Petrogenesis and Tectonic Implications of A-type Granites in Zhaheba in the East Junggar Region of Xinjiang,China:Evidence from Geochronology,Geochemistry and Sr-Nd Isotopic Compositions  

作　　者：TANG Hejun MENG Guixiang WU Zhenhan WANG Zhaolin DENG Zhen YAN Jiayong QI Guang XUE Ronghui 

机构地区：[1]Chinese Academy of Geological Sciences,China Geological Survey,Ministry of Natural Resources,Beijing 100037,China [2]SinoProbe Center,Chinese Academy of Geological Sciences,China Geological Survey,Ministry of Natural Resources,Beijing 100037,China

出　　处：《Acta Geologica Sinica(English Edition)》2022年第3期938-953,共16页地质学报（英文版）

基　　金：This work was supported by the National Key Research and Development Program of China(2018YFC0604002);the Geological Survey program of China Geological Survey(DD20221643-6);the Fundamental Research Funds of Chinese Academy of Geological Sciences(JKY21021,JKY202122).

摘　　要：The magma source,petrogenesis,tectonic setting and geochronology of the late Paleozoic A-type granites widely exposed in the Zhaheba area,East Junggar,have thus far not been well-constrained.A better understanding of these issues will help to reveal the magmatic processes and continental growth of Central Asia.The A-type granites in Zhaheba include the Ashutasi alkaline granites and the Yuyitasi syenogranites,which were emplaced at 321.5±4.8 Ma and 321.7±0.6 Ma,respectively.The major rock-forming minerals are orthoclase,perthite,arfvedsonite and quartz,which exhibit the following principal geochemical characteristics of A2-type granites.(1)Their REE distribution curves each exhibit a‘V’-shaped pattern and a marked depletion in Eu.They are rich in large-ion lithophile elements Rb,Th and U as well as high-field-strength elements Nb,Ta,Zr and Hf,but significantly depleted in Ba,Sr,P and Ti.(2)Their(^(87)Sr/^(86)Sr)i values(0.7021-0.7041),εNd(t)values(4.57-5.16)and REE distribution patterns are in basic agreement with those of the Kalamaili A-type granite belt in East Junggar.The T DM2 values of the alkaline granites and syenogranites range from 661 to 709 Ma.The A-type granites may be the products of upwelling asthenosphere-triggered partial melting of immature lower crust.The alkaline granites were late-stage products of crystallization and differentiation.Compared to the syenogranites,the alkaline granites are significantly lower in K_(2)O,Na_(2)O,Al_(2)O 3,FeO,MgO and CaO,but significantly higher in incompatible elements(e.g.,SiO_(2),Rb,and Sr).The magmatic crystallization temperatures of the syenogranites and alkaline granites are 874℃ and 819℃,respectively.As their age gradually decreases(peak ages:322 Ma and 307 Ma,respectively),there is a gradual decrease in the T_(DM2)of the A-type granites and a gradual increase in theεNd(t)value from the Ulungur belt to the Kalamaili belt in East Junggar.The study of A-type granites is therefore one of the keys to understanding the laws and mechanisms of crusta

关 键 词：A-type granite Zircon U-Pb Sr-Nd isotopes POST-COLLISION East Junggar 

分 类 号：P588.121[天文地球—岩石学] P597.3[天文地球—地质学]