Geological Characteristics And Genesis Of Gegeqi Lead-zinc Deposit In Inner Mongolia

The Huogeqi lead-zinc deposit in Inner Mongolia is located in the western part of the Middle-Late Proterozoic Wolf Mountain rift trough in the northern margin of the North China Craton.Based on field geological surveys,this paper combines research methods such as microscopic identification,isotope geochemical analysis,zircon dating,and sulfide Rb-Sr dating.The geological background,geological characteristics,geochemical characteristics of the ore deposits,metallogenic age,and genesis of the various lead-zinc deposits were studied.Lead-zinc ore Huogeqi metallic minerals are pyrrhotite,galena,sphalerite.The gangue mineral combination is divided into two types,one is mainly quartz,sericite,and calcite,and the other is diopside,calcite,tremolite,and quartz.Ore structure includes block structure,disseminated structure,strip structure,vein structure and breccia structure,etc.The wall rock alteration of lead-zinc deposits is mainly composed of actinolitization,tremolite,and muscovitization and Carbonation.The isotope geochemical characteristics show that the sulfur isotopes of the metal sulfides in each Huogeqi area ranged from-3.1 to 23.5‰,with an average value of+14.5‰.It is speculated that the source of sulfur is mainly sulfate in marine sedimentary strata.Studies of lead isotopes have shown that galena,chalcopyrite,and pyrite are mainly derived from cratonized crust.U-Pb dating of lead-zinc ore bodies and diorite zircons shows that:zone of magmatic zircons is growth.The zircon U-Pb weighted average ages of the diorite body and lead-zinc ore body are 274.1±1.3 Ma(MSWD=0.58)and 274.3±4.2 Ma(MSWD=2.1),indicating that the diorite body is in the West China stage Product of magmatic activity.Based on the Rb-Sr dating of lead-zinc ore body sulfide samples,the ore-forming ages with isochronous ages of 267.2±2.5 Ma(MSWD=1.5)were obtained.Mineralization of age later than Genesis aged about 7 Ma.The Huogeqi Pb-Zn deposit has a close relationship with Hercynian magmatic hydrothermal processes.Analysis of zircon Hf isotope of lead-zinc ore and diorite,¹⁷⁶Hf/¹⁷⁷Hf ratios are between 0.282388?0.282479 and 0.282394?0.282514,respectively.?Hf(t)<0,reflecting the characteristics of the ancient material cycle or transformation.The projection point is located between the Hf isotope evolution line of the chondrite and the 1.8 Ga ancient crust,and is close to the ancient crust evolution line.The corresponding Hf two-stage loss model age ranges from 1779 to 1509 Ma,reflecting that the magma originated from Paleoproterozoic crustal material.Based on the analysis of the ore body characteristics,petrographic characteristics,geochemical characteristics and diagenesis and ore age of the Huogeqi Pb-Zn deposit,the Huogeqi Pb-Zn deposit was considered to be an epigenetic hydrothermal deposit.