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Chromium Chemistry in Natural Waters, Iceland Deformation Mechanisms in Martian Shergottites

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Chromium Chemistry in Natural Waters, Iceland Deformation Mechanisms in Martian Shergottites 1414 Goldschmidt2013 Conference Abstracts Chromium chemistry in natural Deformation mechanisms in Martian waters, Iceland Shergottites HANNA KAASALAINEN1*, ANDRI STEFÁNSSON1, KACZMAREK M.-A.*12, GRANGE M.1, REDDY S.M.1, INGVI GUNNARSSON2 AND STEFÁN ARNÓRSSON1 AND NEMCHIN A.1 1Institute of Earth Sciences, University of Iceland, Sturlugata 1Department of Applied Geology, The Institute for Geoscience 7, 101 Reykjavik, Iceland, Research, Curtin University of Technology, GPO Box (*correspondence: [email protected]) U1987, Perth, WA 6845, Australia 2Present address: Reykjavik Energy, Bæjarhalsi 1, 110 2Now at University of Lausanne, Institute of Earth Sciences, Reykajvik, Iceland UNIL Mouline, Géopolis, CH-1016 Lausanne, Switzerland Chemistry of Cr and Fe was studied in non-thermal and (*correspondence: [email protected]) geothermal waters in Iceland. Chromium (Cr) is typically present at low concentrations (<1 µg/l) in natural waters, but Nakhla and Zagami are both clinopyroxene-rich basaltic elevated concentrations have been observed in waters with shergottite, with some Fe-rich olivine. The microstructure, the low pH values, e.g. acid mine drainage, and in association preferred orientation of pyroxene using Electron Backscatter with industrial activities. Chromium occurs in two oxidation Diffraction (EBSD) method and the gochemistry are combined states, Cr(III) and (VI), these being characterized by different to study subsamples of both Zagami and Nakhla to decipher (bio)chemical behaviour and solubility. As Cr(VI) is known to deformation processes that have occurred on Mars. be toxic but Cr(III) an essential micronutrient, it is important Nakhla displays a granular texture, essentially composed to determine the two oxidations states. Iron (Fe) is known to of augite, fayalite, plagioclase and magnetite. Our Zagami play an important role in the chemistry of Cr through sample, formed by olivine, plagioclase, and whitlockite is part adsorption on and incorporation in Fe containing minerals, and of the “coarse grained” portion of Normal Zagami texture [1, by affecting the distribution of Cr species. In natural waters, 2] with long prism of clinopyroxene underlying a weak iron is present in two oxidation states (Fe(II) and (III)) and preferrential orientation. Complete maps of both Zagami and understanding its chemistry is complicated by fast oxidation Nakhla samples and detailed maps of clinopyroxene single kinetics, importance of colloidal forms and low solubility in grains were obtained with EBSD. Both samples show a strong the pH range of most natural waters (pH>6). preferred orientation of clinopyroxene and CPOs display Samples were collected from non-thermal surface and several point concentrations on <001> axes within a girdle. spring water, surface geothermal water and geothermal well The relationship between the microstructure and CPOs discharges, and analyzed for their major and trace element inferred the possible activation of (100)[001] and (010)[100] composition. Chromium and Fe speciation was determined in slip systems. Moreover, the several point concentrations on selected samples. The sampled waters showed wide range of clinopyroxene <001> axis might correspond to twinning. composition with temperature, pH and total dissolved solids in Geochemical maps of clinopyroxene single grains the range of 0-184°C, 2.0-9.6, and 35-4030 mg/l, respectively. highlight chemical zoning from augite core to pigeonite rims. The total dissolved Fe and Cr concentrations were between <1 Phases indexation with the EBSD is concordant with the µg/L to 360 mg/L and <0.01 and 660 µg/L, respectively. The geochemistry and highlights no variation in the slip system highest concentrations were associated with steam-heated from cores to rims, suggesting either no variation of acid-sulfate waters with the lowest pH values, whereas the deformation during the evolution of the geochemical system, concentrations in neutral to alkaline waters were low, typically or a late deformation event. Inspection of clinopyroxene single <1 µg/L Cr and <100 µg/L Fe. grains show that Nakhla clinopyroxenes have almost no The main processes controlling Cr chemistry were found internal deformation, rather than Zagami clinopyroxenes to depend on the water pH and rock leaching. At a low pH, showing complicate microtexture with possible activation of Cr(III) becomes released into solution through leaching of Cr- several slip systems. containing minerals contained in basaltic rocks. At neutral to Our results suggest a composite deformation related to alkaline pH, Cr leaching from rock is limited and Cr(III) magmatic deformation (preferred orientation and prismatic concentrations may be further reduced and controlled by clinopyroxene) and to the shock event (single grain internal solubility of Cr(III)-Fe(III) mineral phases. However, Cr(VI) deformation and twinning). mobility is enhanced associated with decreasing importance of mineral surface complexation. Indeed, Cr(VI) was frequently [1] Stolper E. M. et al. 1979. Geochimica Cosmochimica Acta. found to dominate over Cr(III) at pH>6 in concentrations of a 43: 589-602. [2] McCoy T. J. et al. 1992. Geochimica few µg/L. Cosmochimica Acta. 56: 3571-3582. www.minersoc.org DOI:10.1180/minmag.2013.077.5.11 Downloaded from http://pubs.geoscienceworld.org/minmag/article-pdf/77/5/1414/2920741/gsminmag.77.5.11-K.pdf by guest on 29 September 2021 Goldschmidt2013 Conference Abstracts 1415 Bioavailability of nanoparticulate Determination the step of karst iron derived from atmospheric formation using GPR and Raman mineral dusts Spectroscopy Methods, South East ENIKÖ KADAR1, JONATHAN J. POWELL3 Anatolia, Turkey 2 AND ZONGBO SHI 12 2 SELMA KADIOGLU AND YUSUF KA!AN KADIO!LU 1Plymouth Marine Laboratory, Prospect Place, the Hoe, 1Ankara University Faculty of Engineering Department of Plymouth PL1 3DH, UK email: [email protected] 2 Geopgysical Engineering, Ankara, Turkey School of Geography, Earth and Environmental Sciences, 2 Ankara University Earth Sciences Application and Research University of Birmingham, B15 2TT, U.K email: Center, Ankara, Turkey ([email protected]) [email protected] 3 Biomineral Research Section, Medical Research Council - Ground Penetrating Radar (GPR) is used to identify the Human Nutrition Research, Elsie Widdowson Laboratory, relatively shallow subsurface features at scale from centimeter Fulbourn Road, Cambridge CB1 9NL email: up to meter. In this study dissolution of soluble rocks (Karst) [email protected] including limestone and dolomitic limestone are examined using GPR and Raman spectroscopy methods around We have studied the composition, Fe dissolution/Fe Adiyaman City in East Anatolia Turkey. Karstification led to lability, particle aggregation/size distribution, surface topology form sinkholes, caves, and underground drainage systems. and zeta potential (i.e. colloidal stability) of Fe-rich Rainwater becomes acidic as it comes in contact with carbon nanoparticles (NPs) formed during simulated atmospheric dioxide in the atmosphere and the soil. As it drains into processing of dust in contact with seawater under a range of fractures in the rock, the water begins to dissolve away the environmentally realistic conditions typical in oceanic waters rock creating a network of passages. The step of the karst to shed light on putative relationships between NP structure formation towards the inner parts of the surface of the and water parameters. These laboratory studies showed that: limestone is determined using 250 and 500 Mhz GPR antenna. (i) despite the close resemblance in micromorphology, NPs GPR attribute volumes is sensible and suggests that the formed from mineral dusts have distinct aggregation formation of the cavities along the fracture packets exist over behaviour from ferrihydrite NPs; (ii) the relatively stable and cavity floors elsewhere but that there is also variation in mondosiperse aggregates of NPs formed during simulated fracture intensity and in orientation over the whole system. cloud processing of mineral dust become more polydisperse The matrix consolidation and dissolution of the rocks are and unstable in seawater; (iii) exopolymeric substances (EPS) observed through the processing of the radar data. extracted from phytoplankton seem to "stabilise" the The microscopically examination and Confocal Raman aggregates of dust derived NPs; iv) dissolved Fe concentration spectroscopy determination studies show the degree of the from NPs, is consistently higher in seawater in the presence of dissolution is increased towards the crack and aid to form EPS and is also affected by sunlight; v) EPS-mediated Fe ankerite, siderite, limonite, hydrous carbonate-sulfates, uptake may be responsible for enhanced bioavailability in vermiculite clay minerals with rare amount of albite and phytoplankton. pyrite. To test the hypothesis that nanoparticulate Fe is more bioavailable than the bulk analogue we have grown marine microalgae on synthetic nano-iron substrates. Algal growth was significantly enhanced when the nanomaterials were added in equimolar concentration compared to Fe-EDTA in the optimised algal growth medium (f/2). NP addition influenced cellular fatty acid composition compared to control treatments, but this was significant only in haptophytes. The NP uptake mechanism proposed is via secretion of an extracellular matrix that binds NPs through which Fe is bioavailable via fagocytotic membrane processes and/or NP dissolution. The implications of the use of such engineered nanomaterials
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