中国大陆印支碰撞造山系及其造山机制

Indosinian collision-orogenic system of Chinese continent and its orogenic mechanism

古特提斯洋盆的闭合导致了诸多的微块体于晚三叠世至中侏罗世(T3-J2)碰撞,形成东亚大陆南部巨型印支造山系。中国大陆的印支碰撞造山系呈现巨大的"T"型复合造山系,位于西部的印支造山系(巴颜喀拉-北羌塘-南羌塘-拉萨印支造山带)形成于"多洋盆、多地体、多岛弧"的古特提斯的构造背景,伴随古特提斯多洋盆的俯冲和闭合,产生广泛的岛弧、增生楔和高压变质带的增生造山,以及多地体的碰撞造山作用,形成大型造山拼贴体,伴随以紧闭同劈理褶皱和逆冲、走滑断裂为特征的地壳变形。而位于中东部的印支造山系为北中国与扬子陆块之间的直接碰撞的产物,在扬子被动陆缘之上形成的松潘-甘孜、南秦岭造山带显示深层滑脱为造山机制的大规模地壳上部剪切应变;由于扬子地壳印支期深俯冲(>100km)和山根挤出机制,造成大别-苏鲁造山带中大规模高压-超高压变质带的出露。

The closure of the large Paleo-Tethyan Ocean at the T3-J2 period induced collisions of many microterrains and formed huge Paleo-Tethys orogenic belts in South Asia, also known as Indosinian orogenic belts. The Indosinian orogenic belts of the Chinese continent and adjacent areas shows a ＂T＂-shaped composite orogeny. Studies have shown that the western Indosinian ＂Bayan Har- North Qiangtang-South Qiangtang-Lasha＂ orogenic belts were formed in the Paleo-Tethys setting of multi-ocean basins, multi-terrains and multi-island arcs＂. Subduction and closure of Paleo-Tethyan ocean basins yielded a wide accretional orogeny in island ares, aceretionary wedges and high-pressure metamorphic belts, as well as large-scale orogenic collage due to multi-terrains collision orogeny charecterized by crustal deformations of syn-cleavage folds, thrusts and strike-slip faults. The eastern Indosinian orogenic system is the direct collision result between the North China and Yangtze blocks. The Songpan-Ganzi and South Qinling orogenic belts located above the Yangtze passive margin show large-scale deep decollement orogenic mechanism between the Upper Proterozoic metamorphic basement and Paleozoie-Triassie covers, as well as intensive shear strain of the Yangtze upper crust. The deep subduction （ 〉 100km） of the Yangtze crust and root extrusion mechanism yielded large-scale high pressure/ultra-high pressure metamorphic belts exposed in the Dabie-Sulu orogenic belt.