西秦岭李坝金矿载金硫化物特征和成因  

Characteristics and genesis of gold-bearing sulfide in the Liba gold deposit,West Qinling

作　　者：陈昱 王玉往[2] 罗建祥 李德东[2] 王建平[1] 龙灵利[2] 张会琼[2] 耿健 CHEN Yu;WANG YuWang;LUO JianXiang;LI DeDong;WANG JianPing;LONG LingLi;ZHANG HuiQiong;GENG Jian(School of Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing 100083,China;Beijing Institute of Geology for Mineral Resources Co.,Ltd.,Beijing 100012,China;Longnan Zijin Mining Co.,Ltd.,Longnan 742500,China)

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083 [2]北京矿产地质研究院有限责任公司,北京100012 [3]陇南紫金矿业有限公司,陇南742500

出　　处：《岩石学报》2025年第4期1387-1405,共19页Acta Petrologica Sinica

基　　金：紫金集团矿山综合找矿预测专项(KCDZKCY-2022-048)资助.

摘　　要：位于西秦岭成矿带的李坝金矿为一超大型金矿床,其成矿物质来源、金的富集和沉淀机制仍存有争议。本文通过详细的野外调查和显微镜观察,研究了矿区黄铁矿和毒砂的产出特征,将地质-成矿作用划分为沉积(-变质)期、成矿前/成矿早阶段、主成矿阶段和成矿晚阶段。不同期次黄铁矿原位主、微量元素、硫同位素地球化学研究表明:沉积期的黄铁矿(Py0)为典型沉积成因,主成矿阶段黄铁矿(Py2)和成矿晚阶段黄铁矿(Py3)总体具热液成因特征,而成矿前和成矿早阶段黄铁矿(Py1)则具有沉积和热液复合成因特点。黄铁矿中Au和As具有良好的正相关性,表明金多以固溶体的形式赋存在黄铁矿和毒砂中。Au、Sb、Pb、Tl在成矿前和成矿早阶段的黄铁矿(Py1)中明显以晶格中类质同象形式存在,而在主成矿阶段和成矿晚阶段则趋于从黄铁矿晶格中分离,Sb、Pb等元素以方铅矿等包裹体的形式赋存于黄铁矿内,Au可能在黄铁矿中分散微细粒状或赋存在其他硫化物中。李坝金矿黄铁矿δ^(34)S值在2.54‰~12.1‰,反映出硫主要来自矿体与围岩地层发生水-岩反应所致的岩浆热液。毒砂的地质温度计估算结果表明,成矿流体从早期到晚期,成矿温度和硫逸度均趋于降低,反映了毒砂矿物的沉淀导致了流体中硫的消耗过程。Liba gold deposit,located in the western Qinling metallogenic belt,is a super-large gold deposit.The source of ore-forming materials and the mechanism of gold enrichment and precipitation are still controversial.Through detailed field investigation and microscopic observation,this paper studies the occurrence characteristics of pyrite and arsenopyrite in mining areas,and delineates the geological-mineralization processes as the sedimentary(-metamorphic)period,pre-mineralization/early mineralization stage,main mineralization stage,and late mineralization stage.In-situ geochemical studies of major,trace elements and sulfur isotopes of pyrite in different stages show that pyrite(Py0)in the sedimentary stage is a typical sedimentary genesis,pyrite(Py2)in the main metallogenic stage and pyrite(Py3)in the late metallogenic stage are generally characterized by hydrothermal genesis,while pyrite(Py1)in the pre-metallogenic and early metallogenic stage has the characteristics of composite genesis of sedimentation and hydrothermal.There is a good positive correlation between Au and As contents in pyrite,which indicates that gold mostly exists in pyrite and arsenopyrite in the form of solid solution.Au,Sb,Pb and Tl in pre-mineralization and early mineralization stage pyrite(Py1)are predominantly incorporated into the crystal lattice through isomorphic substitution,but tend to separate from the crystal lattice of pyrite in the main stage of mineralization and in the late stage of mineralization.Sb,Pb and other elements exist in pyrite in the form of inclusions such as galena,while Au may be finely dispersed in pyrite or exist in other sulfides.Theδ^(34)S value of pyrite in Liba gold mine is 2.54‰~12.1‰,which reflects that sulfur mainly comes from magmatic hydrothermal solution generated by water-rock reaction with surrounding rock strata.The geological thermometer estimation results of arsenopyrite show that the ore-forming temperature and sulfur fugacity of ore-forming fluids tend to decrease from early stage to late st

关 键 词：载金硫化物 微量元素 硫同位素 成因机制 李坝金矿 

分 类 号：P578.2[天文地球—矿物学] P597.2[天文地球—地质学] P618.51