Abstract: 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 H₂O-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. 88 g/ cm³ ). 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 40Ar/39Ar age is 135 ±3 Ma ( early Cretaceous), which is analyzed by laser ⁴⁰Ar-³⁹Ar method.

Key words: fluid inclusion, chronology, Ag-Pb-Zn polymetallic ore deposit, Inner Mongolia

摘要： 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. 88 g/ 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 ～74 MPa, 成矿深度为 3. 7 ～7. 0 km。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±3 Ma, 为白垩纪早期。

关键词: 流体包裹体, 成矿年代, 银铅锌多金属矿床, 内蒙古