内蒙古银都银铅锌多金属矿床成矿流体特征及成矿年代学研究

Study on Characteristics of Ore-Forming Fluid and Chronology in the Yindu Ag-Pb-Zn Polymetallic Ore Deposit,Inner Mongolia

内蒙古银都银铅锌多金属矿床属于特大型银矿床,经研究,确定成矿过程经历了早、中、晚3个阶段,分别形成以闪锌矿-磁黄铁矿-黄铜矿、方铅矿-磁黄铁矿、萤石-白云母-碳酸盐为代表的矿物组合。其中,早阶段为锌、铜的主成矿阶段,中阶段则是银铅锌的成矿阶段,晚阶段矿化较弱。激光拉曼显微探针分析表明成矿流体为H2O-CO2-CH4-NaCl体系。包裹体研究显示成矿流体具有低盐度(2%～5%)、低密度(0.72～0.88g/cm3)的特点,成矿温度随着成矿流体的演变,逐渐降低,早、中、晚阶段分别为340.5℃,282.4℃及260.3℃,成矿压力为37～74MPa,成矿深度为3.7～7.0km。经对萤石-白云母-碳酸盐阶段白云母的激光探针40Ar-39Ar年代学测定,确定成矿年代为135±3Ma,为白垩纪早期。

Yindu Ag-Pb-Zn polymetallic ore deposit,Inner Mongolia,is a oversize silver deposit.The ore-forming process includes three stages,i.e.the early,middle and late stages,which are characterized by mineral assemblages of sphalerite-pyrrhotite-chalcopyrite,galena-pyrrhotite and fluorite-muscovite-carbonate,respectively.The early stage is the main mineralizing stage related to Cu and Zn mineralization,the middle stage is related to Ag,Pb and Zn mineralization,and the last stage,the end of ore-forming process,has weak mineralization.Through the analysis of Laser Raman microprobe,it shows that the ore-forming fluid is H2 O-CO2 -CH4 -NaCl system.Based on fluid inclusion study,it has been recognized that the ore-forming hydrothermal fluid has the features like low salinity（2% -5%）,low density（0.72-0.88g/cm^3）.With the evolution of ore-forming hydrothermal fluid,ore-forming temperature decreases gradually.The temperature of early,middle and last stage is 340.5℃,282.4℃ and 260.3℃,respectively.The ore-forming pressures are from 37 to 74 km,which reflect the mineralizing depth ranges from 3.7 to 7.0 km.The muscovite ^40 Ar/^39 Ar age is 135±3 Ma（early Cretaceous）,which is analyzed by laser 40 Ar/39 Ar method.