NOBLE-GAS FRACTIONATION DURING THE DEGASSING OF MELTS

A simple model for equilibrium noble gases partitioning amongst solid, melt, and gas phases, and extraction of the gas (vesicles) from the s ystem was used to study the relationships between the rate of noble ga s fractionation and parameters controlling the degassing process. The following results are inferred: (i) the lower the ratio of a gas-phase volume (vesicles) divided by the volume of melt, the higher the degre e of noble gas fractionation in the melt; (ii) relative excess of both lighter (Ne) and heavier (Xe) noble gases over Ar occurs providing a high solid/melt partition coefficient for Xe and a small melt fraction .