X‐ray fluorescence determination of the FeO/Fe2O3tot ratio in igneous rocks

Abstract

AbstractThis study was performed to search for the possibility of assessing the FeO/Fe2O3tot ratio in rocks using K‐ and L‐series of the X‐ray fluorescence (XRF) spectrum. The uncertainty in the determination of the FeO/Fe2O3tot ratio was compared from the obtained ratios of Kβ2, 5‐/Kβ1, 3‐ and Lβ‐/Lα1, 2‐line intensities. The measurements were implemented by a conventional XRF spectrometer, S4 Pioneer. The assessment of the uncertainty in FeO/Fe2O3tot determination in mineral powder fractions proved that the Kβ2, 5/Kβ1, 3 ratio of lines could be selected as the analytical signal. A relative standard deviation of FeO content in the collection of 48 reference materials of igneous rocks varies within the range of 5–16%, depending on the range of the FeO/Fe2O3tot ratio and the FeO content. The best accuracy was attained for FeO/Fe2O3tot >0.45 with FeO contents varying within 5–15%. In the andesite and basalt samples, the relative standard deviation was <4%. In granite rocks, the error reached 23% at fairly low content of FeO <3%. For the igneous rock samples at a ratio FeO/Fe2O3tot >0.25, the XRF determination of FeO content can be performed at an accuracy comparable with that of wet chemical analysis. The XRF method is preferred because it is fast and convenient for sample preparation. It could be used as an analytical technique in routine geochemical investigations. Copyright © 2009 John Wiley & Sons, Ltd.