Evidence for Permo Triassic collision in Far East Asia: The Korean collisional orogen

摘要

Eclogites from paragneiss in the Korean Peninsula are characterized by a peak pressure assemblage of garnet+ omphacite+quartz+rutile, that is overprinted by multiphase symplectites involving augite, amphibole, orthopyroxene, ilmenite and plagioclase and by a similar high-pressure assemblage with a pronounced absence of the omphacite component in clinopyroxene formed during the peak and orthopyroxene in the retrograde stage. Eclogites were metamorphosed at a minimum pressures of -20-23 kbar at temperatures of __840-1000 °C, equivalent to a crustal depth of __70-75 km, whereas high-pressure granulite in Late Paleozoic rocks underwent metamorphic conditions of__ 18-19 kbarat __950 °C with a minimum crustal depth of __60-65 km. The presence of the eclogites and high-pressure granulite suggests deep-seated subduction of crustal complexes with meta_morphism at different crustal levels. The eclogites were exhumed quickly resulting in near- isothermal decompression. On the other hand, the multistage exhumation of the high-pressure granulites suggests retro-grade overprinting after initial decompression, The similarity of these petrological characteristics, metamorphic conditions and also the regional structural styles with those of the Sulu belt (China) strongly suggests the existence of a Permo-Triassic Alpine-type "Korean collision belt" in Far East Asia. This model provides a better understanding of the paleogeograpic evolution of Permo-Triassic East Asia, including a robust tectonic correlation of the Korean collision belt with the Qinling-Dabie-Sulu collision belt.