Study On Deformation Of Faults In Batang Region In Western Sichuan

Batang area,in Western of Sichuan province,is an important component part of the Eastern Tethyan tectonic belt,which is the subject position of the Jinsha River suture zone located in the central part of the Jinshajiang fault zone,eastern of Sanjiang orogenic belt,western of the Yangtze plate and southwestern margin of Songpan-Ganzi orogenic belt. The study on deformation including geometry, kinematics and dynamics of faults in Batang area, and the geological evolution of the region play an importance role in understanding the formation and evolution of the Songpan- Ganzi orogenic belt and Yangtze plate.The Batang area fracture include in this paper main refers to Moshi-Batang fault,Sama-Sangqu fault,Changgai-Namakuo fault and Chalong-Ranbu fault. The Batang fracture is a dextral strike slip active fault,which cuts the Jinshajiang fracture zone and formed slightly later than the Jinshajiang tectonic belt. The author systematic described the Batang fracture geometry characteristics by using the structural analysis theory,studied the tectonic kinematics and dynamics of the fracture and deeply discussed the fracture tectonic deformation period in study area and regional tectonic evolution.This paper argues that the Batang fracture have experienced at least 5 periods of tectonic deformation since the late Indosinian. The first period occurred in the late Indosinian stage and experienced the NEE-SWW extrusion,during which formed huge lenticular breccias of the Moxi-Batang fault,structural lenticles of the Shama-Sangqu fault and tectonic breccias of the Chalong-Ranbu fault. The second deformation period mainly manifested that the early sinistral movement of the Moxi-Batang fault with the NNW-SSE direction of the principal stress during the late Indosinian movement. The third stage occurred in the Yanshanian stage,the maximum principal stress is NEE-SWW direction,under the extrusion the Sama-Sangqu fault zone formed vertical striation. The fourth deformation period showed the overall dextral movement of the Moxi-Batang fault,which occurred in the Himalayan stage and formed at the nearly E-W direction?s maximum principal stress. The fifth deformation period occurred in Himalayan stage,with the nearly S-N to extrusion(the ?1 direction is steep),formed the fracture zones with the broken rock surrounding the Moxi-Batang fault and the normal faults due to the tensile stress of local area.It is the multi period and multi direction of the regional stress that created the complex structure features of Batang fracture.