SOLUBILITY STUDY OF THE MH BUFFER ASSEMBLAGE IN HCL SOLUTIONS AT 300-DEGREES-C AND 500 BAR

Using a gold cell hydrothermal apparatus the solubility of the MH (mag netite + hematite)buffer assemblage in HCl aqueous solutions was deter mined at 300-degrees-C and 500 bar. The activity of ions in hydrotherm al solutions was estimated, and the experiment data were treated by ri dge regression and iteration to fit to all possible Fe speciation sche mes. The result showed that the dominant Fe species in solutions was F eOH+ under the run conditions. The equilibrium constant for the dissol ution reaction was obtained, K-57.161. DELTAG5,FeOH+0 value of -260.3 kJ/mol at 300-degrees-C and 500 bar was calculated. Fe basically exist s as Fe-OH species in hydrothermal solution under geologically reasona ble conditions of pH and chloride concentration.