Geological-geochemical Characteristics And Genesis Of Dafangshan Gold Deposit In The West Of Henan Province

Dafangshan gold deposit in the west of Henan province is located in southern margin of north China craton and the transition zone of the North Qinling orogenic belt, which is typical vein hydrothermal gold deposit.Based on the analysis of the ore-forming geological conditions, geochemical characteristics and fluid inclusions, author researches on source of the ore-control ling factors, the genesis of deposit and etc. The main achievements are made as follows:1. The deposit geological features were studied, especially the geological features of vein-J1, J2and vein-C8, C9. Orebody feature was studied about location, shape, occurrence, scale, and variation of grade of orebody, texture and structure of ores, wall rock alteration and ore-forming stages.2. Through the analysis of the ore-forming geological background and characteristics of deposit geology, orebody, ore and wall-rock alteration, the ore-forming process of Dafangshan Gold deposit is divided into three stages and six phases, based on the relationship of mineral association combination,3. The ore-forming geological conditions were probed from the relationship between mineralization and stratum, structure, magma rock aspect. The gneiss stratum of Taihua group greenstone belt provided some material for deposit; The orebody was controlled by the structure which is the most important factor at mineralization stage; The magmatic rock of Yanshanian is the beneficial parent rock of mineralizing.4. Hydrogen and oxygen isotopes, sulfur isotope and lead isotope analysis in Dafangshan indicate that the mineralizing solution is magmatic water, the sulfur mainly from magmatic rock. The major source of lead is mantle and crust.It has orogenic belt characteristics.5. Fluid inclusions are classified into four mian types. These inclusions are mainly LV inclusions. Homogenization temperature indicates that ore-forming fluid is low to moderate temperature hydrothermal. The mineralization temperature and salinity tended to decrease with the conduct of the mineralization. It inferred that ore-forming fluid mainly from the magma by the value of the Na+/K+.6. Based on the analysis of characteristics of geology and geochemistry, Dafangshan is a low to moderate temperature hydrothermal type gold deposits, which is related to Yanshanian magmatic rocks and controlled by structural altered fracture zone. Figures:59, Tables:14, Referens:114.