The Study On Metamorphic And Deformation Characteristics Of The Main Fault Zone In The Tongbai Orogen

Tongbai orogenic belt is between the Yangtze Plate and North China Plate, east of Qinling-Dabie orogenic belt.Westward acrossing the Nanyang basin it connect with the Qinling orogenic belt,to the east,it connect with the Dabie orogenic belt directly. There developed several major fault zones in Tongbai orogenic belt, which are the productions of different stages in the evolution of orogenic belts, and they represent the whole process of the orogenic belts.There must exist certain inner links in the tectonic deformation between the fault zone and the orogenic belts.The study of the fault zone can provide reliable basis for the evolution of the orogenic belt.Considering the outcropping situation, deformation of the fault belt, and the work-load of this paper, we chose two representative fault zones separately from the south and north:the south Yindian-Malong fault zone, the north Dahe-Guxian fault zone. Through our detailed studies of the tectonic deformation, we calculated the kinematics characteristics; the strain of rocks in the fault belt is mainly strong strength; simple shear; the deformation temperature is about 400 ℃,the metamorphic phase is epidote amphibolite facies; the paleostress direction is NNE-SSW, the shear displacement distance is 860-1000m;and the timing of shearing is during middle Jurassic to early Cretaceous. All the above analysises provide important information for understanding the tectonic evolution of Tongbai orogenic belt.