| Zhao ping fracture zone is one of the important gold mineralization belts in Jiaoxibei area. The gold deposits in this fracture zone belong to the typical hydrothermal vein gold deposit. Gold ore body is the product of interaction between surrounding rock and ore-forming hydrothermal solution. Gold mineralization has the most direct contact with the wall rock alteration. Therefore, to study the Zhao ping fracture zone altered rock has positive significance for understanding the process of gold mineralization, the ore-forming mechanism and geological prospecting.In this paper, the existing data of Zhao ping fault as the basis, the altered rock of the northern section of Zhao ping fault and its typical gold deposit(the Ling long gold mine) as the main research object. Research the spatial distribution characteristics of altered rock, the petrography characteristics of altered rock, the geochemistry and clay minerals of altered rock. And discusses the relationship between altered rock and gold mineralization, and the prospecting significance of altered rock.Through the above research, has obtained the following understanding:(1)Altered rock spatial distribution characteristics and petrography characteristicsWall rock alteration are developmental in the study area. Altered rocks are mainly distributed along the fault on both sides. Alteration types include potash feldspathization, solidification, sericitization, pyritization, carbonatization, etc. The alteration zoning is obvious; the footwall alteration zone is most complete. Generally by the center to the footwall, followed by beresitization zone- sericite-quartz alteration zone- potash feldspathization zone- not altered granite zone. Observed altered rock under the microscope, discovery the alteration types, intensity of alteration, mineral composition is consistent with the field alteration zoning. The gold mineral is native gold and electrum, mainly have inclusion gold, intergranular gold and fissure gold occurrence in pyrite and quartz,(2) The altered rock geochemical characteristics and the characteristics of clay mineralsAltered rock major element analysis showed that with the increase of alteration degree, Si, K elements are moved into the rock, while the Na, Ca elements are moving out of rock; REE analysis shows that, with the increase of alteration degree, the total amount of REE show decreasing trend. LREE and HREE fractionation is obvious, the REE distribution curve was obvious right deviation form; trace element analysis shows that, Rb, Ba content in general with the mineralization intensity(intensity of alteration) increased; the correlation analysis of mineralization elements and gold mineralization showed that, Au elements and Ag, As, Bi, Co, Ni elements has a significant positive correlation. From the granite-potash feldspathization granite –serictolite-silicified rock- beresitization-containing metal sulfide quartz vein, the main mineralization elements content increase in turn; altered rock clay mineral analysis shows that: fault gouge samples containing the majority of illit-smectite mixed layer, and mineral ore samples do not contain illite-smectite mixed layer mineral. Combining with the data analysis, speculated that the illite crystallinity and gold grade has a positive correlation.(3) The relationship between the evolution of alteration and gold mineralizationStudies suggest that the migration process of ore bearing hydrothermal fluid along the fracture zone, as the temperature and pressure decreases, first of all to form potash feldspar alteration, gold activation and migration in complex form potassium feldspathization, ore bearing hydrothermal fluids from alkaline to acidic changes. Hydrothermal fluid and rock to exchange material, and the formation of sericitization, silicification, pyrite, chalcopyrite and other metal sulfide as precipitation. Changes in the p H value of the solution and reduced sulfur activity reduced, destroy the stability of the complexes of gold, gold complexes decomposed, and precipitation of Au in a favorable tectonic area, enrichment and mineralization.(4) Prospecting Significance(prospective areas of mineralization proposed)According to alteration mineralization distribution of Zhao ping fault and its footwall secondary faults, put forward 2 prospecting areas of Zhao ping fault: Lu Ge Zhuang south to Qian hua yuan section in the North of the of Zhao yuan city and Guo Jia Bu area in the South of Zhao yuan city. |
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