Characteristics and significance of the fluid inclusions and stable isotopes from the Nanyangtian scheelite deposit in Malipo, Yunnan

The petrographic examination of the fluid inclusions in quartz from the garnet-tourmaline quartz vein-type scheelite ores from the Nanyangtian stratified skarn-type scheelite deposit in Malipo, Yunnan shows that the inclusions related to the mineralization consist of liquid-rich, gas-rich and daughter crystals-bearing fluid inclusions. The homogenization temperatures of the inclusions in garnet and quartz from the skarn-type ores range between 128℃ and 250℃, and the salinities between 0.7% and 8.1%. The homogenization temperatures of the fluid inclusions in quartz from the tourmaline quartz vein-type scheelite ores range between 181℃ and 325℃, and the salinities between 1.57% and 15.76%. The densities of 0.75 to 0.95 g/cm³ for the ore-forming solutions suggest the mesothermal, medium-to low-salinity and low-density ore-forming fluids for the above-mentioned ores. The hydrogen and oxygen isotope determinations indicate that these ore-forming fluids originated from the formation water (metamorphic water), which was subjected to later mixing and modification by magmatic water. The sulfur isotope values for the Nanyangtian scheelite deposit fall into the sulfur isotopic fields of the sedimentary rocks, metamorphic rocks and evaporate sulfates. It can be seen that the Nanyangtian scheelite deposit may be assigned to the sedimentary-metamorphic skarn-type deposit rather than the classifical skarn-type deposit.