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Mineralogical and oxygen isotopic study of a new ultrarefractory inclusion in the Northwest Africa 3118 CV3 chondrite

Xiong, Yong and Zhang, Ai-Cheng and Kawasaki, Noriyuki and Ma, Chi and Sakamoto, Naoya and Chen, Jia-Ni and Gu, Li-Xin and Yurimoto, Hisayoshi (2020) Mineralogical and oxygen isotopic study of a new ultrarefractory inclusion in the Northwest Africa 3118 CV3 chondrite. Meteoritics and Planetary Science . ISSN 1086-9379. (In Press)

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Calcium‐aluminum‐rich inclusions (CAIs) are the first solid materials formed in the solar nebula. Among them, ultrarefractory inclusions are very rare. In this study, we report on the mineralogical features and oxygen isotopic compositions of minerals in a new ultrarefractory inclusion CAI 007 from the CV3 chondrite Northwest Africa (NWA) 3118. The CAI 007 inclusion is porous and has a layered (core–mantle–rim) texture. The core is dominant in area and mainly consists of Y‐rich perovskite and Zr‐rich davisite, with minor refractory metal nuggets, Zr,Sc‐rich oxide minerals (calzirtite and tazheranite), and Fe‐rich spinel. The calzirtite and tazheranite are closely intergrown, probably derived from a precursor phase due to thermal metamorphism on the parent body. The refractory metal nuggets either exhibit thin exsolution lamellae of Fe,Ni‐dominant alloy in Os,Ir‐dominant alloy or are composed of Os,Ir,Ru,Fe‐alloy and Fe,Ni,Ir‐alloy with troilite, scheelite, gypsum, and molybdenite. The later four phases are apparently secondary minerals. The Zr,Sc,Y‐rich core is surrounded by a discontinuous layer of closely intergrown hibonite and spinel. The CAIs are rimmed by Fe‐rich spinel and Al‐rich diopside. Perovskite has high concentrations of the most refractory rare earth elements (REEs) but is relatively depleted in the moderately refractory and volatile REEs, consistent with the ultrarefractory REE pattern. Based on this unusual Zr,Sc,Y‐rich mineral assemblage, the layered distribution in CAI 007, and the REE concentrations in perovskite, we suggest that CAI 007 is an ultrarefractory inclusion of condensation origin. In CAI 007, hibonite, spinel, and probably Al‐rich diopside are ¹⁶O‐rich (Δ¹⁷O ~–22‰) whereas perovskite and davisite are ¹⁶O‐poor (Δ¹⁷O ~–3‰). Such oxygen isotope heterogeneity suggests that the UR inclusion formed in the various degrees of ¹⁶O‐rich nebular setting or was originally ¹⁶O‐rich and then experienced oxygen isotope exchange with ¹⁶O‐poor fluid on the CV3 chondrite parent body.

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Zhang, Ai-Cheng0000-0002-5758-0726
Ma, Chi0000-0002-1828-7033
Additional Information:© 2020 The Meteoritical Society. (Received 27 March 2020; revision accepted 09 September 2020) We appreciate the editorial effort from Dr. Michael Zolensky and the helpful comments from Dr. Sasha Krot and Dr. Makoto Kimura, which improved the quality of the manuscript. We also thank Dr. Naotaka Tomioka for helpful discussion of identifying mineral phases under TEM and Dr. Juan Li for assistance during EBSD analysis. This work was financially supported by the B‐type strategic Priority Program of the Chinese Academy of Sciences (Grant XDB41000000), a pre‐research Project on Civil Aerospace Technologies funded by CNSA (Grant D020204), National Natural Science Foundation of China (Grant 41673068, 41973061), and the Natural Science Foundation of Jiangsu Province of China (Grant BK20170017).
Funding AgencyGrant Number
Chinese Academy of SciencesXDB41000000
China National Space AdministrationD020204
National Natural Science Foundation of China41673068
National Natural Science Foundation of China41973061
Natural Science Foundation of Jiangsu ProvinceBK20170017
Record Number:CaltechAUTHORS:20201014-111855264
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Official Citation:Xiong, Y., Zhang, A.‐C., Kawasaki, N., Ma, C., Sakamoto, N., Chen, J.‐N., Gu, L.‐X. and Yurimoto, H. (2020), Mineralogical and oxygen isotopic study of a new ultrarefractory inclusion in the Northwest Africa 3118 CV3 chondrite. Meteorit Planet Sci. doi:10.1111/maps.13575
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:106055
Deposited By: George Porter
Deposited On:14 Oct 2020 19:15
Last Modified:14 Oct 2020 19:15

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