Upper mantle convection beneath northwest China and its adjacent region driven by density anomaly

摘要

We assume that the density anomalies,which are transformed from seismic tomography data,are corresponding to temperature distribution in a convective mantle. We take density anomalies as the driving force for mantle convec-tion and solve the basic equation with given boundary conditions in a wave-number domain by using the FFT arithmetic. Using the physical model of upper mantle convection and the seismic tomography data supplied by XU et al,we calculated upper mantle convection beneath northwestern China and adjacent region. The flow patterns in the upper mantle show that there are upward and divergent flows in the basin regions,such as Tarim,Qaidam,Junggar and Kazakhstan,where the lithosphere is thin. There are downward and convergent flows in the mountain regions,such as Tianshan,Kunlun and Qilian,where the lithosphere is thick. In addition,because of the divergent flow under the Tarim Basin the upper mantle material in this region is driven southward to the north part of Tibetan Plateau and northward to Tianshan Mountain. Maybe,it is one of the reasons for the recent uplift of the Tianshan Mountain.