Detrital garnet and chromian spinel chemistry of Permian clastics in the Renge area, central Japan: Implications for the paleogeography of the East Asian continental margin

摘要: Abstract The Japanese Islands comprise a complex assembly of allochthonous continental shelf deposits and subduction-related accretionary complexes. paleogeography Permian clastic strata was restored based on chemical analysis detrital garnets chromian spinels, which are useful for provenance discrimination. Detrital garnet assemblages from the rocks in Japan characterized by grandite-rich assemblage grandite-poor assemblage. Most trench-fill complexes contain assemblage, is composed spessartine-rich almandine, grossular-rich rarely pyrope-rich commonly associated with spinels volcanic rock fragments. It suggested that sediments were derived arc non-calcareous contact-metamorphic along North China Block, where pelitic granulites including almandine extensively exposed northern margin. Ophiolite high-P/T schist also crop out central part Analyses suggest calc-alkaline association calcareous skarn deposits. Sediments lack ophiolite detritus. A overlain rocks. This indicates detritus increased supply extended through fore-arc basin to trench. northernmost Renge area yield particularly uvarovite-rich andradite back-arc basalt, very similar composition Japan. Hence, we conclude existed region subduction zone Block.