湘东北传梓源206号伟晶岩脉地球化学、锆石U-Pb年代学和Hf同位素组成及其地质意义  

Geochemistry,zircon U-Pb chronology and Hf isotopic composition of the Chuanziyuan No.206 pegmatite vein in northeastern Hunan Province of South China,and their geological significance

作　　者：成永生 张泽文[1,2,3] 徐卓彬 毛春旺 黄建中 周芳春 张立平 黄志彪 苏俊男 陈虎 陈剑锋 文春华 周瑶 王丹平[1,2,3] CHENG Yongsheng;ZHANG Zewen;XU Zhuobin;MAO Chunwang;HUANG Jianzhong;ZHOU Fangchun;ZHANG Liping;HUANG Zhibiao;SU Junnan;CHEN Hu;CHEN Jianfeng;WEN Chunhua;ZHOU Yao;WANG Danping(Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring,Ministry of Education(Central South University),Changsha 410083,China;Key Laboratory of Non-Ferrous Resources and Geological Hazard Detection,Changsha 410083,China;School of Geosciences and Info-Physics,Central South University,Changsha 410083,China;Geological Bureau of Hunan Province,Changsha 410014,China;311 Brigade of Hunan Nuclear Geological Bureau,Changsha 410100,China;Hunan Institute of Geological Survey,Changsha 410116,China)

机构地区：[1]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),湖南长沙410083 [2]有色资源与地质灾害探查湖南省重点实验室,湖南长沙410083 [3]中南大学地球科学与信息物理学院,湖南长沙410083 [4]湖南省地质院,湖南长沙410014 [5]湖南省核工业地质局三一一大队,湖南长沙410100 [6]湖南省地质调查院,湖南长沙410116

出　　处：《中南大学学报（自然科学版）》2023年第7期2739-2757,共19页Journal of Central South University:Science and Technology

基　　金：湖南省重点研发计划项目(2019SK2261);中南大学研究生自主探索创新项目(2022ZZTS0503);湖南省自然资源厅科技计划项目(2021-21);广西岩溶动力学重大科技创新基地开放课题(BL202105);湖南省科技人才托举工程项目(2020TJ-Q01);长沙市自然科学基金资助项目(kq2202090);湖南省科技创新领军人才项目(2020RC4003);国家自然科学基金资助项目(41672076,42130810);湖南省科技创新团队项目(2021RC4055)。

摘　　要：位于湘东北幕阜山南缘的传梓源稀有金属矿床是我国近年新发现的大型伟晶岩型锂铌钽矿床。针对矿区内伟晶岩的形成年龄、物质来源和大地构造背景等问题,选择206号脉的锂辉石钠长石伟晶岩及白云母钠长石伟晶岩,开展全岩地球化学、锆石微量元素和Hf同位素分析以及锆石LA-ICP-MS U-Pb定年。研究结果表明:花岗伟晶岩表现出高硅、富铝、富碱、贫钙、贫磷、贫镁、钙碱性及过铝质特征;微量元素含量很低,属轻稀土元素相对富集的右倾型;微量元素富集Rb、Th、Nb、Zr、Hf,相对亏损Ba、Ti、Yb、Lu;锆石颗粒较小(粒径为50~150μm),阴极发光强度较弱,大部分锆石为弱振荡环带或无环带,少部分锆石发育韵律环带,前者锆石U质量分数相对较高(>4000×10^(-6)),后者锆石U质量分数相对较低(<4000×10^(-6));但这些锆石大部分w(Th)/w(U)较小(<0.1),具有热液锆石特征。两件锆石U-Pb协和年龄分别为(144.2±1.43)Ma和(145.1±1.79)Ma,可以代表花岗伟晶岩脉的形成时代,表明传梓源伟晶岩型稀有金属矿床形成于早白垩世,与燕山期岩浆热液活动密切相关。花岗伟晶岩脉中锆石Hf同位素标准化值(εHf(t))为-6.3~-5.4,二阶段模式年龄为1592~1537 Ma,与幕阜山花岗岩Hf同位素组成相似。从大地构造环境来看,区内花岗伟晶岩的形成与燕山期太平洋板块向欧亚大陆俯冲紧密相关,主要受制于后造山的伸展构造背景,属冷家溪群减压熔融的产物。The Chuanziyuan rare metal deposit,located in the southern margin of the Mufu Mountain in northeastern Hunan Province of South China,is a newly discovered large pegmatite-type lithium-niobiumtantalum deposit in China in recent years.In view of the scientific problems of the formation age,material source and tectonic background of the pegmatite in the mining area,the lithium pyroxene albite pegmatite and muscovite albite pegmatite in the No.206 vein of the Chuanziyuan mining area were selected,and analysis was carried out on whole-rock geochemistry,zircon trace elements and Hf isotope,and LA-ICP-MS U-Pb dating on zircon.The results show that the granite pegmatite is characterized by high silicon,rich aluminum,rich alkali,poor phosphorus,poor magnesium,alkaline and peraluminous.This pegmatite also has very low trace elements and is characterized by right-leaning chronite-normalized REE patterns.Trace elements are enriched in Rb,Tu,U,Nb,Zr and Hf,relatively deficient in Ba,Ti,Yb and Lu.Zircon grains are small in size(particle diameter is 50~150μm),and that the cathodoluminescence intensity is weak.Most of the zircon crystals are weakly oscillatory or ring-free and have relatively higher zircon U mass concentration(>4000×10^(-6)),whereas a small part of them exhibit rhythmic rings and feature relatively lower zircon U mass concentration(<4000×10^(-6)).Nevertheless,most of these zircon crystals are endowed with very low w(Th)/w(U)ratios of less than 0.1,suggesting a hydrothermal origin.LA-ICP-MS U-Pb dating on zircon yield two ages of(144.2±1.43)Ma and(145.1±1.79)Ma,which can represent the emplacement ages of granitic pegmatite veins,indicating the Chuanziyuan deposit formed in the late Jurassic to earliest early Cretaceous and closely related to the Yanshanian magmatic hydrothermal activity.The Hf isotopes of zircon standardized value(εHf(t))range from-6.3 to-5.4,and the two-stage model ages range from 1537 Ma to 1592 Ma,which is similar to the Hf isotopic composition of Mufushan granite.From the perspective of

关 键 词：锆石U-Pb年代学 Hf同位素 花岗伟晶岩 岩浆演化 湘东北传梓源稀有金属矿床 

分 类 号：P611.12[天文地球—矿床学]