Geological-geochemical Characteristics Of Jiuzhanggou Gold Deposit,Songxian,Henan Province

Jiuzhanggou gold deposit is located between two secondary tectonic units,which is the south margin of North China landmass in North China plate and the North Qinling Mountains tectonic belt.It adjacents to Tantou-Songxian depression in south.The structure is developed in the area with frequent magmatic activity and good metallogenic conditions The exposed stratas are Neoarchean Taihua Group Complex,Xionger Group of Mesoproterozoic Erathem Changchengian System,Gaoshanhe Group of Jixianian System,Guandaokou Group of Neoproterozoic Qingbaikouan System,Cenozoic Paleogene System,Neogene System and Quaternary System.The ore body is controlled by F1,which is steep inclined structural alteration zone with NNE trending.The surrounding rock alteration and mineralization are strong,and the alteration zoning is obvious.The silicification and pyrite mineralization is closely related to gold mineralization.The ore deposits are divided into metallogenic epoch and supergene stage.The mineralization period consists of four stages: I potash feldspathization stage,which is a prelude to mineralization;II quartz-disseminated pyrite stage,the homogenization temperature is range from 325.2? to 379.0?,and the salinity is 2.3 wt%Na Cl.eqv to 10 wt%Na Cl.eqv;III gold-polymetallic sulfide phase is the main stage of mineralization,and the homogenization temperature is range from 220.2 ? to 379.0?,the salinity is 2.6 wt%Na Cl.eqv to 8.6 wt%Na Cl.eqv;IV quartz-carbonate stage with weak mineralization and low temperature,which is the end of metallogenic period.The mineralization depth is estimated from 1.64 km to 3.65 km.The range of total amount of rare earth elements in gold ores is large(?REE=88.94×10-6~596.36×10-6),and it is consistent with the complex sources of ore-forming materials and the multi-periods strong fluid activity about ore-forming materials.The geochemistry of the deposit shows that the ore-forming material of the deposit is mainly derived from Wuzhangshan rock mass.The zircon LA-ICP-MS U-Pb dating shows that the emplacement age of Wuzhangshan granite is 177.3Ma ± 1.7Ma.According to the summary of previous studies,the metallogenic age of Jiuzhanggou gold deposit is the late Jurassic epoch,which is later than the emplacement age of Wuzhangshan rock mass.This suggests that the deposit belongsgenetically to the middle shallow-seated mesotherm post-magmatism hydrothermal type.Through the study of geochemical exploration,it is concluded that the top-bottom axial zoning sequence of primary halos of the Jiuzhanggou gold deposit is Cu-Bi-W-Au-Hg-As-Sb-Pb-V-Mo-Ag-Zn.And it shows the reversed axial zonality characteristics.Combined with analytical study of the erosion coefficient of ore body,it is considered that the main ore body M1 in Jiuzhanggou gold deposit is likely to extend to the deeper.