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 language | English |
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Pages (from-to) | 332-336 |
Number of pages | 5 |
Journal | Journal of Synchrotron Radiation |
Volume | 10 |
Issue number | 4 |
DOIs | |
Publication status | Published - 1 Jul 2003 |
Externally published | Yes |
Keywords
- Controlled oxygen fugacity
- Mid-ocean ridge basalts
- Oxidation states
- Silicate melts
- Spectroscopy furnaces
- XANES