Accurate Calculation Procedure for V-x Parameters of Hydrothermal Gold Ore Fluid Inclusions

Determining the V-x parameters of H2O–NaCl–CO2 fluid inclusions (total density of inclusions, gas content, homogenization pressure, etc.) is of great value for the exploration of hydrothermal deposits. However, previous accurate calculation methods are only applicable to H2O–NaCl–CO2 fluid inclusions with homogenization temperature above 300 °C and CO2 phase homogenization temperature above the CO2 clathrate melting temperature. In this paper, a new calculation method is proposed to accurately solve the V-x parameters of H2O–NaCl–CO2 fluid inclusions with complete homogenization temperature lower than 300 °C. The algorithm first determines the salinity of inclusions with respect to the melting temperature of CO2 clathrate and the partial homogenization temperature of the CO2 phase and then determines the internal pressure of inclusions when CO2 clathrate is completely melted. The V-x parameters of the inclusions are then iteratively solved. The new algorithm does not require a visual estimation of the volume fraction of the CO2 phase as an input parameter. It is possible to avoid the significant error brought about by traditional method of calculating the inclusion V-x parameters involving visual estimation of the CO2 phase volume fraction. A computer program is developed on the basis of the new method and is applied to the analysis of fluid inclusions in medium and low temperature hydrothermal gold ore