从红河剪切带走滑运动看东亚大陆新生代构造

THE RED RIVER STRIKE-SLIP SHEAR ZONE AND CENOZOIC TECTONICS OF EAST ASIA CONTINENT

用U-Pb法对红河剪切带左行走滑运动进行了精细年代学分析,确定这一运动时期至少是从35Ma到22Ma,与南海张开的时间大致吻合。将这两个事件联系在一起,提出在太平洋板块加速俯冲的作用下,南海作为主动盆地发生的扩张活动,引起华南板块在晚白垩世到中新世中期发生了由SE向NW方向的运动,与印度板块一起推挤三角形青藏高原,使其发生第一次的隆升。与此同时,华南内部及周边地区发生强烈变形。印支块体在其两侧的印度和华南板块共同挤压下,向东南滑出,沿红河剪切带发生左行走滑运动。

Although the formation of Tibetan plateau has been debated since twenties years ago, it is widely accepted that the plateau was the direct product of the collision between India and Eurasia, whereas there are several intracontinental collisions in the long earth history, but we don't have the evidences that such huge plateau was always appeared in collisions. We have remarked that Tibet has a geographical and geophysical triangle shape, at its southwestern side, the India continent, which continued to move northward since the collision, surely play an important role in Tibetan plateau uplift, but at its eastern border how does South China Block (SCB) behaved? The SCB is originally believed to be stable or passively eastward extrusion with the central Tibet during the late Cenozoic. The Red River-Ailao Shan fault, as its west boundary, have been demonstrated to be left leteral strike-slip during Tertiary, at least from 35 to 17 Ma. At southern end of this fault, the South China Sea in south of the SCB, which was formed in related to the southeast ward extrusion of Indochina, as proposed by Tapponnier et al. (1986), began to open at late Cretaceous and active at same time with the fault, but those were difficult to related to the collision India-Asia which have occurred at 45 Ma. Detail geological analyses up on the Longmen Shan (northwest of the SCB), the Qinlin belt (north of the SCB), and the interior of SCB showed that they were also active during the early Cenozoic. Here we first propose a testable model that the SCB moved north-westward with the active opening of South China Sea from late Cretaceous to middle Miocene, this movement with the northward pulsing of India contributed together to raising the plateau Tibetan, and squeezed the Indochina block extruded out of the Tibetan region. This movement perhaps due to subduction of the Pacific plate in its eastern boundary, which northwestward motion rate have had changed for several times during Cenozoic.