贵州水银洞金矿床成矿流体不混溶的包裹体证据

The evidence from fluid inclusions for the immiscibility of the ore-forming fluids in the Shuiyindong gold deposit,Guizhou Province

通过对水银洞金矿床中流体包裹体的观测和热力学参数计算,探讨了成矿流体不混溶的热力学条件。研究结果表明,该矿床石英中的流体包裹体分为H_2O包裹体、CO_2包裹体和CO_2-H_2O包裹体三大类,并以富含CO_2-H_2O包裹体为特征,CO_2-H_2O包裹体可进一步划分为富H_2O相CO_2-H_2O包裹体和富CO_2相CO_2-H_2O包裹体。加热时富H_2O相CO_2-H_2O包裹体完全均一成H_2O相;而富CO_2相CO_2-H_2O包裹体完全均一成CO_2相,而且二者的完全均一温度和完全均一压力一致,说明它们是同时期捕获的CO_2-低盐水不混溶流体包裹体组合。它们形成时的热力学条件是:形成温度236℃,形成压力324 bar(1bar=10~5Pa);共存两相流体密度:低盐水相0.900 g/cm^3,CO_2相0.314 g/cm^3;共存两相中CO_2的摩尔分数:低盐水相0.0376,CO_2相0.7337;水溶液含盐度w(NaCl)约为1.3%。

Based on the microthermometry and thermodynamic parameters of fluid inclusions in the Shuiying-dong Au deposit,we have studied the thermodynamic conditions of the immiscibility of the ore-forming fluids. The results show that the fluid inclusions in quartz are divided into three categories：H2O inclusions,CO2 inclusions and CO2-H2O inclusions.The CO2-H2O inclusions can be further classified into H2O-rich CO2-H2O inclusions and CO2-rich CO2-H2O inclusions.When heated,the homogeneous phase state of H2O-rich CO2-H2O inclusions was the H2O phase,while that of CO2-rich CO2-H2O inclusions was the CO2 phase.Moreover, they have the same homogeneous temperature and pressure.This suggests that they were CO2 and low-salt water immiscible fluid inclusions having been trapped in the same period.The thermodynamic conditions of their formation are the formation temperature of 236℃,pressure of 324 bar,low-salt water phase density 0.900 g/cm3,CO2 phase density 0.314 g/cm3,the CO2 mole fraction of 0.0376 in low-salt water phase and 0.7337 in CO2 phase,and aqueous solution salinity w（NaCl）（？）l.3%.