2025/01/08 by Yonghua Cao, Chang-Ming Xing, Christina Yan Wang +1 · 1 voice
Chemistry · Materials Science · #Corrosion Behavior and Inhibition #Petroleum Processing and Analysis
paper · doi:10.2138/am-2024-9467
openalex publication_date 2025/01/08 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
Abstract Pyroxene is an important carrier of ferric iron in basalt and the upper mantle. Understanding the influence of pyroxene crystallization on the oxygen fugacity of magma relies on accurate knowledge of the oxidation state of iron, expressed as the Fe3+/ΣFe ratio, in pyroxene. To accurately determine the Fe3+/ΣFe ratio in pyroxene using electron probe microanalysis, we present nine natural pyroxene samples, including one aegirine, one hedenbergite, one diopside, and six augites, for the calibration of the flank method for pyroxene. The aegirine sample is rich in the aegirine end-member with a Fe3+/ΣFe ratio of 0.98 ± 0.01 (1σ), while the hedenbergite sample is rich in the hedenbergite end-member and free of ferric iron. The augite and diopside samples contain variable ferric iron, with the Fe3+/ΣFe ratios varying from 0.21 to 0.39. Based on the flank positions of FeLα and FeLβ determined by natural andradite and almandine, we measured the Fe Lβ/Lα ratios at the flank positions for the pyroxene samples. The results demonstrate a positive linear relationship between the Fe Lβ/Lα ratios and the Fe2+ content of the pyroxene samples. The Fe2+ contents and Fe3+/ΣFe ratios of the pyroxene samples, as determined through a multiple linear regression equation, align closely with those obtained by Mössbauer spectroscopy. This method yields the Fe2+ content and Fe3+/ΣFe ratios with an error of ±0.3 wt% and ±0.06, respectively, for calcic pyroxene containing 7 wt% total FeO. These well-characterized natural pyroxene samples can serve as reference materials for determining the Fe3+/ΣFe ratio in unknown calcic pyroxene.