大陆俯冲作用及青藏高原周缘造山带的崛起

CONTINENTAL SUBDUCTION AND UPLIFTING OF THE OROGENIC BELTS AT THE MARGIN OF THE QINGHAI-TIBET PLATEAU

青藏高原周缘造山带于新生代时崛起。周缘造山带中古老变质地体的折返与3种挤 出作用方式有关：喜马拉雅"逆冲－伸展"型挤出、祁连山"反向逆冲"型挤出和阿尔金"逆冲－转换"型挤出。据地质与地球物理综合研究推测，造山带的折返与周缘大陆岩石圈向内的俯冲作用有关：印度板块岩石圈向北俯冲至雅鲁藏布江缝合带下约 200 km处，西伯利亚板块往南低角度插入祁连山 40 km以下，塔里木地块沿阿尔金北缘边冲断层呈铲式往南俯冲于阿尔金山下100km处，扬子地块呈入体插入青藏高原东部中地壳下面。是否存在扬子地块往西运动及大陆俯冲作用尚待探究。

The orognic belts at the margin of the Qinghai - Tibet Plateau have already been u-plifting since Cenozoic. The exhumation of the old metamorphic complex in these marginal oro-genic belts is related to three types of extrusion: (1) 'thrust-extension' related to extrusion ofHimalayan type; (2) 'opposite thrust' related to extrusion of Qilianshan type; (3) 'thrust-transformation' related to extrusion of the Altun type. On the basis of geologied and geophysi-cal study, it is postulated that the exhumation of the orogenic belts is correlated to the inwar-subduction of the continental lithosphere around the plateau, i. e. (1) the Indian plate subduct-ed northward down to about 200 km deep under the Yalung Zangbo suture zone; (2) TheSiberian plate subducted southward at a low-angle down to 40 km deep beneath the Qilianshan;(3) The Tarim terrain subducted along the northern marginal thrust fault of the Altun Moun-tain southward down to 100 km deep under the Altun Mountain; (4) The Yangtze platewedged into the middie crust of the eastern Qinghai - Tibet Plateau. However, further study isneeded to verify the existence of westward movement of the Yangtze plate and that of the conti-nental subduction.