青藏高原新生代地堑构造研究中几个问题的讨论

青藏高原新生代近南北走向地堑构造是高原现今最为显著的构造现象，对探讨青藏高原构造演化具有重要意义，也是现今高原研究的热点构造问题之一。针对目前地堑构造研究中存在的分布范围、形成时代和形成机制等关键问题，根据笔者新的研究和对以往研究资料综合分析认为，地堑构造广泛发育于喜马拉雅地体、冈底斯地体和羌塘地体，地堑构造形成于14～7Ma。地堑构造是高原地壳南北向强烈挤压短缩隆升之后，构造体制发生转变并在深部热动力学机制作用下快速隆升的结果，地堑构造标志着高原隆升作用由早期挤压短缩机制向晚期深部热动力机制的转变，并非高原隆升达到最大高度重力塌陷的标志。

A Discussion on Several Problems Regarding to the Cenozoic Grabens in the Qinghai-Tibet Plateau

The approximate N-S trending grabens formed in east-west extension are the most distinct structures of the Qinghai-Tibet Plateau. The study of grabens will provide important evidences for the Cenozoic evolution of the Qinghai-Tibet Plateau, so it's a hot spot of tectonics studies. Spatial distribution, ages, forming mechanisms and relationship with the uplifting of the plateau are key problems of graben study today. Base on the new field works in Shuanghu and Tuotuohe regions of central Tibet by us and the datum have been obtained by other researches on the grabens. We proposed that, the graben structures are distributed in the most part of plateau; including Himalayan, Gangdese and Qiangtang block. The grabens were forming in 14-7 Ma. And the N-S extensional structures of Tibet is the result of the Plateau rapid uplift as a whole caused by deep underground dynamics after the crust shortening deformation of the Plateau, but not the result of gravitational collapse that followed the plateau uplifting to the highest elevation. The formation of the grabens indicate that the plateau uplifting mechanism changed from early compressive stage to the late deep theremo-dynamic mechanical stage.