Oblique collision and convergence factor on the northern margin of the Qinling orogenic belt

Abstract：The Luonan-Luanchuan fault zone on the northern margin of the Qinling Mountains is a convergence belt between the North China plate and Qinling orogenic belt with the natures of SW-NE-directed subduction and sinistral strike-slip motion. It shows an association style of imbricate structure and duplex structure. The structures of different natures on the northern margin of the Qinling Mountains make up a regular pattern, with their distribution direction and kinematic mode coinciding with the kinematic features of ｔｈｅ convergence plate. The results of deformation analysis indicate that the deformed rocks in the area are mainly the product of the middle and upper crust. The triaxial ratio of rock finite strain is X∶Y∶Z = 8.86∶4.32∶1 and the strain ellipsoid is flat-ellipsoidal. The convergence factors are as follows： in the Luonan area the direction of plate convergence is 22° and the angle between the plate convergence direction and plate boundary is 73° and in the Luanchuan area the direction of plate convergence is 31° and the angle between the plate convergence direction and plate margin is 82°. This shows ｔｈａｔ the collision and convergence between the Qinling orogenic belt and the southern margin of the North China plate have the typical features of oblique convergence.