中天山比吉盖布鲁斯台辉长岩LA-ICP-MS锆石U-Pb年龄及其构造环境  

LA-ICP-MS ZIRCON U-PB AGE AND TECTONIC SETTING OF THE GABBRO IN BIJIGAIBULUSITAI,MIDDLE TIANSHAN MOUNTAIN

作　　者：米宝昕 靳刘圆 李平 刘宏 王洪刚 王晓晨 MI Bao-xin;JIN Liu-yuan;LI Ping;LIU Hong;WANG Hong-gang;WANG Xiao-chen(Geological Society of Xinjiang Uygur Autonomous Region,Urumqi,Xinjiang 830000,China;Institute of Geological Survey of Xinjiang Uygur Autonomous Region,Urumqi,Xinjiang 830000,China;Institute of Geological Exploration Technology of Anhui Province,Hefei,Anhui 230031,China;Inner Mongolia Second Hydrogeological and Engineering Geological Prospecting Institute,Ordos,Inner Mongolia 017000,China)

机构地区：[1]新疆维吾尔自治区地质学会,新疆乌鲁木齐830000 [2]新疆维吾尔自治区地质调查院,新疆乌鲁木齐830000 [3]安徽省勘查技术院,安徽合肥230031 [4]内蒙古自治区第二水文地质工程地质勘查院,内蒙古鄂尔多斯017000

出　　处：《安徽地质》2020年第2期89-95,共7页Geology of Anhui

基　　金：国家重点研发计划项目“天山-阿尔泰增生造山带深部矿产潜力评价及系列编图(2018YFC0604001-04)”;新疆地质勘查基金项目“新疆区域地质调查片区总结与服务产品开发(DD18-060)”共同资助。

摘　　要：比吉盖布鲁斯台辉长岩位于中天山南缘中段,是为数不多的基性侵入岩体。本次研究围绕中天山南缘比吉盖布鲁斯台辉长岩展开,锆石LA-ICP-MS U-Pb定年获得岩浆结晶年龄为(334.9±3.2)Ma,成岩时代为早石炭世晚期。辉长岩SiO2含量为48.43%~49.56%,具有高CaO含量(13.16%~14.04%)和高Al2O3含量(20.44%~22.11%)的特征。轻重稀土元素分馏明显,富集轻稀土元素,Eu正异常(δEu=1.82~2.24)。岩石地球化学研究表明,辉长岩富集大离子亲石元素(Ba、U、Sr)和亏损高场强元素(Nb、Ta、Th),具火山弧特征。结合岩石的锆石LA-ICP-MS定年结果和区域地质背景分析,认为比吉盖布鲁斯台辉长岩可能是中天山南缘大洋俯冲消减作用的产物,表明至少在晚石炭世,南天山洋还存在俯冲消减事件。The Bijigaibulusitai gabbro is located in the middle part of the southern margin of the middle Tianshan Mountain,and is one of the few basic intrusive rock masses.This study was carried out around the gabbro on the southern margin of the middle Tianshan Mountain.The age of magmatic crystallization obtained by LA-ICP-MS zircon U-Pb dating was(334.9±3.2)Ma,and the diagenetic time was late Early Carboniferous.The content of SiO2 in gabbro is 48.43%~49.56%,which is characterized by high CaO content(13.16%~14.04%)and high Al2O3 content(20.44%~22.11%).The fractionation of light and heavy rare earth elements was obvious,and the light rare earth elements were enriched with positive Eu anomaly(δEu=1.82~2.24).Petrogeochemical studies show that gabbro is rich in large ionic lithophile elements(Ba,U,Sr)and deficient in highfield elements(Nb,Ta,Th),with volcanic arc characteristics.Combined with the zircon LA-ICP-MS dating results and the regional geological background,it is suggested that the Bijigaibulusitai gabbro may be the product of subduction in the southern margin of the middle Tianshan Mountain,indicating that at least in the late Carboniferous,there was subduction in the southern Tianshan ocean.

关 键 词：比吉盖布鲁斯台 辉长岩 LA-ICP-MS锆石U-PB定年 南天山洋 俯冲消减 

分 类 号：P587[天文地球—岩石学]