Open AccessA furnace design for XANES spectroscopy of silicate melts under controlled oxygen fugacities and temperatures to 1773 K
Author(s) -
Berry Andrew J.,
Shelley J. Michael G.,
Foran Garry J.,
O'Neill Hugh St. C.,
Scott Dean R.
Publication year - 2003
Publication title -
journal of synchrotron radiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.172
H-Index - 99
ISSN - 1600-5775
DOI - 10.1107/s0909049503007556
Subject(s) - xanes , silicate , oxidation state , mineral redox buffer , oxygen , spectroscopy , basalt , quenching (fluorescence) , atmosphere (unit) , analytical chemistry (journal) , chemistry , metal , materials science , geology , metallurgy , environmental chemistry , geochemistry , thermodynamics , fluorescence , physics , organic chemistry , quantum mechanics
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 Cr 2+ /Cr 3+ ratio has been identified directly in an Fe‐bearing melt. At typical terrestrial oxygen fugacities around half the Cr is present as Cr 2+ , even though this oxidation state has never been identified in a terrestrial material and only Cr 3+ is observed after quenching to a glass. Cr 2+ oxidizes to Cr 3+ on cooling in the presence of Fe 3+ according to the electron exchange reaction Cr 2+ + Fe 3+ → Cr 3+ + Fe 2+ . This illustrates the importance of the in situ determination of metal oxidation states in melts.