Geochemical Characteristics And Geological Significance Of Nianbo Formation Volcanic Rocks In Western Gangdese,Tibet

The Linzizong group volcanic rocks is an important part of the Gangdise tectonic-magmatite belt,which is a product of magmatism of the collision of Indian and Eurasia plates,and abundant information from the end of Subduction of the Neotethys to the collision of Indian and Eurasian Plates were recorded.The study area is located in Cuoqin area,western section of the Gangdise belt,and was held between the Bangong Nujiang suture zone and the Yarlung Zangbo Suture Zone,tectonic location belongs to the Lunggar and Gongbogyamda composite island-arc belt,in which department,This article mainly to the Nianbo formation volcanic rocks as the research object,mainly obtains from the Nianbo formation Vocanic rock lithology,and Gangdis Shiquanhe area,Xainza area in wave group volcanic rocks and for comparative analysis,explore the Gangdis Nianbo formation Vocanic rocks into rock,magmatic evolution,the characteristic of the magma source and the tectonic setting,at the same time,the time limit and the way of collision between India and Eurasia plate are discussed.Study area Nianbo formation volcanic rocks mainly consist of dacite rock,rhyolite,rhyolitic pyroclastic tuffs,According to the major element diagrams,show that the study area Nianbo formation volcanic rocks belong to high potassium aluminum calc alkaline and high K calc alkaline acidic lithology combination.Shoshonitic appears as the product of the intracontinental volcanic activity,and the increase of aluminum,high potassium rock and K₂O content showed a large amount of crustal matter was inolved.The spider diagram of trace elements shows that the volcanic rocks enriched in large ion Pro stone elements?Rb,K,La,Ce,Nd?,lack of high field strength elements?Nb,Ti,P?,and island arc volcanic rocks with similar characteristics,The volcanic rocks lack of Ba and Sr,and relative to K and La,Nb is less,and Rb/Sr ratio is greater than 1,all about which shows large amounts of crustal material was involved,and reflects the characteristics of crust source remelting,dual control of partial melting and fractional crystallization of magma,magma mixing occurred in the magma after the formation of magma migration pathway.REE analysis shows LREE enrichment,hree,with different degree of Eu loss,Ce basically no exception.Comparative study found Gangdis Nianbo formation volcano rock belong to Medium acidic volcanic rock,and the source of the Nianbo volcanic rocks is associated with the melting of the crustal material and the mixing of the mantle source material or crust mantle mixing,but rock material is mainly derived from the crust remelting,magma mixing occurred after the formationed of magm,and tectonic environment of the Nianbo formation is from syn-collision to post-collision and the plate.