THERMODYNAMIC PROPERTIES OF AQUEOUS SPECIES AND THE SOLUBILITIES OF MINERALS AT HIGH PRESSURES AND TEMPERATURES: THE SYSTEM AL2O3-H2O-KOH

Abstract

Experimental solubilities reported in the literature for magnetite, hematite, pyrite, and pyrrhotite over wide ranges of pressure and temperature have been combined with experimental dissociation constants for aqueous species and density and calorimetric data for Fe-bearing electrolyte solutions to generate an internally consistent set of standard partial molal thermodynamic properties and revised HFK equations of state coefficients for Fe2+, Fe3+, Fe(OH)+, Fe(OH)2 0, Fe(OH)3-, Fe(OH)2+, Fe(OH)2+, Fe(OH)3 0, Fe(OH)4-, FeCl+, FeCl2 0, FeCl2+, FeCl2+, FeCl3. The regression calculations were carried out by taking explicit account of Setchenow coefficients and Debye-Hueckel extended-term parameters together with stability constants for aqueous polyatomic clusters of alkali halides generated by Oelkers and Helgeson (1992). The thermodynamic properties and equations of state parameters retrieved from the calculations permit accurate prediction of equilibrium constants for hydrothermal reactions involving aqueous iron species at high temperatures and pressures, as well as the aqueous solubility of Fe-bearing minerals in electrolyte solutions with ionic strengths [approx lt] 5 from 25 to 1,000 C and 1 to 5,000 bars.