Recoilless resonance spectroscopy of meteoritic iron oxides

Recoilless resonance spectra taken at 80°K and 300°K were used to identify oxidation products present in meteorites. Wolf Creek (a completely oxidized iron meteorite) contains (in order of decreasing abundance) αFeOOH, βFeOOH, γFe2O3, Fe3O4, and γFeOOH. The dark chondrite fragments in the Cumberland Falls achondrite have spectra containing mainly βFeOOH. The unequilibrated ordinary chondrite Clovis (no. 1) has γFeOOH as the chief oxidation product. Absorption spectra should be recorded at several temperatures in order to avoid ambiguities arising from the presence of superparamagnetic ultrafine particles of iron oxides. A comparison of the Mössbauer spectra of the dark portion of Cumberland Falls with two recent chemical analyses demonstrates that it is not possible to correctly apportion iron among the metal, sulfide, and silicate phases without knowledge of the ferric iron content, which can be determined only by resonance spectroscopy.