Аннотация:. CO2 is the major component of fluids under conditions of granulite and amphibolite facies metamorphism in the lower and middle continental crust. Its sources can be both mantle magmas at the base of the crust (external sources) and graphite and carbonates in the protolith (internal sources). This paper presents preliminary results of experiments on the interaction of garnet-two-mica schist with CO2 and CO2-H2O fluids at 900oC and 500 MPa, simulating the effect of a fluid from an external source. The experimental products include the initial quartz, garnet, apatite and ilmenite, and newly formed products of peritectic melting reactions: potassium feldspar, spinel, sillimanite, orthoamphibole, coexisting with a peraluminous alkaline-calcic rhyolitic melt. In the Raman spectra of the melt, characteristic bands of silicate glasses, quartz, pyroxene and a wide band of OH- were identified, but no signs of dissolved carbon in forms of CO2 or CO32- were detected. The Raman spectra of gas bubbles in glasses contain peaks of CO2, N2 and quartz. However, the density of CO2 in the bubbles in experiments with CO2 fluid 0.68±0.02 g/cm3 indicates that, probably, CO2 was dissolved in the melt and separated just during non-isobaric quenching. A noticeably higher CO2 density, 0.85-1.00±0.05 g/cm3, in experiments with H2O-CO2 fluid indicates that the CO2-rich fluid coexisted with the melt under experimental conditions.
