Determination of [Fe2+]/[Fe3+]-ratios in arfvedsonite by Mössbauer spectroscopy

The Mössbauer absorption spectra of arfvedsonite are composed of three quadrupole doublets which are ascribed to Fe²⁺ in M₁ and M₂ sites and to Fe³⁺ in M₂ sites. The relative intensities of the resonances are a measure of the distribution of iron at the different sites, but it is necessary to correct for a difference between the recoil-free fractions. At room temperature Fe²⁺] seems detected with an efficiency of only about 85% of that of Fe³⁺]. Results of Fe²⁺]/Fe³⁺] determinations by Mössbauer spectroscopy and by wet chemical analysis of a series of arfvedsonite samples, separated from various rocks from the Ilimaussaq intrusion, south Greenland, are compared and agree reasonably well.