Abstract:

The Sandaogou Pb-Zn-Ag deposit is an important part of the Pb-Zn-Ag ore concentration area in Western Henan Province. The Pb-Zn-Ag mineralization shows three stages: the early stage is characterized by quartz-pyrite; the middle stage includes quartz-(Pb-Zn-Ag)sulfide; and the late stage includes quartz-calcite. Three types of fluid inclusions are trapped in quartz, which are water inclusions, gas inclusions and CO₂-H₂O inclusions. The temperatures of the ore-forming fluids in the early, middle and late stages are 260-360 ℃, 200-320 ℃ and 160-260 ℃, respectively. The salinity of the ore-forming fluid is in a range of 4%-10% in the early stage, 6%-12% in the middle stage, 4%-8% in the late stage, and the salinity increases in the beginning and then decreases. The densities of the ore-forming fluid are between 0.58 and 1.06 g/cm³, with a mean value of 0.86 g/cm³. The ore-forming fluids are highmiddle temperature, low salinity and low density fluids. In the early mineralization stage, δD values are from -67.5‰ to -75.1‰ and δ¹⁸Owater values are from 6.4‰ to 11.1‰; in the middle mineralization stage, δD value is -106.8‰ and δ¹⁸Owater value is 5.0‰; in the late mineralization stage, δD is from -86.4‰ to -100‰ and δ¹⁸Owater values are from -0.7‰ to 2.2‰. The results show that the ore-forming fluids were derived from the magmatic water or the metamorphic water, and mixed with meteoric water in the major stage and the late stage. We preliminarily present that the genesis of the Sandaogou deposit was mid-temperature hydrothermal vein type Pb-Zn-Ag deposit, and it was the result of the post Yanshanian magmatic ore-bearing hydrothermal filling mineralization.