ケイ酸塩メルトに対する希ガス溶解度の研究

抄録

Noble gas solubility in liquid is dependent on both interaction energy between solute and solvent and molar volume of noble gas in solvent. The molar volume is more effective on the solubility in silicate melt than the interaction energy. Although ionic porosity (IP) had been considered to control noble gas solubilities, this parameter cannot apply to the solubilities in silicate melts with low IP. We found that noble gas solubilities in silicate melt are correlated with the NBO/Si (non-bridging oxygens per silicon) ratio in wide range of silicate melt composition, independently of nature of network modifying cations. However, solubility data for aluminosilicate melt falls off the correlation line. Although Al³⁺ is in tetrahedral coordination in aluminosilicate melts with sufficient M⁺ and M²⁺ cations for charge-balance, the solubility data can fall on the correlation line if we treat oxygens bonding with MAl⁴⁺ or M_0.5Al⁴⁺ as non-bridging oxygen. This means that the solution of noble gas in silicate melt is mainly dependent on the network of SiO₄.