Geochronology Of The Deformed Dikes From Feidong Segment Of The Tan-Lu Fault Zone And Its Tectonic Significance

The Feidong segment of the Tan-Lu Fault Zone is located in south Zhangbaling Massif between the Dabieshan and Sulu areas. A large-scale NNE-striking sinistral ductile shear belts are exposed in Xiwei and Taohuayuan areas in this segment. There are two phases of deformation in Taohuayuan ductile shear belt, the dikes deformed in D2 event. And a low angle ductile normal fault near the strike-slip ductile shear belts at Xiwei areas, represents the extensional tectonics. We study the tectonic deformation features of the strike-slip ductile shear belts and the normal fault, as well as the LA-ICP-MS zircon U-Pb geochronology, major and trace elements analysis of the dikes in the shear zone. The intrusion age of dikes range from 133 Ma to 125 Ma, related to the magma activity of the same period. The dating result of undeformed dike demonstrates that the low angle ductile normal fault ended before 126 Ma, and the dating of deformed dike imply the strike-slip movement of the Tan-Lu Fault Zone took place after 125 Ma. According the regional tectonic analysis, this strike-slip movement could be occurred in the late Early Cretaceous. Therefore, the extensional activities of Tan-Lu Fault Zone started as early as 130 Ma, and the normal faulting did not last during the Early Cretaceous. Lithosphere thinning and craton destruction might cause the extensional activities, and the strike-slip movement correlated with the subduction of Pacific plate.