Study On The Geological Characteristics And Enrichment Regularities Of Mineralization Of Linjiang Copper Deposit,Jilin Province

The Ji'an-Changbai area is an important non-ferrous metallogenic belt in Jilin Province.The Paleo-Pacific Plate subducted in Mesozoic caused intense magmatic activities in the area,forming numerous deposits.The Linjiang copper deposit is located in Liudaogou Town,Linjiang City,Baishan City,Jilin Province.The geotectonic location belongs to the eastern section of the northern edge of North China,and the eastern edge of the Liao-Ji-Chao activity belt.The main strata in the mining area is Zhengzhumen Formation of the Laoling Group,and the lithology is mainly composed of marble inclusions.The structure of the mining area is developed.The Liudaogou-Tongshan fault(F1)and the Binghugou-Xiaotong-kuanggou fault(F2)trend to northeast.They controlled the magmatic emplacement and mineralization hydrothermal migration in the area,and the layers in the strata.And the inter-layer fracture zone in the formation provided space for mineralization.The intrusive rocks in the mining area are mainly granodiorite.The LA-ICP-MS zircon U-Pb geochronology study shows that the emplacement time of the rock is(125±1)Ma,ie,Early Cretaceous.The deposit is mainly composed of six ore belts,Tongshan,Liudaogou,Xiaotong-kuanggou,Binghugou,Cuocaodingzi,Toudaobeicha,and 200 ore bodies.The ore belt generally trend to NW,tends towards SW,intermittently extends 600-800 meters,and is150-200 meters wide.The single ore body is generally small in size,generally extending from 30 to 65 meters.Only more than 10 pieces are larger than 100 meters and the thickness is generally 2-5 meters.The shape of the ore body is relatively complex,and it is mostly lenticular or irregularly pulsed.The expansion and contraction are obvious.The types of ore mainly include chalcopyrite ore,spot copper ore,bornite-chalcopyrite ore and so on.The main metal minerals in the ore are chalcopyrite,bornite,chalcocite and molybdenite,followed by galena,sphalerite and pyrite;gangue minerals are mainly quartz,epidote,calcite,garnet and so on.The ore structures are mainly metasomatic,solid solution separation,and semi-automorphic-heteroparticle,they are forming because of mainly compact massive,disseminated,mass-like,and vein-like structures.The types of wall rock alterations include skarnization,long petrochemical,silicification and carbonate carbonization,secondary sericitization,and chlorite,among which the distribution of skarnization is most closely related to copper mineralization.It is an important prospecting mark in this area.The Linjiang copper deposit has experienced three mineralization periods:skarn period,quartz sulphide period and epigenetic oxidation period,in which the copper ore body mainly forms in the quartz sulphide period.Fluid inclusion studies have shown that the ore-forming fluid is a low-salt(7~13%NaCl),low-density(0.61~0.87 g/cm~3)fluid with a metallogenetic temperature of280?~340?and a metallogenic pressure of 50~75MPa,the metallogenic depth is5.6~7.0km.Hydrogen and oxygen isotope data show that the ore-forming fluid is dominated by magmatic water,with a small amount of atmospheric precipitation mixed in later stages.The study of sulfur isotopes shows that the ore-forming materials are mainly mantle sources,some of which are derived from wall rocks and have the characteristics of mixing crust and mantle.The copper ore body is produced in the contact zone between granodiorite and marble.Folds and fractures are important ore-controlling structures.The granodiorite body brings ore-forming fluids,metallogenic materials and heat sources.Comprehensive analysis shows that the Linjiang copper deposit is of the skarn type copper deposit,and the parental rock is granodiorite.The time of emplacement of the rock can represent the metallogenic age.Combined with the regional background,the deposit was formed in the active continental margin environment where the lithosphere stretched and thinned under the subduction of the Eurasian Plate from the Paleo-Pacific Plate.The orebody distribution of the Linjiang copper deposit is controlled by the structure of the contact zone,and the mineralization intensity and scale are directly related to it.The marble of Zhenzhumen Formation is a favorable combination of ore-forming lithology and an ideal ore-bearing horizon in the area.The argillaceous marble is easily broken due to tectonic action and formed interlaminar fractures,providing a passage and space for the migration and accumulation of copper elements.Folding ends and fractured structures control the movement of mineralized hydrothermal fluids,providing a favorable space for copper mineralization.The flow of the rock mass highlights the front edge,the development of the rock branches,the depressions of the rock body,and the footwalls of the larger rock branches.The ore-forming hydrothermal fluids are fully accounted for,and the copper mineralization is more concentrated,often forming high grade rich deposits.The study concluded that the Linjiang Copper Mine has good metallogenic conditions,and there is the potential to find skarn-type copper deposits in the periphery of the mining area or porphyry-type copper-molybdenum mineralization in the deep part of the mining area.