Mineralogy of five new Antarctic ureilites, LEW86216, LEW85328, Y-791839, Y-75154, Y-8448, and the origin of their chemical variations of pyroxene

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Mineralogical studies of mafic silicates in heavily shocked ureilites, LEW86216,Y-75154,Y-791839,and moderately shocked ureilite LEW85328 were performed to reveal the chemical variations and textures produced by shock events on the ureilite parent body. Y-8448 is one of common ureilites, but such ureilites are found in relatively small numbers in Antarctica. Olivines in Y-75154 and LEW86216 show granoblastic textures and the carbonaceous veins are disrupted. Their pyroxenes show chemical variations toward enstatite. They are among the most heavily shocked ureilites. Grain rims of Y-791839 and LEW85328 show chemical variations due to shock. The chemical trends of all these heavily shocked ureilites cover the entire range of known individual ureilites. Shock effects of these ureilites are interpreted to have been produced during the break-up of their parent body. Their chemical variations may be applied to study of the chemical differentiation by the planetesimal-scale collision in the earliest stage of ureilite formation.
国立極地研究所の論文