Siderophile elements in Martian meteorites and implications for core formation in Mars |
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| Institution: | 1. Department of Chemistry, Faculty of Science, Tokyo Metropolitan University, Hachioji, Tokyo 192-03, Japan;2. Institut für Mineralogie and Geochemie, Universität zu Köln, 50674 Köln, Germany;1. Institut für Planetologie, Westfälische Wilhelms – Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany;2. Origins Laboratory, Department of Geophysical Sciences, The University of Chicago, IL 60637, USA;1. Institute of Meteoritics, Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131, United States;2. Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131, United States;3. Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Rd., NW, Washington, DC 20015, United States;1. Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences, Washington University in St. Louis, One Brookings Drive, St. Louis, MO 63130, USA;2. Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093, USA;3. Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964, USA;1. School of Geographical and Earth Sciences, University of Glasgow, Gregory Building, Lilybank Gardens, Glasgow G12 8QQ, UK;2. Scottish Universitites Environmental Research Centre, Rankine Avenue, Scottish Enterprise Technology Park, East Kilbride G75 0QF, UK;1. Institut für Mineralogie, Universität Münster, Corrensstr. 24, D-48149 Münster, Germany;2. Czech Geological Survey, Klárov 3, CZ-118 21 Prague 1, Czech Republic;3. Isotope Laboratory, Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195, USA;4. Institut für Geologie, Universität Bern, Baltzerstr. 1+3, CH-3012 Bern, Switzerland;1. Institut de Physique du Globe de Paris, Université de Paris, CNRS, 1 rue Jussieu, Paris 75005, France;2. Institut Universitaire de France, Paris, France |
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| Abstract: | Noble metals, Mo, W, and 24 other elements were determined in six SNC meteorites of presumably Martian origin. Based on element correlations, representative siderophile element concentrations for the silicate mantle of Mars were inferred. From a comparison with experimentally determined metal/silicate partition coefficients of the moderately siderophile elements: Fe, Ni, Co, W, Mo, and Ga, it is concluded that equilibrium between core forming metal and silicates in Mars has occurred at high temperatures (around 2200°C) and low pressures (<1 GPa). This suggests that metal segregation occurred concurrently with rapid accretion of Mars, which is consistent with the inference from excess 182W in Martian meteorites (Lee and Halliday, 1997). Concentrations of Ir, Os, Ru, Pt, and Au in the analyzed Martian meteorites, except ALH84001, are at a level of approximately 10?2–10?3 × CI. The comparatively high abundances of noble metals in Martian meteorites require the addition of chondritic material after core formation. The similarity in Au/La and Pt/Ca ratios between ALH84001 and the other Martian meteorites suggests crystallization of ALH84001 after complete accretion of Mars. |
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