The Tectonic Evolution And Uplift Mechanism Of Ruoergai Block In West Sichuan Plateau

Ruoergai block is located in the northeastern margin of Qinghai-Tibet Plateau, its unique geotectonical position is very important for the research of the tectonic evolution history of the eastern edge of Qinghai-Tibet Plateau, the mutual restriction between the Orogenic belt as well as the uplift of the Qinghai-Tibet Plateau . Based on the filed geological survey and geological profile combined with a variety of geological data. The paper established a regional tectonic pattern,systematically analyzed a variety of tectonic deformation characteristics of the region and deformation style and researched into the evolution and tectonic uplift mechanism of Ruoergai block in West Sichuan Plateau block.Xikang group of Triassic occupied the main part of the tectonic deformation in Ruoergai region’s cap rock . The tectonic deformation and style show the large levels in the region, the tectonic deformation of Xikang group exhibits the arcuate structure convex to the south and the deformation of the capping-sliding type under the north-south contraction of the system. The deformation was mainly incline fold and overturned fold and its movement mainly point from north to south, with the development of fault-related fold structural style. We divided the large-scale arc decollement tectonic deformation into upper, middle and lower tectonic levels, according to the characteristics of the units’tectonic deformation.Ruoergai and adjacent areas experienced six stages of development and evolution,i.e the formation of Proterozoic basement, early Paleozoic passive continental margin, late Paleozoic complex passive continental margin,Triassic passive continental margin to foreland basin, Jurassic - Paleogene intercontinental strike-slip basin and Cenozoic orogenic uplift.The research shows that the West Sichuan Plateau was gradually uplift as soon as Qinghai-Tibet Plateau uplift since 60Ma,according to quantitative analysis of thermal chronology and semi-quantitative estimate analysis of river terraces uplift.In the stage of the uplift process, substantial uplift occurred in the region in late Miocene, the average uplift rate of Miocene (N1) was about 0.45mm/a,the average uplift rate of Pliocene (N2) was about 0.65mm/a.The uplift of the plateau is founded on rich sedimentary material basis and the context of far-reaching tectonic activity. The thick sedimentary flysch-like formation in Ruoergai region, was composed of several thousand meters of flysch-type clastic rock,which made up of thick deposition material basis of the plateau’s uplift.In addition,in the late Himalayan uplift of Qinghai-Tibet Plateau mechanism of the regional stress.The uplift of the plateau is closely related to the thrust system in the wastern Qinling orogenic belt under the strong contraction mechanism in the late Neogene.