湘北仁里伟晶岩型稀有金属矿田的地质特征及成矿机制概述  

Geological features and formation mechanism of pegmatite-type rare-metal deposits in the Renli orefield, northern Hunan, China—an overview

作　　者：李建康[1] 李鹏 黄志飚 周芳春 张立平 黄小强 LI Jiankang;LI Peng;HUANG Zhibiao;ZHOU Fangchun;ZHANG Liping;HUANG Xiaoqiang(MNR Key Laboratory of Metallogeny and Mineral Resource Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China;Hunan Geological Disaster Investigation and Monitoring Institute,Changsha 410011,China)

机构地区：[1]中国地质科学院,矿产资源研究所,自然资源部成矿作用与资源评价重点实验室,北京100037 [2]湖南省地质灾害调查监测所,湖南长沙410011

出　　处：《地学前缘》2023年第5期1-25,共25页Earth Science Frontiers

基　　金：国家重点研发计划项目(2019YFC0605200);国家自然科学基金项目(42002109,41872096);中国地质调查局地质调查项目(DD20221684,DD2022169)。

摘　　要：湘北仁里稀有金属伟晶岩矿田位于江南造山带中段,由仁里铌钽铍矿床、永享-传梓源锂铍铌钽矿床和黄柏山锂铍铌钽矿床组成,是我国近年来东部新发现的特大型花岗伟晶岩型锂铍铌钽矿田。该矿田内各伟晶岩脉围绕矿田北部的幕阜山西南缘花岗岩杂岩体成群成带分布,自杂岩体向外,微斜长石型、微斜长石-钠长石型、钠长石型和钠长石-锂辉石型伟晶岩依次产出。仁里矿床5号脉是区内规模最大的铌钽矿脉,表现出岩浆和热液两阶段成矿的特征;永享-传梓源矿床206号脉是区内规模最大的锂辉石伟晶岩脉,锂辉石遭受了强烈的晚阶段热液交代作用,多转化为腐锂辉石;黄柏山矿床603号脉是区内新发现的锂辉石伟晶岩矿脉,具有交代作用弱、品位高的特点。仁里5号脉的流体包裹体特征显示该矿脉的热液阶段成矿作用较为发育,由流体包裹体显微测温结果估算5号脉核部带形成于约550℃、约350 MPa。综合已有资料,仁里矿田表现出:燕山期(约130 Ma)陆内造山作用成矿,陆内造山作用使高成熟度的沉积基底,即新元古代冷家溪群,深熔产生花岗质岩浆;在岩浆的多阶段侵入活动中,晚阶段二云母花岗岩浆分异出伟晶岩熔体;伟晶岩在经历热液交代作用改造后,富集铌钽,但贫化Li。因此,陆内造山过程中变泥质岩深熔作用、“体中体”式岩浆分异模式、岩浆和热液两阶段成矿作用叠加构成了仁里矿田的成矿特色。The Renli orefield in northern Hunan is a newly discovered pegmatite Li-Ta-Nb orefield in eastern China.It is located in the middle Jiangnan orogenic belt and consists mainly the Renli Nb-Ta-Be deposit,Yongxiang-Chuanziyuan Li-Be-Nb-Ta deposit and Huangbaishan Li-Be-Nb-Ta deposit.Pegmatite dikes in the northern orefield distribute along the southwestern margin of the Mufushan complex,forming distinct pegmatite zonation.Outwards from the complex,the pegmatite types are divided into microcline,microcline albite,albite and albite spodumene.Among the pegmatite dikes,Renli No.5 is the largest Nb-Ta ore body,which exhibits two-stage magmatic-hydrothermal mineralization characteristics;Yongxiang-Chuanziyuan No.206 is the largest spodumene dike in the area,where spodumene occurs mostly as pseudomorph due to strong late-stage metasomatism;and Huangbaishan No.603 is a newly discovered spodumene dike characterized by high-grade Li 2O and weak metasomatism.Hydrothermal fluid played an important role in the rare-metal mineralization of Renli No.5,which is evidenced by the occurrence of quartz-hosted fluid inclusions.Fluid inclusion microthermometry reveals the Renli No.5 core formed at~550℃and~350 MPa.According to existing data,the Renli orefield formed during the Yanshanian intracontinental orogeny(~130 Ma).The data show that during intracontinental orogeny granitic melts formed from basement rocks,i.e.the anatexis of the Neoproterozoic Lengjiaxi Group;then during multi-stage granitoid intrusion the late-stage two-mica granitic melts fractionated into pegmatite-forming melt;finally the hydrothermal metasomatism resulted in Nb and Ta enrichment and Li depletion in pegmatites.Thus,rare-metal mineralization in pegmatites in the Renli orefield can be characterized by metapelite anatexis during intracontinental orogeny,granitic magma differentiation,and two-stage magmatic-hydrothermal mineralization.

关 键 词：稀有金属伟晶岩 仁里矿田 幕阜山花岗岩杂岩体 陆内造山 热液成矿作用 

分 类 号：P611.1[天文地球—矿床学] P611.2[天文地球—地质学]