Electron microprobe technique for the determination of iron oxidation state in silicate glasses (original) (raw)

We present a new calibration for the determination of the iron oxidation state in silicate glasses by electron probe micro-analysis (EPMA) with the "flank method". This method is based on the changes in both intensity and wavelength of the FeLα and FeLβ X-ray emission lines with iron oxidation state. The flank method utilizes the maximum difference for the FeLα and FeLβ spectra observed at the peak flanks between different standard materials, which quantitatively correlates with the Fe 2+ content. Provided that this correlation is calibrated on reference materials, the Fe 2+ /ΣFe ratio can be determined for samples with known total Fe content. Two synthetic Ferich ferric and ferrous garnet endmembers, i.e. andradite and almandine, were used to identify the FeLα and FeLβ flank method measuring positions that were then applied to the measurement of a variety of silicate glasses with known Fe 2+ /ΣFe ratio (ranging from 0.2 to 1.0). The measured intensity ratio of FeLβ over FeLα at these flank positions (Lβ/Lα) is a linear function of the Fe 2+ content (in wt%). A single linear trend can be established for both garnets and silicate This is a preprint, the final version is subject to change, of the American Mineralogist (MSA) Cite as Authors (Year) Title. American Mineralogist, in press.

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