Fluid inclusions and Rb-Sr isotopic dating of the Wangpingxigou Pb-Zn deposit, Henan Province, China

The Wangpingxigou Pb-Zn deposit is the largest vein-type deposit located to the north of the Checun-Lushan fault along the southern margin of North China Craton. Fluid inclusion study indicates that from the early, middle to late stage of mineralization, homogenization temperatures of fluid inclusions decrease from 280 386 C, through 180 - 350 degrees C, to 120 - 230 degrees C; salinities vary from 3 - 7 wt.% NaCl equiv., 3.55 - 17.43 wt.% NaCl equiv., to 3.06 - 13.51 wt.% NaCl equiv. Calcite daughter minerals in fluid inclusions can be recognized in the middle stage of mineralization. Fluid inclusions with contrasting salinities are homogenized to divergent phase at similar temperatures, which demonstrates that it was fluid-boiling that resulted in the release of CO2 and rapid precipitation of ore-forming material. Five sphalerite grains from Wangpingxigou sulfide ores yield an Rb-Sr isochron age of 117 +/- 27 Ma. In conclusion, the ore-forming fluids of the Wangpingxigou deposit are of CO2-H2O-NaCl +/- CaCl system. It is a typical orogenic-type Pb-Zn deposit formed during transition from collisional compression to extension and can be genetically addressed using the tectonic model for collisional orogeny, metallogeny and fluid flow (CMF mode1).