阿拉善地块南缘构造活动特征与青藏高原东北缘向外扩展的最新边界

青藏高原向北东方向扩展的方式及最新扩展边界的位置,是目前青藏高原东北缘构造变形研究的热点.基于近年来对阿拉善地块南缘及邻区活动构造运动特征调查和定量研究结果,重点总结了阿拉善地块南缘活动断裂几何图像及运动特征,指出以前普遍认为的稳定阿拉善地块内部在新生代晚期发育了一系列规模不等、运动性质各异的活动断裂,这些活动断裂是青...

Tectonic Activity in the Southern Alashan Block and the Latest Boundary of Outward Expansion on the Northeastern Tibetan Plateau,China

Recently,the most controversial and attractive issue in studying the tectonic deformation of the northeastern Tibetan Plateau is the way of northeastward expansion of Tibetan Plateau and the location of the latest active boundary of the northeastern Tibetan Plateau.Based on the investigation and quantitative research of active tectonics in the southern Alashan block and its adjacent regions,the geometry and kinematics of active faults located at the southern Alashan block were summarized.It is pointed out that Alashan block,which has been considered as a stable block,is actually composed of a set of active faults with different sizes and motion characteristics in the Late Cenozoic.These faults are either newly formed during the outward extension of the plateau or the results of reactivation of preexisting faults.The control of these faults on regional geomorphology leads to the geomorphological and tectonic boundary of the southern Alashan block.Combining the research results of Cenozoic deformation,tectonic geomorphology,low-temperature thermalchronology,geodesy and modern seismicity,it is proposed that the northeastern Tibetan Plateau has been expanding outward in a sequential way since the Late Cenozoic and forms two crucial boundaries.One is dominantly controlled by the North Qilian Shan fault since Late Miocene(10 Ma).The another is the latest active boundary which mainly consists of thrust faults located at the southern Alashan block paralleling to North Qilian Shan fault since Pliocene(3-2 Ma).In the present tectonic and geomorphic framework,the southern Alashan block has become the latest component of the northeastern Tibetan Plateau.