湘西花垣矿田热液方解石稀土元素地球化学  

REE geochemistry of the hydrothermal calcites from the Huayuan orefield,in the western Hunan,China

作　　者：胡宇思 叶霖[1] 韦晨 黄智龙[1] 王浩宇 HU Yu-si;YE Lin;WEI Chen;HUANG Zhi-long;WANG Hao-yu(State Key Laboratory of Ore Deposit Geochemistry,Chinese Academy of Sciences,Guiyang 550081,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院地球化学研究所,矿床地球化学国家重点实验室,贵州贵阳550081 [2]中国科学院大学,北京100049

出　　处：《矿物学报》2020年第4期441-449,共9页Acta Mineralogica Sinica

基　　金：贵州省科学基金(编号:黔科合基础[2017]1421);国家自然科学基金项目(编号:41673056,U1812402);国家重点研发计划(编号:2017YFC0602502)。

摘　　要：近年来,位于扬子板块东南缘的花垣铅锌矿田取得重大找矿突破,杨家寨和大脑坡等一系列大型-超大型铅锌矿的发现,该区新增铅锌资源储量已经超过1000万t,有望成为世界级铅锌资源基地。虽然该矿田地质地球化学研究已经积累了较多成果,但关于铅锌成矿流体的来源及其演化过程研究相对薄弱,制约了花垣矿田的成矿机制深入。本文通过对该矿田不同成矿阶段热液方解石稀土组成研究,并与矿区围岩和不同时代地层对比,探讨矿田内铅锌成矿流体来源及其演化。研究表明,不同成矿阶段的方解石稀土元素及配分模式差异明显,其中成矿早晚2阶段方解石REE与围岩较相似,而主成矿阶段方解石明显富集REE,暗示成矿流体不可能完全由赋矿地层提供,应有来自下伏地层以及基底岩石相对富集REE的流体加入,这种流体可能携带了大量的Pb、Zn成矿物质,为铅锌矿成矿提供了物质来源。此外,成矿早阶段到主成矿阶段,δEu值均小于1,暗示成矿早阶段到主成矿阶段的流体呈现相对还原的特征;而成矿晚阶段方解石的δEu远大于1,表明成矿晚阶段热液流体呈现较氧化特征,总体而言,本区成矿环境在铅锌成矿过程中由相对还原向相对氧化的演化。An important breakthrough of the exploration of Pb-Zn resources in the Huayuan Pb-Zn orefield,located in the southeastern margin of Yangtze Block,has been obtained in recent years.With the discovery of several large and/or super-large Pb-Zn deposits,such as the Yangjiazhai and Danaopo deposits,over 10 Mt of contained Pb-Zn resources have been newly increased.Therefore,the Huayuan orefield is expected to become a world-class lead and zinc resource base.Although many outcomes on studies of geology and geochemistry of this orefield have been published,researches on the source and evolution process of the ore-forming fluid are not well carried out yet.This has limited to deeply discuss the mineralization mechanism of the Huayuan orefield.In this study,the rare earth elements(REE)compositions of the hydrothermal calcites of different stages have been analyzed for comparing with those of host rocks and different strata in order to discuss the source and evolution of ore-forming fluids in this orefield.The results display that the REE contents and distribution patterns of calcites of different ore stages are obviously different.The REE contents of calcites of the pre-ore and post-ore stages are similar to those of host rocks,but those of the main ore stage calcites are obviously higher than those of calcites formed in other stages,suggesting that the ore-forming fluid could be partly derived from the ore-hosted strata with the input of relatively REE-rich fluids derived from the underlying strata and/or basement.The ore-forming fluid could also carry a large amount of metals(Pb,Zn,etc.)for the Pb-Zn mineralization.In addition,δEu values of calcites formed in the early to main ore stages are all less than 1,indicating that the ore-forming fluids of the early and main ore stages are relatively reduced.However,δEu values of the late ore stage are much higher than 1,suggesting the ore-forming fluid at late stage is relatively oxidized.Overall,the ore-forming fluid was envolved from the relatively reduced in the early and

关 键 词：热液方解石 稀土元素 成矿流体来源 成矿过程 铅锌矿床 

分 类 号：P571[天文地球—矿物学] P618.4[天文地球—地质学]