R5: Extraterrestrial materials

[R5-19] Crystallization history of unusual petrological textures in the NWA 7203 angrite

「発表賞エントリー」

*Hideyuki Hayashi¹, Takashi Mikouchi², Martin Bizzarro³ (1. EPS, U. Tokyo, 2. UM, U. Tokyo, 3. U. Copenhagen)

Keywords:NWA 7203, Angrite, Crystallization history, Xenocryst

We studied NWA 7203angrite which shows a quenched texture with largegrain size variations to clarifyits crystallization history. According to our study, we proposethat fine-grained areas first rapidly crystallized with olivine xenocrysts as crystallization seeds, and second the melt composition changed to slightly more Mg-rich, and finally coarse-grained areas were subsequently formed. However, there remains the possibility that the texture was formed by decrease of the cooling rate.