内蒙古好力宝斑岩型铜钼矿床流体特征和矿床成因

Ore-forming fluids characteristics and deposit genesis of Haolibao Porphyry Cu-Mo Deposit,Inner Mongolia

好力宝矿床位于西拉木伦成矿带东部,为斑岩型铜钼矿床。矿体主要赋存于斜长花岗斑岩的角砾岩带中,与斜长花岗斑岩关系密切,成矿作用划分为3个阶段:石英-黄铜矿-黄铁矿-辉钼矿阶段(Ⅰ)、黄铁矿-方铅矿-闪锌矿-辉钼矿-石英脉阶段(Ⅱ)、石英-方解石-萤石阶段(Ⅲ)。流体包裹体测试结果表明:流体包裹体主要为气液两相包裹体(L型)、含CO 2包裹体(C型)和纯CO 2包裹体(PC型)。成矿Ⅰ阶段主要包括L型、C型和PC型流体包裹体,为典型的高温(集中在380.0℃~400.0℃)、中低盐度(集中在7.50%~8.50%)的CO2-NaCl-H2O体系;成矿Ⅱ阶段主要包括L型和C型流体包裹体,属于高温(集中在330.0℃~350.0℃)、低盐度(集中在4.25%~5.00%)的CO2-NaCl-H2O体系;成矿Ⅲ阶段仅包括L型流体包裹体,属于中低温(集中在280.0℃~300.0℃)、低盐度(集中在2.00%~2.75%)的NaCl-H2O体系。氢-氧同位素测试结果显示,δD V-SMOW为-115.8‰~-94.5‰,δ18O H2O为-8.32‰~0.28‰,暗示成矿流体主要来源于岩浆,含有少量大气降水。研究结果表明,该矿床成矿流体为中高温、中低盐度流体,流体不混溶促使金属矿物发生沉淀富集。

Haolibao Deposit,located in the east of Xilamulun metallogenic belt,is a porphyry Cu-Mo deposit.Ore bodies are mainly hosted in breccia zone of plagioclase granite porphyry,and are closely related to plagiogranite porphyry.The mineralization can be divided into 3 stages:quartz-chalcopyrite-pyrite-molybdenite stage(Ⅰ);pyrite-galena-sphalerite-molybdenite-quartz vein stage(Ⅱ);quartz-calcite-fluorite stage(Ⅲ).The results of fluid inclusions test show that the fluid inclusions are mainly gas-liquid two-phase inclusions(L type),CO2-containing inclusions(C type)and pure CO2 inclusions(PC type).StageⅠmainly includes L,C and PC type fluid inclusions,which are typical high temperature(380℃-400℃)and medium-low salinity(7.5%-8.5%)CO2-NaCl-H2O system;Stage Ⅱ mainly includes L and C type fluid inclusions,belonging to high temperature(330℃-350℃)and low salinity(4.25%-5.00%)CO2-NaCl-H2O system;Stage Ⅲ only includes L type fluid inclusions,belonging to the medium-low temperature(280℃-300℃)and low salinity(2.00%-2.75%)NaCl-H 2O system.The results of H-O isotope test is that δD V-SMOW is-115.8‰--94.5‰,δ18O H2O is-8.32‰-0.28‰,implying that the ore-forming fluid of the deposit is mainly from magma with a small amount of meteoric water.The results show that the ore-forming fluid of the deposit is of medium high temperature and low salinity,and the immiscibility of fluid promotes the precipitation and enrichment of metal minerals.