This paper proposes the quantitative wavelength-dispersive X-ray fluorescence (XRF) technique of divalent iron
content determination in igneous rocks and reports specifics of this technique in terms of classifying rocks into
ultrabasic, basic, intermediate and acid ones. Unlike the widely used technique of titration, the proposed XRF
technique does not require a labor-consuming procedure for sample preparation. In the fields of FeKβ5 line,
and FeKβ′ and FeKβ″ satellites relative intensities of XRF emission spectrum lines are dependent on the valence
state of iron inminerals. The ratio FeKβ5/FeKβ1,3 is preferred as the analytical parameter. The XRF method allows
divalent iron content (expressed as FeO oxide) over 1.5% to be measured in igneous rocks of ultrabasic and basic
compositions by the common calibration equation with the error below 10 rel. %, that is comparable with the
error of titrimetric analysis. The samples of igneous rocks of intermediate composition and granodiorites should
be analyzed using calibration equations obtained with certified reference materials corresponding in composition
to the study samples. For the samples of alkaline rocks the errors of FeO content determination might be
in excess of 50 rel. %.
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