喜马拉雅─祁连山地壳构造与大陆─大陆碰撞过程

THE CRUSTAL STRUCTURES FROM HIMALAYA TO QILIAN AND ITS IMPLICATIONS FOR CONTINENT CONTINENT COLLISION PROCESS

在青藏高原，利用远震波形及演所得的Moho界面深度，其横向变化很大．在班公缝合带附近，Moho界面出现10余公里的错断．羌塘块体的Moho界面向北倾斜，而柴达木和巴颜喀拉的Moho界面向南倾斜．利用近震Pn的走时验证远震波形反演所得的Moho界面深度，两者的结果十分吻合．综合近来地球物理观测的结果。我们得到喜马拉雅─祁连山的地壳构造图，它贯穿印度─欧亚的碰撞带和中生代的陆─陆碰撞带．特提斯喜马拉雅和拉萨块体的地壳是由多个双向冲断层所组成，它们可以解释为在不同时期中，印度次大陆曾经数次向拉萨块体地壳挤入，而且羌塘块体的地壳也向拉萨块体的地壳挤入．测量冲断层的水平长度，可以定量估算自50Ma陆─陆碰撞以来，印度次大陆和羌塘块体向特提斯喜马拉雅和拉萨块体地壳挤入的长度．

Crustal structures from Himalaya to Qilian in west China were compiled by using the results from the vertical reflections, wide-angle reflections, refractions and receiver functions. This profile of crustal structures crosses both the Eocene collision zone of India - Eurasia and older Mesozoic collision zones. The strong inclined reflection interfaces of INDEPTH underneath Gangdese were compared with the wide -angle reflection profile. They exhibit the same characteristics. Similar to the MHT in INDEPTH vertical reflection profile, the north -dipping and south -dipping wide angle reflections in Lhasa block are interpreted as the main crustal thrusts extended respectively to the ground surfaces at the near south to Yaruzampbo suture and Tangula. It shows that both the india crust and the crust north to Tangula have been penetrated into Tethyan Himalaya and Lhasa block. The surficial thrusts and thermal chronological results were incorporated to construct a logical model of India-Eurasia collision and process of crustal shortening. The total crustal shortening due to the penetrations from india and north Qiangtang to Tethyan Himalaya and Lhasa block were estimated.