P-T estimations of metasedimentary origin mylonite along the MTL in the Ohshika district, Nagano

Abstract

Kashio mylonite zone is exposed in the Oshika villege, Nagano, and widely extends along the Meadiean Tectonic Line (MTL) from Aoki to Kashio Rivers. The pelite origin mylonite shows a white thin layer within granitic mylonite. Based on the chemical analyses of recrystallized minerals, the P-T conditions of weakly and highly deformed pelite-origin mylonites ranged from 590~600 ℃ / 0.3-0.45 GPa, and 400~540 ℃ / 0.9 GPa, respectively. Our P-T estimations imply that Kashio mylonite zone was formed by two different mylonites related to HT-LP type and LT-HP type metamorphism.