四国中央部，笹ヶ谷地域における秩父帯北帯の地質構造

概要

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The Sasagatani fault in central Shikoku was considered to be a tectonic boundary betweenthe Sanbagawa high-P/T metamorphic belt and the Chichibu non-high-P/T belt. Metamorphicminerals of the greenstones around the Sasagatani fault are examined. Alkali amphibole, alkalipyroxene, actinolite, stilpnomelane and pumpellyite are found not only on the north side of thefault, but also on the south side. Strata around the Sasagatani fault have undergone thepumpellyite-actinolite facies metamorphism. Thus, the Sasagatani fault is not an upperboundary fault of the Sanbagawa metamorphic rocks.The Nanokawa thrust occurs in the Jurassic accretionary complexes of the NorthernChichibu Terrain in the Sasagatani Area. The greenstones of the hanging wall of the thrust haveundergone the pumpellyite-actinolite facies metamorphism, whereas those of the footwall haveundergone the prehnite-pumpellyite facies metamorphism. The Nanokawa thrust is a largeoverthrust, which has a different metamorphic grade between the hanging wall and footwall.The thrust is probably a southern boundary of the Jurassic accretionary deposits which haveundergone the Sanbagawa metamorphism.
徳島大学総合科学部の論文