内蒙古巴林右旗巴彦查干岩体年代学与地球化学：对古亚洲洋闭合时间的限定  

Geochronology and Geochemistry of Bayanchagan Pluton in Balinyouqi, Inner Mongolia:Implication for Timing of Closure of Paleo-Asian Ocean

作　　者：杜继宇[1,2] 陶楠[2] 郭建超 江斌[2] 杜贯新 Du Jiyu;Tao Nan;Guo Jianchao;Jiang Bin;Du Guanxin(College of Earth Sciences,Jilin University,Changchun 130061,China;Shenyang Center of Geological Surey,China Geological Survey,Shenyang 110034,China)

机构地区：[1]吉林大学地球科学学院,吉林长春130061 [2]中国地质调查局沈阳地质调查中心,辽宁沈阳110034

出　　处：《地球科学》2019年第10期3361-3377,共17页Earth Science

基　　金：中国地质调查局项目(Nos.12120115031101,DD20190039-06,DD20160048-01,DD20160048-02,DD20190039,DD20190042,DD20190360)

摘　　要：古亚洲洋闭合时限一直存在争议.对巴林右旗巴彦查干岩体进行了地球化学、锆石U-Pb测年和Lu-Hf同位素研究,确定其时代和成因,探讨区域构造背景.巴彦查干岩体岩性为二云母二长花岗岩.测年显示,花岗岩侵位于232.0~241.7 Ma,为中晚三叠世.花岗岩富硅和铝,贫镁和铁,属强过铝系列(A/CNK=1.10~1.25),富集轻稀土和大离子亲石元素,亏损重稀土和Nb、Ta等高场强元素,具S型花岗岩特征.锆石的εHf(t)值为-1.8^+4.01,二阶段模式年龄(tDM2)在1006~1380 Ma之间.上述研究表明,原始岩浆起源于加厚陆壳的部分熔融.结合内蒙古东南部蛇绿混杂岩、晚古生代岩浆岩带和沉积环境、三叠纪碰撞相关花岗岩带等研究,推测古亚洲洋东段的闭合发生在晚二叠世;三叠纪进入陆陆碰撞阶段.It is a highly controversial topic about the closure of the Paleo-Asian Ocean.Based on the geochemistry,zircon U-Pb dating and Lu-Hf isotope studies of Bayanchagan pluton in Balinyouqi,in this paper,it discusses its formation age,petrogenesis and the regional tectonic setting.Bayanchagan pluton is two-mica monzogranites.LA-ICP-MS zircon U-Pb dating indicates the two-mica monzogranite formed in the Middle-Late Triassic(232.0-241.7 Ma).The two-mica monzogranite is high in SiO2,Al2O3 and low in MgO,Fe2O3,belonging to strongly peraluminous series(A/CNK=1.10-1.25),enriched in light rare earth elements and large ion lithophile elements,and depleted in heavy rare earth elements and high field strength elements(Nb,Ta),showing that it is S-type granite.Hf isotopic analysis results showεHf(t)values of-1.8 to+4.01,two-stage model ages ranging from 1006 Ma to 1380 Ma,respectively,indicating that the primary magma was derived from the partial melting of a thickened crust.Combined with the studies of the ophiolitic melange,magmatic belt and sedimentary environment of Late Paleozoic,collision related granites,and so on,it is suggested that the eastern segment of the Paleo-Asian Ocean closed in the Late Permian-Early Triassic,and was at the period of continental collision during Triassic.

关 键 词：巴林右旗 中晚三叠世 S型花岗岩 年代学 地球化学 古亚洲洋 

分 类 号：P597[天文地球—地球化学]