ABSTRACT

Water solubilities in albite (Ab)-orthoclase (Or) join and JR-1 rhyolite melts at 1000°C and up to 2000 bars were determined by the “excess of water” method using an internally heated pressure vessel (IHPV) with rapid quenching and a secondary ion microprobe mass spectrometer (SIMS). We have found that secondary hydration of run product glass with coexisting aqueous fluid occurs during quenching. The hydration is significant in sodium-rich glass. The bulk analysis of such secondary hydrated run-products will cause overestimation of the water solubility, while the true water solubility can be obtained by micro-analysis on non-attacked portion of the glass. The apparent compositional dependence in the published water solubility data could be due to the secondary hydration of run product glass. Newly determined water solubility for the Ab-Or join and rhyolite melts is expressed as H₂O (mol%) = 0.19 √P_H2O (bar), at 1000°C.