Assessment Of The Geochemical Anomalies And Prospecting Targets Of Fangzhichang Gold And Copper Deposit In Antu County

There is obvious geochemical anomaly and Au-Cu mineralized alteration belt in theFangzhichang area, Antu county. The geological background and geological conditions of themineralization in this district are both advantageous. Luoquangou-Jinkuangtun-Fangzhichang Au-Cu-Fe mineralization belt, one mining area of them is Fangzhichang area,are formed in the north-east direction. The Fangzhichang Au-Cu mineralization was affectedby the structure apparently. The fracture and crack are developing in here and most of themare north-east direction. Especially, interlayer crack, which is the different lithologycontacting position of P1m or P1m and P1k, is the main ore controlled structure of Au-Cumineralization alteration zone in this area.The Fangzhichang area in Antu county is located on the connected belt of the intenselyactivive block and complex geotectonic environment. There is the orogenic belt, which hasmany complex magma activities, concluding the Late Hercynian, Indosinian and Yanshanianespecially. The P1m and P1k are developed in this area. The main ore-bearing layers on thecontact belt between metamorphic mica-arkose of P1m and banding crystal limestone of P1k.The condition of the mineralizing tectonic setting in this area is the transition of large duplexinverted anticline and the condition of mine-controlling structure is the pressure-shearfracture in north-east direction. The intrusive rocks of Fangzhichang area are the lateHercynian and Yanshan granite.The rocks of Fangzhichang area have been altered highly. There are3mineralizationtypes: Au-Cu mineralization, Cu-Fe mineralization and Fe mineralization formed3minepoints separately, among them the Au-Cu mineralization is primary. The FangzhichangAu-Cu ore body is developed inside the Au-Cu mineralization alteration belt and the mainalterations are chloritinzation, silicification, kaolinization and tremolite. The metal mineralizations conclude malachite, limonite, pyrite and covellite distributed in the alteredrocks as fine-grained infection. The rocks have the crushing squeeze and ductile deformation.The cause type of the mineralization belongs to the interlaminar shear crushing hydrothermalalteration rock type.The1:200000and1:50000stream sediment survey and1:50000adding density ofstream sediment survey have been done in the Preliminary work of Fangzhichang area Antucountry. The geochemical soil survey of13.3km has been done in the HTS2-2abnormalrange of the1:50000stream sediment encryption survey. Au, As, Sb, Ag, Cu, Zn, Sn, Pb, Biwere analysed. The background values and exceptions lower limit of each element wereidentified and the element anomalies range was determined.Correlation, cluster and factor analysis were carried out on the analytical data of676samples derived for the1:1000geochemical soil survey. The analysis results are the elementscombination related to gold mineralization, concluding Au, As, Sb and the elementscombination related to copper mineralization, concluding Zn, Sn, Pb. Ag and Bi are related tosilver and bismuth mineralization separately. According to the combination analysis of theelements related to gold,4abnormal combinations are found and the anomaly number is Z1,Z2, Z3and Z4, they have different scale, among them Z1and Z2have a large scale and theabnormal morphologies are obviously and consisted with the mineralization belt. It wasconsidered as the key anomaly and put anomaly inspected.Some methods were carried out on Z1, Z2soil anomalies, including geochemical soilsurvey, heat-released mercury survey, radon survey and radioactivity survey. According to theverified results,4significant anomalies were confirmed, concluding Z（1、2）-1, Z（1、2）-2, Z（1、2）-3and Z（1、2）-4. Z（1、2）-1is consistent with the location of the known ore bodies, associated withthe analysis of the geological conditions, these4anomalies were considered as mineralizedanomalies and were confirmed as prospecting targets.According to the explored trenching, geological logging and chemical analysis,3samples had been analysied. The content of Au is1.39×10^-6, Cu is1.108×10-2, Ag is 55.9×10^-6in one of the limonitic copper ore, the content of Au is0.26×10^-6, Cu is0.109×10-2,Ag is5.0×10^-6in another limonitic copper ore, the content of Au is0.09×10^-6, Cu is0.08×10-2,Ag is5.0×10^-6in the limonitic rock, it is a new discovered ore body. The same methods aresuggested to verify on the Z3, Z4soil anomalies to expand prospecting effect.Assessment of the Geochemical Anomalies is a gradually prospecting process. In theprimary stage of geochemical exploration, geochemical stream sediment survey, geochemicalstream sediment encryption survey, geochemical soil survey have the prospecting effect ongradually reduce the mine target area, however, because of the large scale of soil anomalies,further inspection and evaluation of anomalies are required before anomalies revealed. Avariety of methods can be used to confirm each other at this stage. These inspection methods,such as geochemical soil survey, heat-released mercury survey, radon survey andradioactivity survey, have obvious mineralization anomaly characteristics and better effect interms of Au-Cu hydrothermal altered deposits which are structural controlling obviously,geochemical soil survey, Radon survey and heat-released mercury survey have more obviousanomaly characteristics and more effectively in the above methods.