Ore Genesis And Mineralization Regularity Of Qiyimuchang Pb-Zn Deposit In Erguna Area, Inner Mongolia

The Qiyimuchang Lead-Zinc deposit is located in the Erguna block of easternHinggan-Mongolia orogenic belt and northwest side of the Tayuan-Xiguitu fault, and hasfavorable metallogenic conditions and abundant lead, zinc and silver mineral resources.Based on analyzing regional geological and mining geology data, field geological survey,comprehensive study and comparing the same type of deposits in the region, someresearches are completed, especially on metallogenic geological conditions, geologicalcharacteristics, ore genesis and mineralization enrichment regularity of the Qiyimuchanglead-zinc deposit.The deposit, occuring in the volcanic rocks of Late Jurassic Tamulangou Formation,is characterized by ore-bearing quartz veins and controlled by the NW and NWW-trendingfaults. The main metallic minerals are composed of arsenopyrite, chalcopyrite, pyrite,sphalerite and galena. The textures of the lead-zinc ore are idiomorphic-allotriomorphicgranular, replacement remnant texture, unmixing of solid solution texture, cataclastictexture and so on. The metallization has close relationship with such wall-rock alterationas silicify, pyritization and fluoritization. Ore-forming process of the deposit can bedivided into hydrothermal period (including arsenopyrite-pyrite stage, quartz-sulphidesstage and quartz-calcite stage) and epidiagenetic period.The microthermometry of fluid inclusions of the quartz-sulphides stage indicates thatthe ore-forming fluid belongs to the low density(0.70~0.98g/cm3), low salinity(0.5~11.9% NaCl eqv), low-medium temperature(132~342℃) of CO2-H2O-NaCl fluid system. Thefluid boiling played an important role in the lead-zinc element enrichment of the deposit.Ore-forming fluid of quartz-calcite stage is a low density(0.70~0.98g/cm3), the lowsalinity(1.4~9.3%NaCl eqv), low-medium temperature(160~280℃) fluid system.Ore-forming conditions, geological characteristics and the characteristic of rare earthelement and trace element in volcanic rock and isotopic element in ore mineral of thedeposit, show that ore-forming materials of the deposit should come from upper mantlewith commingling of the crust. The partition model between the ore and volcanic rock issimilar, which indicates that they have the congruent source and they are products indifferent magmatic times. This paper concludes that the deposit is one ofmesothermal-epithermal polymetallic deposits hosted by the Mesozoic volcanic rocks andassociated with the hypabyssal or ultra hypabyssal magmatism.Comprehensive comparison of similar deposits in the region showed that volcanicrocks of Tamulangou Formation is advantageous for ore-forming of Pb, Zn, Agdeposits.Deep faults could dominate the tectonic evolution of Erguna block, and theirsecondary fractures are the main host and transportation for deposits. The structural jointoften is in favour of hosting hydrothermal vein type deposits that could yield large-scaleorebodies.Orebodies in this deposit output in lenticular in the horizontal direction, theirthickness, grade, occurrence reached maximum in the middle. The industrial value ishigher from deep to shallow ministry in the vertical. Northeastward trending faults andsecondary NW buried faults are major ore-controlling structure, they are very importantore-hunting evidence. Medium silicify alteration and quartz stringer are the most favorablemineralization. Secondary iron-manganese and zone of gossan of the surface are importantindicator of prospecting for mines.