Mass transport in a fault zone; Effects of fracturing and host rock lithology

Niwa, Masakazu   ; Kurosawa, Hideki; Mizuochi, Yukihiro*; Tanase, Atsushi*

Fault zone development has the potential to impact regional groundwater flow. Groundwater flow plays an important role in mass transport and nuclide migration. Thus understanding mass transport along fault zones is one of the major subjects for topical issues such as geological disposal of radioactive waste. In this study, we analyzed whole-rock chemical composition of fault rocks from well-studied outcrops of the Atera Fault in central Japan. We particularly focused on REE, U, Th, as an analogue of radionuclides included in high-level radioactive waste. As a result, it is suggested that heterogeneity of host rock lithology presented as mixing of fragments of mafic volcanic rocks in the fault core has a great influence on the material transport in the fault zone, as well as water-rock interaction and clay mineral formation caused by fracturing.