延边闹枝铜金矿床的矿物流体包裹体特征与成矿作用研究

Characteristics of fluid inclusions and mineralization in Naozhi copper-gold deposit, Yanbian area

闹枝铜金矿床是延边内生金铜矿集区内的典型矿床之一,矿体主要为含金黄铜矿黄铁矿石英脉型。笔者运用显微测温、激光拉曼探针,对其矿物内的流体包裹体进行了系统研究。实验结果表明:①流体包裹体的类型主要为气液两相包裹体,其次为纯气相、富气相包裹体及纯液相包裹体,还有少量含子晶的多相包裹体;②流体包裹体的均一温度为150～410℃,与黄铁绢英岩、石英-黄铁矿、石英-多金属硫化物及石英方解石脉4个矿化蚀变阶段相对应的流体包裹体的均一温度分别为350～410℃、290～350℃、210～290℃、150～210℃;③流体包裹体的盐度w(NaCleq)为1.74%～20.97%,Ⅰ、Ⅱ、Ⅲ、Ⅳ矿化阶段成矿流体的盐度w(NaCleq)分别为2.396%～5.548%、2.24%～8.68%、1.74%～20.97%和6.3%;④流体包裹体的气体成分主要为H2O和CO2。结合前人的研究成果,笔者进一步确定该矿床的成矿流体具有深源岩浆热流体性质,在流体上升过程中曾发生过弱的沸腾作用,并在硫化物石英脉、多金属硫化物石英脉、方铅矿脉以及石英方解石脉形成过程中,伴有少量地下水或大气水的加入。

The Naozhi Au-Cu deposit is a typical endogenic deposit in Yanbian and consists mainly of quartz vein-auriferous ore bodies. The fluid phases associated with auriferous quartz veins were investigated using microthermometry and Raman microprobe. Some conclusions have been reached through petrographic observation： ① there are mainly gas-liquid biphase （L＋V） inclusions, subordinately pure volatile （V）, volatile-rich （RV） and pure liquid inclusions （L）, and minor daughter minerals-bearing polyphase inclusions （L＋V＋S）; ② homogenization temperatures of fluid inclusions range from 150 ℃to 410℃, and the homogenization temperatures of four successive ore-forming stages characterized respectively by pyritization-sericitization- silification （stage Ⅰ）, quartz-pyrite （stage Ⅱ）, quartz-polymetallic sulfides （stage Ⅲ）, and quartz-calcite （stage Ⅳ） are 350～410℃, 290～350℃, 210～290℃, and 150～210℃ respectively; ③ the salinities w（NaCleq） of these fluid inclusions vary between 1.74% to 20.97%, and the salinities w（NaCleq） of Ⅰ,Ⅱ, Ⅲ, Ⅳ ore-forming stages are 2.396%～5.548%, 2.24%～8.68%, 1.74%～20.97% and 6.3%,respectively; ④ the volatiles are mainly composed of H2O and CO2. Combined with previous researches on Naozhi deposit fluid inclusions, the authors have further confirmed that the ore-forming fluids from the upper-mantle or lower-crust boiled slightly during their upward migration to the earth＇s surface, that sulfide quartz veins, polymetallic sulfides-rich quartz veins and galena veins were formed successively with the evolution of the ore fluids, with the participation of a bit of groundwater or meteoric water, and that the formation of quartz and calcite veins meant the end of the ore-forming process.