Metamorphic evolution of the Susunai metabasites in southern Sakhalin, Russian Republic |
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| Authors: | M SAKAKIBARA H OFUKA G KIMURA H ISHIZUKA S MIYASHITA M OKAMURA & O A MELINIKOV |
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| Institution: | Department of Earth Sciences, Faculty of Science, Ehime University, Matsuyama 790, Japan (email:;), Token Geotekku Co. Ltd, Tohoku branch, Sendai 981, Japan,;Department of Earth Sciences, CIAS, University of Osaka Prefecture, Sakaki 593, Japan,;Department of Geology, Faculty of Science, Kochi University, Kochi 780, Japan,;Department of Geology and Mineralogy, Faculty of Science, Niigata University, Niigata 950–21, Japan,;Institiute of Marine Geology and Geophysics, Far East Branch, Russian Republic |
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| Abstract: | The Susunai Complex of southeast Sakhalin represents a subduction-related accretionary complex of pelitic and basic rocks. Two stages of metamorphism are recognized: (1) a local, low- P / T event characterized by Si-poor calcic amphiboles; (2) a regional, high- P / T event characterized by pumpellyite, actinolite, epidote, sodic amphibole, sodic pyroxene, stilpnomelane and aragonite. The major mineral assemblages of the high- P / T Susunai metabasites contain pumpellyite+epidote+actinolite+chlorite, epidote+actinolite+chlorite, epidote+Na-amphibole+Na-pyroxene+chlorite+haematite. The Na- amphibole is commonly magnesioriebeckite. The Na-pyroxene is jadeite-poor aegirine to aegirine-augite. Application of empirically and experimentally based thermobarometers suggests peak conditions of T =250–300 °C, P= 4.7–6 kbar. Textural relationships in Susunai metabasite samples and a petrogenetic grid calculated for the Fe3+-rich basaltic system suggest that pressure and temperature increased during prograde metamorphism. |
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| Keywords: | metabasites prograde metamorphism pumpellyite-actinolite facies Sakhalin Susunai Complex |
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