The Geochemical Characteristics And Ore Genesis Of The Bayanwula Pb-Zn-Ag Deposit,West Segment Of Southern Great Xing'an Range

The Bayanwula Pb-Zn-Ag deposit is a medium-sized deposit in the Hexigten Banner,Inner Mongolia,on the southern side of the Weilasituo deposit.Ore bodies mainly occur as vein type and are hosted in the Baoyintu group.The ore bodies are controlled obviously by the faults.Greisenization,silicification and ferritization are the main indicators for prospecting.The main metallic mineral of Bayanwula Pb-Zn-Ag deposit is galena,sphalerite,chalcopyrite,arsenopyrite,pyrrhotite and sil-ver-bearing minerals.The hydrothermal mineralization of Bayanwula Pb-Zn-Ag de-posit can be divided into three stages:cassiterite-wolframite-arsenopyrite-pyrite-quartz stage?stage??,poly metallic-sulphide-quartz stage?stage??,sphaler-ite-fluorite stage?stage??.Two types of inclusions have been identitified in the ores,fluid inclusion and magmatic inclusion.Homogenization temperatures of fluid inclusions for early to late stages range from 320 to 420?,161 to 359?,120 to 260?,respectively.Fluid salinities show a range from 4.1 to 11.9 wt.%NaCl_eqv,2.1 to 10.5 wt.%NaCl_eqv and 2.0to 6.7 wt.%NaCl_eqv,respectively.The analytic results on fluid inclusions by Laser Raman suggest that the gas phases are rich in H₂O,CO₂ and CH₄.The fluid?¹⁸O_H2O and?D_H2O2O values vary from 2.54 to 6.34‰and-143.0 to-77.6‰.The analytic results shows that the ore-forming fluid of the Bayanwula de-posit is a mixture of magmatic fluid and meteoric fluid.The dominant mechanism for ore deposition is inferred as fluid mixing.The S isotope compositions and the Pb iso-tope compositions of sulfides are suggesting a more single source of mineral material,and is derived from the deep magmatic hydrothermal of lower crust or upper mantle.Study of chronogy shows that the formation of Bayanwula Pb-Zn-Ag deposit was early Cretaceous?about 127 Ma?,similar to the metallogenic epoch of the Sn-W-Pb-Zn-Ag deposit in the region.It may be closely related to large-scale acid magma intrusion and the Sn-Pb-Zn-Ag mineralization in the early Cretaceous.The Bayanwula deposit and the Weilasituo deposit are similar in the metallogen-ic geological background,the metallogenic temperature pressure environment and the metallogenic epoch.The metallogenic material were all derived from the magma.In conclusion,Bayanwula Pb-Zn-Ag deposit is a typical mesothermal and hy-drothermal vein deposit.The Bayanwula deposit and the Weilasituo deposit are dif-ferent temperature endmembers in the same metallogenic system.