Research On Geology And Geochemistry Of Ag-Au-Pb-Zn Deposits In Northern Neixiang Ore Cluster, Henan, And The Exploration Guiding

During the new round of land and resource investigation, significant progress hasbeen made for the exploration of silver-gold-lead-zinc in the east part of NorthQinling Mountains (namely Henan section) and an important eye-catchingsilver-gold-lead-zinc concentration area has been discovered in the northern part ofNeixiang in Henan. Based on the collection of related materials and research to theregional geology, veins with various occurrence from typical deposits likeYindonggou deposit, Zhouzhuang deposit and Dongqinggou deposit in this oreconcentration area are chosen as the researching object of deposit geology andgeochemistry. Based on this research, ore-forming fluid, ore-forming material source,genesis and mineralization are concluded in this paper. Prospecting direction is alsoput forward to serve for a new round of exploration.This ore-concentration area is located in the center of Erlangping terrene of theNorth Qinling orogenic belt. In this area, the main outcropping strata are Xiaozhaiformation and Huoshenmiao formation of Erlangping group. In the former formation,small-grained carbonaceous clasolite occurs and the background value of ore-formingelements like Au and Ag is comparatively high. Fault structure is well-developed andmagmation was frequent in this area. The ore-bodies are controlled by secondary faultof the regional fault and characterized by small thickness and many paragenetic andassociated minerals. The forming of ore-bodies can be divided into three stages,namely, early stage or quartz-pyrite stage, middle stage or quartz-lead-zinc polymetalsulfide stage, and late stage or quartz-carbonate (calcite) stage.The characteristics of ore fluid inclusions, REE, and stable isotope geochemistryshow that ore-forming fluid is mainly characterized by deoxidization. Theore-forming fluid of early and middle stage comes from magmatic water ormetamorphic water, but the fluid of late stage is mixed with the meteoric water ofepizone. It is of great possibility that ore-forming materials come from Xiaozhaiformation of Erlangping group and Yanlinggou formation of deep Qinling group.However, ore-forming fluid and materials of different veins in different deposits havesame source.As to the development of ore-forming system of fluid, in Mesozoic era, Qinlingtrough was completely closed, and the North-qinling orogenic belt was in theenvironment of continental collision. Yangtze plate moved towards north and collidedwith North China plate. The strata of Qinling group subducted to the bottom ofErlangping terrene through Zhuyangguan-Xiaguan fault, which induced thedevelopment of fluid-mineralization system. During the up-moving process, theore-forming fluid contacted with the rock of Xiaozhai formation of Erlangping group and strong water-rock interaction occurred. Ore-forming material was extracted fromthe wall rock; fluid with ore-forming material moved to favorable space, then mineraldeposited and formed ore bodies. The deposits in the area should be formed inYanshanian stage.Fault structure with NE-NNE strike and NW-NWW strike are bothore-containing structures in the ore-concentration area, but mainly the former. In thisarea, the junction of linear structure and ring structure and the anomaly distributionarea of stream sediment are important prospecting direction of the same type deposits.