Comparative Study On Mineralization Between Yinmin Copper Deposit In Yunnan Dongchuan And Luiswishi Copper-cobalt Deposit In Democratic Republic Of The Congo

Marine sandstone-type copper deposits are produced in marine clastic-carbonate formation,they have large copper resources and high economic value.Yinmin copper of Dongchuan copper belt and Luiswishi copper-cobalt deposit of Katanga metallogenic belt are the types of Marine sandstone type copper deposit,development Stratiform copper body.In this paper,by comparing the two deposit geological characteristics,geochemical characteristics and mineralization,Gain the following knowledge:Through the geological characteristics of the two deposits,found that have multiple metallogenic characteristics,mainly occurs in the sandy dolomite,carbonaceous slate and carbonaceous dolomitic shale.The copper ore bodies are stratified,with band-like,laminated and vein-like copper ores.The main ore minerals are chalcopyrite,bornite and chalcocite,etc.,and gangue minerals are dolomite,quartz and calcite,etc..They are highly similar in ore-hosting lithology,orebody characteristics,mineralization combination,alteration and other geological characteristics,but also different in ore-hosting rock age and co-generation ore species.By comparing the geochemical characteristics of the two deposits,it is found that the fluid systems are composed of oxidized ore-bearing brine and reduced fluid.The inclusions homogenization temperature and salinity(200-360?,14%-49%)of Luiswishi copper-cobalt deposit are higher than those of Yinmin copper deposit(140-300?,12%-44%).The types and quantity of salt daughter are also more abundant,and the source of fluid is more abundant.The carbon and oxygen isotopic composition shows that the source of carbon is not only the dissolution of Marine carbonate,but also the dehydroxy of organic matter.The decrease of?¹³C value in ore-bearing dolomite veins may be due to the mixing reaction of ore-bearing fluid and reducing fluid,or the exchange of carbon isotopes in carbon-bearing strata.Both of them have a wide range of sulfur isotopic characteristics,indicating that the sulfur source is abundant.Marine evaporite and sulfate provide the main sulfur sources,and the reduction reaction of organic matter of sulfate promotes the generation of reduced sulfur,which leads to the characteristics of large range of sulfur isotope values.Through summarizing the metallogenic regularity of the two deposits,it is found that the stratiform copper body is controlled by the transverse faults with good connectivity,and the transverse faults are the important channel of ore-forming fluid migration.The ore-bearing rocks are generally sandy and permeable,such as sandy dolomite and stromatolite dolomite,etc.,or fine clastic and argillaceous rocks rich in organic matter,such as carbonaceous slate of Heishan Formation in Yinmin area and carbonaceous dolomitic shale of Mine Formation in Luiswishi area.The mineralization intensity of the copper body is obviously controlled by the oxidation-reduction environment,and its interface is a favorable area for mineralization.By comparing the mineralization with the Luiswishi copper-cobalt deposit,it is found that the mineralization of Marine sandstone type copper deposit and Yinmin copper deposit is basin brine metasomatism,and the mineralization mechanism is the mixing of two types of fluids.The sand slate of the Heishan Formation is the barrier layer,the sandy dolomite of the Luoxue Formation is the main sedimentary layer,forming a fluid-closed physical and chemical trap.The oxidized ore-bearing brine migrates through the fracture structure to the vicinity of the redox interface,and penetrates into the sandy dolomite with higher porosity or the organic-containing slate.The mixing of mineral-bearing brine and reducing organic-containing fluids changes the physical and chemical conditions of the mineralization environment,resulting in reduced metal solubility and precipitation,forming a multi-layer stratified copper orebodies in the Dongchuan Group and The minerals zoning of “hematite,chalcocite,bornite,chalcopyrite,pyrite”.