西藏甲玛铜多金属矿床流体包裹体研究  

Fluid inclusion study on Jiama copper-polymetallic deposit,Tibet

作　　者：陈红瑾 王立强[1] 胡古月[1] 顾枫华 唐攀 张忠坤 周敖日格勒 CHEN HongJin;WANG LiQiang;HU GuYue;GU FengHua;TANG Pan;ZHANG ZhongKun;ZHOU Aorigele(MNR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China;Faculty of Geosciences and Environmrntal Engineering,Southwest Jiaotong University,Chengdu 611756,Sichuan,China;Tibet Huatailong Mining Development Co.Ltd.,Lhasa 850212,Tibet,China)

机构地区：[1]中国地质科学院矿产资源研究所国土资源部成矿作用与资源评价重点实验室,北京100037 [2]西南交通大学地球科学与环境工程学院,四川成都611756 [3]西藏华泰龙矿业开发有限公司,西藏拉萨850212

出　　处：《矿床地质》2022年第2期303-323,共21页Mineral Deposits

基　　金：国家重点研发计划(编号:2018YFC0604106);国家自然科学基金项目(编号:41902100);西藏自治区科技计划项目(编号:XZ201901-GB-24);中国地质科学院院基本科研业务费(编号:KK2017、SYSCR2019-03);中国地质调查局二级项目(编号:DD20190167)联合资助。

摘　　要：甲玛铜多金属矿床是西藏冈底斯中段东部的超大型矿床,主要由角岩型铜钼矿体、斑岩型钼铜矿体以及矽卡岩型铜多金属矿体构成。根据矿物组合与脉体穿插关系,将角岩型和斑岩型矿体中各类热液脉体分为成矿早阶段A脉、转换阶段B脉以及成矿晚阶段D脉。A脉包括具有钾长石蚀变晕的石英脉、石英+钾长石±黄铜矿±辉钼矿脉、石英+黑云母脉、黑云母+黄铜矿±黄铁矿脉,有微弱矿化;B脉主要为石英±辉钼矿±黄铜矿±黄铁矿脉,为主成矿阶段;D脉包括黄铁矿脉、石英+黄铁矿±黄铜矿±辉钼矿脉,矿化微弱。研究发现矿床共发育6种类型的流体包裹体,分别为富液相的气液两相包裹体(L)、富气相的气液两相包裹体(V)、纯气相包裹体(PV)、富CO_(2)的富气相包裹体(V_(CO_(2)))、含石盐子晶的多相包裹体(S1,升温过程中气泡晚于子晶消失达到均一)和含石盐子晶的多相包裹体(S2,升温过程中子晶晚于气泡消失达到均一)。A脉主要发育L、V、PV、V_(CO_(2))、S1、S2型包裹体,均一温度集中在300~500℃,盐度w(NaCl_(eq))为0.6%~43.3%;B脉发育L、V、PV、V_(CO_(2))、S1、S2型包裹体,均一温度集中在350~450℃,盐度w(NaCl_(eq))为1.0%~47.4%;D脉只发育L型包裹体,均一温度介于250~397℃,盐度w(NaCl_(eq))为1.1%~9.9%。从成矿早阶段到成矿晚阶段,高温、高盐度、高氧逸度的流体逐渐演化为中温、低盐度的流体。笔者通过压力估算得到甲玛矿床A、B、D脉阶段的成矿深度分别约为3.2 km、3.2 km、3 km。主成矿阶段水岩反应引起的流体CO_(2)逃逸、pH值降低、氧逸度降低以及体系压力骤降是导致硫化物沉淀的主要因素。The Jiama copper-polymetallic deposit,one of the super-large skarn-porphyry deposits in China currently being mined,is located in the eastern part of the Gangdese porphyry Cu belt,Tibet,China.The deposit is com-posed of hornfels-type Cu-Mo ore body,porphyry-type Mo-Cu ore body and skarn-type Cu,Mo,Pb,Zn,Au,Ag ore body.According to the vein types and crosscutting relationships,the mineralization in Jiama deposit was di-vided into three stages:early ore-forming stage(A vein),main ore-forming stage(B vein)and late ore-forming stage(D vein).A veins usually with weak mineralization,mainly include quartz veins with K-feldspar alteration halo,quartz+K-feldspar±chalcopyrite±molybdenite veins,quartz+biotite veins,biotite+chalcopyrite±pyrite veins;B veins mainly comprise quartz±molybdenite±chalcopyrite±pyrite veins;D veins include pyrite veins and quartz+pyrite±chalcopyrite±molybdenite veins.Fluid inclusions in quartz from the early and main ore-forming stages mainly include liquid-rich,vapor-rich、pure vapor、CO_(2)-rich and daughter mineral-bearing fluid nclusions;where-as the late ore-forming stage minerals only contain liquid-rich fluid inclusions.The fluid inclusions from A vein through B vein to D vein have homogenization temperatures ranging from 300~500℃,350~450℃,250~397℃and salinities w(NaCl_(eq))ranging from 0.6%to 43.3%,1.0%to 47.4%,and 1.1%to 9.9%,respectively.It reveals that from early to late ore-forming stage,the fluids evolved from high-temperature,high-salinity and high-oxygen fugacity to middle-temperature and low-salinity.The pressure estimation in Jiama deposit indicates that the ore forming depth in A vein,B vein and D vein are probably 3.2 km,3.2 km and 3 km respecively.The major factors influencing the participation of ore-forming elements in Jiama deposit are CO_(2)escaping,pH values increasing,variation of oxidation-reduction and the plunge of pressure.

关 键 词：地质学 流体包裹体 流体来源与演化 甲玛铜多金属矿床 冈底斯 西藏 

分 类 号：P618.41[天文地球—矿床学] P618.65[天文地球—地质学]