玲珑金矿床成矿流体的物理化学

PHYSICAL CHEMISTRY OF ORE-FORMING FLUIDS IN THE LINGLONG GOLD DEPOSIT

玲珑金矿床为胶东著名的含金石英脉型矿床。作者详细研究了与金矿化密切相关的脉石英流体包体特征及其均一温度、爆裂温度、气液相成分。运用热力学分析和数学地质方法,计算了成矿流体盐度、密度、压力,以及成矿环境的Eh和pH等物理化学参数。为矿床成因研究提供了众多的实际资料。

Located some 150 km west of Yantai, Shandong Province, the Linglong gold deposit consists of a series of hydrothermal ore veins filling NEE-striking faults within the Linglong granite formed by metasomatism of Jiaodong Group (Precambrian metamorphic rocks). Hydrothermal mineralization might be divivided into four stages; ①Dpyrite-quartz; ②quartz-pyrite; ③polymetallic sulfides and ④carbonates, with the major gold-associated minerals being quartz, pyrite, chalcopyrite, pyrrhotite, sphalerite, galena and calcite, and the major wall rock alterations including silicification, sericitization,pyritization and potassic alteration.Studies on fluid inclusions in quartz from ore veins indicate that there exist mainly two types of fluid inclusions, i. e. aqueous (or saline) inclusions containing a certain amount of CO_2, and CO_2-rich inclusions, with the occasional presence of CO_2, liquid and gas three-phase inclusions. Homogenization temperatures of fluid inclusions at the early mineralization stages range from 200℃ to 370℃, and can reach as high as 450℃ for a few critical inclusions. The minimum ore-forming pressures vary in the lange of 2.13×10~7～6.27×10~7 Pa for Stage Ⅰ and 2.17×10~7～8.63×10~7 Pa for Stage Ⅱ. Ore-forming fluids are characterized by high concentration of CO_2 and relatively low salinity. Average X_(co_2) (wt%) values are 8.2～14.5 and 8.4～25.3 for Stage Ⅰ and Stage Ⅱ respectively, whereas fluid salinities (equiv. wt% NaCl)are correspondingly 2.6～6.5 and 4.2～5.8. Other physicochemical conditions for oreforming fluids of the initial stages are pH 5.04～5.77, Eh -0.53～-0.55, m_(Na)+0.2～0.5, m_K+0.037～0.87, m_(Cl)-0.2～0.6 and densities 0.83～0.87g/cm^3.