广西贵港新民铜多金属矿床成矿机制研究  

Study on metallogenic mechanism of Xinmin copper polymetallic deposit in Guigang,Guangxi

作　　者：陈港 陈懋弘[1] 李杨林 王昱 吴启强[3] CHEN Gang;CHEN MaoHong;LI YangLin;WANG Yu;WU QiQiang(MNR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,CAGS,Beijing 100037,China;Kunming University of Science and Technology,Faculty of Land Resources Engineering,Kunming 650093,Ynunan,China;No.6 Geological Team of Guangxi,Guigang 537100,Guangxi,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评价重点实验室,北京100037 [2]昆明理工大学国土资源工程学院,云南昆明650093 [3]广西壮族自治区第六地质队,广西贵港537100

出　　处：《矿床地质》2022年第3期506-526,共21页Mineral Deposits

基　　金：国家重点基础研究发展计划(973计划)课题《改造型花岗岩钨锡稀有金属成矿作用》(编号:2012CB416704);广西壮族自治区部门前期地质勘查项目《广西大瑶山地区多期次岩浆活动及成矿作用研究》(编号:桂地矿地[2014]17号)共同资助。

摘　　要：广西贵港新民铜多金属矿床位于大平天山岩体的南东边缘,是大平天山岩浆热液成矿系统的重要组成部分。矿床以切层产出的热液脉型矿体为主,顺层的层状矽卡岩型矿体为辅。系统的野外测量和研究表明,脉状矿体形态简单,主要受控于近直立的北北西向断层;层状矽卡岩型矿体主要受围岩地层中的灰岩夹层控制。为查明成矿流体的类型、性质、演化特征及成矿物质来源,文章对石英流体包裹体进行了系统的显微测温、成分及H-O-S同位素测试分析,在此基础上,探讨了矿床成矿机制,并进一步完善了大平天山岩浆热液成矿系统。研究结果表明,新民铜多金属矿床可以分为以下4个成矿阶段:矽卡岩阶段、早期金属硫化物阶段、晚期金属硫化物阶段、方解石-石英脉阶段。矽卡岩阶段均一温度为398~286℃,盐度w(NaCl_(eq))=13.0%~6.2%;早期金属硫化物阶段均一温度为374~163℃,盐度w(NaCl_(eq))=9.3~4.3%;晚期金属硫化物阶段均一温度为340~151℃,盐度w(NaCl_(eq))=8.0%~2.6%;方解石-石英脉阶段均一温度为298~150℃,盐度w(NaCl_(eq))=5.4%~1.6%。主成矿阶段(早期和晚期金属硫化物阶段)成矿流体以高中温、中盐度的NaCl-H_(2)O-CO_(2)±N_(2)体系为主,流体沸腾和流体混合是矿质沉淀的主要原因。H-O同位素组成(δD值介于-86‰~-64‰,δ^(18)O_(H_(2)O)值介于0.33‰~7.47‰)显示成矿流体与岩浆热液有关,且后期有大气降水混入。硫化物的δ^(34)S值介于-1.4‰~2.6‰,推测硫源与晚白垩世岩浆-热液系统有关。新民铜多金属矿床为晚白垩世区域岩石圈减薄、伸展环境下形成的岩浆热液充填交代矿床,并与邻区的Au-Cu-Pb-Zn-Ag矿床共同构成了大平天山岩浆热液成矿系统。The Xinmin copper-polymetallic deposit in Guigang of Guangxi is located on the southeastern edge of the Dapingtianshan pluton.The deposit is mainly composed of hydrothermal vein-type orebodies produced by cutting layers,supplemented by stratabound skarn-type orebodies.Systematic field observations and studies have shown that the vein-like orebodies have a simple shape and are mainly controlled by suberect NWW-trending faults.Stratabound skarn-type orebodies are mainly controlled by limestone interlayers in the surrounding rock strata.In order to find out the types,properties,evolution characteristics and source of ore-forming fluids,this paper conducted systematic micro-temperature measurement,composition and H-O-S isotope analysis of quartz fluid inclusions.The results show that the Xinmin copper-polymetallic deposit can be divided into the following four mineralization stages:skarn stage,early metal sulfide stage,late metal sulfide stage and calcite-quartz vein stage.The fluid inclusion in the skarn stage have homogenization temperatures of 398℃~286℃,with salinities(w(NaCl_(eq)))of 13.0%~6.2%.The fluid inclusion in the early metal sulfide stage have homogenization temperatures of 374℃~163℃,with salinities(w(NaCl_(eq)))of 9.3%~4.3%.The fluid inclusion in the late metal sulfide stage have homogenization temperatures of 340℃~151℃,with salinities(w(NaCl_(eq)))of 8.0%~2.6%.The fluid inclusion in the calcite-quartz vein stage have homogenization temperatures of 298℃~150℃,with salinities(w(NaCl_(eq)))of 5.4%~1.6%.The ore-forming fluids in the main mineralization stage(early and late metal sulfide stages)are dominated by the NaCl-H_(2)O-CO_(2)±N_(2)system of high to medium tem‐perature and salinity.Fluid boiling and mixing are the main reasons for ore precipitation.The oxygen and hydrogen isotopic compositions(δD=-86‰~-64‰,δ^(18)H_(2)O=0.33‰~7.47‰)show that the ore-forming fluid is related to magmatic hydrothermal fluid,and was mixed with atmospheric precipitation in the later period.Theδ^

关 键 词：地球化学 岩浆热液成矿系统 矿床成因 新民铜矿 广西贵港 

分 类 号：P618.41[天文地球—矿床学]