Origin of the metamorphosed clasts in the CV3 carbonaceous chondrite breccias of Graves Nunataks 06101, Vigarano, Roberts Massif 04143, and Yamato‐86009

Kaori JOGO1, Motoo ITO2, Shigeru WAKITA3, Sachio KOBAYASHI2, and Jong Ik LEE1
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13272]
1Division of Earth-System Sciences, Korea Polar Research Institute, 26 Songdomirae-ro, Yeonsu-gu, Incheon 21990,South Korea
2Kochi Institute for Core Sample Research, JAMSTEC B200 Monobe, Nankoku, Kochi 783-8502, Japan
3Center for Computational Astrophysics, National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka,Tokyo 181-8588, Japan
Published by arrangement with John Wiley & Sons

We observed metamorphosed clasts in the CV3 chondrite breccias Graves Nunataks 06101, Vigarano, Roberts Massif 04143, and Yamato‐86009. These clasts are coarse‐grained polymineralic rocks composed of Ca‐bearing ferroan olivine (Fa24–40, up to 0.6 wt% CaO), diopside (Fs7–12Wo44–50), plagioclase (An52–75), Cr‐spinel (Cr/[Cr + Al] = 0.4, Fe/[Fe + Mg] = 0.7), sulfide and rare grains of Fe‐Ni metal, phosphate, and Ca‐poor pyroxene (Fs24Wo4). Most clasts have triple junctions between silicate grains. The rare earth element (REE) abundances are high in diopside (REE ~3.80–13.83 × CI) and plagioclase (Eu ~12.31–14.67 × CI) but are low in olivine (REE ~0.01–1.44 × CI) and spinel (REE ~0.25–0.49 × CI). These REE abundances are different from those of metamorphosed chondrites, primitive achondrites, and achondrites, suggesting that the clasts are not fragments of these meteorites. Similar mineralogical characteristics of the clasts with those in the Mokoia and Yamato‐86009 breccias (Jogo et al. 2012) suggest that the clasts observed in this study would also form inside the CV3 chondrite parent body. Thermal modeling suggests that in order to reach the metamorphosed temperatures of the clasts of >800 °C, the clast parent body should have accreted by ~2.5–2.6 Ma after CAIs formation. The consistency of the accretion age of the clast parent body and the CV3 chondrule formation age suggests that the clasts and CV3 chondrites could be originated from the same parent body with a peak temperature of 800–1100 °C. If the body has a peak temperature of >1100 °C, the accretion age of the body becomes older than the CV3 chondrule formation age and multiple CV3 parent bodies are likely.

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