Rapid exhumation and slow cooling of ultrahigh-pressure eclogite in the North Dabie complex zone, central China
北大别超高压榴辉岩的快速折返与缓慢冷却过程

Metamorphic petrology of ultrahigh-pressure (UHP) eclogites was studied in the North Dabie complex zone (NDZ), central China. The results suggest that the eclogites underwent UHP and HP eclogite-facies metamorphism, and subsequent HP granulite-facies overprinting and amphibolite-facies retrogression. The symplectites formed by HP granulite- and amphibolite-facies metamorphism and the occurrence of compositionally zoned minerals such as garnet and clinopyroxene show a rapid exhumation of UHP eclogites in the region, whereas their metamorphic temperature and pressure conditions at various stages and ages indicate they experienced a relatively slow cooling process after peak UHP metamorphism. This may be one of major reasons to be rarely preserved coesite and related evidences for UHP metamorphism in the rocks from the NDZ. In addition, these provide further evidence on a multi-slice successive exhumation model that the detachment and decoupling occurred at variable depths within subducted continental crust and multi-slices of the UHP rocks were successively exhumed during the continental collision between the South China and North China blocks.