%0 Journal Article %1 Schaefer2004 %A Schaefer, L. %A Fegley, B. %D 2004 %J Icarus %K ABLATION; ALKALI ATMOSPHERE; DIFFERENTIAL DRIVEN EARLY ELEMENTS; EVAPORATION FRACTIONATION; GAS-PHASE; INCLUSIONS; INFRARED ISOTOPIC MAPPING NEBULA; RICH SILICATE SOLAR SPECTROMETER; VOLCANICALLY VOLCANISM; %N 1 %P 216--241 %T A thermodynamic model of high temperature lava vaporization on Io %V 169 %X We modified the MAGMA chemical equilibrium code developed by Fegley and Cameron (1987, Earth Planet. Sci. Lett. 82, 207-222) and used it to model vaporization of high temperature silicate lavas on Io. The MAGMA code computes chemical equilibria in a melt, between melt and its equilibrium vapor, and in the gas phase. The good agreement of MAGMA code results with experimental data and with other computer codes is demonstrated. The temperature-dependent pressure and composition of vapor in equilibrium with lava is calculated from 1700 to 2400 K for 109 different silicate lavas in the O-Na-K-Fe-Si-Mg-Ca-Al-Ti system. Results for five lavas (tholeiitic basalt, alkali basalt, Barberton komatiite, dunite, and a molten type B I Ca, AT-rich inclusion) are discussed in detail. The effects of continuous fractional vaporization on chemistry of these lavas and their equilibrium vapor are presented. The predicted abundances (relative to Na) of K, Fe, Si, Al, Ca, and Ti in the vapor equilibrated with lavas at 1900 K are lower than published upper limits for To's atmosphere (which do not include Mg). We predict evaporative loss of alkalis, Fe, and Si during volcanic eruptions. Sodium is more volatile than K, and the Na/K ratio in the gas is decreased by fractional vaporization. This process can match To's atmospheric Na/K ratio of 10 3 reported by Brown (2001, Icarus 15 1, 190-195). Silicon monoxide is an abundant species in the vapor above lavas. Spectroscopic searches are recommended for SiO at IR and mm wavelengths. Reactions of metallic vapors with S- and Cl-bearing volcanic gases may form other unusual gases including MgCl2, MgS, MgCl, FeCl2, FeS, FeCl, and SiS. (C) 2003 Elsevier Inc. All rights reserved.

@article{Schaefer2004, abstract = {We modified the MAGMA chemical equilibrium code developed by Fegley and Cameron (1987, Earth Planet. Sci. Lett. 82, 207-222) and used it to model vaporization of high temperature silicate lavas on Io. The MAGMA code computes chemical equilibria in a melt, between melt and its equilibrium vapor, and in the gas phase. The good agreement of MAGMA code results with experimental data and with other computer codes is demonstrated. The temperature-dependent pressure and composition of vapor in equilibrium with lava is calculated from 1700 to 2400 K for 109 different silicate lavas in the O-Na-K-Fe-Si-Mg-Ca-Al-Ti system. Results for five lavas (tholeiitic basalt, alkali basalt, Barberton komatiite, dunite, and a molten type B I Ca, AT-rich inclusion) are discussed in detail. The effects of continuous fractional vaporization on chemistry of these lavas and their equilibrium vapor are presented. The predicted abundances (relative to Na) of K, Fe, Si, Al, Ca, and Ti in the vapor equilibrated with lavas at 1900 K are lower than published upper limits for To's atmosphere (which do not include Mg). We predict evaporative loss of alkalis, Fe, and Si during volcanic eruptions. Sodium is more volatile than K, and the Na/K ratio in the gas is decreased by fractional vaporization. This process can match To's atmospheric Na/K ratio of 10 3 reported by Brown (2001, Icarus 15 1, 190-195). Silicon monoxide is an abundant species in the vapor above lavas. Spectroscopic searches are recommended for SiO at IR and mm wavelengths. Reactions of metallic vapors with S- and Cl-bearing volcanic gases may form other unusual gases including MgCl2, MgS, MgCl, FeCl2, FeS, FeCl, and SiS. (C) 2003 Elsevier Inc. All rights reserved.}, added-at = {2009-11-03T20:21:25.000+0100}, author = {Schaefer, L. and Fegley, B.}, biburl = {https://www.bibsonomy.org/bibtex/294a066b57b09b73e7b5b6bd782341d28/svance}, interhash = {2a6603a6b69d7d1bafd64d556b911769}, intrahash = {94a066b57b09b73e7b5b6bd782341d28}, journal = {Icarus}, keywords = {ABLATION; ALKALI ATMOSPHERE; DIFFERENTIAL DRIVEN EARLY ELEMENTS; EVAPORATION FRACTIONATION; GAS-PHASE; INCLUSIONS; INFRARED ISOTOPIC MAPPING NEBULA; RICH SILICATE SOLAR SPECTROMETER; VOLCANICALLY VOLCANISM;}, number = 1, owner = {svance}, pages = {216--241}, timestamp = {2009-11-03T20:22:13.000+0100}, title = {A thermodynamic model of high temperature lava vaporization on Io}, volume = 169, year = 2004 }