Study On The Geological Characteristics And Tectonic Attribute Of Late Paleozoic Oceanic Crust Type Rocks In Buqingshan Area,the South Margin Of East Kunlun Mountains

The Buqingshan tectonic mélange belt (BTMB) in south margin of the East KunlunMountains is a suture zone with important geological significance. In the thesis,chooseHaerguole ophiolite and Haerguole seamount basalt which in south margin of the EastKunlun Mountains Buqingshan area as main object of study.Through the study of detailedfield geological survey,petrography,rock geochemistry,isotope dating and combined withthe regional research data,explore the formation tectonic environment of Haerguoleophiolite and Haerguole seamount basalt,the tectonic evolution of Southern margin area ofEast Kunlun from Paleozoic to early Mesozoic. At the same time, some advances andpreliminary cognitions are proposed as follows.1、Make sure the Haerguole ophiolite is MOR-type ophiolite and formed in EarlyCarboniferous.Rock types of Haerguole ophiolite are relatively complete,includeserpentinite,gabbro,diabase, allgovite,basalt and deep-sea siliceous argillaceous rock.Basicrocks of gabbro,diabase and basalt are belong to sub alkaline series,they have similarcharacteristics of rare earth elements,namely the LREE relative loss and HREEenrichment,the chondrite normalized REE distribution curves are left leaning.Useing basaltto distinguish enviroment,the results show the basalt formed in mid-oceanic ridgesenvironment,and then determine the Haerguole ophiolite formed in mid-oceanic ridgesenvironment,Haerguole ophiolite is MOR-type ophiolite.Haerguole gabbro zircon U-Pb ageis332.8±3.1Ma,this age is the crystallized age of the gabbro,which shows the formation ageof Haerguole ophiolite is Early Carboniferous.2、Make sure the Haerguole seamount basalt is symbiotic combination of OIB andN-MORB,and formed in Early Carboniferous.In Buqingshan area,the basalt are symbiosiswith limestone,have typical structure of seamounts. Geochemical characteristics show thatHaerguole seamount basalt including series of alkaline and alkaline series,alkaline basalt asthe oceanic island basalt (OIB),and alkaline basalt as normal mid-ocean ridge basalt(N-MORB),namely Haerguole seamount basalt is symbiotic combination of OIB andN-MORB,and OIB covered in N-MORB.The OIB of Haerguole seamount basalt wasformed in seamount which near the ocean ridge or ocean island environment.The N-MORB of Haerguole seamount basalt was formed in ocean ridge environment.The LA-ICP-MSzircon U-Pb age of Haerguole seamount basalt is（340.8±2.8）Ma（MSWD=0.082），whichindicate that the Haerguole seamount basalt formed in Early Carboniferous,Haerguoleseamount basalt and Haerguole ophiolite may be the product of the same ocean basin.3、According to the nature and age of Haerguole ophiolite and Haerguole seamountbasalt,and combining the Buqingshan-Anemaqen and structural belt and regional data,thetectonic evolution in southern margin of the East Kunlun Mountains from late Paleozoic toearly Mesozoic can be divided into three stages:Buqingshan-Anemaqen oceanic crustspreading stage from early Carboniferous to middle Permian,Buqingshan-Anemaqenoceanic crust subduction stage from late Permian to middle Triassic andcollide-to-orogenesis stage from late stage of middle Triassic to early stage of lateTriassic.The tectonic evolution of East Kunlun in Late Paleozoic was controlled byPaleotethys Ocean,which in the southern margin of East Kunlun.