SOLUBILITY OF NEON, ARGON, KRYPTON, AND XENON IN BINARY AND TERNARY SILICATE SYSTEMS: A NEW VIEW ON NOBLE GAS SOLUBILITY - NMR, RAMAN, AND INFRARED SPECTROSCOPY

Abstract

We determined solubility of Ne, Ar, Kr, and Xe in binary silicate melts (Na2O-SiO2 and MgO-SiO2) and ternary silicate melts (Na2O-CaO-SiO2 and CaO-MgO-SiO2) at total pressures of 1.10-1.99 kbars and temperatures of 1200-1600°C. The results confirm previous inference that solubility decreases from Ne to Xe and that its temperature dependence is weak. Solubilities appear to correlate very well with the NBO/Si (Non-Bridging Oxygen per Silicon) ratio, independently of the nature of the network modifying cations. This correlation is better than the correlation previously reported with other physical parameters such as melt density, molar volume, and ionic porosity. The large portion of noble gases dissolves in the most polymerized structure unit, suggesting that noble gases dissolving in silicate melts do not exist near network modifying cations or in free volume induced by the cations in silicate melts. Based on the thermodynamic model that the logarithm of bulk equilibrium constant is represented by sum of individual fractions of anionic structure units, we determined the equilibrium constants in anionic structure units formed by bridging oxygens (three-dimensional unit) and by non-bridging oxygens together with bridging oxygens (sheet and chain units) in Na2O-SiO2 system, respectively.