Synthetic Fluid Inclusions in the Systems NaCl‐H2O and NaCl‐CO2‐H2O: Dissolution Temperatures of Halite

Abstract

Abstract. This study examined the effect of CO2 on NaCl solubility in hydrothermal fluid, with the synthetic fluid inclusion technique. Fluid inclusions of 30–40 wt% NaCl and 5 mol % CO2 were synthesized, and their halite dissolution temperatures, Tm(halite), were measured. The solubilities of NaCl in CO2‐bearing aqueous fluid were obtained at 160–320d̀C under vapor‐saturated pressures. The Tm(halite) value in aqueous fluid with 5 mol % CO2 obtained in this study agrees with that of Schmidt et al. (1995), showing that 5 mol % CO2 reduces the solubility of NaCl by about 1 wt%.Calculation of magnetite solubility suggests that 5–10 mol % CO2 decreases magnetite solubility by 4.5–8.9 % relative to the magnetite solubility in CO2‐free solution. Therefore, an increase of CO2 content in ore‐forming solutions may cause deposition of iron minerals and produce ore deposits.