Study on the intracontinental deformation of the Mian-Lue suture belt,western Qinling
西秦岭勉略带陆内构造变形研究

The Mian-Lue suture belt in western Qinling orogenic belt, which is formed from the paleo-tethys ocean subducted north-direction, is the latest assemble belt between the north and south China plate. The subducted-collisional process of this main suture belt is charactered by a series of ductile thrust-nappe structures. This process formed a complex tetonic belt imbricated with different tetonic slabs, such as the Predevonian slab, the Devonian-Carboniferous slab and the ophiolitic melange slab, etc. And the collisional process was continuous from 245Ma to 230Ma. Recently, the author studied the ductile and brittle left-lateral shear deformation in the Mian-Lue suture belt, and indicated that the timing of the sinistral shear deformation along the orogenic belt is 223±2Ma. This age consistents with the initial age (225Ma) of the post-collisional tectonic environment that determined by the post-collisional granite. And we consider that the ductile strike-slip shear deformation is the earliest intracontinental deformation process. It means that the collision between the Yangtze and north China plate switched to the intracontinental deformational stage rapidly. And the mainly deformational mode is lateral slip displacement along the orogenic belt. In addition, the growth of the brittle left-lateral strike-slip faults along the orogenic belt in the Mian-Lue suture belt, indicates the process along the orogenic belt from the deep earth to shallow crust is uniform. Therefore, the continental collision quickly switches to intracontinental deformation with slipped displacement after the direct collision. This displacement represents the slip between collisional continents relatively or the lateral extrusion of the intensively deformationed part of the collisional belt along the orogenic belt. This mode reduced the shortening and thickening of the crust within the collision.