矿床地球化学国家重点实验室知识库

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.