Noble gas solubility in binary CaO-SiO2 system

New noble gas solubility measurements in binary CaO-SiO2 melts at 1100 bar and 1600 degrees C are presented. The range of estimated solubilities is He: 8.64-35.8, Ne: 6.54-27.6, Ar: 1.09-8.92, Kr: 0.524-5.67, and Xe: 0.181-2.48 (x 10(-5) cm(3)STP/g-bar). The solubility is greater for the lighter noble gases and is a strong function of melt composition; the solubility increases with increasing SiO2 and decreasing CaO contents. It is generally known that CaO produces non-bridging oxygen by breaking the SiO4 network, and thus the correlation between the solubility and SiO2 content suggests that noble gases dissolve in the SiO4 network. It is known that the network is formed by limited anionic structure units. Tn the case of CaO-SiO2 melts, most noble gases would be accommodated by two anionic units; chain and three-dimension structural units. The equilibrium constants of He, Ne, Ar, Kr, and Xe for chain and three-dimension structure units are 26.9, 19.6, 3.49, 1.71, and 0.613 (x 10(-4)) and 15.1, 11.3, 4.05, 2.68, and 1.23 (x 10(-3)), respectively. It is concluded that noble gases dissolve in the three-dimension structure units more than in the chain units.