R6: Plutonic rocks, volcanic rocks and subduction factory

[R6P-04] Genesis and development processes of fractures in granite: petrographic indicators of hydrothermal alteration

*Takashi Yuguchi¹, Eiji Sasao², Yuya Izumino¹ (1. Yamagata Uni. Sci., 2. JAEA)

Keywords:Macroscopic fracture, Microvoid, Alteration indicator, Biotite chloritization, Toki granite

This study analyzes the relationships among alteration indicators, areal microvoid fractions in altered minerals, and macroscopic fracture frequencies in the Toki granite, central Japan, to establish the genesis and development processes of fractures in granite. Petrographic alteration indicators as innovative methods are proposed to evaluate the extent of hydrothermal alteration and fracture frequency within granites. Samples with high macroscopic fracture frequencies correspond to a high number of areal microvoid fractions and large alteration indicators.