青藏高原北部的碰撞造山及深部动力学——中法地学合作研究新进展

Collision-Orogeny of the Northern Qinghai-Tibet Plateau and Its Deep Dynamics

本文展示了中法 1995～ 2 0 0 0年青藏高原北部地学研究的如下主要新进展 :①完成 80 0 0km长的青藏高原北部及中部天然地震岩石圈探测剖面 ,确定若干条岩石圈断裂 ,发现与新生代火山喷发有关的青藏高原中部深处的低速、低密度体 ,塔里木地块俯冲于阿尔金山之下 ;②提出阿尔金断裂形成于 2 2 0～ 2 40Ma和左行平移 40 0km的科学依据及确定其新生代变形量 ;③确定祁连南缘 35 0km长的高压 超高压变质带 ,提出其可能代表早古生代时期北中国板块与扬子板块之间西部界限的新认识 ;④根据加里东期蛇绿岩、花岗岩及俯冲杂岩带的新发现 ,初步建立了古碰撞造山格架 ;⑤提出高原隆升的“地幔底辟和内向陆内俯冲”的新假设。

The paper reported the main new progresses on the northern Qinghai-Tibet plateau made by the Sino-France team during 1995～2000.They are:①completed total 8 000 km long natural seismic profiles cross the northern boundary and central part of the plateau, identified several deep-cut lithospheric faults and low velocity and low density bodies under the central part of the plateau related to Cenozoic volcanic eruption, the Tarim block subducted beneath the Altun Mts;②found the evidence that the Altyn Tagh fault formed in 220～240 Ma and at least 400 km sinistral offset since, and determined quantitatively deformation in Cenozoic;③discovered 350 km long high-ultrahigh pressure metamorphic belt in the south border of the Qilian terrane,which brobably represented the Early Paleozoic boundary between the North China and Yangtze plates;④according to new discoveries of caledonian ophiolite,granite are subducted complex established paleo-collision orogenic framework of northern Qinghai-Tibet plateau;⑤proposed a new model .“Mantle diapir and inward intracontinental subduction”,to explain the uplift of the Qinghai-Tibet Plateau.