SOLUBILITY OF WATER AND CARBON-DIOXIDE IN AN ICELANDITE AT 1400 DEGREES-C AND 10 KILOBARS

The concentrations of water and carbon dissolved in an icelandite glas s quenched from 1400 degrees C and 10 kbar were measured using Fourier transform infrared spectroscopy and elemental analyses of carbon and hydrogen. Only carbon dioxide and water were observed in the fluid pha se as analysed after quenching with a qudrupole mass analyser. The mol e fraction of carbon dioxide in the fluid phase ranged from 0.36 to 0. 95. Carbon is dissolved as carbonate except at the highest CO2 fluid f ugacity, where a small amount of molecular CO2 is observed. Dissolved carbon in the glasses, calculated as CO2, remained constant at approxi mately 1 wt%, in spite of the different CO2 fluid fugacities. Water wa s dissolved as molecular water and as hydroxyl groups, the hydroxyl co ncentration in the quenched glasses remaining almost constant over the whole interval, whereas the molecular water dissolves in accordance w ith Henry's law. Molecular water peaks at 5200 cm(-1) and 1630 cm(-1), the hydroxyl peak at 4500 cm(-1), and the carbonate peaks at 1400 cm( -1)-1550 cm(-1) have been calibrated using elemental analyses of C and H in the quenched glasses. As molecular water decreases in the melt t he higher wavenumber carbonate peak is observed to move towards the mo lecular water peak at 1630 cm(-1) causing a split of the carbonate pea ks, ranging from 45 cm(-1) to 100 cm(-1).