9508128 Delaney This research will measure precisely the ferric/ferrous ratios in micrometer-sized areas of a suite of glasses using synchrotron microXANES spectroscopy. Samples characterized by Mossbauer spectroscopy and wet chemical analysis will be used to calibrate the relationship between synchrotron microXANES measurements and ferric/ferrous ratios in the glasses. This technique provides, for the first time, the possibility of measuring cation partition coefficients for ferrous or ferric iron (instead of just elemental iron) because measurements of oxidation state can be made in coexisting phases on a petrologically realistic scale. To calibrate the influence of oxygen fugacity on the ferric/ferrous ratio of glasses, several glasses will be equilibrated at a range of superliquidus temperatures in a controlled fugacity atmosphere and quenched to form glasses.
