Structure of H2O-saturated peralkaline aluminosilicate melt and coexisting aluminosilicate-saturated aqueous fluid determined in-situ to 800 C and 800 MPa

The structure of H2O-saturated silicate melts and of silicate-saturated aqueous solutions, as well as that of supercritical silicate-rich aqueous liquids, has been characterized in-situ while the sample was at high temperature (to 800 degrees C) and pressure (up to 796 MPa). Structural information was obtained with confocal microRaman and with FTIR spectroscopy. Two Albearing glasses compositionally along the join Na2O center dot 4SiO(2)-Na2O center dot 4(NaAl)O-2-H2O (5 and 10 mol% Al2O3, denoted NA5 and NA10) were used as starting materials. Fluids and melts were examined along pressure-temperature trajectories of isochores of H2O at nominal densities (from PVT properties of pure H2O) of 0.85 g/cm3 (NA10 experiments) and 0.86 g/cm(3) (NA5 experiments) with the aluminosilicate + H2O sample contained in an externally-heated, Ir-gasketed hydrothermal diamond anvil cell.