The geological evidences for the tectonic transition in late Mesozoic in North China

Abstract：There were two intensive igneous activities in North China. The early stages of magmatism is charecteristized by Jurassic high-Sr quartz diorites and the latter stage is charateristic of Cretaceous shosholites. These rock series represent two different geological setting of crust thichenning and lithospheric thinning, respectively. The transition of two igneous activities occurred at about 130 Ma. The development of Cretaceous alkaline rocks in North China shows that in the lithosphere extension occurred in Cretaceous. This conclusion can also been verified by seism profile, the ages of extensional and compressional structures, the ages of metamorphose core complexes, strike-slip ages of Tanlu fault zone. The lithosphere extension took place in the Early Cretaceous, and the boundary of Late Jurassic-Early Cretaceous is the tectonic turnning point in North China.