黔东南九星铜多金属矿床流体包裹体地球化学研究

Geochemical study of fluid inclusions of the Jiuxing copper polymetallic deposit in the southeastern Guizhou

九星铜多金属矿床成矿组分复杂、多阶段成矿特征显著,为研究不同阶段流体成矿作用及其演化特征,本文对该矿床成矿阶段进行了划分,并在此基础上开展了较系统的流体包裹体岩相学观察、显微测温、激光拉曼成分、氢氧同位素组成和LA-ICP-MS原位元素分析。结果显示,该矿床可分为S1石英-磁铁矿、S_(2)石英-铜硫化物、S3石英-铅锌硫化物和S4石英-少量黄铁矿或磁铁矿四个成矿阶段;流体包裹体主要为富液相和富气相的气液两相包裹体,成矿流体均一温度为140~280℃、盐度为6%~12%NaCleqv、密度为0.737~1.060 g/cm^(3),具中低温、中低盐度和中低密度特征;从S1~S4,石英流体包裹体的δD_(SMOW)值为-57.0‰~-32.7‰,δ^(18)OH_(2)O值为3.4‰~4.5‰,反映成矿流体的水大都来源于变质水,仅在成矿最晚的S4阶段有少量大气降水的加入。此外,各阶段成矿流体中均富含Fe、Cu、Pb、Zn等主要成矿元素,具明显的多金属成矿特点。S2主成矿阶段成矿温度相对较高,Cu最富集,成矿作用也最为强烈,CO_(2)含量较其他阶段都高,指示富CO_(2)的流体可能更有利于Cu的搬运与富集。从S1~S4,成矿流体经历了温度从高到低、成矿作用从强到弱、流体来源由变质水到变质水+少量大气降水的演化过程。

The Jiuxing copper polymetallic deposit is characterized with complicated ore-forming components,and remarkable multiple ore-forming stages.In order to deeply study the fluid mineralization and evolution characteristics at different stages of the deposit,in this paper,we have made a detailed classification of the ore-forming stages and the subsequent systematic petrographic observation,microthermometry,laser Raman spectrometry of fluid inclusions,hydrogen and oxygen isotopic composition analyses,and the LA-ICP-MS in-situ element analysis.The results show that four ore-forming stages of the deposit have been classified.They include S1 of the quartz-magnetite stage,S2 of the quartzcopper sulfides,S3 of the quartz-Pb-Zn sulfides,and S4 of the quartz-(pyrite or magnetite).The fluid inclusions are mainly liquid-rich and gas-rich two-phase inclusions.They have homogenization temperatures of 140~280℃,salinities of 6%~12%NaCleqv,and densities of 0.737~1.060 g/cm^(3).The inclusion fluids are characterized with medium to low temperatures,salinities and densities.The δD_(SMOW) and δ^(18)OH_(2)O values of fluids in inclusions in quartzs of the S1,S2,S3,S4 metallogenic stages vary from-57.0‰to-32.7‰,from 3.4‰to 4.5‰,respectively,indicating that the oreforming fluid was basically derived from metamorphic water,with only a small amount of meteoric water added in the latest S4 stage of mineralization.In addition,the ore-forming fluids of all stages are rich in Fe,Cu,Pb,Zn and other major oreforming elements,showing obvious characteristics of polymetallic mineralization.It is worth noting that the mineralization fluid of the S2 main mineralization stage has relatively high temperature,the highest content of Cu.The mineralization of the S2 stage is the strongest one.Meanwhile,the CO_(2)content of fluid in this S2 stage is higher than those of fluids in other stages,indicating that the CO_(2)-rich fluid could be more conducive to the transportation and enrichment of Cu.Generally,from the S1 to the S4 stage,the ore-forming fluid could have experienced a process of evolution from high to low temperatures,from strong to weak mineralizations,with its sources from whole metamorphic water to main metamorphic water and minor meteoric water.