华南幕阜山北缘含稀有金属伟晶岩成矿时代及成矿过程  

Metallogenic Age and Process of Rare Metal-Bearing Pegmatites from the Northern Margin of Mufushan Complex,South China

作　　者：李乐广 王连训[1] 朱煜翔 马昌前[1] 佘振兵[1,2] 曹亮[3] 冷双梁 闫育荞 Li Leguang;Wang Lianxun;Zhu Yuxiang;Ma Changqian;She Zhenbing;Cao Liang;Leng Shuangliang;Yan Yuqiao(School of Earth Sciences,China University of Geosciences,Wuhan 430074,China;State Key Laboratory of Biogeology and Environmental Geology,China University of Geosciences,Wuhan 430078,China;Wuhan Center of Geological Survey,China Geological Survey,Wuhan 430205,China;Hubei Geological Survey,Wuhan 430034,China)

机构地区：[1]中国地质大学地球科学学院,湖北武汉430074 [2]中国地质大学生物地质与环境地质国家重点实验室,湖北武汉430078 [3]中国地质调查局武汉地质调查中心,湖北武汉430205 [4]湖北省地质调查院,湖北武汉430034

出　　处：《地球科学》2023年第9期3221-3244,共24页Earth Science

基　　金：湖北省自然资源厅科技项目(No.ZRZY2020KJ04);国家自然科学基金面上项目(No.42072082);中国地质调查局花岗岩成岩成矿中心开放基金项目(No.PMGR202001).

摘　　要：华南晚中生代幕阜山复式岩体是我国重要的稀有金属成矿区,人们在该岩体南缘已发现仁里‒传梓源等超大型稀有金属矿床,但对其北缘广泛发育的含稀有金属伟晶岩的成矿时代和成矿作用研究较为有限.以幕阜山北缘4个主要的伟晶岩密集区:断峰山、北港镇、麦市镇和黄泥洞含稀有金属伟晶岩为研究对象,通过详细的野外地质调查、岩相学、矿物化学和铌钽铁矿U-Pb年代学研究工作,探讨了幕阜山北缘稀有金属(Li-Be-Nb-Ta)的成矿时代、赋存状态和成矿过程.年代学研究表明幕阜山北缘含稀有金属伟晶岩成矿于136~138 Ma,略滞后于幕阜山花岗岩类的侵位年龄,从而与其构成连续的花岗岩类侵位序列,代表了高演化末期的岩浆产物.岩相学及矿物化学研究表明,Li主要赋存于锂云母、透锂长石和锂电气石中,Be赋存于绿柱石中,Nb主要赋存于铌铁矿和铌锰矿中,Ta赋存于细晶石和铌锰矿中.矿物化学特征记录了熔体的演化过程,分离结晶作用是控制稀有金属不断富集的主要因素.幕阜山南、北缘在锂赋存矿物方面存在差异,成矿温压条件的不同可能是造成锂成矿差异的原因.华南幕阜山大规模含稀有金属伟晶岩成矿作用表明幕阜山地区在早白垩世处于伸展背景.The Late Mesozoic Mufushan complex in South China is one of the most important rare metal mineralization areas in China,and giant rare metal deposits such as Renli-Chuanziyuan have been ascertained in its southern margin.In contrast,the metallogenic age and metallogenesis of rare metal-bearing pegmatites widely exposed in the northern are far from being understood.In this work,four major pegmatite concentrated areas in the northern margin of Mufushan including Duanfengshan,Beigang,Maishi and Huangnidong are studied.Based on detailed field investigation,petrography,mineral chemistry and columbite U-Pb dating,we discuss the metallogenic age,identify the occurrence of rare-metal(Li-Be-Nb-Ta),and decipher the mechanism of rare-metal(Li-Be-Nb-Ta)mineralization.Columbite U-Pb dating results show that the rare-metal mineralization of the northern Mufushan pegmatites occurred at 136-138 Ma,slightly postdating the Mufushan granitoids and together constituting a sequential granite emplacement,which represents products of extreme magmatic fractionation.Petrographic observations and mineral chemistry suggest that the major host minerals for Li are lepidolite,petalite and elbaite,for Be are beryl,for Nb are columbite and manganocolumbite,and for Ta are microlite and manganocolumbite.Chemical compositions of rare metal minerals record the evolution process of melt,indicating that fractional crystallization played a predominant role in controlling the successive enrichment of rare-metals.There are some differences in the Li-bearing minerals between the southern and northern margins of Mufushan,which may be due to the different P⁃T conditions.The large-scale rare metal mineralization of pegmatites indicates that the Mufushan area was in an extensional setting in the Early Cretaceous.

关 键 词：成矿时代 成矿作用 矿物化学 含稀有金属伟晶岩 幕阜山 岩石学 矿物学 

分 类 号：P611[天文地球—矿床学] P618[天文地球—地质学]