(英) Nanokawa thrust of the Northern Chichibu Terrain in Middle West Shikoku (日) 四国中西部,秩父帯北帯の名野川衝上断層
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(英) In the Northern Chichibu Terrain in Middle West Shikoku, the Nanokawa thrust occurs in the Jurassic accretionary complexes. Along the Nanokawa thrust, greenstones and pelitic semi-schists of the Nakatsuyama Unit are thrust over chaotic formations, sandstones and greenstones of the Niyodogawa Unit. The strata of the Nakatsuyama Unit dip gently and are slightly folded, whereas those of the Niyodogawa Unit 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 grades between the hanging wall and footwall. The Nanokawa thrust extends toward west to the north of the Torigatayama limestones. The thrust does not extend to the Kurofujigawa thrust, which occurs near the Mikabu greenstones. (日) 四国中央部,名野川地域の秩父北帯で,名野川衝上断層の位置を明らかにするために,緑色岩類中に含まれる変成鉱物が検討された.名野川衝上断層の上盤には,アルカリ角閃石,アルカリ輝石,アクチノ閃石,パンペリー石などの変成鉱物が含まれるのに対し,下盤には,ブドウ石,パンペリー石が含まれ,前者はパンペリー石-アクチノ閃石相,後者はブドウ石-パンペリー石相の変成作用を示している.この衝上断層の上盤の地層は,ゆるやかな向斜・背斜を作っているのに対し,下盤は高角の構造をとっていることが明らかにされた
Akihiro Murataand前川 寛和 : Nanokawa thrust of the Northern Chichibu Terrain in Middle West Shikoku, Natural Science Research, Faculty of Integrated Arts and Sciences, The University of Tokushima, Vol.21, 65-75, 2007.
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