• journal_title：American Mineralogist
• Contributor：Penelope L. King ; Tsun-Kong Sham ; Robert A. Gordon ; M. Darby Dyar
• Publisher：Mineralogical Society of America
• Date：2013-01-01
• Format：text/html
• Language：en
• Identifier：10.2138/am.2013.3959
• journal_abbrev：American Mineralogist
• issn：0003-004X
• volume：98
• issue：1
• firstpage：110
• section：Articles

Cerium L₃ absorption edge (L₃-edge) X-ray absorption near edge structure (XANES) spectra were obtained from ~7 × 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/ΔE ~ 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 L₃-edge and Ti K-edge excitation cannot be resolved with solid-state detectors. We show that both Ce³⁺ and Ce⁴⁺ are present in our titanite samples by examining the Ce L₃-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 Ce³⁺/Ce⁴⁺. We present a new approach for predicting and evaluating multivalent trace element substitution in titanite and other minerals.