新疆东昆仑土窑洞地区新元古代早期侵入岩年代学、地球化学及其构造意义  

Geochronology,Geochemistry and Tectonic Implications of Early Neoproterozoic Tuyaodong Intrusive Rocks in the East Kunlun Orogen in Xinjiang

作　　者：席振 马德成[2,3] 李欢[2] 高光明 向夏楠[1] XI Zhen;MA Decheng;LI Huan;GAO Guangming;XIANG Xianan(School of Municipal and Geomatics Engineering,Hunan City University,Yiyang,Hunan 413000,China;Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring,Ministry of Education,Central South University,Changsha,Hunan 410083,China;No.701 Geological Team,Xinjiang Nonferrous Geoexploration Bureau,Changji,Xinjiang 831100,China)

机构地区：[1]湖南城市学院市政与测绘工程学院,湖南益阳413000 [2]中南大学有色金属成矿预测与地质环境监测教育部重点实验室,湖南长沙410083 [3]新疆有色地质勘查局701队,新疆昌吉831100

出　　处：《现代地质》2023年第6期1609-1623,共15页Geoscience

基　　金：国家自然科学基金资助项目(42101005);新疆维吾尔自治区中央返还两权价款项目(K15-1-LQ06);有色金属成矿预测与地质环境监测教育部重点实验室(中南大学)开放基金资助项目(2022YSJS13);湖南省教育厅科学研究优秀青年项目(19B097)。

摘　　要：东昆仑造山带西段发育元古宙花岗质岩浆岩,其岩浆活动时限及构造环境仍存争议,制约了对东昆仑造山带元古代构造演化过程的深入认识。本文通过对东昆仑西段土窑洞花岗岩类进行LA-ICP-MS锆石U-Pb年代学和全岩元素组成研究,探讨区域构造演化。土窑洞二长花岗岩和正长花岗岩具有片麻状构造,发育白云母等富铝矿物。岩石具有高SiO_(2)(67.37%~76.35%)、Al_(2)O_(3)(12%~14.25%)和K_(2)O(1.59%~6.01%),低TiO_(2)(0.16%~0.56%)、Na_(2)O(2.13%~3.86%)和CaO(0.9%~4.25%),A/CNK平均为1.02,A/NK平均为1.47。两类岩体球粒陨石标准化配分曲线和原始地幔标准化蛛网图较为一致,其轻稀土元素富集(La/Yb)_(N)=5.04~16.76),有明显铕负异常(δEu平均0.47)。原始地幔标准化蛛网图显示岩石富集Rb、K和Th,亏损Nb、Ba、Sr、P和Ti,CaO/Na_(2)O比值(0.35~1.41)较高。岩浆锆石^(206)Pb/^(238)U加权平均年龄为(932.7±2.4)Ma,表明岩体形成于新元古代早期。综合分析认为土窑洞正长花岗岩和二长花岗岩属于S型花岗岩,其岩浆源于陆壳上部含少量泥质成分的碎屑沉积物质,形成于同碰撞挤压背景,为东昆仑造山带响应Rodinia超大陆汇聚作用的物质记录。The western section of the East Kunlun Orogen(EKO)developed Proterozoic granites,and the magmatic timeframe and tectonic setting remain controversial,which restricts our understandings of the Proterozoic EKO tectonic evolution.Here,we investigate the regional tectonic evolution via LA-ICP-MS zircon U-Pb dating and whole-rock elemental analysis of the Tuyaodong granitoids in the western EKO.The monzonite and syenogranite show gneissic structure and have Al-rich minerals such as muscovite.The rocks have high contents of SiO_(2)(67.37%-76.35%),Al_(2)O_(3)(12%-14.25%),and K_(2)O(1.59%-6.01%),but low TiO_(2)(0.16%-0.56%),Na_(2)O(2.13%-3.86%),and CaO(0.9%-4.25%),with average A/CNK=1.02 and A/NK=1.47.The chondrite-normalized REE patterns and primitive mantle-normalized spider-diagram of the monzonite and syenogranite are similar,which are enriched in LREE((La/Yb)_(N)=5.04-16.76)and have obvious negative Eu anomaly(averageδEu=0.47).The primitive mantle-normalized trace element diagrams show that the rocks are enriched in Rb,K and Th,depleted in Nb,Ba,Sr,P and Ti,and have high CaO/Na_(2)O ratios(0.35 to 1.41).The zircon^(206)Pb/^(238)U weighted average age of the granite is(932.7±2.4)Ma,indicating that the rock was formed in the Early Neoproterozoic.Comprehensive analysis suggests that the Tuyaodong monzonite and syenogranite belong to S-type and their magmas were originated from melting of clastic sediments with minor muddy components in the upper crust.They may have formed in the same collisional extrusion setting,which is in response to the Rodinia supercontinent assembly in the EKO.

关 键 词：S型花岗岩 新元古代 东昆仑 RODINIA超大陆 土窑洞 

分 类 号：P588.12[天文地球—岩石学] P595[天文地球—地质学] P597.3