西藏班戈雪如岩体岩石成因及构造意义——来自LA-ICP-MS锆石U-Pb年龄、地球化学特征及Hf同位素证据  

Petrogenesis and tectonic implications of Xueru pluton, in Ban’ge County, Xizang (Tibet): Constraints from LA-ICP-MS zircon U-Pb age , geochemical characteristics and Hf isotopic compositions

作　　者：高轲 刘治博[2] 宋扬[2] 李发桥 滕磊[3] 郑卫红 GAO Ke;LIU Zhibo;SONG Yang;LI Faqiao;TENG Lei;ZHENG Weihong(Chengdu Center,China Geological Survey,Chengdu,610081;Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing,100037;School of Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing,100083;Southeast Sichuan Geological Team,Chongqing Municipal Bureau of Geology and Mineral Exploration and Development,Chongqing,400038)

机构地区：[1]中国地质调查局成都地质调查中心,成都610081 [2]中国地质科学院矿产资源研究所,北京100037 [3]中国地质大学(北京)地球科学与资源学院,北京100083 [4]重庆市地质矿产勘查开发局川东南地质大队,重庆400038

出　　处：《地质论评》2019年第5期1170-1186,共17页Geological Review

基　　金：国家自然科学基金资助项目(编号:41702080);中国地质调查局项目(编号:DD20190147);国家重点研发计划深地资源开采项目(编号:2018YFC0604103; 2016YFC0600308)的成果~~

摘　　要：西藏班戈雪如岩体对探讨班公湖—怒江成矿带在班戈地区的区域构造演化具有重要指示意义。本文根据似斑状二长花岗岩精确的岩石地球化学、锆石U-Pb定年和Lu-Hf同位素数据,探讨了雪如岩体的成岩时代、岩石类型、物质来源及其构造背景。锆石LA-ICP-MS U-Pb加权平均年龄为78.59±0.55 Ma(MSWD=0.96),形成时代为晚白垩世中期,与前人获得的雪如岩体的成岩年龄基本一致。岩石地球化学显示,岩体属于高钾钙碱性系列,铝饱和指数A/CNK=1.03~1.04,为过铝质花岗岩。岩石整体富集大离子亲石元素Th、U、Zr、Hf和LREE,不同程度的亏损Nb、P、Ti和HREE等元素,具有中等的负Eu异常(δEu=0.71~0.73)。锆石εHf(t)值为-10.05~0.37,均值为-3.34。岩石属于I型花岗岩类,总体显示其源区以壳源物质为主。雪如岩体显示同碰撞构造背景,代表的是班公湖—怒江洋闭合之后羌塘地块与拉萨地块碰撞的产物,反映在晚白垩世中期已经处于碰撞挤压和陆壳抬升阶段。Objectives:Xueru pluton is an important indicator to discuss the regional development and evolution of Bangong Lake—Nujiang River metallogenic belt in Ban’ge area.It is essential to carry out geochronological,Lu-Hf isotope study and petrogeochemical analysis for better understanding of the porphyritic monzonitic granite.Methods:On the basis of detailed field work,the petrogeochemical testing and LA-ICP-MS zircon U-Pb dating age are carried out on the porphyritic monzonitic granite.Results:LA-ICP-MS zircon U-Pb age 78.59±0.55 Ma(MSWD=0.96),belongs to the interim of the Late Cretaceous and is basically consistent with the diagenesis age obtained by predecessors.Petrogeochemical researches indicate that the granite belongs to high-K calc-alkaline,and is peraluminous granite with A/CNK=1.03~1.04.The granite is enriched in Th,U,Zr,Hf and LREE,depleted in Nb,P,Ti and HREE,with medium negative Eu anomly(δEu=0.71~0.73).The value of zirconεHf(t)is-10.05~0.37,and the mean value is-3.34.Petrogechemical analysis shows that the granite has the characteristics of I-type granite.Its source rock is continental crust and it is from partial melting.Conclusions:Comprehensive studies indicate that the granite formed in the syn-collision background,which represents the collision event between Qiangtang block and Lhasa block after the closure of Bangong Lake—Nujiang River ocean.

关 键 词：岩石地球化学 锆石U-PB定年 HF同位素 构造背景 雪如岩体 西藏班戈 

分 类 号：P581[天文地球—岩石学] P597.3[天文地球—地质学]