Solubility and partitioning of water in synthetic forsterite and enstatite in the system MgO-SiO2-H2O±Al2O3

Kevin J. Grant*, Simon C. Kohn, Richard A. Brooker

*Corresponding author for this work

    Research output: Contribution to journalArticle

    48 Citations (Scopus)

    Abstract

    The solubility of water in coexisting enstatite and forsterite was investigated by simultaneously synthesizing the two phases in a series of high pressure and temperature piston cylinder experiments. Experiments were performed at 1.0 and 2.0 GPa at temperatures between 1,100 and 1,420°C. Integrated OH absorbances were determined using polarized infrared spectroscopy on orientated single crystals of each phase. Phase water contents were estimated using the calibration of Libowitzky and Rossman (Am Mineral 82:1111-1115, 1997). Enstatite crystals, synthesized in equilibrium with forsterite and an aqueous phase at 1,350°C and 2.0 GPa, contain 114 ppm H2O. This is reduced to 59 ppm at 1,100°C, under otherwise identical conditions, suggesting a strong temperature dependence. At 1,350°C and 1.0 GPa water solubility in enstatite is 89 ppm, significantly lower than that at 2.0 GPa. In contrast water solubility in forsterite is essentially constant, being in the range 36-41 ppm for all conditions studied. These data give partition coefficients DH2O en/fo in the range 2.28-3.31 for all experiments at 1,350°C and 1.34 for one experiment at 1,100°C. The incorporation of Al2O3 in enstatite modifies the OH stretching spectrum in a systematic way, and slightly increases the water solubility.

    Original languageEnglish
    Pages (from-to)651-664
    Number of pages14
    JournalContributions to Mineralogy and Petrology
    Volume151
    Issue number6
    DOIs
    Publication statusPublished - Jun 2006

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