Early Cretaceous extensional reworking of the Triassic HP-UHP metamorphic orogen in Eastern China

Corresponding to the Early Mesozoic continental subduction between the North China Block (NCB) and the South China Block (SCB), the Tongbaishan-Hong'an- Dabieshan-Sulu massifs are famous for their HP-UHP metamorphism. More than 50% of the HP-UHP Orogenic Belt was significantly reworked by Early Cretaceous extensional tectonics. This Early Cretaceous event with a fast cooling period, at 130-120 Ma, superimposed on the Early Mesozoic HP-UHP orogenic belt and intensively changed the architecture of this orogen. Each individual segment documents different Early Cretaceous extensional structures, namely the central Tongbaishan domain is a metamorphic core complex (MCC) represented by an A-type non-cylindrical antiform; the central Dabieshan domain is a typical Cordilleran-type migmatite-cored MCC; the Southern Sulu UHP domain is a "wedge-shaped" structure exhumed by a simple detachment fault. These late stage extensional structures expose the previous HP-UHP orogenic belt as fragments along the NCB-SCB boundary. The geodynamic setting of this Early Cretaceous extensional tectonics along the HP-UHP orogen is a part of a 1000km-scale crustal extension belt that is widespread in eastern Eurasia continent from Trans-Baikal to the central part of SCB. Convective erosion or delamination of the mantle lithosphere might be considered as a possible mechanism for mantle removal.