东昆仑西段原特提斯洋洋盆闭合时间——来自新疆木孜塔格地区同碰撞花岗岩的证据  

Time constraints on the closure of the Proto-Tethys Ocean in the western part of the East Kunlun orogenic belt:Evidence from the syn-collision granites in the Muztag area,Xinjiang

作　　者：王坤 蔡志超 王玺 王艳慧 李鑫浩 曾水石 李腾鑫 韩亦菲 WANG Kun;CAI Zhichao;WANG Xi;WANG Yanhui;LI Xinhao;ZENG Shuishi;LI Tengxin;HAN Yifei(He’nan Academy of Geology,Zhengzhou 450001,He’nan,China;He’nan Geochemical Ecological Restoration Engineering Research Center,Zhengzhou 450001,He’nan,China;School of Earth Sciences,East China University of Technology,Nanchang 330013,Jiangxi,China)

机构地区：[1]河南省地质研究院,河南郑州450001 [2]河南省地球化学生态修复工程技术研究中心,河南郑州450001 [3]东华理工大学地球科学学院,江西南昌330013

出　　处：《地质通报》2023年第9期1556-1570,共15页Geological Bulletin of China

基　　金：河南省地质研究院院管省财政项目《黄河下游郑州-兰考段活动构造驱动下河道演变规律研究》(编号:2023-907-XM016-KT04)《基于数字地球的地质图动态更新——郑州市、洛阳市、三门峡市地质图构建与动态更新》(编号:2023-901-XM002-KT01);中国地质调查局项目《新疆木孜塔格地区1∶5万地质矿产综合调查》(编号:12120115020801)。

摘　　要：通过对东昆仑造山带西段木孜塔格地区二长花岗岩的锆石U-Pb年龄和地球化学数据研究,探讨其成因及构造环境,为东昆仑造山带的构造演化提供新信息。对木孜塔格地区出露的中粗粒二长花岗岩和中细粒二长花岗岩进行了LA-ICP-MS锆石U-Pb测年,获得其206 Pb/238 U年龄加权平均值分别为415±4 Ma(MSWD=2.9)和419±6 Ma(MSWD=4.3),表明该花岗岩形成于早泥盆世。全岩地球化学分析结果显示,木孜塔格地区中粗粒和中细粒二长花岗岩均具有高硅、低镁和低钛特征,铝饱和指数大于1.0,主体为钙碱性弱过铝质花岗岩系列。稀土元素配分图和微量元素蛛网图显示,2类花岗岩富集轻稀土元素和Rb等元素,而亏损Nb、Ta、Yb、Y等高场强元素,结合CaO/Na_(2)O和Al_(2)O_(3)/TiO_(2)值及区域地质资料,推测木孜塔格地区花岗岩应形成于同碰撞构造环境,且岩浆源区为贫粘土沉积物的陆壳。综合造山带已有研究成果,提出东昆仑造山带原特提斯洋的闭合在时空上表现出差异性,整体呈现出纵向上北部和中部早于南部,横向上东段早于西段的特征。This paper discusses the rock genesis and tectonic environment of the monzonitic granite from the Muztag area in the western part of the East Kunlun orogenic belt,and provides new information for the tectonic evolution of the East Kunlun orogenic belt,through the study of zircon U-Pb ages and geochemical data.LA-ICP-MS zircon U-Pb dating of the medium-coarse and medium-fine grained monzogranites from the Muztag area yield 206 Pb/238 U ages of 415±4 Ma(MSWD=2.9)and 419±6 Ma(MSWD=4.3),respectively.These geochronological data show that the intrusive rocks were formed in the Early Devonian.Whole-rock geochemical results suggest that the monzonitic granite samples of the Muztag area are characterized by high silicon,low titanium and magnesium contents,as well as large Aluminum Saturation Index(A/CNK)values.These are indicative of calc-alkaline weakly peraluminous granitic series.Moreover,the monzonitic granite samples are relatively enriched in light rare earth elements(LREE)and Rb element,but depleted in high field-strength elements of Nb,Ta,Yb and Y.In combination with the moderate values of CaO/Na_(2)O,low values of Al_(2)O_(3)/TiO_(2) and regional geological data,it is proposed that monzonitic granite of the Muztag area could be formed in the syn-collision tectonic environment and be derived from the continental crust with characteristics of deficient-clay sediments.By compiling previous studies of the East Kunlun belt,it is suggested that closure time of the Proto-Tethys ocean in the East Kunlun orogenic belt has significant spatio-temporal difference characterized by trending from north and central to south direction vertically and by shifting from east to west in the horizontal direction.

关 键 词：东昆仑造山带 同碰撞构造环境 早泥盆世 原特提斯洋 地质调查工程 

分 类 号：P588.121[天文地球—岩石学] P534.44[天文地球—地质学]