The Ophiolites in the Outer Zone of Southwest Japan and their development mechanism

The main results by this studiesmainly using the automatic X-ray fluorescence analyser(system 3080), are as follows；For 61 samples of cherts, siliceous mudstones，mudstones and tuffs from the Ogawa belt and the Nishiyama II belt in the Togano Group (middle -upper Jurassic of the Chichibu Southern Belt, we analysed chemically：11 major and 9 minor components. As a resultbecame clear that the cherts of the Ogawa belt is of pelagic in origin and those of the Nishiyama2. bulk chemical compositions and relic clinopyroxene化学the most metabasalts from the Shimanto Belt in Kyushu, Shikoku and Kii Peninsula，show much closer to those of the ocean floor basalt(the present-day abyssal tholeiite). On the other贪污,the relic clinopyroxenes in the metadoleritic rocks have kaline magma affinity. Conclusively，the fact that thetholeiitic and alkaline rocks are mixed within the mudstone-melanges as exoticbodies contiguous to each other，indicates a complicated accretion process of the Shimanto Belt.3. the serpentinites in theKurosegawa Tectonic Zone of eastern part of Kii Peninsula show processes of development as follows；(1) rocks serpentinized once at about 300 C.(2)他们heated at higher temperature ofabout 400 - 500 C and metamorphosed olivine and clinopyroxene were formed.(3)他们metamorphosed again to the serpentinized rocks during serpentinite-melange development.4. the MikabuOphiolites at Kichijou-san(Aichi Prefecture) are intensively sheared and broken. As a result，they consist of high P/T and high T/P metamorphic rocks and might been mixed each other bycomplicated process of melange development.5. The meta-basic rocks in The sheared mudstone matrix ofthe Kamuikotan Ophiolite Belt consist of calc-alkalinetholeiitic and alkaline rocks.他们可以混合复杂tectonic process。

The main results by this studies, mainly using the automatic X-ray fluorescence analyser(system 3080), are as follows;1. For 61 samples of cherts, siliceous mudstones, mudstones and tuffs from the Ogawa belt and the Nishiyama II belt in the Togano Group (middle - upper Jurassic) of the Chichibu Southern Belt, we analysed chemically: 11 major and 9 minor components. As a result, it became clear that the cherts of the Ogawa belt is of pelagic in origin and those of the Nishiyama II belt is of hemipelagic.2. The bulk chemical compositions and relic clinopyroxene chemistry of the most metabasalts from the Shimanto Belt in Kyushu, Shikoku and Kii Peninsula, show much closer to those of the ocean-floor basalt(the present-day abyssal tholeiite). On the other hand, the relic clinopyroxenes in the metadoleritic rocks have alkaline magma affinity. Conclusively, the fact that thetholeiitic and alkaline rocks are mixed within the mudstone-melanges as exotic bodies contiguous to each other, indicates a complicated accretion process of the Shimanto Belt.3. The serpentinites in the Kurosegawa Tectonic Zone of eastern part of Kii Peninsula show processes of development as follows;(1) this rocks were serpentinized once at about 300゜C. (2) They heated at higher temperature of about 400゜ - 500゜C and metamorphosed olivine and clinopyroxene were formed. (3) They were metamorphosed again to the serpentinized rocks during serpentinite-melange development.4. The Mikabu Ophiolites at Kichijou-san(Aichi Prefecture) are intensively sheared and broken. As a result, they consist of high P/T and high T/P metamorphic rocks and might have been mixed each other by complicated process of melange development.5. The meta-basic rocks in the sheared mudstone matrix of the Kamuikotan Ophiolite Belt consist of calc-alkaline, tholeiitic and alkaline rocks. They might be mixed by complex tectonic process.