Aqueous speciation of zinc chloride in supercritical hydrothermal solutions from 500 to 700°C and 0.5 to 1.0 kb

Aqueous speciation of zinc to 2N chloride solution was determined experimentally at 500 to 700°C and 0.5 to 1.0 kb by monitoring the effect of NaCl on ion exchange equilibria in the system CaTiO₃-ZnTiO₃-CaCl₂-ZnCl₂-H ₂O. The Ca/(Ca + Zn) value of the 2N aqueous chloride solution in equilibrium with both CaTiO₃ and ZnTiO₃ decreased with the increase of NaCl under all experimental conditions. This is due to the formation of tri-chloro zinc complex. The formation constant of tri-chloro zinc complex was estimated to be 1.1, 2.1 and 2.7 at 500, 600 and 700°C, 1 kb, respectively, and 2.6 at 600°C, 0.5 kb in logarithm. The formation constant of tri-chloro zinc complex increases with increasing temperature and decreasing pressure. This suggests that zinc can be effectively leached from rocks and magmas under higher temperature and lower pressure conditions.