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Progress in Earth and Planetary Science
Fig. 10 | Progress in Earth and Planetary Science

Fig. 10

From: The responses of the four main substitution mechanisms of H in olivine to H2O activity at 1050 °C and 3 GPa

Fig. 10

Variation of molar H2O concentration with molar Sc concentration for [triv] experiments conducted at constant water activity but variable in Sc concentration and at fixed bulk Sc concentration. Note that the latter experiments show no correlation between forsterite water concentration and Sc concentration, for reasons discussed in the text. For comparison, we have also plotted data from Berry et al. (2007a), which were similar experiments but at 1400 °C and 1.5 GPa and performed with a variety of trivalent cations in addition to Sc (Al, V, Ga, Y, In, Gd, Dy, Tm and Lu). Both sets of data confirm a consistent increase of \( {C}_{{\mathrm{H}}_2\mathrm{O}} \) with the availability of an R3+ cation at fixed water activity, but the deviation from the expected stoichiometry for the substitution may indicate that the absorption coefficient used in this study to calculate \( {C}_{{\mathrm{H}}_2\mathrm{O}} \) is in error; the value obtained by Withers et al. (2012) may be more appropriate (see text for further discussion)

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