Metallogenic Fluid Characteristics Research Of LingLong Gold Deposit In East Shandong Province

Linglong gold deposit, located in Zhaoyuan, the Northwest in Jiaodong, is one of the most significant quartz-vein type gold deposits in China.Based on the research on mineral deposit, this paper tries to reveal the elements’migration during the whole progress of alteration and mineralization, it also analyzes the petrofacies of the fluid inclusions by testing their homogenization temperature, salinity and compositions in order to calculate the fluid density, pressure, as well as other physicochemical parameters, such as Eh, pH, fo₂ and fCo₂. Afterwards, the conclusions are demonstrated in the following:（1）The results of the alteration zoning within wall rock and the element’s migration indicate that the content of metallogenic elements including gold tends to increase successively during the alteration progress that unaltered biotite monzonitic granite - potash feldspathization granite - sericitization granite– beresite– silicatization– ore body. The metallogenic elements are enriched in the sericitization period, while the silicatization is abated correspondingly. In the metallogenetic stage, the wall rock plays a big role to cool down the metellogenic fluid and change its physicochemical condition so as to generating/precipitating the gold.（2）In No.55 mineral vein, the typical lode in Xishan, gas-liquid water soluble inclusions and three-phase inclusions are dominant in the main mineralization stage with few pure gas inclusions.In the first stage, the homogenization temperature of inclusions mostly range from 325℃to 350℃, the salinity are concentrated from 9.5 to 11.0%, the fluid density is between 0.67 and 0.86g/cm³. Comparatively, the homogenization temperature, the salinity and the fluid density are 200-375℃, 6.5-10.5% and 0.56-1.01g/cm³, respectively.In the second and third stages, the pressure and mineralization depth of the three-phase inclusions are 96～227 MPa and 6.2～11.04 Km. On the level of -50m, the different inclusions sharing quite similar homogenization temperature coexist, which apparently shows that there had once been boiling fluids.（3）The inclusions of Dongshan and Xishan share the same types, particularly No.47 lode which on behalf of the Dongshan district. In the first stage, their homogenization temperature mostly range from 250 to375℃, the salinity are concentrated from 4.0 to10.0%, the fluid density is between 0.67 and0.97 g/cm³. In the second and third stages, the pressure and mineralization depth of the three-phase inclusions are 110-250MPa and 6.9-12.48 Km. On the level of -670m, the different inclusions sharing quite similar homogenization temperature coexist, which apparently shows that there had once been boiling fluids.（4）The analysis results state that the majority gases are H₂O and CO₂, the minorities are N₂, CO, H₂ and CH₄. The fluid contains different types of cations that many a Na⁺ and Ca²⁺, certain Mg²⁺ and K⁺, minor Al³⁺, Fe³⁺. The majority of anions are Cl^- and SO₄^2- , then F^-, occasionally with HCO₃^-, NO₃^- and OH^- . The calculated physicochemical parameters, including pH, Eh and lgfO2, are 4.17⁶.74 （av.5.18）, -0.68^-0.51 （av.-0.60）, -29.81^-36.66（av.-32.11）. These above prove that the mineralization fluid generally tends to be acidic or weak acidic reducing fluid.The above conclusions contribute to do the further analysis on the ore genesis in the future.