The Geological Features And Genetic Type Of Dachang Orefield's 91 And 92 Tin Polymetallic Ore Body In Guangxi

Dachang ore field located in the Southwestern margin of the Jiangnan oldland,and the middle of Danchi metallogenic belt.As an importantnonferrous metal mining industry base of China and a famous ultra-largetin-polymetallic deposit in the world,with the proven tin metal ranks firstin the world and associated with Cu,Zn,Pb,Sb,Ge,In,Cd and Se etc,it hasthe great significance both in academic and economic.After nearly 60 yearsof research and development,the deposit has accumulated abundant data invarious aspects,but the genesis of the deposit is still in dispute.Based on the work of predecessors and through field geologicalobservation and analysis,metallogenic background of Dachang Orefield andthe geological characteristics,metallogenic structure types,metallogenicstructure series and ore body genesis of No.91 and No.92 orebodies havebeen studied in detail.The main achievements and understandings are asfollows:(1)Danchi metallogenic belt is a tectonic complex influenced byHercynian,Indosinian and Yanshanian periods,including rock mass,orebody,stratum,fold and fracture.Its tectonic mineralization is influenced byHercynian exhalative-sedimentary,Indosinian strata-slip folds andYanshanian magmatism.(2)Microscopic observation shows that the ore structure of No.91 andNo.92 orebodies is mainly semi-automorphic-automorphic granularstructure,followed by crushing structure and sieve structure,and the orestructure is rhythmic laminated striped structure and reticulated veinstructure.The metallogenic structure types of ore bodies can be divided intosyngenetic sedimentary metallogenic structure,structural metallogenicstructure and superimposed metallogenic structure.(3)Through structural analysis,the metallogenic structural series ofDachang orefield can be divided into three types: sedimentary metallogenicstructural series,compressive metallogenic structural series andcompression-strike-slip metallogenic structural series.They correspond tothree tectonic series: early(Hercynian)exhalative-sedimentary metallogenicseries,middle(Indosinian)shear zone metallogenic series and late(Yanshanian)granite metallogenic series.(4)According to the analysis of siliceous rock genesis,source ofore-forming materials and ore-controlling factors of No.91 and No.92 orebodies,it is considered that sulfur comes from lower rock mass and strata,and lead mainly comes from crust and magmatic rocks.Establishment ofmetallogenic model of No.91 and No.92 orebodies in Dachang orefield(5)In conclusion,the No.91 and No.92 ore bodies are polygeneticcompound deposits formed by Hercynian jet deposits,followed byIndosinian and Yanshanian mineralization successively.