Publication Date:
2012-12-22
Description:
Cerium L 3 absorption edge ( L 3 -edge) X-ray absorption near edge structure (XANES) spectra were obtained from ~7 x 5 μm areas on green titanite and brown titanite (both with total Ce ~ 0.6 wt%) using the X-ray microprobe at the Pacific Northwest Consortium–X-ray Science Division (PNC-XSD) Insertion Device (ID) line of the Advanced Photon Source (APS). Using a wavelength-dispersive X-ray (WDX) fluorescence detector with a bent LiF (220) crystal monochromator ( E / E ~ 1000), we have overcome the challenge of having to measure trace amounts of Ce in a Ti-rich sample of which the energy of the fluorescence X-rays from Ce L 3 -edge and Ti K -edge excitation cannot be resolved with solid-state detectors. We show that both Ce 3+ and Ce 4+ are present in our titanite samples by examining the Ce L 3 -edge XANES spectra. Our results show that to correctly determine trace element substitution mechanisms in titanite (and other minerals), it is necessary to determine multivalent element concentrations, including Ce 3+ /Ce 4+ . We present a new approach for predicting and evaluating multivalent trace element substitution in titanite and other minerals.
Print ISSN:
0003-004X
Electronic ISSN:
1945-3027
Topics:
Geosciences
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