R8: Metamorphic rocks and tectonics

[R8P-11] Brittle fractures of albite porphyroblasts in the pelitic schists of the Sanbagawa metamorphic belt, Kanto Mountains

*Mutsuko Inui¹, Shuto Kojima¹, Yoshiya Nagatsuma¹ (1. Kokushikan Univ.)

Keywords:albite porphyroblast, brittle deformation, fragmentation, potassium feldspar, Sanbagawa metamorphism

Microstructures found in the Sanbagawa metamorphic schists in Nagatoro area indicate brittle fracturing of albite. Large albite grains often exhibit cracks filled with potassium feldspar, which was not normally observed in the host schists. Groups of smaller albite grains were found, each distributed lenticularly within quartzose matrix. It is suggested that the non-existence of the albite porphyroblasts can be explained by total fragmentation of once formed albite porphyroblasts.