A history of violence: insights into post-accretionary heating in carbonaceous chondrites from volatile element abundances, Zn isotopes and water contents

Mahan, Brandon, Moynier, Frédéric, Beck, Pierre, Pringle, Emily A., and Siebert, Julien (2018) A history of violence: insights into post-accretionary heating in carbonaceous chondrites from volatile element abundances, Zn isotopes and water contents. Geochimica et Cosmochimica Acta, 220. pp. 19-35.

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Abstract

Carbonaceous chondrites (CCs) may have been the carriers of water, volatile and moderately volatile elements to Earth. Investigating the abundances of these elements, their relative volatility, and isotopes of state-change tracer elements such as Zn, and linking these observations to water contents, provide vital information on the processes that govern the abundances and isotopic signatures of these species in CCs and other planetary bodies. Here we report Zn isotopic data for 28 CCs (20 CM, 6 CR, 1 C2-ung, and 1 CV3), as well as trace element data for Zn, In, Sn, Tl, Pb, and Bi in 16 samples (8 CM, 6 CR, 1 C2-ung, and 1 CV3), that display a range of elemental abundances from case-normative to intensely depleted. We use these data, water content data from literature and Zn isotopes to investigate volatile depletions and to discern between closed and open system heating. Trace element data have been used to construct relative volatility scales among the elements for the CM and CR chondrites. From least volatile to most, the scale in CM chondrites is Pb-Sn-Bi-In-Zn-Tl, and for CR chondrites it is Tl-Zn-Sn-Pb-Bi-In. These observations suggest that heated CM and CR chondrites underwent volatile loss under different conditions to one another and to that of the solar nebula, e.g. differing oxygen fugacities. Furthermore, the most water and volatile depleted samples are highly enriched in the heavy isotopes of Zn. Taken together, these lines of evidence strongly indicate that heated CM and CR chondrites incurred open system heating, stripping them of water and volatiles concomi- tantly, during post-accretionary shock impact(s).

Item ID: 62753
Item Type: Article (Research - C1)
ISSN: 1872-9533
Keywords: Moderately volatile elements, carbonaceous chondrites, volatity, heated meteorites, shock impacts
Copyright Information: © 2017 Elsevier Ltd. All rights reserved.
Funders: IDEX USPC, French National Research Agency (ANR), Sorbonne Paris Cité (SPC), European Research Council (ERC), Region Île-de-France SESAME (RIFS)
Projects and Grants: IDEX USPC PhD fellowships, ANR Project VolTerre, grant no. ANR-14-CE33-0017-01, SPC UnivEarthS Labex program, ANR-10- LABX-0023 and ANR-11-IDEX-0005-02, ERC H2020 framework program/ERC grant agreement #637503 (Pristine), ANR chaire d’excellence Sorbonne Paris Cité, RIFS grant no. 12015908
Date Deposited: 28 Jun 2020 21:52
FoR Codes: 37 EARTH SCIENCES > 3703 Geochemistry > 370302 Inorganic geochemistry @ 50%
37 EARTH SCIENCES > 3703 Geochemistry > 370303 Isotope geochemistry @ 50%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970104 Expanding Knowledge in the Earth Sciences @ 100%
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