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.