Silicate mineral dissolution at pH 4 and near standard temperature and pressure

The dissolution of labradorite, microcline, enstatite, augite and forsterite in acidified deionized water was investigated at near standard temperature and pressure and constant pH of 4.00 to determine the kinetics of the release of silica, and cations. Saturation indices and mass balance calculations suggest that after 700 hours, the release of silica from forsterite and augite was controlled by the precipitation of a solid silica phase, whereas silica mass transfer from the feldspars and enstatite was essentially as silicic acid. Iron release from the pyroxenes and olivine was probably controlled by the precipitation of iron oxyhydroxide phases. Linear-rate constants calculated after 700 hours for release of magnesium ranged from 10^?15.2 to 10^?14.4 M · cm^?2 s^?1 for augite and forsterite respectively. Linear-rate constants for the release of cations from feldspars ranged from 10^?15.8 to 10^?15.3 M · cm^?2 s^?1.