A furnace design for XANES spectroscopy of silicate melts under controlled oxygen fugacities and temperatures to 1773 K

Andrew J. Berry, J. Michael G. Shelley, Garry J. Foran, Hugh St C. O'Neill, Dean R. Scott

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59 Citations (Scopus)

Abstract

A controlled-atmosphere furnace has been constructed for X-ray absorption spectroscopy experiments under imposed oxygen fugacities at temperatures up to 1773 K. The use of the furnace is demonstrated in a study of the oxidation state of Cr in a basaltic silicate melt (mid-ocean ridge basalt) by K-edge XANES spectroscopy. This is the first time the Cr2+/Cr3+ ratio has been identified directly in an Fe-bearing melt. At typical terrestrial oxygen fugacities around half the Cr is present as Cr2+, even though this oxidation state has never been identified in a terrestrial material and only Cr3+ is observed after quenching to a glass. Cr2+ oxidizes to Cr3+ on cooling in the presence of Fe3+ according to the electron exchange reaction Cr2+ + Fe3+ → Cr3+ + Fe2+. This illustrates the importance of the in situ determination of metal oxidation states in melts.

Original languageEnglish
Pages (from-to)332-336
Number of pages5
JournalJournal of Synchrotron Radiation
Volume10
Issue number4
DOIs
Publication statusPublished - 1 Jul 2003
Externally publishedYes

Keywords

  • Controlled oxygen fugacity
  • Mid-ocean ridge basalts
  • Oxidation states
  • Silicate melts
  • Spectroscopy furnaces
  • XANES

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