Petrotectonics of Sulu-Dabie metamorphic belt,Central and East China

Abstract

The Sulu-Dabieshan metamorphic belt separates the North China and Yangtze cratons. This metamorphic belt is further divided into three petrological-tectonic units which are respectively equivalent to a root zone of an Andean-type magmatic arc (northern Dabie terrane), continental collision suture zone (southern Dabie terrane) and metamorphosed cover sediments of the Yangtze continental margin (Susong metamorphic complex). They are regularly located in the space from north to south in Dabieshan and roughly from northwest to southeast in Sulu region in spite of being strongly reconstructed by the Tan-Lu Fault. The occurrence of the Mesozoic granites and alkali dike swarm are also regular in the space. They occur in the Dabie area, especially in the northern Dabie terrane. These facts support a suggestion that there was subduction of the Yangtze Plate under the North China Plate or obduction of the North China Plate over the Yangtze Plate. Up to now, no evident remnant of old occean crust has been identified. Ultrahigh pressure metamorphic (UHPM) rock-bearing southern terrane is possibly a root of continent-continent collision zone representing a suture between the North China and Yangtze Plates. The fact that UHPM lenses were tectonically emplaced into not-high pressure metamorphic host gneisses indicates deeply subducted rocks uplifted to middle-upper crust after continental collision. The UHPM rocks and related rocks occurring on the surface at the moment suffered at least two stages of uplifting and exhumation.