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Heterogeneous accretion of Earth inferred from Mo-Ru isotope systematics

Hopp, Timo and Budde, Gerrit and Kleine, Thorsten (2020) Heterogeneous accretion of Earth inferred from Mo-Ru isotope systematics. Earth and Planetary Science Letters, 534 . Art. No. 116065. ISSN 0012-821X.

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The Mo and Ru isotopic compositions of meteorites and the bulk silicate Earth (BSE) hold important clues about the provenance of Earth's building material. Prior studies have argued that non-carbonaceous (NC) and carbonaceous (CC) meteorite groups together define a Mo-Ru ‘cosmic’ correlation, and that the BSE plots on the extension of this correlation. These observations were taken as evidence that the final 10–15% of Earth's accreted material derived from a homogeneous inner disk reservoir with an enstatite chondrite-like isotopic composition. Here, using new Mo and Ru isotopic data for previously uninvestigated meteorite groups, we show that the Mo-Ru correlation only exists for NC meteorites, and that both the BSE and CC meteorites fall off this Mo-Ru correlation. These observations indicate that the final stages of Earth's accretion were heterogeneous and consisted of a mixture of NC and CC materials. The Mo-Ru isotope systematics are best accounted for by either an NC heritage of the late veneer combined with a CC heritage of the Moon-forming giant impactor, or by mixed NC-CC compositions for both components. The involvement of CC bodies in the late-stage accretionary assemblage of Earth is consistent with chemical models for core-mantle differentiation, which argue for the addition of more oxidized and volatile-rich material toward the end of Earth's formation. As such, this study resolves the inconsistencies between homogeneous accretion models based on prior interpretations of the Mo-Ru systematics of meteorites and the chemical evidence for heterogeneous accretion of Earth.

Item Type:Article
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URLURL TypeDescription
Hopp, Timo0000-0002-4056-5431
Budde, Gerrit0000-0003-0762-779X
Kleine, Thorsten0000-0003-4657-5961
Additional Information:© 2020 The Author(s). Published by Elsevier Under a Creative Commons license - Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) Received 19 September 2019, Revised 30 November 2019, Accepted 30 December 2019, Available online 17 January 2020. We gratefully acknowledge Addi Bischoff, Knut Metzler, the Institute of Meteoritics, University of New Mexico, and NASA for providing samples. US Antarctic meteorite samples are recovered by the Antarctic Search for Meteorites (ANSMET) program, which has been funded by NSF and NASA, and characterized and curated by the Department of Mineral Sciences of the Smithsonian Institution and Astromaterials Curation Office at NASA Johnson Space Center. We further thank Ulla Heitmann for technical support and sample preparation. This research received funding to Thorsten Kleine from the European Research Council under the European Community's Seventh Framework Program (FP7/2007-2013 Grant Agreement 616564 ‘ISOCORE’) and was supported by the Deutsche Forschungsgemeinschaft (SFB-TRR170, subproject B3). This is TRR 170 publication No. 85. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Funding AgencyGrant Number
European Research Council (ERC)616564
Deutsche Forschungsgemeinschaft (DFG)SFB-TRR170
Subject Keywords:late stage accretion; heterogeneous accretion; siderophile elements; nucleosynthetic isotope anomalies; isotope dichotomy; origin of volatiles
Record Number:CaltechAUTHORS:20200313-142323454
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Official Citation:Timo Hopp, Gerrit Budde, Thorsten Kleine, Heterogeneous accretion of Earth inferred from Mo-Ru isotope systematics, Earth and Planetary Science Letters, Volume 534, 2020, 116065, ISSN 0012-821X,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:101914
Deposited By: George Porter
Deposited On:16 Mar 2020 14:03
Last Modified:16 Mar 2020 14:03

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