Gold Solubility in Reduced Carbon-Bearing Fluid

Abstract

The paper presents first experimental data on gold solubility in CO–CO₂ and C–O–S fluids with a low H₂O concentration under reduced conditions, a pressure of 200 MPa, and a temperature of 950°C. Gold solubility in C–O–S fluid is approximately 27 ppm. The estimate of gold solubility in CO–CO₂ fluid with 10–15 mol % CO is less accurate, and the solubility is no lower than 2–3 ppm but may reach 200–300 ppm. The high gold solubility in reduced CO₂ fluid determined in the course of this research, and our earlier estimates of high platinum solubility (Simakin et al., 2016), may explain the deposition of mineralization of these noble metals in the Guli intrusion, polar Siberia, as a result of fluid extraction of these metals and their redeposition at a temperature slightly below the solidus. The reduction of the largely oxidized CO₂ fluid, which was determined using mineralogical sensors, was likely related to the subsolidus oxidation of olivine.