Petrologic study on the Paleozoic ophiolites and high-P metamorphic rocks in Japan (especially in the Joetsu belt)

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Ishiwatari & Tsujimori (2003) synthesized the time-space distribution of ophiolites and high-P metamorphic rocks in Japan and Russian Primorye, and concluded geological continuity between the two areas before the Miocene opening of the Sea of Japan. They further postulated a hypothesis that the Japanese Late Paleozoic ophiolites and high-P metamorphic belts extend to the west to the Chinese Sulu-Dabie collision zone via Yaeyama (western Ryukyu Islands), detouring Korea. Ishiwatari, Sokolov & Vysotskiy (2003) found that ophiolites in Japan and Russian Far East are characterized by common occurrence of highly depleted harzburgite and opx-type cumulate, and postulated that the Mariana-type ophiolite (and blueschist) formation and the Nankai-type accretion of sediments repeated one after another through the Phanerozoic time, resulting in the multiple ophiolite belts. Ichiyama & Ishiwatari (2004) studied the Yakuno ophiolite in the Yakuno Town area, and concluded that this ophiolite formed … More in a back-arc environment, not in an oceanic plateau as postulated by some geologists. Ishiwatari & Ichiyama (2004) compiled geologic and petrologic data about ultramafic lavas and the Alaskan-type intrusive rocks occurring in the accretionary complexes in Japan, Russian Primorye and Sakhalin, and northeastern China, and concluded that these peculiar rocks may have formed by a superplume magmatism of 2,000 km diameter which hit subductien zones in the East Asian margin in the Jurassic time, though some of them represent Permian superplume activity in an oceanic environment. Ichiyama & Ishiwatari (2005) reported a HFSE-rich picrite (meimechite) sills and hyaloclastites intercalated in the Late Permian chert sequence overlying a huge limestone-greenstone body of Mt. Funafuse-yama in the Mine belt, a Jurassic accretionary complex. They find that the magma resembles ultramafic magmas in the Permian Siberian LIP, and postulated a superplume-related, HIMU-source origin. Shimizu & Ishiwatari (in preparation) studied Late Paleozoic high-pressure metamorphic rocks (glaucophane schist and pelitic schist) of the Joetsu belt, and concluded that the belt consisted of a combination of high-P and medium-P metamorphic belts. Less