Hydrogen diffusion in clinopyroxene: dehydration experiments

Hydrogen diffusivity of one clinopyroxene megacryst from Nushan, eastern Ch ina parallel to [001]* crystallographic direction was measured by high-temp erature sequential dehydration experiments at 950 degreesC and 850 degreesC , which was (6.5+/-1.5) x 10(-12)(m(2)/s) and (1.8+/-0.7)x10(-12)(m(2)/s) r espectively. From these results and the previous published data, it seems t hat the correlation between hydrogen diffusivity and Fe content suggested b y Dyar et al. (1996) possibly does not exist. Clinopyroxene megacrysts from alkali basalts appear to be possible reliable samples for the study of the water evolution and hydrogen isotope compositions of the upper mantle.