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Formation, preservation and extinction of high-pressure minerals in meteorites: temperature effects in shock metamorphism and shock classification

Hu, Jinping and Sharp, Thomas G. (2022) Formation, preservation and extinction of high-pressure minerals in meteorites: temperature effects in shock metamorphism and shock classification. Progress in Earth and Planetary Science, 9 . Art. No. 6. ISSN 2197-4284. PMCID PMC8732827. doi:10.1186/s40645-021-00463-2.

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The goal of classifying shock metamorphic features in meteorites is to estimate the corresponding shock pressure conditions. However, the temperature variability of shock metamorphism is equally important and can result in a diverse and heterogeneous set of shock features in samples with a common overall shock pressure. In particular, high-pressure (HP) minerals, which were previously used as a solid indicator of high shock pressure in meteorites, require complex pressure–temperature–time (P–T–t) histories to form and survive. First, parts of the sample must be heated to melting temperatures, at high pressure, to enable rapid formation of HP minerals before pressure release. Second, the HP minerals must be rapidly cooled to below a critical temperature, before the pressure returns to ambient conditions, to avoid retrograde transformation to their low-pressure polymorphs. These two constraints require the sample to contain large temperature heterogeneities, e.g. melt veins in a cooler groundmass, during shock. In this study, we calculated shock temperatures and possible P–T paths of chondritic and differentiated mafic–ultramafic rocks for various shock pressures. These P–T conditions and paths, combined with observations from shocked meteorites, are used to constrain shock conditions and P–T–t histories of HP-mineral bearing samples. The need for rapid thermal quench of HP phases requires a relatively low bulk-shock temperature and therefore moderate shock pressures below ~ 30 GPa, which matches the stabilities of these HP minerals. The low-temperature moderate-pressure host rock generally shows moderate shock-deformation features consistent with S4 and, less commonly, S5 shock stages. Shock pressures in excess of 50 GPa in meteorites result in melt breccias with high overall post-shock temperatures that anneal out HP-mineral signatures. The presence of ringwoodite, which is commonly considered an indicator of the S6 shock stage, is inconsistent with pressures in excess of 30 GPa and does not represent shock conditions different from S4 shock conditions. Indeed, ringwoodite and coexisting HP minerals should be considered as robust evidence for moderate shock pressures (S4) rather than extreme shock (S6) near whole-rock melting.

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URLURL TypeDescription CentralArticle
Hu, Jinping0000-0003-0415-4616
Sharp, Thomas G.0000-0003-2287-9370
Additional Information:© The Author(s) 2021. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit Received 28 August 2021. Accepted 18 December 2021. Published 05 January 2022. We thank Dr. Naotaka Tomioka and an anonymous reviewer for their careful review and constructive comments. We also thank Dr. Erin Walton and an anonymous reviewer for reviewing an earlier version of this manuscript. We acknowledge the late Prof. Ahmed El Goresy for his many contributions to the study of HP minerals in shocked meteorites. We miss and gratefully thank the late Paul DeCarli who shared his wealth of knowledge on shock and mineral physics with us since early 2000s. We thank Dr. Paul Asimow for the guidance on thermodynamic calculations. The study was initially funded by NASA Cosmochemistry Grant 12-COS12-0002. JH is supported by NASA Solar System Workings Grant 80NSSC18K0532 and NSF Award 1725349. TGS is supported by NASA Emerging Worlds Grant 17-EW17_2-0090. Contributions. TGS conceived the initial concepts of this study. JH and TGS designed this study. JH performed the thermodynamic calculations. JH and TGS wrote the manuscript. All authors read and approved the final manuscript. Availability of data and materials. All data generated or analyzed during this study are included in this published article. The authors declare that they have no competing interests.
Funding AgencyGrant Number
Subject Keywords:Chondrite, Martian meteorite, Shock metamorphism, High-pressure minerals
PubMed Central ID:PMC8732827
Record Number:CaltechAUTHORS:20220121-870668000
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Official Citation:Hu, J., Sharp, T.G. Formation, preservation and extinction of high-pressure minerals in meteorites: temperature effects in shock metamorphism and shock classification. Prog Earth Planet Sci 9, 6 (2022).
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:113052
Deposited By: George Porter
Deposited On:21 Jan 2022 23:56
Last Modified:24 Jan 2022 18:12

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