Iron valence in the hydration layer of obsidian: characterization by X-ray absorption spectroscopy

• Published in: Microchemical journal Vol. 71; no. 2; pp. 185 - 191
• Main Authors: Lytle, Farrel W., Pingitore Jr, Nicholas E.
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier B.V 2002; Elsevier
• Subjects: Age dating; Analytical chemistry; Chemistry; Earth sciences; Earth, ocean, space; Exact sciences and technology; Geochronology; Hydration; Iron valence; Isotope geochemistry. Geochronology; Obsidian; Spectrometric and optical methods; X-Ray absorption spectroscopy; Obsidian; X-Ray absorption spectroscopy; Age dating; Hydration; Iron valence; Geologic ages; Geochronology; X ray absorption spectrometry; Transition metal Ions; Chemical analysis; Iron ion; Intermediate valence; X ray fluorescence spectrometry; Qualitative analysis; Igneous rocks; Synchrotron radiation
• ISSN: 0026-265X; 1095-9149
• DOI: 10.1016/S0026-265X(02)00010-3

We used a combined fluorescent X-ray and electron yield measurement of the Fe K-edge X-ray absorption near edge structure (XANES) of Modena obsidian to determine the original valence, Fe
2+, and change in valence to Fe
3+ during atmospheric hydration. We believe this to be the first observation of the valence change of Fe during the hydration of obsidian. The combination of the spectra measured with the electron channel and the X-ray channel resulted in apparent sensitivity from hours to geologic time. The technique may prove useful in age dating archaeological and geological specimens of obsidian.