Sandstone Composition in Mobile Belt : An Example from Japanese Islands

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The following summary of the research results is obtained.1. Sandstone and sands from the Cretaceous Hidaka Supergroup, Jurassic of the northern Kitakami Belt, Jurassic Tanba Group, Cretaceous-Paleogene Shimanto Supergroup, Permian of Ultra-Tanba Zone, Triassic of the Maizuru Belt, Cretaceous Izumi Group, Permian of the Chichibu Belt, core samples from thenkai Trough and others were studied by means of the chemical analysis. The studies have revealed chemical features of clastics from the staple basins in Japan, and a distinctive character of chemical composition of sandstones in each geologic time. The studies also have resulted in the relation between the type of magmatic arc and chemical features of sandstone.2. Modal analysis of sandstones from many basins has revealed the character of times on sandstone composition.(1) Sandstones from the Permian in the inner belt of southwest Japan and in the Chichibu Belt belong predominantly to a quartz-deficient intermediate volcanic sand petrofacies.(2) Sandstones from the Jurassic in the Oshima Belt, northern kitakami Belt, Mino Belt, Tanba Belt and Chichibu Belt belong to a quartz-rich granitic sand petrofacies.(3) Cretaceous sandstones show regional variation in modal composition. Sandstones from such basins situated on the Eurasian margin as Shimanto, Yezo and Hidaka belong to quartz-rich to quartz-deficient, acidic to intermediate volcanic sand petrofacies.