青藏高原隆升的主因—大陆板块内的盆-山碰撞作用

在地壳运动中,盆地和山脉的形成机制是不可分割而有联系的。上地幔的波动起伏引起地壳上部物质的分配,在重力均衡作用的支配下,地壳物质由上地幔的隆升区域向拗陷区域蠕动,因而形成大陆板块内的盆地和山脉的分异和盆-山运动。高耸的喜马拉雅山和青藏高原就是塔里木盆地、卡拉库姆盆地和印-恒盆地等巨大盆地的扩张作用挤压而造成的。盆-山运动是真正的造山运动。

A MODEL FOR THE UPLIFTING OF THE QINGHAI-TIBET PLATEAU. EVIDENCE FROM BASIN-MOUNTAIN COLLISION INCONTINENT

Large basins both in western and eastern China are formed by spreading. The spreading process of basin may be divided into two types, the mantle uplift and the normal fault ones. The stress that results in the spreading of basin comes from the activity of mantle underlying. The basin spreading undoubtedly effects the surrounding areas, resulting in the uplifting of mountain or plateau, eruption of volcano,activity of granitic magma,metamorphism and earthquake. We include all of these into a basin-mountain system, which forms the main tectonic framework of a continent. In the view of basin-mountain system, it is inferred that the uplifting of the Qinghai-Tibet Plateau is caused by the spreading happening in the surrounding basins of Tarim, Karakumy and Indus-Ganges. The Yarlung Zangbo Suture Belt was formed as early as 54 Ma ago,i. c. at the time the South Tethys was closed. From 54 Ma to 20 Ma, neither high mountain nor plateau was formed and the topography was characterized by an elevation of less than 500-1, 500 m, suggesting the collision between plates had ended. The formation of the plateau began at about 20 Ma B. P. or later because of the spreading of the basins. The molasse formation in the piedmont deprpssions of the Himalayas Pamirs, Kunlun Mts and Tienshan Mts provides an excellent evidence for the time of the plateau uplifting. The collision, since that time, has taken place along the boundary between the basins and the plateau, but not along the convergent belt between the plates. The volcanic activities and earthquakes distributed along the boundary of the plateau are resulted from the basin spreading and underthrusting into the plateau