COMPATIBILITY RELATIONS OF ALUMINUM SILICATES IN SYSTEMS MGO-AL2O3-SIO2-H2O AND K2O-MGO-AL2O3-SIO2-H2O AT HIGH PRESSURES

On basis of experimental data available in system MgO-Al//2O//3- SiO//2-H//2O as well as in SiO//2- rich portion of system K//2O- MgO-Al//2O//3- SiO//2- H//2O, Schreinemakers analyses of phase relations in pressure range 4 to 11 kb at various temperatures were undertaken, and three pressure temperature grids constructed; in general at highest pressures stable aluminum silicates kyanite and sillimanite were found to coexist, in presence of free quartz, with Mg-rich phases talc, gedrite, enstatite, and phlogopite; at lower pressures these parageneses are replaced by different ones, such as chlorite-quartz, chlorite- muscovite, cordierite- muscovite, and cordierite-K feldspar.