Genesis And Tectonic Significance Of Paleozoic Granites In Aquedun Area?East Kunlun

As an important part of the central orogenic belt,Qimantage area is located in the west of east Kunlun.In recent years,there are found a series of late-early Paleozoic high-ultrahigh pressure rock in the east,so how to rediscover the tectonic evolution of the early Paleozoic in East Kunlun is important.The granite formed in the collision orogenic belt is important material record of the various stages of orogeny,the research of source characteristics and formation mechanism is of great significance to scientific problems such as inversion of the formation of crust,the interaction between the crust and the mantle material during the orogenic process.There are many granites in the Qimantage Aquedun region.This paper has selected the granites of Ordovician and Devonian to discuss geochemical characteristics and tectonic setting and petrogenesis,combining previous studies and group's research results,based on the method of LA-ICP-MS U-Pb zircon age and systematic geochemical.Paqitong Ordovician rock mass is compossed of augite diorite and monzonitic granite,a surge of contact between both.Augite diorite takes the age of 452±2.5Ma and monzonitic granite is 448±5.4Ma.A/CNK present that the granite is High-k calc alkaline-shoshonite series and metaluminous.The trace element Chondrite normalized spider diagrams shows that it enriched in LILEs(like Ba,Th)and depleted in HFSEs(Nb,P,Ti,Ta).The REE distribution curves are of right inclination,which indicates LREE enrichment and the deficiency of HREE,with low negative Eu anomalies.Ordovician rock mass is I type suggesting that it was fomed in an island-arc or active continental margin environment,representing the subduction phase in orogenesis.Tanbei Moutain granites has the age of 384±4.6Ma?393±4.9Ma,shows it invading in the Middle Devonian.The rock type is monzonite and tonalite.A/CNK(0.95-1.02)present that the granite belongs to calc alkaline-High-k calc alkaline granites and it is metaluminous-peraluminous.It enriched in LILEs(likeRb,K,Th)and depleted in HFSEs(Nb,P,Ti,Ta)with LREE enrichment and deficiency of HREE.Monzonite shows negative Euanomalies.Devonian granite is I type,representing that it was formed in a relative extension environment during post-orogenic or late orogenic evolution.Tectonic evolution process of early Paleozoic early-late Paleozoic has experienced three tectonic phases: Cambrian-Ordovician oceanic crust subductionm which has developed a large number of I type arc granite;Silurian-early Collision orogenic which has developed a series of high-ultrahigh pressure rock;Devonian later post orogenic extension stage which has developed maoniushan formation molasse formation and A type granite.