TERRAIN SUBDIVISION OF THE NORTHERN QINGHAI-XIZANG (TIBET) PLATEAU AND ITS TECTONIC EVOLUTION
CHEN BING-WEI;WANG YAN-BIN(Insititue of Geology, Chinese Academy of Geological Sciences , Beijing 100037 )ZUO GUO-CHAO (Geologic Institute, Geologic & Minerals Bureau of Gansu Province,Lanzhou 730000)
Applying the tectonostratigraphic-terrain analysis,we carried out an anatomical study on the geological structure of a strip (900 km long and 100 km wide )along the Golmud-Ejin Qi Geotraverse.Based on existing data, we recognized three tectonic units consisting of terrain groups:from south to north, the Qinghai-Xizang (Tibet) terrain group, Guxiyu terrain group and Junggar-South Mongolia terrain group. These groups underwent rifting and dispersing in the Early Paleozoic and amalgamation in the Late Paleozoic. Since the Mesozoic, there have been two stages of intense compression (one southward and the other northward) in the period of intracontinental activity, leading to the crustal deformation and shortening that gave rise to the present tectonic framework of the northern Qinghai-Xizang (Tibet) plateau and its adjacent regions.