EPMAによるFe2+/Fe3+およびMn2+/Mn3+比の見積もり

Abstract

We have reinvestigated the relationship between the relative intensities of Lα and Lβ X-ray emission peaks, [Lβ/Lα], and Fe2+/Fe3+ or Mn2+/Mn3+-ratios in silicate minerals. For Fe-bearing silicates, two kinds of regression lines were obtained; (1) 0≤[Fe2++/(Fe2++Fe3+)]≤0.74: [Lβ/Lα]Fe=0.1414×[Fe2+/(Fe2++Fe3+)]+0.4121 (R2=0.986), (2) 0.74≤[Fe2+/(Fe2++Fe3+)]≤1.00: [Lβ/Lα]Fe=0.8024×[Fe2+/(Fe2++Fe3+)]-0.0798 (R2=0.973). By using these regression lines, it is possible to estimate semiquantitative Fe2+/(Fe2++Fe3+)-ratio of Fe-silicates containing total FeO more than 5 wt.%. For Mn-bearing silicates, a regression line of [Lβ/Lα]Mn=0.46×[Mn2+/(Mn2++Mn3+)]+0.554 (R2=0.968) was obtained. However, even if samples contain total MnO more than 10 wt.%, standard deviation of [Lβ/Lα]Mn-ratio for each sample is large. Thus, [Lβ/Lα]Mn-ratio can not be used for semiquantitative determination of Mn2+/(Mn2++Mn3+)-ratio but gives us qualitative information.