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The storage capacity of fluorine in olivine and pyroxene under upper mantle conditions

Research output: Contribution to journalArticle

  • Tobias Grützner
  • Simon C. Kohn
  • David W. Bromiley
  • Arno Rohrbach
  • Jasper Berndt
  • Stephan Klemme
Original languageEnglish
Pages (from-to)160-170
Number of pages11
JournalGeochimica et Cosmochimica Acta
Volume208
Early online date5 Apr 2017
DOIs
DateAccepted/In press - 29 Mar 2017
DateE-pub ahead of print - 5 Apr 2017
DatePublished (current) - 1 Jul 2017

Abstract

Abstract We present new experimental results on the fluorine storage capacity of olivine and orthopyroxene in the Earth’s mantle. Experiments were performed in the system MgO-SiO2 + MgF2 at temperatures between 1350 °C and 1700 °C and pressures up to 17 GPa. Electron microprobe measurements show that fluorine concentrations in olivine reach up to 5100 µg/g. The storage capacity of fluorine in olivine shows only a small pressure dependence but a strong temperature dependence with a positive correlation between increasing temperature and fluorine storage capacity. Fluorine concentrations found in enstatite are one order of magnitude smaller and reach up to 670 µg/g. Our data show that concentrations of fluorine in fluorine-saturated olivine are in the same range as water concentrations in olivine. Nevertheless, fluorine and water solubility in olivine show opposing behavior with increasing pressure and temperature. The fluorine solubility in olivine increases with increasing temperature but is not much affected by pressure. In contrast, water solubility in olivine has previously been shown to decrease with increasing temperature and increase with increasing pressure. Our experiments show that nominally fluorine-free minerals like forsterite and enstatite are capable of storing the entire fluorine budget of the upper mantle, without the need to invoke accessory phases such as apatite or amphibole.

    Research areas

  • Fluorine, Olivine, Pyroxene, Upper mantle, Saturation, Storage capacity

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