Granulite Xenoliths from the Sumikawa Granite Body, Niigata Prefecture, Japan : Finding of Spinel+Quartz Assemblage from the Japanese Islands

抄録

Spinel+quartz assemblage is one of the indicators of ultrahigh-temperature (UHT) metamorphism. Metamorphic xenoliths of granulite facies occur in the Sumikawa Granite, Niigata Prefecture. We found the spinel+ quartz assemblage from a pelitic metamorphic xenolith in the granite body. The metamorphic textures show a clockwise P-T-t path and the metamorphic reactions follow the order;Grt+Sil=Spl+Qtz, and Spl+Qtz=Crd. According to thermodynamic model, the spinel+quartz assemblage in this rock is thought to be stable at T>860°C and P>600MPa. This assemblage was presumably generated by metamorphism in the lower crust in the Uetsu area.