The Study Of Geological Characteristics,Geochemical Characteristics And Metallogenic System Of The Bianjiadayuan Pb-Zn Polymetallic Deposit In Inner Mongolia,China

Bianjiadayuan Pb-Zn polymetallic deposit,which is a newly discovered deposit in the middle and southern part of the Daxing' anling metallogenic belt in Inner Mongolia,is a medium-scale deposit with reserves of Pb,Zn,Ag,Sn and a large number of associated metal minerals.There are three types of deposits:porphyry tin-copper-molybdenum deposit,cryptoexplosive breccia-type lead-zinc-silver deposit,sub-volcanic hydrothermal vein type lead-zinc-silver deposit.The orebodies are strictly controlled by the structure.The porphyry-type tin-copper-molybdenum deposits are produced in the quartz porphyry bodies.The cryptoexplosive breccia-type lead-zinc-silver deposits are produced in the cryptoexplosive breccia,The sub-volcanic hydrothermal vein type lead-zinc-silver deposit are produced in the Permian Zhesi group and the structural fissure of pyroxene diorite.In this paper,based on the previous research work,the geochemical characteristics of rock,the geochemical characteristics of ore and the characteristics of Mineragenetic fluid are studied,and the metallogenic system is discussed and the metallogenic model is established.(1)The monzonitic granite and quartz porphyry in the study area have similar geochemical characteristics,both of which are high-kalcium alkaline aluminous rocks,all of which are A-type granites with S-type granite characteristics,and are closely related to the formation of Sn ore.The results show that the monzonitic granite and quartz porphyry are continental-continental uplift with continental crust remelting magma.The pyroxene diorite is a high-kalcium alkaline aluminate rock.The rare earth element character shows that the pyroxene diorite has the characteristics of subduction zone,and the formation of magma is closely related to subduction.(2)The geochemical characteristics of the ore in the study area show that the lead-zinc polymetallic deposit belongs to the medium-temperature magmatic hydrothermal deposit,and the ore-forming fluid has the characteristics of rich Cl;the rare earth element indicates that the seawater is added during the mineralization process.The redox environment experienced by mineral hydrothermal fluids has changed.(3)The study of fluid inclusions shows that the inclusions in the western region are mainly rich gas type(G type)and rich liquid type(L type),mainly rich liquid inclusions.Ore-forming fluids show medium-temperature,medium-salinity,medium-low-density characteristics,and mineralization pressures and depths are shallow.The salinity,density,pressure and depth of ore-forming fluids in the eastern area are slightly lower than those in the west area,showing the invasion path of magma from west to east.(4)The metallogenic elements of the lead-zinc-silver-tin polymetallic deposit can be summarized as "three system",namely magmatic system,tectonic system and ore-bearing hydrothermal fluid system.The magmatic system is the material source and heat source center.The Structure system provides the ore-forming and ore-bearing space,and the ore-bearing hydrothermal fluid system provides the conditions for the migration of the ore-forming material.