| The western Sichuan and eastern Tibet region is located in the turning position where the east west trending eastern Tethys tectonic domain changes to be the north-south trending one.There arethree plate tectonic systems in this region,i.e.The Bayan Har,Qiangtang and Lhasa plate tectonicsystems,each consisting of a suture zone,an island-arc fold belt,a back-arc basin fold belt,and aback-basin rise.The tectonic framework of this Tethys domain was formed via five stages of geological cvolution:1.collision of the Geondwana land and Laurasia land along the Batang suture zone during the LotePermian;2.floor sprcading of the Jinshajiang Tethys Sea,subouction of the oceanic crust,and conti-nent-continent collision,which resulted in the Bayan Har plate tectonic system during the Triassic pe-ried;3.floor sprcading of the Nujiang Tethys Sea,subduction of the oceanic crust,and continent continent collision, which led to for mation of the Qiangtang plate tectonic system during the Jurassicperiod;4floor spreading of Yarlung Zangbo Tethys Sea,sutxluction of the oceanic crust,and conti-nent-continent collision,which brought about forming the Lhasa pfate tectonic system during the Cre-taceous-Eocene;5.intracontinental convergence and uplifting of the Qinghai-Tibet plateau during theCenozoic Era.It has been suggested that the plateau was fotmd under the northward complessive stress exted bythe Indea plate,through three stages:1. thickening of the lower and middle crust of the overridingptates caused by the subduction of the oceanic crust mainly during the Cretaceous-Eocene;2.folding,faulting and orogeny which made the upper crust of the overriding plates shortened and thickenedmainly during the Oligocene-Miocene;3.Overall uplifting of the plateau since the Pliocene. |