Calculation of Muscovite-Paragonite-Alkali Feldspar Phase Relations

摘要: Experimental data on K-Na exchange between NaCl-KCl-H2O fluids and alkali feldspars or white micas, end-member dehydration reactions of mica (± quartz to feldspar plus corundum (or Al2SiO5) H2O have been used evaluate potentials coexisting feldspar. Calculations using these Margules parameters for excess molar Gibbs energies feld-spars micas permitted the construction a projected binary phase diagram dehydration. Extrapolation higher temperatures pressures gives topology wholly consistent with field evidence. The subsolidus univariant curves intersect H2O-saturated minimum-melting curves. At greater than about 6 kbar common assemblage Ms+Or+Ab+Q could undergo at lower disappearance paragonite kyanite-sillimanite isograd in more aluminous rocks. apparent restriction anatexis rocks above second sillimanite may imply that activity is usually less unity high-grade regional metamorphism.