江西牛形坝-柳木坑银金多金属矿床银矿物与银的赋存状态  

The compositions of silver-bearing minerals and the occurrence of silver in the Niuxingba-Liumukeng silver-gold polymetallic deposit,Jiangxi Province,China

作　　者：岳秋雨 翟德高[1] 赵刚 赵青青 贺根文 刘家军[1] YUE Qiu-yu;ZHAI De-gao;ZHAO Gang;ZHAO Qing-qing;He Gen-wen;LIU Jia-jun(School of Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing 100083,China;Gannan Geological Survey Team,Bureau of Geology and Mineral Resources Exploration and Development of Jiangxi Province,Ganzhou 34100,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]江西省地质矿产勘查开发局赣南地质调查大队,江西赣州341000

出　　处：《矿物学报》2023年第3期311-324,共14页Acta Mineralogica Sinica

基　　金：国家自然科学基金项目(编号:41973038)。

摘　　要：牛形坝—柳木坑矿床位于江西银坑矿田,为赣南于都—赣县矿集区典型的银金多金属矿床。通过野外调查与矿物组成研究,将该矿床的成矿作用划分为3个阶段,分别为石英-黄铁矿-毒砂阶段(Ⅰ)、石英-方铅矿-闪锌矿-硫盐矿物阶段(Ⅱ)、石英-碳酸盐阶段(Ⅲ)。银矿化主要集中于第Ⅱ成矿阶段。电子探针(EPMA)成分分析结果显示,矿石中银的赋存形式以独立银矿物、显微包体银等可见银的形式存在。独立银矿物包含银锑黝铜矿((CuAg)_(12)(SbAs)_(4)S_(13))、黝锑银矿((CuAg)_(12)(SbAs)_(4)S_(13))、硫锑铜银矿((AgCu)_(16)Sb_(2)S_(11))、辉银矿-螺状硫银矿(Ag_(2)S);显微包体银则主要为银锑黝铜矿((CuAg)_(12)(SbAs)_(4)S_(13)),均赋存于方铅矿中。本次研究发现了较独特的银锑黝铜矿-黄铜矿-方铅矿交代的出溶结构,指示成矿流体可能富含Pb-Cu-Sb-Ag。结合前人对该矿床的研究,成矿热液温度、氧逸度下降以及pH上升等物理化学条件变化是导致银从成矿流体中沉淀的主要因素。此外,在该矿床中还发育有大量铋矿物,如块硫铋银矿(AgBi3S5)、硫铋银矿(AgBiS_(2))、硫铜铋矿(CuBiS_(2))。大量铋矿物的出现及其与银矿物密切共生现象指示了二者可能具有密切成因联系,本文认为铋的存在对流体中银矿化富集具有促进作用。The Niuxingba-Liumukeng deposit,located in the Yinkeng orefield of Jiangxi Province,is a typical Ag-Au polymetallic deposit in the Yudu-Ganxian metallogenic belt.Based on the field investigation and mineralogical studies,three stages of the hydrothermal mineralization of this deposit have been identified.They include the quartz-pyrite-arsenopyrite stage(I),the quartz-galena-sphalerite-sulfosalt stage(Ⅱ),and the quartz-carbonate stage(Ⅲ).The silver mineralization occurred mainly in the StageⅡ.The results of electron probe microanalysis(EPMA)show that the silver occurred in forms of independent silver minerals and micron sized silver mineral inclusions in the ores.The independent silver minerals include tetrahedrite[(CuAg)_(12)(SbAs)_(4)S_(13)],freibergite[(CuAg)_(12)(SbAs)_(4)S_(13)],polybasite[(AgCu)_(16)Sb_(2)S_(11))]and argentite-acanthite[(Ag_(2)S)].The micron sized Ag-bearing mineral inclusion is dominated by tetrahedrite[(CuAg)_(12)(SbAs)_(4)S_(13)]hosted in galena.In this study,we found a unique exsolution texture of tetrahedrite-chalcopyrite-galena,indicating that the ore-forming fluid could be rich in Pb-Cu-Sb-Ag.Combined with our new data and the previous studies of the deposit,we have proposed that the physicochemical condition variations,including the decrease of temperature and oxygen fugacity and the increase of pH,could be main factors causing the significant precipitation of silver from the ore-forming fluid.In addition,a large amount of bismuth-bearing minerals,e.g.,pavonite(AgBi3S5),matildite(AgBiS_(2)),emplectite(CuBiS_(2))have been identified in ores of the deposit.The close intergrowth between these bismuth-bearing and silver-bearing minerals indicates that they may have a close genetic relationship.It is believed that the presence of bismuth in the ore-forming fluid could promote the silver enrichment and mineralization of the deposit.

关 键 词：牛形坝-柳木坑矿床 银矿物 铋矿物 银赋存形式 富集机理 

分 类 号：P572[天文地球—矿物学] P575.1[天文地球—地质学]