The Petrology and Geochemistry of CY Chondrites: A Study of Yamato 82162 and Yamato 980115

Russell S. S., Spratt J., King A. J.

82nd Annual Meeting of The Meteoritical Society 2019

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“Three unusual carbonaceous chondrites – Yamato 82162, Yamato 86720, and Belgica 7904 – were studied by a consortium in 1992 [1]. Along with several meteorites found since then (e.g. Yamato 86789, Yamato 86029, Yamato 980115, Dhofar 1988 and Dhofar 2066), these aqueously altered and dehydrated meteorites have bulk oxygen isotope compositions heavier than any other carbonaceous chondrite group (typical δ18O ~22 ‰ [2]) and an unusual mineralogy [3]. Although they experienced later thermal metamorphism, this cannot explain their distinct compositions [4]. Thus, while they are often linked to the CI or CM chondrites, it has been suggested they represent a new group of meteorites, the CYs [1, 4]. These meteorites are of particular interest as their extremely dark colour may suggest a relationship to the Hayabusa2 target Ryugu [5]. Here, we have studied the mineralogy, geochemistry and petrology of two of these meteorites, Yamato 980115 (Y-980115) and Yamato 82162 (Y-82162). “