INJECTION VEINS OF CRUSHING-ORIGINATED PSEUDOTACHYLYTE AND FAULT GOUGE FORMED DURING SEISMIC FAULTING

This paper describes the injection veins of crushing-originated pseudo tachylyte and fault gouge formed along the Iida-Matsukawa fault in gra nitic cataclasite, southern Nagano Prefecture, central Japan. The pseu dotachylyte, which shows a dense and aphanitic appearances, and fault gouge occur as simple veins (fault vein) along the main fault plane an d as complex network veins (injection vein) in the neighboring catacla site. Locally, the injection veins of pseudotachylyte and fault gouge can be traced back to the fault veins. Powder X-ray diffraction patter ns and petrological analysis indicate that both of the pseudotachylyte and fault gouge consist entirely of fine-grained angular clasts and t hat the pseudotachylytes and fault gouges have a similar X-ray diffrac tion patterns with that of the host granite. The similarity of chemica l compositions and distribution patterns of grain size also show that the injection veins of pseudotachylyte and fault gouge have the same s ource material as that of fault veins. Field occurrences and petrologi cal characteristics strongly suggest that the injection veins of pseud otachylyte and fault gouge formed during seismic faulting by a rapid i ntrusion and fluidization of crushed fine-grained materials generated in the shear zone in a gas-solid-fluid system.