Abstract
Ductile to brittle fault rocks including pseudotachylyte are narrowly distributed along the NE-SW trending Asuke Shear Zone in the Inagawa granite bodies of the Ryoke Belt, Chubu region, SW Japan. The Asuke Shear Zone is composed of many small-scale shear zones with left-stepping en echelon arrangement (P shear orientation for sinistral shear zone). Kinematic indicators and stretching lineations in mylonite and foliated pseudotachylyte of the small-scale shear zones indicate sinistral - extensional shear. These lines of evidence suggest that the Asuke Shear Zone has thicken under transtensional tectonic regime. The existence of mylonitized pseudotachylyte and mylonitized cataclasite, and fractured mylonite suggests that the major deformation along the shear zone took place in cataclastic-plastic transition regime. Pseudotachylyte fault veins tend to generate along the P shear whereas cataclasite along the Y and R1 shear surfaces. This result is explained by that frictional fusion preferentially occurs along mesoscopically transpressional fault surface where the rate of heat production per unit area is relatively high.
