青藏高原北缘深部地壳结构特征及其形成机制探讨

柴达木盆地－祁连山地区位于青藏高原北缘，同青藏高原主体一样，该区具有多层地壳结构特征，并普遍出现壳内低速层，地壳厚度是华北及华南地区的2倍以上。其形成可能与地壳的横向挤压缩短及幔源物质的底侵作用有关。随着底侵作用增强，地壳厚度加大，岩石圈厚度则越趋于减薄，地壳上部表现为拉张，下部发生壳幔深熔及幔源流体的交代作用，从而导致了地壳低速层，地热和浅源地震的发育。同时，这也是青藏高原出现热壳冷幔的原因之一。

The Crustal Structure of the Northern Margin of Qinghai-Tibet Plateau and Its Genetic Analysis

Qaidam basin-Qilian mountain is situated on the north margin of Qinghai-Tibet plateau. Like the main part of the plateau, there commonly exist a muti layer crustal structure and the low velocity layers. The crust thickness of the region is twice more than that of northern and southern China. It may be caused by the transverse compressive shortening and the upper mantle underplating .With the crust underplating getting strong, the thickness of the crust increase , and the lithospheric thickness tend to decrease. A tension condition in the upper crust and the deep melting or the mantle derived fluid replacement in the lower crust exist, which bring on the low velocity layers,terrestrial heat and shallow earthquake in the crust . It is also the reason showing hot crust and cold mantle in Qinghai-Tibet plateau region.