四国中央部伊野地域における秩父帯北帯の名野川衝上断層周辺の地質構造

概要

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The Nanokawa thrust occurs in the Jurassic accretionary complexes of the Northern Chichibu Terrain in the Ino Area， Central Shikoku. Along the thrust，greenstones and pelitic semi-schists are thrust over chaotic formations，sandstones and greenstones. The strata of the hanging wall of the thrust dip gently and are slightly folded，whereas those of the footwall dip steeply to the north. Metamorphic minerals of the greenstones of the hanging wall and footwall of the Nanokawa thrust are examined. The greenstones of the hanging wall contain alkali amphibole， alkali pyroxene， stilpnomelane and pumpellyite， and have undergone the pumpellyite-actinolite facies metamorphism. On the other hand， those of the footwall contain prehnite and pumpellyite， and have undergone the prehnite-pumpellyite facies metamorphism. The Nanokawa thrust is a large overthrust， which has a different metamorphic grade between the hanging wall and footwall. The Nanokawa thrust， which runs to the north of Shirakidani limestone body in Central Shikoku， and to the north of the Torigatayama limestone body in Middle West Shikoku， is probably a southern boundary of the Jurassic accretionary deposits which have undergone the Sambagawa Metamorphism.