【摘 要】
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New isotopic,geochemical and geochronological data justify the widespread occurrence of middle Paleocene to early Eocene (60-53 Ma) post-subduction felsic magma
【机 构】
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Far East Geological Institute,Far Eastern Branch,Russian Academy of Sciences,pr.100-letiya Vladivost
论文部分内容阅读
New isotopic,geochemical and geochronological data justify the widespread occurrence of middle Paleocene to early Eocene (60-53 Ma) post-subduction felsic magmatism across the entire Sikhote-Alin territory (southeast-ern Russia),conform with previous observations in Northeast China,the southern Korean Peninsula,and the Inner Zone of Japan.This igneous activity in East Asia coincided with the reactivation (after tectonic quiescence between-93-60 Ma) of left-lateral strike-slip displacements along the Tan-Lu and Central Sikhote-Alin faults and with the post-60 Ma cessation of subduction/accretion recorded in the Shimanto belt of SW Japan.The Sikhote-Alin post-subduction igneous A-type rocks present diverse mineralogical and geochemical features that suggest interactions of the subducting plate with anhydrous mantle upwelling through slab tears in the continental mar-gin.The middle Paleocene-early Eocene magmatism is not related to subduction but is synchronous with strike-slip tectonics and the termination of accretionary prism development,suggesting a shift in tectonic regime from oceanic plate subduction at a convergent margin to parallel sliding and initiation of a transform continental mar-gin.These new observations are inconsistent with the current tectonic model of 60-50 Ma Izanagi-Pacific ridge subduction beneath East Asian continental margin.
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