Analysis Of Carboniferous Alkaline Granites Geochemical Characteristics And Tectonic Environment In Chakultu Area, East Junggar

The Central Asian orogenic belt is a typical accretive orogenic belt.The Eastern Junggar orogenic belt is located in the south-central part of the Central Asian orogenic belt.It is located between the Kazakhstan plate and the Siberian plate.One of the most significant areas of crust hyperplasia,the paper takes the Carboniferous granite in the Chakultu area of eastern Junggar,Xinjiang as the research object.Based on the 1:50,000 geological mapping,the petrology and dating of the granite in the Chakultu area The study of geology and geochemistry reveals the information about the origin,migration and magma evolution of magma,establishes the magmatic rock sequence in Chakultu region of Xinjiang,and then discusses the tectonic environment during Carboniferous.The main conclusions are as follows:(1)Through field geological mapping and isotope dating,the U-Pb ages of zircons obtained from biotite monzonite and alkaline granite are 315.5±3.9Ma and 315±3.5Ma,respectively.Time,indicating that the diagenetic ages are all in the late Late Carboniferous.(2)In order to ascertain the genetic environment of magmatic rocks in the work area,a rock geochemical study of magmatic rocks was carried out.The results showed that the alkaline granite in Qakultu area is rich in silicon(average content of SiO2 is 72.78%)and rich in alkali(Na2O+ K2 O is 7.26%~9.86%),with characteristics such as calcium-depleted and low-titanium,all belong to high-calcium-calcium-alkaline peraluminous granite.On the normalized spider map of trace elements in magmatic rocks,the overall enrichment of large ion philophile elements(LILE,such as K,Rb,Ba),and the loss of high field strength elements(HFSE,such as Ta,Nb,and Ti)and P indicate that this The magmatic rocks in the area are characterized by rich mantle.(3)The rare earth element curve of granite has a right-inclined characteristic with obvious negative Eu anomaly,which is consistent with the characteristics of type A granite.According to the ratio of trace elements and related discriminant maps,alkaline granite belongs to A2 type granite in terms of genetic type,formed in the post-collision tectonic environment.(4)Comprehensive analysis shows that the history of ocean-land subduction evolution has ended before 315 Ma in the eastern Junggar area and entered the post-collision tectonic environment.