云南都龙锡锌多金属矿床成矿流体特征及矿床成因

Ore-forming Fluid Characteristics and Metallogenesis of the Dulong Sn-Zn Polymetallic Ore Deposit in Yunnan Province

云南都龙锡锌多金属超大型矿床是我国重要的锡矿资源基地,伴生铅、银、铜、铁、铟和镉等组分。针对该矿床的成矿作用与成因机制问题,以矿床脉石矿物为研究对象,开展了流体包裹体的离子色谱和气相色谱分析,查明了石英、方解石、萤石中流体包裹体的气相和液相成分。结果表明,石英流体包裹体气相成分以CO2和H2O为主,其次为N2,方解石流体包裹体气相成分以CO2、H2O和N2为主,含有少量H2;流体包裹体液相成分相对富Na^+、Ca^2+、Cl^-,F^-含量相对较少。流体中的氮气可能来源于有机质和花岗岩中含钾硅酸盐矿物的分解,CO2等气相成分可能参与成矿作用;成矿流体为富Cl^-、贫F^-的弱酸性、还原性溶液,可与金属矿物阳离子结合形成络合物,有助于金属的迁移;矿床形成可能主要经历了两个阶段,早中期阶段的水—岩反应,中晚期阶段的天水混入和矿物沉淀,成矿晚期矿床受岩浆热液叠加改造。

Dulong Sn-Zn polymetallic superlarge ore deposit in Yunnan province is an important tin resource base in China,associated with lead,silver,copper,iron,indium and cadmium.In view of the metallogenesis and genetic mechanism of the ore deposit,the ion chromatography and gas chromatography analysis of fluid inclusions were carried out with gangue minerals as the research object,and the gas and liquid phase components of fluid inclusions in quartz,calcite and fluorite were identified.The results show that the gas phase compositions of fluid inclusions in quartz are mainly CO2 and H2O,followed by N2.The gas phase compositions of fluid inclusions in calcite are mainly CO2,H2O and N2,with a small amount of H2.The liquid phase compositions of fluid inclusions are relatively rich in Na^+,Ca^2+and Cl^-,but F^-content is relatively low.The nitrogen in the fluid may come from the decomposition of organic matter and silicate minerals bearing potassium in the granite,and the gaseous components such as CO2 may involve in the mineralization.The ore-forming fluid is a weak acid and reductive solution rich in Cl^-and poor in F^-and can combine with metal mineral cations to form complex,which is helpful for metal migration.The formation of the ore deposit may have undergone two stages:water-rock reaction in the early and middle stage,rainwater mixing and mineral precipitation in the middle and late stage,and magmatic hydrothermal superimposition in the late metallogenic stage.