延边地区五凤-五星山金矿床成矿流体与成矿作用研究

Ore-forming fluid and mineralization of Wufeng-Wuxingshan gold deposit,Yanbian area

五凤-五星山金矿床是延边地区重要的金矿床类型之一。五凤金矿床、五星山金矿床位于石人火山断陷盆地的南北端,相距近3 km。五凤矿体产在金沟岭组火山岩内,为脉状,五星山矿体产在碱性花岗岩与次粗面安山岩接触带上,为网脉-浸染状。笔者运用显微测温、激光拉曼探针技术,对矿床中各个矿化阶段石英内的流体包裹体进行研究。实验结果表明：1流体包裹体类型主要为气液两相包裹体,纯液相包裹体,少量含CO_2三相的包裹体;2均一温度变化范围在110~440℃之间,与石英脉阶段（Ⅰ）、含硫化物-石英脉阶段（Ⅱ）、方解石石英脉阶段（Ⅲ）以及方解石-沸石阶段（Ⅳ）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440~350℃、340~220℃、220~160℃、160~110℃;3盐度w（NaCleq）变化在0.53%~9.47%之间,Ⅰ、Ⅱ、Ⅲ、Ⅳ矿化阶段成矿流体的盐度w（Na Cleq）分别为2.23%~4.63%、9.47%~2.88%、3.85%~1.21%和0.87%左右;4气体成分主要为H_2O、CO_2,少量H_2S、CH_4、N_2。上述结果和硫、碳、氢氧同位素数据,与成矿有关的岩浆作用研究成果,表明该矿床为低硫化型浅成低温热液金矿床,初始成矿流体为大气水,有少量岩浆水参与的中低温、低盐度,还原性流体,成矿物质源于壳幔相互作用的安山质岩浆,成矿机制为流体沸腾作用,可能伴有部分围岩的硫化作用。

The Wufeng-Wuxingshan deposit is a type of important gold deposit in Yanbian. The genetically related Wufeng and Wuxingshan Au orebodies are located 3 km apart in the Shiren volcanic fault basin. Wufeng orebodies consist of vein type ones occurring in Jingouling Group volcanic rocks, and Wuxingshan orebodies occur as stockwork-disseminated ones hosted in the contact zone between alkali-feldspar granites and sub-trachyandensite.The fluid inclusions in quartz from different mineralization stages were investigated using microthermometric measurements and Raman microprobe. Some conclusions have been reached： 1 There are lots of aqueous-biphase（ L＋ V）, mono-phase liquid fluid inclusions（ L） and a few CO_2-bearing three-phase inclusions;2 homogenization temperatures range from 110℃ to 440℃ and those of four successive mineralization stages characterized by quartz-veins stage（ stage Ⅰ）, sulfide-bearing quartz-veins stage（ stage Ⅱ）, calcite-quartz stage（ stage Ⅲ）, and calcite-zeolite stage（ stage IV） are 440℃ to 350℃, 340℃ to 220℃, 220℃ to 160℃,and 110℃ to 160℃, respectively; 3 the salinities w（ Na Cleq） in the whole mineralization process are between0. 53% and 9. 47%, and those ofⅠ,Ⅱ,Ⅲ, Ⅳ mineralization stage w（ NaCleq） are 2. 23% ~ 4. 63%, 9. 47% ~2. 88%, 3. 85% ~ 1. 21% and 0. 87%, respectively; 4 the compositions of the volatile are mainly H_2O, CO_2 and a small amount of H_2S, CH_4, N_2. Combined with recent studies of the magmatism associated with the mineralization, the authors hold that the Wufeng-Wuxingshan gold deposit belongs to a low sulfidation type epithermal deposit, and the ore-forming fluids are characterized by intermediate-low temperature, low salinity and reductivity, they consist of meteoric water with the addition of a little magmatic water, the metallogenic materials may have been derived mainly from andesitic magma induced by crust-mantle interaction, and the metallogenic mechanism seems to have been boiling of the ore-forming fluids possibly accompanied by wall-rock sulfidation.