A preliminary 3D model of lithospheric structure in China

Abstract：According to rheological behaviors of the lithosphere, the authors have divided the lithosphere of China into three layers. i.e., elastic upper crust, plastic lower crust and lithospheric mantle, and pointed out that they have different structures and complicated relationships. In the Xinjiang area, four basins and three ranges were formed by thrusting and overlapping in the upper crust, overlain on a series of EW-striking antiforms and synforms of the lower crust. The uplifting of the central part of the Tibetan plateau was as a whole caused by the hydraulic pressure due to the partial melting of its lower crust and lithospheric mantle, but the uplifting of the border parts is of the differential nature. In North China, the upwelling of ashenosphere material destroyed lithospheric mantle and formed a mushroom cloud structure in which the new-born mantle and the residue mantle existed side by side, and grabens occurred in the elastic upper crust. There exists no evidence for the subduction of the Pacific plate under the continent of China, except for things in a limited area of northeast China. The violent deformation of eastern China was produced by the upwelling of ashenospheric materials instead of by the subduction of the Pacific plate. So the tectonic forces nowadays in China constitute a dual system which includes the subduction of the Indian plate in the west and the uplifting of the ashenosphere in the east. The boundary of the two different tectonic forces is the north-south seismic belt. To the west of the north-south seismic belt, the lithosphere is under a compression regime, whereas to the east of the north-south seismic belt, the lithosphere is under an extensional regime. The reason for the seismicity of North China is that the elastic crust of this area was thinned by strong geothermal activity, which resulted in the considerable lowering of the elastic limit.