投稿时间：2021-07-23
修订日期：2022-01-19
网络发布日期：2022-05-06
中文摘要: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CO2的富气相包裹体（VCO2）、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、VCO2、S1、S2型包裹体，均一温度集中在300~500℃，盐度w（NaCleq）为0.6%~43.3%；B脉发育L、V、PV、VCO2、S1、S2型包裹体，均一温度集中在350~450℃，盐度w（NaCleq）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（NaCleq）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CO2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。
Abstract: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 composed 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 divided 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、CO2-rich and daughter mineral-bearing fluid nclusions; whereas 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（NaCleq）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 oreforming 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 CO2 escaping, pH values increasing, variation of oxidation-reduction and the plunge of pressure.
keywords:geology fluid inclusions fluid origin and evolution Jiama copper-polymetallic deposit Gangdese Tibet
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基金项目: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)和中国地质调查局二级项目(编号:DD20190167)联合资助
引用文本：
陈红瑾,王立强,胡古月,顾枫华,唐攀,张忠坤,周敖日格勒.2022.西藏甲玛铜多金属矿床流体包裹体研究[J].矿床地质,41(2):303~323CHEN HongJin,WANG LiQiang,HU GuYue,GU FengHua,TANG Pan,ZHANG ZhongKun,ZHOU Aorigele.2022.Fluid inclusion study on Jiama copper-polymetallic deposit, Tibet[J].Mineral Deposits41(2):303~323
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