Bulletin of the Graduate School of Integrated Arts and Sciences, Hiroshima University. II, Studies in environmental sciences Volume 4
2009-12-31 発行

広島県三段峡地域における節理の形成過程 <論文>

Development of joints in the Sandankyo Area, Hiroshima Prefecture, Southwest Japan <Articles>
Hayashi, Takaya
Nakai, Shinichi
Tsushima, Atsuo
Joints are markedly developed in the acidic welded tuff of the Sandankyo Area, Hiroshima Prefecture, Southwest Japan. Six sets of joint are distinguished in this area, namely N-S set, NESW set, NNE-SSW set, NW-SE set, NNW-SSE set, and horizontal set. It is considered that NESW, NNE-SSW, NW-SE, and NNW-SSE sets of joint were formed by the simple shear due to NE-SW strike-slip faulting with right-lateral shear sense. Detailed microscopy shows that N-S and NE-SW sets of joint contain narrow quartz vein with newly recrystallized muscovite, and cut by the other sets. This suggests that, preceding the NE-SW faulting, WNW-ESE extention accompanied with granite porphyry intrusion formed N-S and NE-SW sets of joint.
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