横断山区地质构造分区

DIVISION OF GEOLOGIC STRUCTURE IN THE HENGDUAN MOUNTAINOUS REGION

位于青藏高原东南部的横断山区,是我国东部环太平洋区与西部古地中海区间的交接过渡地带,也是我国地质结构最为复杂的一个区域。作者根据1981—1985年在当地考察资料,将本区分出5条具洋壳性质的强变形构造带,2块具陆壳性质的地块,它们相间并列。文章论述了各条块的发育特征及区域演化历史。

The Direction of structural lines coincid with the relief in the Hengduan Mountainous Region. It turns abruptly from W-E in the northwest to S-N in the middle part and NW in the southeast. It show a shape of 'S' con-verese. This region is located to the west of Yangtze massiff and the south of Kunlun-Qinling tectonic zone on the geology, it is conneced with Indosinian and SE Asia in the south, and with Qinghai-Xizang Plateau in the west on the tectonic. This region is located between circum-Pacific and Paleotethys domain. It is the most complex region in the geologic structure of China.Based on nature of the earth crusts, i. e., oceanic or continental crusts, this region may be divided into following tectonic units; Bayankala-Songpan terrene, Ganzi-Litang structural zone, Yidun island arc zone, Zhongzan block, Jinshajiang structural zone, Qamdu block and Nujiang structural zone.There are all ophiolite finded in the Ganzi-Litang, Jinshajiang and Nujiang structural zones. They are distincted several zones of oceanic crust.Tectonic development in this region could be divided mainly into stages as follows, it was same a region of shallow water of eastern Tethys in the early Paleozoic. Crust broke and drifted awey from Yangtze massiff because of tenso-shearing during the late Paleozoic. Crust converged and collided agian because of Press-shearing from Permian to Triassic. After Triassic continents were formed and gentle uplifting. Qinghai-Xizang Plateau was formed because it has been uplifting fast since Quaternary, same time valley and range regions were formed as prensent along a structural direction.