Discussion On Relationship Between Magmatic And The Evolution Of The Basin's Deep Dynamics In Eastern Qiangtang Basin

On the basis of the 1:250,000 regional geological survey of the Cêgnêsheet, this dissertation mainly studies how the magmatism rebuild the basin dynamics in eastern Qiangtang basin. With the analysis of macroscopic characters and petrological and geochemical data of magmatite from Mesozoic to Cenozoic in eastern part of Qiangtang basin, we focused on magmatism during intracontinental orogenenic process, to determine how it controlled tectonic position of eastern Qiangtang basin and coupling of basin and orogenic process, at the same time we provided dynamic evidences to recover Meso-Cenozoic prototype basin.In study area, the igneous rocks consist of intrusive and volcanic rocks. the intrusive rock in this area are called Tanggula mountain Rock which is part of Tanggula magmatic belt. According to extrusive era and characteristics of volcanic rocks, they were classified into four different types:(1) early Jurassic volcanic rocks in Nadigangri formation; (2)late Permian volcanic rocks in Nuoribagaribao formation;(3)late Jurassic-early Cretaceous volcanic rocks in Danrong formation;(4) Cenozoic volcanic rocks in Chabaoma formation;The Tanggulashan rock mass was formed by magmatism during seduction and collision of plate. The regional structural geological analysis and isotope dating result suggested the rock mass was the product of island arc environment formed during Gonghu-Nujiang oceanic crust subducted into Qiangtang continent in early period of late Triassic. Volcanic rocks in Nuoribagaribao formation is formed in active continental margin near continent, where was similar to the regional extensional environment in post-collision period, the magma was from depleted mantle. Volcanic rocks in Nadigangri formation could be nothing to do with plate subduction,but it was formed in extensional environment near continental margin which might be similar to rift. Volcanic rocks in Danrong formation represented the characteristic of intracontinent which was formed in extensional environment on continent near active continental margin. Volcanic rocks in Chabaoma formation should be belonged to high pressure type trachyt,formed by the magma beneath thickened crust, the exact extrusive era could be mid-late period of Miocene.The research on magmatism and character of key structural interface and its deformation characters indicate that this area was undergone multi-stage geological history:(1)forming basement in pre-Carboniferous;(2)forming cover rock from carboniferous to late Cretaceous ;(3)Cenezoic intracontinental compression-plateau uplifting stage. The second secent is detailly classified several following stages: early Carboniferous passive continental margin basin stage; middle Permian extensional rift stage;mid-late Triassic tectonic development stage; early-middle Jurassic basin stage; late Cretaceous foremountain fault basin stage;...