Geology,Geochemistry And Metallogenesis Of The Lengshuikeng Ag-Pb-Zn Ore Field In Jiangxi Province

The Lengshuikeng Ag-Pb-Zn ore field in Jiangxi Province is one of the most important Ag-Pb-Zn ore areas in Wuyishan polymetallic metallogenic belt.This ore field contains two types of deposits,porphyry and stratabound-type deposits.At present,the research of a single type of deposits is already high,but the systemic synthetical research between the two types of deposits is still significantly weak.There still needs more in-depth work.In this paper,on the basis of the full collection and collation of previous data,by taking detailed surface and tunnel geological observation and indoor research work,and combined with the modern mineralization theory,we have studied the geological characteristics of the two types of the Lengshuikeng Ag-Pb-Zn ore field.Linked with geochemical characteristics and stable isotope characteristics,we discussed the era of rock and ore,determined the source of ore,ore-forming fluid source,and then ore genesis are investigated.The mineralization of porphyry deposit in the Lengshuikeng Ag-Pb-Zn ore field always occurred in the alkaline granite porphyry and its contact zone;and the mineralization of stratabound-type deposit is located in the volcano rock strata which contacted the alkaline granite porphyry,hidden in the depth of the ore field.The ore of the two types of deposits has its own characteristics.The geochemical analysis shows that,the magma of ore bearing porphyry and volcano rock of the ore area are all from the middle-upper crust rocks melt;and the carbon and oxygen,sulfur,lead isotopic geochemistry of the Lengshuikeng Ag-Pb-Zn ore field reveals that,the ore-forming material and fluid comes mainly from the porphyry magma system,partly from strata.The eruption of Daguding Group and Ehuling Group Volcanic in Late Jurassic was caused by compression on a crustal rock remelting,and the forming time is about 157Ma.In the interval of thevolcanic eruption,there formed felsic volcanic breccia and ironmanganese carbonate based sedimentary layers.Because of the role of regional compression,there formed the thrust nappe structure(F2 fracture in the mining area),and the caused interlayer structure of the volcanic strata provided space for magma shallow-much shallow emplacement.With the stress from compression to tension conversion,the granitic magma which was from the melting of middle-upper crustal rocks rised along the tensile structure and emplaced in the collapse site of the volcanic rocks.The forming time is about 156Ma.The much shallow emplacement of granite porphyry provided convenient conditions for a large number of meteoric water to penetrate the rock.The ore-bearing magmatic fluids in the progress of the rock emplacement occurred mineralization in the different sites with conditions such as temperature and pressure changes and the addition of atmospheric water.