内蒙古林西地区萤石矿床流体包裹体研究

Fluid inclusion study of fluorite deposits in Linxi region, Inner Mongolia

内蒙古林西地区是我国东部重要的萤石矿集区之一,对该区四个萤石矿床的流体包裹体研究发现,主要发育液相包裹体,还发育少量气相包裹体、含子矿物多相包裹体。显微测温结果显示成矿流体均一温度集中在140～270℃之间,盐度变化范围为0.18%～4.65%NaCleqv,密度变化范围为0.61～0.95 g/cm3,属中低温、低盐度、低密度的NaCl-H2O体系流体;激光拉曼结果表明包裹体成分以H2O为主,含有H2和C3H6。根据显微测温结果,认为水/岩反应很可能是该区萤石沉淀的主要机制。结合地质特征以及普遍低的均一温度和盐度,认为该区萤石矿具有大气降水热液成因特征,成因类型属于中低温热液裂隙充填型萤石矿床。

Linxi region, Inner Mongolia, is one of the most important fluorite ore districts in eastern China. Studies on four fluorite deposits show that fluid inclusions are mostly liquid inclusions, with a few gas inclusions and few daughter mineral-bearing multiphase inclusions. Microthermometry results show that homogenization temperature of ore-forming fluid concentrates between 140-270 ℃; whereas salinity ranges from 0.18% to 4.65%NaCleqv; and density ranges from 0.61 to 0.95 g/cm3. The ore-forming fluid belongs to NaC1-H20 fluid system, which is characterized by middle-low temperature, low salinity and low density. The compositions of fluid inclusions are mainly H20, with some H2 and C3H6. Microthermometry results suggest that water-rock reaction is the principal mechanism of fluorite precipitation. According to the geologic feature and the low homogenization temperature and salinity, these fluorite deposits are characterized by hydrothermal origin of meteoric water. The fluorite deposits belong to middle-low temperature hydrothermal type deposit.