鄂东南地区鸡冠嘴铜金矿床Au-Ag-Bi-Te-Se矿物学研究与金银富集机理  

Mineralogy of the Au-Ag-Bi-Te-Se assemblages in the Jiguanzui Cu-Au skarn deposit,Daye District,southeastern Hubei Province

作　　者：张伟[1,2] 王宏强[1] 邓晓东 胡浩[1] 李建威[1] 

机构地区：[1]中国地质大学地质过程与矿产资源国家重点实验室中国地质大学资源学院,武汉430074 [2]中国地质调查局,北京100037

出　　处：《岩石学报》2016年第2期456-470,共15页Acta Petrologica Sinica

基　　金：国家重点基础研究发展计划973项目(2012CB416802);中国地质大学(武汉)中央高校基本科研业务费专项资金(CUG120102;1210491A05);科技部国家重点实验室自主研究课题(MSFGPMR201205)联合资助

摘　　要：鸡冠嘴铜金矿床是鄂东南地区典型的矽卡岩型铜金矿床。矿体主要赋存于下三叠统大冶组大理岩中,矿石矿物以黄铜矿和黄铁矿及少量金银矿物为主,与矿化有关的蚀变包括矽卡岩化、硅化、绿泥石化、碳酸盐化、钾长石化等。根据野外观察和镜下鉴定将成矿过程划分为干矽卡岩阶段、湿矽卡岩阶段、硫化物阶段和碳酸盐阶段,其中硫化物阶段为金矿化的主要阶段。矿相学研究、扫描电子显微镜-能谱分析和电子显微探针分析结果表明,主要载金矿物为黄铜矿和黄铁矿,金的赋存状态包括可见金和不可见金,可见金以银金矿为主,其次为自然金和含银自然金,不可见金为纳米级自然金。主要载银矿物是黄铜矿和斑铜矿,银矿物多以可见银(硒银矿、碲银矿和辉银矿等)产出,包括独立银矿物和显微包体银;不可见银主要以次显微包体的形式分布于硫化物中。鸡冠嘴铜金矿床是高温岩浆热液与碳酸盐岩地层发生接触交代作用形成的,Au在高温热液中可能主要以氯络合物、碲络合物或碲化物熔体的形式搬运。随着矽卡岩化等蚀变作用的进行和热液温度的降低,热液中氯被消耗的同时硫逸度快速上升,Au主要以金硫络合物的形式在热液中运移,硫化物阶段早期大量Bi-Te-S矿物及少量纳米级自然金以显微包裹体的形式包裹于近于同时沉淀的黄铁矿中,随后碲银矿、辉银矿及硫铋铜矿与硫化物及石英和碳酸盐矿物共生产出。成矿流体演化过程中由于温度和硫逸度的进一步降低导致金络合物不稳定,当Logf Te2<-20且-14<Logf Se2<-10时,金矿物与硒化物与黄铜矿近于同时沉淀,或充填于先期沉淀的黄铁矿微裂隙和其他矿物之间的空隙中。综合分析表明,鸡冠嘴铜金矿床成矿过程中Te和Bi对Au的富集具有重要重用。The Jiguanzui Cu-Au skarn deposit is mainly hosted in the carbonate of the Lower Triassic Daye Group. The ore minerals mainly include pyrite,chalcopyrite and various Au-Ag minerals. There exist many hydrothermal alterations mainly including skarn,potash feldspathization,silicification,chloritization,and carbonation in the deposit. The mineralization process can be divided into four stages,which is prograde skarn stage（ stage1）,retrograde skarn stage（ stage2）,sulfides stage（ stage3） and carbonate stage（ stage4）. The precipitation of Au occurs in sulfides stage（ stage3）. Microscope,scanning electron microscopy observations and electron microprobe analysis suggest the main occurrence of Au and Ag are visible Au and Ag minerals,with minor amounts of invisible Au and Ag in sulfides minerals. Visible gold is widespread as irregular electrum minerals,and occurs mainly as inclusions in chalcopyrite and porosities and microfractures filling in pyrite. And the occurrence of invisible gold is nanoparticle native gold in pyrite.Visible silver mainly occur as Ag mineral（ naumannite,hessite and argentite） distributing in chalcopyrite and bornite whereas invisible Ag occurs mainly as nano-submicron particles in sulfides. In high temperature（ 〉400℃）,Cu and Au is extracted from the magma and possibly transported as Au-Telluride melts or complexes like [Au Cl2]-or [Au Te2]3-. As hydrothermal fluid altered with the wall rocks,large numbers of Cl precipitate with skarn minerals. In addition,the temperature of the fluid decreases slowly. In the early sulfides stage,Bi-Te-S minerals precipitate as inclusions in pyrite. Then numerous Ag,Bi and Cu combine with S and Te respectively as Ag2 Te,Cu3Bi S3 with sulfides,quartz and carbonates. After hydrothermal fluid migrates into the favorable fault belts,the changes of pressure,temperature,p H and f O2 lead to instability of the metal complex. On the condition of Logf Te2〈- 18 and- 14 〈Logf Se2〈- 10,Au and Ag precipitate as native gold bearing Ag,electr

关 键 词：鸡冠嘴铜金矿 金(银)的赋存状态 成矿机理 鄂东南 

分 类 号：P618.41[天文地球—矿床学]