Experimentally determined solidi in the Ca-bearing granite system NaAlSi3O8-CaAl2Si2O8-KAlSi3O8-SiO2-H2O-CO2

The phase relationships of melting of synthetic granite in the presence of an H2O-CO2 fluid were determined. These results provide constraints on the maximum temperatures of regional metamorphism attainable in vapor-saturated metapelitic and quartzofeldspathic rocks that escaped widespread melting. At pressures below 10 kbar, a fluid phase of XH2O = 0.75, 0.5, and 0.25 limits temperatures to below ~700-725, ~800-825, and ~850-875??C, respectively. As a consequence, the formation of granulite does not require CO2 concentrations in a coexisting fluid to exceed an XCO2 of 0.25-0.5. -from Authors