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摘要
A model based on a thermodynamic framework for CO2 concentrations and speciation in natural silicate melts at graphite/diamond-saturated to fluid-saturated conditions is presented. The model is simultaneously calibrated with graphite-saturated and fluid-saturated conditions allowing for consistent model predictions across the CCO buffer. The model was calibrated using water-poor (<= 1 wt% H2O) silicate melts from graphite-to CO2-fluidsaturation over a range of pressure (P=0.05-3 GPa), temperature (T=950-1600 degrees C), composition (foiditerhyolite; NBO=0.02-0.92; wt% SiO2 similar to 39-77, TiO2 similar to 0.1-5.8, Al2O3 similar to 7.5-18, FeO similar to 0.2-24 MgO similar to 0.1-24, CaO similar to 0.3-14, Na2O similar to 1-5, K2O similar to 0-6), and f(O2) (similar to QFM +1.5 to similar to QFM -6). The model can predict CO2 concentrations for a wide range of silicate melt compositions from ultramafic to rhyolitic compositions, i.e., melts that dissolve carbon only as carbonate anions CO32- and those that dissolve carbon both as CO32- and as molecular CO2 mol as a function of pressure, temperature, and oxygen fugacity. The model also does a reasonable job in capturing CO2 solubility in hydrous silicate melts with <= 2-3 wt% H2O. New CO2 solubility experiments at pressures >3 GPa suggest that the newly developed CO2 solubility model can be satisfactorily extrapolated to similar to 4-5 GPa. Above 5 GPa the model poorly reproduces experimental data, likely owing to structural change in silicate melt at pressures above 5 GPa. An Excel spreadsheet and a Matlab function are provided as online supplementary materials for implementing the new CO2 solubility model presented here.
- 出版日期2018-5-25
