EFFECT OF INCONGRUENT DISSOLUTION ON MINERAL SOLUBILITY DATA DERIVED FROM QUENCH EXPERIMENTS

Abstract

Weight-loss experiments in a double-capsule setup remain, to date, the most reliable source of mineral solubility data at HP and HT for geologically relevant systems. Recent experimental results (Verlaguet et al., 2006: Geochim. Cosmochim. Acta, 70 (7), 1772-1788) obtained for the Al2O3-SiO2-H2O and K2O-Al2O3-SiO2- H2O systems show that, in contradiction to what is generally assumed for quench experiments, incongruent dissolution products are likely to crystallize in the outer tube of the setup where most of the fluid is located. This result suggests that mineral solubility derived using the double-capsule setup are systematically overestimated. By modelling fluid reaction paths in simulated dissolution experiments (Al2O3-SiO2-H2O system), it appears that the overestimation of the aqueous species concentration in the high-pressure and high-temperature fluid can reach 50 to 100 % when pure water is used as starting fluid. The effect of changing the composition of the initial fluid on the derived solubility is discussed. © 2007 E. Schweizerbart'sche Verlagsbuchhandlung.