西秦岭洛坝外围铅锌矿中金、锑的成矿作用:来自硫化物原位微区和C-O-S同位素的证据  

Mineralization of gold and antimony in Pb-Zn deposit periphery of Luoba,West Qinling,China:Evidence from in situ trace elements and C-O-S isotopes

作　　者：牛永杰 戴霜 郭东宝 李海亮[3] 曹向飞 移亚龙 马志涛 马延忠 NIU YongJie;DAI Shuang;GUO DongBao;LI HaiLiang;CAO XiangFei;YI YaLong;MA ZhiTao;MA YanZhong(MNR Key Laboratory of Strategic Mineral Resources of the Upper Yellow River,School of Earth Sciences,Lanzhou University,Lanzhou 730000,China;MOE Key Laboratory of Western China's Environmental Systems,College of Earth and Environmental Sciences,Lanzhou University,Lanzhou 730000,China;Lanzhou Mineral Exploration Institute of Gansu Nonferrous Metal Geological Exploration Bureau,Lanzhou 730000,China;Gansu Division of China Building Materials Industry Geological Exploration Center,Tianshui 741000,China)

机构地区：[1]兰州大学地质科学与矿产资源学院,自然资源部黄河上游战略性矿产资源重点实验室,兰州730000 [2]兰州大学资源环境学院,西部环境教育部重点实验室,兰州730000 [3]甘肃省有色金属地质勘查局兰州矿产勘查院,兰州730000 [4]中国建筑材料工业地质勘查中心甘肃总队,天水741000

出　　处：《岩石学报》2025年第4期1367-1386,共20页Acta Petrologica Sinica

基　　金：甘肃省省委组织部2024年度重点人才项目(2024RCXM62);甘肃省科技计划(重点研发)资助项目(22YF7GA073);甘肃省自然资源厅青年团队项目和重点攻关项目(202203)联合资助.

摘　　要：洛坝铅锌矿是西成矿集区内重要的大型铅锌矿田,近年来随着外围及深部找矿工作的持续推进,首次发现了金、锑矿化,但有关其矿化的相关科学问题尚未开展研究。本文通过硫化物原位微量、单矿物微量元素扫面、原位C-O-S同位素分析,确定了洛坝外围铅锌矿中金、锑的矿化类型及赋存状态,并查明了金、锑成矿流体特征。结果显示,辉锑矿、毒砂及少量车轮矿是锑的主要载体矿物,毒砂(平均Au含量917×10^(-6))及含砷黄铁矿是金的主要载体矿物,金主要以“不可见金”形式赋存,其矿化类型与类卡林型金矿基本一致。毒砂及辉锑矿均指示出Sb、Ag、As、Pb、Cu的元素富集特征,暗示研究区内金、锑成矿可能为同一地质事件的产物。方解石C、O同位素分析表明,Ⅰ阶段方解石δ^(13)C V-PDB介于-0.94‰~1.61‰,δ^(18)O SMOW介于8.14‰~12.89‰,指示出成矿流体主要受花岗岩侵入作用影响;Ⅱ阶段方解石δ^(13)C V-PDB介于0.23‰~5.17‰,δ^(18)O SMOW介于11.33‰~17.81‰,显示出成矿流体受碳酸盐溶解作用影响。此外,矿石的岩相学特征及MgO-CaO二元图解均表明成矿后期去碳酸盐化作用显著,且热液脉体中基本不含Fe或Fe含量极低(33.9×10^(-6)~0.438×10^(-6)),说明地层碳酸盐岩溶解作用释放的Fe^(2+)与含Au-Sb-(As-Hg)低温热液流体反应可能是金、锑成矿的关键因素。同时,黄铁矿、毒砂及闪锌矿的S同位素范围较广(-23.80‰~15.33‰),综合表明了研究区内铅锌、金、锑成矿多期次、多阶段的基本特征。Luoba is a large-scale Pb-Zn deposit discovered in the eastern part of the Xicheng mineral district within the West Qinling metallogenic belt.In recent years,geological exploration and mining at Luoba have revealed extensive Au and Sb mineralization.However,no detailed study has been carried out on the occurrence of gold and antimony in this newly discovered deposit at Luoba.Therefore,this study used situ trace elements of sulfides(LA-ICP-MS),elemental mapping and C-O-S isotope microanalysis to reveal the occurrence and mineralization style of gold and antimony in the Luoba deposit.At the same time,the characteristics of gold and antimony ore-forming fluids were also identified.The results indicate that stibnites,arsenopyrite and bournonites are the main Sb-bearing minerals,arsenopyrites(average Au content 917×10^(-6))and arsenic-bearing pyrites are the main Au-bearing minerals.Au presents as Au+in the As-rich zones of pre-existing pyrite grains and arsenopyrite,which is consistent with the occurrence of Au in the Carlin-like deposit.Arsenopyrite and stibnite indicate the element enrichment characteristics of Sb,Ag,As,Pb and Cu,indicating that the gold and antimony mineralization may originate from the same geological events.Calcite C,O isotope analysis resultsδ^(13)C V-PDB 0.23‰~5.17‰andδ^(18)O SMOW 11.33‰~17.81‰in StageⅠ,indicates that the ore-forming fluids are primarily influenced by granite intrusion;StageⅡδ^(13)C V-PDB 0.23‰~5.17‰andδ^(18)O SMOW 11.33‰~17.81‰,indicates that the ore-forming fluids are primarily influenced by carbonate dissolution.Furthermore,both the petrographic characteristics of the ore and the MgO-CaO binary diagram indicate a significant decarbonation process occurred during the later stages of mineralization,and the hydrothermal vein bodies almost does not Fe contain,with concentrations ranging from 33.9×10^(-6) to 0.438×10^(-6),indicates that the reaction between Fe^(2+)ions,released via the dissolution of formation carbonate rocks,and Au-Sb-(as Hg)-bearing

关 键 词：西成 硫同位素 碳氧同位素 成矿流体 卡林型金矿 

分 类 号：P597.2[天文地球—地球化学] P618.51[天文地球—地质学] P618.66