锡田矿田石英脉型钨矿床成矿流体

Ore-forming fluid of quartz-vein type tungsten deposits, Xitian orefield, eastern Hunan, China

采用"流体包裹体组合(FIA)"的研究方法,对矿田主成矿期早、中、晚阶段的流体包裹体进行显微测温和拉曼探针的分析。结果表明:早阶段流体包裹体主要为水溶液包裹体和CO_2三相包裹体,中阶段主要为富液相水溶液包裹体和CO_2两相包裹体,晚阶段主要发育水溶液包裹体。从早阶段到晚阶段,流体包裹体的均一温度逐渐降低,盐度先升高再降低。3个阶段中水溶液包裹体的组分主要为水,除CO_2外,还检测到少量H_2S、CH_4和N_2。早阶段成矿流体在演化过程中发生以CO_2逸失为特征的流体不混溶作用,是该阶段含矿流体中络合物分解并沉淀成矿的主要因素;中阶段成矿元素沉淀的主导因素则是流体的混合作用;而晚阶段成矿元素沉淀的主导因素推测为流体体系的自然冷却。

According to cross-cutting relations and minerals assemblages, three stageswere cataloged in the vein type deposits： early quartz-（molybdenite）-wolframite veins, middle quartz-（wolframite）-sulfide veins and late quartz-pyrite-fluorite veins. Based on detail petrography of fluid inclusion assemblage （FIA）, fluid inclusions of three stageswere studied by microthermometric and Raman microspectroscopic analysis. Mainly aqueous and CO2-H2O three-phase inclusions in quartz-（molybdenite）-wolframite veins, liquid-rich aqueous and CO2two-phase inclusions in quartz-（wolframite）-sulfide veins and only aqueous inclusions in quartz-pyrite-fluorite veinswere found.The results show that the homogenization temperature of the fluid inclusions decreasesfrom early veins to late veins, whilethe salinitiesof fluid inclusions increase in middle veins and decrease in late veins. According to Raman microspectroscopic results,thefluid inclusions of three stages is mainly H2O, moreover, minor CO2, rare H2S, CH4and N2.Themetals precipitation are fluid immiscibility caused by CO2escaping in early stage, fluid mixing in middle stage and natural cooling of fluid system in late stage.