The Genetic Mineralogy And Deep Forecast Of The Lingshou Shihu Gold Mine In Hebei

The Lingshou Shihu Gold Mine with limit measured reserve, locating in Hebei Province, is in urgent need for sustainable resource into production. This study carries out research on regularity of gold formation and exploration prospecting of the mine in deeper area and outer-ring based on previous geological and scientific work, combining with genetic mineralogy and geochemical mapping method.Shihu Gold Mine locates in the middle region of the Taihang Mountain Rise in the North China Craton. The high-metamorphic and middle-high-migmatised metamorphic rocks belonging to Fupin Group Tuanbokou Formation and Nanying Formation occur in the mining area. The magmatic rocks typically consist of the Mapeng rock and neutral-acid dykes of the Yanshan Mountain stage. The ore field is in the northwest wind of the Chenzhuang Syncline. And the east-pitching anticline structure and SN, NW and EW fault developed. The ore formation process can be divided into 4 stages: pyrite-quartz stage, quartz-pyrite stage, polymetal-sulfide stage and quartz-carbonate stage. Additionally, the alternations comprise silication, phyllic alteration, pyrite-phyllic alteration, chloritization and carbonization.The thermoelectricity of pyrite: high-value of P type andαP ranging110μV/℃~140μV/℃parallel gold-rich ore block; the ore formation temperature calculated ranges 154.9℃~325.5℃indicating medium-low temperature deposit; and the change of P% values display rhythmic distribution from 560m level to 180m level. The decrepitation temperature of pyrite: decrepitation temperature curves are summarized as 3 basic types; pyrites with medium-low temperature peaks or none-peak range from initiation to 368℃have better gold-bearing advantage.The regions which have low value of thermo luminous intensity or medium-low temperature peak are favorable section for gold mineralization. The study also discusses the petrographic characters, homogenization temperature and other mineralogical information of quartz fluid inclusions. The quartz fluid inclusions can be mainly classified into 3 types. The homogenization temperature ranges 102～440℃, while salinity rangs1.4～10.78%. Ore-forming fluids rich in Na +, Ca2 +, K +, SO42-, Cl-and a small amount of F-, theoretically belong to the NaCl-H2O system. The hydrogen and oxygen isotope data from different mineralization stages show that original precipitation drop into origin hydrothermal fluid to form ore-forming fluid. In aspects of prospecting criteria, the Mapeng Rock is the parent rock of ore formation; NW or NNW to SN trend shattered and faulted zones contacting with the Mapeng Rock are preferred for gold-formation; the alteration from potassic alteration to pyrite-phyllic alteration zone is a sign of approaching ore body; gold-rich pyrites have characters of P-type thermoelectricity, thermoelectric coefficient ranging 110μV/℃~140μV/℃, the B-type depreciation curve and depreciation temperature ranging 170℃~160℃; while gold-rich quartz that normally are dark gray and xenoblastic have thermo luminous characters of double-peak, high-intensity and peak-temperature lower than 200℃; homogenization temperatures of fluid inclusions range between 170~353℃, with the average temperature of 274℃; The salinity range of 3.06~8.47%, with the average salinity of 5.77%; the fluid of main ore-forming stage with density range of 0.81~0.87g/cm3, ore pressure67.6 ~72.8Mp, forming depth of 2.0~2.2km; the ore-bearing hydrothermal pH value is between 4.74~5.56, with the average of 5.22.According to field observation and laboratory research, combined with gold grade of data analysis, the result shows that the gold-rich ore body occurs equally with elevation declining from north to south. It is predicted that the prospecting areas are as follows:ⅠProspecting Area: Regions between 19th lines and 31th lines at the elevation of 200m to-40m, between 3th lines to 11th lines at the elevation of-40m to 200m;ⅡProspecting Area: Regions near 41th line at the elevation of -200m level, between 7th line and 15th line at the elevation of -400m level.