Genetic Mineralogy And Metallogenic Prognosis Of Yi Xingzhai Gold Deposit In Fan Shi County, Shan Xi Province

After being explored for twenty years, the proved reserve of Yi Xingzhai gold deposit is close to exhausted. Supported by t"Mineral prediction of Yi Xingzhai gold deposit in Fan Shan county, Shan Xi province"(No. 200714009), this thesis focus on genetic mineralogy in order to supply the scientific evidence for the prospective prognosis in depth and periphery.This mine is located in the northern part of medium zone of north china craton, where tectonic movement and magmatic activities are active. The Sun Zhuang rock mass, in the south of the deposit, is related to the ore-forming genetically. The auriferous ore bodies which are controlled by the Northern west fault, are in the complex of Heng Shan Mountain. The ore type is composed by quartz vein, structural altered rock type and crypto-explosive breccia type.The results of the morphologies, elemental components and geochronology of zircons show that Sun Zhuang body mass are water-rich, alkali deep source intrusive rock.The hessonite-demantoid and epidote-clinozoisite represent two stages of skarnized process respectively. The zonal structure of garnet and epidote indicates that the T, P, Eh, pH et., in the crypto-explosive breccia pipe have changed with the energy accumulation or release of the magma and hydrothermal fluid.The component in the quartz fluid inclusions is composed of CO2, H2O, Na+and Cl-.The homogeneous temperature is between 130~380℃. pH:6.24~6.45, Eh:-0.8~ -1.3, salinity: 9.01~20.96, density: 0.84~0.87 and mineralization depth: 1.57~2.64km. The cell parameters of quartz are correlated with mineralization intensity positively and with metallogenic depth negatively. The curves shape of thermoluminescence of major metallogenic stages are two-peak pattern. The curve peak locations are between 238~258℃and 310~324℃. FTIR index of quartz powder is between 2~4, the half-width of the asymmetric stretching vibrational band 1085 cm-1 and the absorption intensity of symmetric stretching vibrational band 800cm-1,780cm-1 are at the range of 30~60cm-1 and 6~10%.The morphological characteristic of pyrite is the combination form of pentagonal dodecahedron and cube. The ratio of S/Fe is over 2 and the concentration of Co, Ni, Pb, Zn and Mo is high in pyrite. The rations of Zr/Hf, Nb/Ta are stable in pyrite of the quartz vein while unstable in the crypt-breccia pipe. The cell parameters of pyrite are correlated positively with tectonic difference stress in the main mineralization stages. The pyrelectric coefficient is at the range of 0~﹣200μV·℃﹣1, over 70% are N type. According to the computation of the thermoelectric, the mineralization temperature is 143.3~323.3℃, wihich is consistent with the fluid inclusion of quartz and shock temperature of pyrite. The fluid inclusion in pyrite are abundant, the temperature interval of explosive is between 210~282℃. The result of stable isotope shows that the ore-forming hydrothermal fluid of the deposit is magmatic fluid at early stage and incorporated some meteoric water in late. The matallogenic material comes from the border between the upper mantle and lower crust. Considering the characteristics of ore forming fluid, it is attributed to hypabyssal-medium-low temperature– magmatic hydrothermal deposit. Based on the tectonic regularity, mineralogy typmorphic characteristics, and mineralogical mapping, thirteen predicting target areas (three of them were in the first list) were proposed in depth and peripheral. Among the first list, there are 2 targets have been verified by drilling hole in field. in the south of 5#.One auferious body is approach to 1m and the gold grade is about 4.99g/t. The other verified target is a porphyritic Molybdenm near the He Wan crypto-explosive breccia pipe, and the result of explored Molybdenm mass body is that the thickness is about 9~15m, the molybdenum grade is 0.05～0.1%...