, TAJANA PREOCANIN2 AND ATIDA SELMANI2

1Karlsruhe Institute of Technology (KIT), Institut für Nukleare Entsorgung (INE), Postfach 3640, 76021 Karlsruhe, Germany

2Department of Chemistry, Faculty of Science, University of Zagreb, Horvatovac 102A, 10000 Zagreb, Croatia In major physical chemistry journals, the question whether

hydroxide ions interact with inert surfaces is currently a hot issue. Macroscopic measurements suggest that such interfaces have isoelectric points of about 2 to 4. This is explained by a strong affinity of hydroxide ions for the interfacial water present at these surfaces. Consequently it is suggested that hydroxide ions can be found at these interfaces and are strongly preferred say at pH 5 compared to protons although the hydroxide ion concentration in bulk solution is 4 orders of magnitude lower than the proton concentration. Molecular Dynamic simulations would predict that protons have a stronger affinity to such surfaces. Also experimental data with proton and hydroxide, at concentrations above millimolar, clearly confirms the prediction of the Molecular Dynamics simulations.

The contradiction of the Molecular Dynamics simulations to the experimental work at lower proton and hydroxide concentrations remains and is probably difficult to resolve and thus the origin of the unexpected pH-dependent behaviour of a wide variety of surfaces that bear no surface functional groups is not clear. Whatever the origin of the pH dependent charging of these inert interfaces might be, it should be important to consider it in mineral surface – electrolyte studies of geochemical interest. Thus for example the isoelectric points of many alumina single crystal samples have been reported to be rather low (actually around pH 4) and they presently remain largely unexplained. More interestingly, available isoelectric points are within or close to the range reported for the inert interfaces. This would indicate that the work on the alumina single crystals might involve reactions that have so far not been considered in the geochemical literature.

We report some experimental results on a range of inert surfaces to show how they all agree with each other and relate them to data on alumina samples. Our data confirm the previously reported experimental data at the millimolar scale. One possible explanation for the continuing discrepancy might be that the extrapolation of results for the above millimolar to the below millimolar concentration range is not appropriate. In particular we show that in some of the systems, we see clear changes in patterns like the salt dependency of zeta-potential at about millimolar concentrations.

Microbial mediated carbon-sulphur-metal cycling in fluidized mud ecosystem off French Guiana

T. LUZAN1*, V. MADRID1, T. WIDGEON1, R.C. ALLER2, J.Y. ALLER2 AND A.Y. CHISTOSERDOV1

1Department of Biology, ULL Lafayette, 411 E. St Mary Blvd, Lafayette, LA 70504, USA (*correspondence: [email protected])

2SoMAS, Stony Brook University, Stony Brook, New York, NY 11794-5000, USA ([email protected]) The fluidized mud ecosystem off the French Guiana coast

is a unique and globally important sedimentary environment. Due to rigorous physical reworking and reoxidation, anoxic and iron-rich sedimentary deposits remain nonsulphidic, even though Corg degradation rates and pore water sulphate (~ 20-28 mM) are relatively high. Benthic microbial communities respire nitrate and manganese oxides in a matter of minutes, but the bulk of organic matter is remineralized through ferric and sulphate respiration. High rates of sulphate and sulphur reduction (~10 – 20 nmol cm-3 day-1 and 5- 60 nmol cm-3 day-1) and high phylogenetic diversity of dsr gene libraries, as well as the dsr mRNA/DNA ratio further confirms the role of a sulphate-and sulphur-reducing microbial guild in biogeochemical cycling. The presence of transient CRS and S0 hints on alternative pathways of the oxidative sulphur transformation. High rates of dark CO2 fixation and fast regeneration of sulphate (up to 80 nmol cm-3 day-1) together with an abundance of ferric hydroxide implies complete reoxidation of solid phase reduced sulphur by yet an unknown microbial chemolithoautotrophic metabolism, which couples metal, sulphur and carbon cycles. Stable isotope probing with 13C bicarbonate revealed a complex chemolithoautotrophic community dominated by sulphur bacteria.


A647

The space expression of nuclide transport in GIS environment

LV KAIYUN1,2 AND ZHANG LITING3 1East China Institute of Technology, Fuzhou, Jiangxi

Province, 344000, China ([email protected])

2China University of Mining & Technology,Beijing ,100083, China ([email protected])

3East China Institute of Technology, Fuzhou, Jiangxi Province, 344000, China ([email protected]) Because of the radioactive pollution source diffusion

process has the characteristics of timeliness and extensity, the uranium tailings impoundment deposit always makes the circumjacent ground water disperse and further result in the ground water’s nuclear pollution. The safe disposal of High Level radioactive Waste (HLW), such as uranium tailings impoundment, is a key problem in the development of nuclear energy, and the radionuclide transport in the ground water is a core research contents in the geological disposal of HLW.

In this paper, the Geographic Information System (GIS) is used in researching of nuclide transport regulation, the main contents include: in virtue of space analysis technology, the dispersing process and distribution of nuclide were simulated by time and space scale, respectively. Areal geology and ground water hydrology were investigated by the establishment of three-dimensional areal hydrogeology model. Space information of nuclide transport could be extracted and transmit from the space model of nuclide transport. Dynamic simulation of space dispersing process of uranic pollution (nuclide) would be achieved.

This work was supported by the Jiangxi Province Natural

Science Foundation of China (Grant No: ) and Key Laboratory of Geospace Environment & Geodesy ministry of Education. China (Grant No:08-01-04)

Protonation enthalpy of magnetite from high temperture electrophoresis S.N. LVOV1*, M. FEDKIN1, V. RODRIGUEZ-SANTIAGO1,

S. VIDOJKOVIC1 AND D.J. WESOLOWSKI2 1The Pennsylvania State University, University Park, PA

16802 USA (*correspondence: [email protected])

2Oak Ridge National Laboratory, Oak Ridge, TN 37831-6110 USA ([email protected]) Surface protonation of metal oxide surface is

acknowledged to be a crtical step in mineral-water interactions in geothermal environments. We used a special high temperture microelectrophoresis cell [1] to investiagte the zeta potential of magnetite (Fe3O4) in aqueous solution at temperatures up to 200°C. From the obtained data, isoelectric pH points (IEP) for magnetite surface were determined (Fig. 1).

Figure 1: Isoelectric points of magnetite versus temperature compared to surface and mass titration PZC data [2,3].

Approximation of the obtained IEP data with the 1-pKa

thermodynamic model [4] and Crystal Chemistry and Solvation Theory [5] allowed us to estimate the standard enthalpy of protonation ($H°prot) of the magnetite surface. The obtained $H°prot values closely agree with those derived from surface titration data [2]. The relatively high protonation enthalpies suggest that temperature should have a pronounced effect on the constants of surface reactions on magnetite.

[1] Rodriguez-Santiago et al. (2009) Rev. Sci. Instr. 79, 093302. [2] Wesolowski et al. (2000) Chem. Geol. 167, 193. [3] Barale et al. (2008) J. Nucl. Mater. 381, 302. [4] Bolt & van Riemsdijk (1982) in Soil Chemistry, Physico-Chemical Models. Elsevier, 459–504. [5] Sverjensky & Sahai (1996) Geochim. Cosmochim. Acta 60, 3773.


High-resolution xSO2 spectra, and sulfur MIF due to SO2 photolysis

J.R. LYONS1*, G. STARK2, D. BLACKIE3 AND J.C. PICKERING3

1IGPP, UCLA, Los Angeles, 595 Charles Young Dr East, Los Angeles 90095-1567 ([email protected])

2Department of Physics, Wellesley College, Wellesley, MA 02481 USA ([email protected])

3Physics Department, Blackett Laboratory, Imperial College, Prince consort Rd., London SW7 2BZ UK It is well known that photolysis of SO2 yields isotopic

mass-independent fractionation of elemental sulfur [1]. Several mechanisms for photolytic MIF have been proposed including 1) self-shielding during photon absorption [2], 2) variations in band oscillator strengths, 3) hyperfine effects, and 4) resonant curve crossing. Here, we focus on the role of self-shielding in SO2. Quantitative evaluation of SO2 self-shielding requires accurate and high-resolution absorption cross section data. We compare high resolution spectra with recently obtained low resolution data [3]. The low-resolution spectra produce sulfur MIF effects when included in photochemical models [4, 5], but not due to SO2 self-shielding. In addition the MIF is of opposite sign in $33S (SO) to the self-shielding case. Our goal here is to reconcile the different MIF signatures obtained for the high and low-resolution measured spectra.

Two cases can be considered. 1) The high optical depth case, and 2) the low optical depth case. The former is required for SO2 self-shielding [2], and is applies to recent laboratory experiments on SO2 [6]. The low-resolution spectra yield the wrong sign in $33S (SO) for this case. We are presently attempting to reduce systematic errors in the high-resolution spectra in order to address the low optical depth case.

[1] Farquhar et al. (2001) JGR. 106, 32829–32840. [2] Lyons (2008) Adv. Quant. Chem. 55, 57–74. [3] Danielache et al. (2008) JGR 113, D17314. [4] Ueno et al. (2009) PNAS, art. #0903518106. [5] Lyons (2009) Chem. Geol. 267, 164–174. [6] Pen & Clayton (2008) EOS Trans. AGU 89 (53) abstract V52B-02.

Riverine chemical fluxes vs. long-term weathering,

Central Panama W.B. LYONS1,2*, S.T. GOLDSMITH1,2, K.M. DEUERLING1,2, L.M. HANNAH1,2

AND R.S. HARMON

1School of Earth Sciences, The Ohio State University, Columbus, OH 43210-1398, USA (*correspondence: [email protected])

2Byrd Polar Research Center, The Ohio State University, Columbus, OH 43210-1002, USA

3Environmental Science Division, ARL Army Research Office, Research Triangle Park, NC 27709, USA Silicate mineral weathering is one of the most important

geologic processes occurring on the earth’s surface. Modern chemical weathering rates are usually determined by calculating solute fluxes in rivers/streams after atmospheric input is subtracted. Determining longer-term rates is problematic, in part, due to the difficulty in accurately dating soil profiles. Here we compare the present day chemical weathering yields determined from the Upper Rio Chagres, central Panama to longer-term rates derived from geochemical profiles of soil pits. Much of this watershed is underlain by mafic-intermediate lithologies (primarily gabbro, diorite, and granodiorite plus an altered andesite of regional extent). Our previous work has demonstrated high dissolved Ca2+ and Mg2+ fluxes in the river system. Longer-term weathering rates have been calculated using the soil profiles and two different methods reported in the literature. Open-system mass transport calculations yield high Mg2+ and Ca2+, plus Na+ loss from the soild derived from mafic rock. These longer-term cation loss values compare favourably with the present-day solute fluxes obtained through river water analysis. Differences in agreement between short and long-term yields could be attributed to both minor exposures of other lithologies in the watershed along with input from weathering of saprolite. Currently, the cation yields from this mafic-intermediate composition watershed in Panama are ~2x higher than from tropical rainforest watersheds underlain by more felsic terrain.

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