关键词: 天山, 上地幔, 构造运动, 深部构造, 低波速带

Abstract: Based on deep geophysical data,the geodynamic features of the upper mantle and possible driving mechanism are dicussed through a description of the basic structure of the upper mantle in the Tianshan seismic belt. It is supposed that horizontal squeezing deformation is one of main causes to make the upper mantle lithosphere shortened and thickened in the western Tianshan and the southern Tianshan adjacent to the western Kunlun; whereas in the central Tianshan and parts of the eastern Tianshan next to the southern edge of the Zhungeer basin,besides horizontal squeezing force caused by the plate movement,hot materials in the upper mantle perhaps flow upward to uppermost mantle,even intrude into the lower crust. As horizontal movement,they will influence the teconic activity of brittle medium in crust,in particular,a detachment layer with low velocity near the Moho under lower crust has become an important feature of the deep tectonics of the seismic region. In addition,since the India-Asia continental collision,the cool and solid root in parts of the Tianshan probably departed from original position and fell into upper mantle due to multiple squeezing deformation and thermal convection of small scales.

Key words: Tianshan, Upper mantle, Tectonic movement, Deep structure, Low-velocity zone