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斯弄多银铅锌(金)矿床位于拉萨地体隆格尔—工布江达弧背断隆带南侧上,是冈底斯北缘Pb-Zn-Ag成矿带中段上发现的首例低硫化型浅成低温热液矿床。矿体赋存在林子宗群火山岩中,受火山活动形成的近南北向次级断裂控制。成矿过程可划分为伊利石-绢云母-玉髓-碧玉±铁锰碳酸盐(Ⅰ),石英-黄铁矿±方铅矿±闪锌矿(Ⅱ),方铅矿-闪锌矿-石英-黄铁矿-绢云母±银矿物±碳酸盐(Ⅲ),辉银矿-硫砷铜银矿-方铅矿±深红银矿±自然银±闪锌矿±黄铜矿(Ⅳ),以及石英±碳酸盐±绢云母(Ⅴ)等五个阶段。本次选取了34件Ⅲ阶段和12件V阶段样品进行包裹体岩相学、显微测温、包裹体的气相及离子色谱和Si-H-O同位素研究,探讨了斯弄多矿床的成矿流体性质、来源和成矿沉淀机制。研究结果表明:斯弄多矿床主成矿期石英和闪锌矿中发育纯液相型(PL)、富液相水溶液型(WL)和富气相水溶液型(WG)三种类型的包裹体,后期无矿石英脉中仅发育PL和WL两种类型。其中Ⅲ阶段石英均一温度为185.6~290.7℃,盐度介于1.57%~5.71%,密度为0.76~0.92 g/cm~3;闪锌矿均一温度为197.2~280.8℃,盐度介于1.22%~5.71%,密度为0.75~0.99 g/cm~3;Ⅴ阶段石英均一温度147.6~218.7℃,盐度介于2.07%~8.94%;密度为0.88~0.98 g/cm~3。成矿流体均具有低温、低压、低密度的特点。Ⅲ阶段石英包裹体中气相成分主要以H_2O和CO_2为主;液相成分中阳离子以Ca~(2+)、K~+为主,阴离子以SO_4~(2–)、Cl~–和F~–为主。Ⅱ阶段成矿流体的δ~(30)Si分布范围为–0.2‰~0.1‰,δD值介于–151‰~–177‰,计算获得的δ~(18)O H_2O值介于–5.02‰~–0.63‰。Si-H-O同位素结果表明,斯弄多矿床成矿流体主要为大气降水;包裹体中大量CO_2和SO_4~(2–)、F~–等酸性气体和离子成分表明流体中仍保留微弱岩浆水的特征。斯弄多矿床Ⅲ阶段流体为不混溶流体,流体沸腾、气体逃逸、热液隐爆是金属物质快速沉淀富集成矿的主要机制。
Located on the southern side of the Langegar-Gongbujiangda arc-back fault zone in the Lhasa terrain, the Sri Lanka-Duoduo lead-zinc (gold) deposit is the first low-sulfur sulfide found in the middle section of the Pb-Zn-Ag metallogenic belt on the northern margin of the Gangdise Type epithermal deposits. Ore bodies occur in the Linzizong volcanic rocks, controlled by volcanic activity near the north-south sub-fault. The mineralization process can be divided into illite-sericite-chalcedony-jasper ± ferromanganese carbonate (Ⅰ), quartz-pyrite ± galena ± sphalerite (Ⅱ), galena-sphalerite - Quartz - Pyrite - Sericite ± Silver Minerals ± Carbonate (Ⅲ), Fluorite - Arsenic Copper Silver Silver - Galena ± Crimson Silver ± Natural Silver ± Sphalerite ± Chalcopyrite Ⅳ), and quartz ± carbonate ± sericite (Ⅴ) five stages. In this paper, 34 phase III and 12 phase V samples were selected to study the petrographic, microscopic temperature measurement of inclusions, gas phase and ion chromatography of inclusions and Si-HO isotope studies. The ore-forming fluids Nature, source and depositing mechanism. The results show that inclusions of pure liquid phase (PL), liquid-rich phase (WL) and gas-rich phase (WG) The late ore-free quartz vein developed only PL and WL two types. Among them, the average temperature of quartz in stage Ⅲ was 185.6 ~ 290.7 ℃, the salinity was 1.57% ~ 5.71%, the density was 0.76 ~ 0.92 g / cm ~ 3, the average temperature of sphalerite was 197.2 ~ 280.8 ℃, and the salinity was 1.22% ~ 5.71%, and the density is 0.75 ~ 0.99 g / cm ~ 3. The average temperature of V stage quartz is 147.6 ~ 218.7 ℃, the salinity is 2.07% ~ 8.94%, and the density is 0.88 ~ 0.98 g / cm ~ 3. Ore fluids have the characteristics of low temperature, low pressure and low density. In the phase Ⅲ quartz inclusions, the main gas components are mainly H_2O and CO_2; the cations in the liquid phase mainly consist of Ca 2 + and K +, and the anions are mainly composed of SO 4 2-, Cl ~ - and F ~ - based. The δ ~ (30) Si distribution range of ore-forming fluids in the Ⅱ stage ranged from -0.2 ‰ to 0.1 ‰ and the δD values ranged from -151 ‰ to -177 ‰. The δ 18 O O values calculated from this calculation ranged from -5.02 ‰ ~ -0.63 ‰. The results of Si-HO isotope indicate that the ore-forming fluid in the Sri Lanka-Tundoo deposit is mainly composed of atmospheric precipitation. The abundance of CO_2, SO_4 ~ (2 -) and F_ ~ and other acid gases and ion components in the inclusions indicate that the magmatic water remains in the fluid feature. The fluid in Stage III of the Soulondo deposit is immiscible fluid. The fluid boiling, gas escaping and hydrothermal implosion are the main mechanisms of rapid metal deposition and mineralization.