Evidence for the presence of chondrule- and CAI-derived material in an isotopically anomalous Antarctic micrometeorite

Bastien Soens, Martin D. Suttle, Ryoga Maeda, Akira Yamaguchi, Matthias Van Ginneken, Vinciane Debaille, Philippe Claeys, Steven Goderis

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Abstract

We report the discovery of a unique, refractory phase‐bearing micrometeorite (WF1202A‐001) from the Sør Rondane Mountains, East Antarctica. A silicate‐rich cosmic spherule (~400 µm) displays a microporphyritic texture containing Ca‐Al‐rich inclusion (CAI)‐derived material (~5–10 area%), including high‐Mg forsterite (Fo98‐99) and enstatite (En98‐99, Wo0‐1). The micrometeorite also hosts a spherical inclusion (~209 µm), reminiscent of chondrules, displaying a barred olivine texture. Oxygen isotopic compositions of the micrometeorite groundmass (δ17O = –3.46‰, δ18O = 10.43‰, ∆17O = –1.96‰) are consistent with a carbonaceous chondrite precursor body. Yet, a relict forsterite grain is characterized by δ17O = –45.8‰, δ18O = –43.7‰, ∆17O = –23.1‰, compatible with CAIs. In contrast, a relict low‐Ca pyroxene grain (δ17O = –4.96‰, δ18O = –4.32‰, ∆17O = –2.71‰) presumably represents a first‐generation silicate grain that accreted 18O‐rich gas or dust in a transient melting scenario. The spherical inclusion displays anomalous oxygen isotope ratios (δ17O = –0.98‰, δ18O = –2.16‰, ∆17O = 0.15‰), comparable to anhydrous interplanetary dust particles (IDPs) and fragments from Comet 81P/Wild2. Based on its major element geochemistry, the chondrule size, and oxygen isotope systematics, micrometeorite WF1202A‐001 likely sampled a carbonaceous chondrite parent body similar to, but distinct from CM, CO, or CV chondrites. This observation may suggest that some carbonaceous chondrite bodies can be linked to comets. The reconstructed atmospheric entry parameters of micrometeorite WF1202A‐001 suggest that the precursor particle originated from a low‐inclination, low‐eccentricity source region, most likely either the main belt asteroids or Jupiter family comets (JFCs).
Original languageEnglish
Pages (from-to)2703-2726
Number of pages24
JournalMeteoritics & Planetary Science
Volume55
Issue number12
DOIs
Publication statusPublished - Dec 2020

Bibliographical note

Funding Information:
This study was funded by the Fonds voor Wetenschappelijk Onderzoek (FWO) Vlaanderen as part of a PhD Fellowship, and carried out using the facilities of the National Institute of Polar Research (NIPR). We specifically like to thank Rei Kanemaru for his assistance during the EPMA analysis. We also like to thank Johan Villeneuve (CRPG) for his assistance during the SIMS measurement time. RM, FV, VD, PhC, and SG acknowledge funding from the Excellence of Science (EoS) project “ET‐HoME.” FV also acknowledges UGent for GOA funding and Teledyne Cetac Technologies for financial and logistic support. VD thanks the ERC StG “ISoSyC” and FRS‐FNRS for funding. MvG, VD, and PhC thank the Belgian Science Policy (Belspo) Brain‐be “Amundsen” project. PhC acknowledges the support of the VUB Strategic Research Program. MDS is supported by the UK’s Science and Technology Facilities Council (STFC) on grant no. ST/R000727/1. Finally, we thank Matthew Genge for his insightful comments during the review of this manuscript.

Funding Information:
This study was funded by the Fonds voor Wetenschappelijk Onderzoek (FWO) Vlaanderen as part of a PhD Fellowship, and carried out using the facilities of the National Institute of Polar Research (NIPR). We specifically like to thank Rei Kanemaru for his assistance during the EPMA analysis. We also like to thank Johan Villeneuve (CRPG) for his assistance during the SIMS measurement time. RM, FV, VD, PhC, and SG acknowledge funding from the Excellence of Science (EoS) project ?ET-HoME.? FV also acknowledges UGent for GOA funding and Teledyne Cetac Technologies for financial and logistic support. VD thanks the ERC StG ?ISoSyC? and FRS-FNRS for funding. MvG, VD, and PhC thank the Belgian Science Policy (Belspo) Brain-be ?Amundsen? project. PhC acknowledges the support of the VUB Strategic Research Program. MDS is supported by the UK?s Science and Technology Facilities Council (STFC) on grant no. ST/R000727/1. Finally, we thank Matthew Genge for his insightful comments during the review of this manuscript.

Publisher Copyright:
© The Meteoritical Society, 2020.

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