Mössbauer study of Fe phases in terrestrial olivine basalts from southern Egypt

Olivine basalts from southern Egypt were studied by ⁵⁷Fe Mössbauer spectroscopy at 297 and 77 K, and by optical microscopy and X-ray diffraction. The ⁵⁷Fe Mössbauer spectra show three-magnetic sextets, three doublets of ferrous (Fe²⁺), and a weak ferric (Fe³⁺) doublet that is attributable to a nanophase oxide (npOx). The magnetic sextets relate to titanomagnetite and the Fe²⁺ doublets to olivine, pyroxene, and ulvöspinel. Variations in the hyperfine parameters of the various Fe components are attributed to changes in the local crystal chemistry. The intensity of oxidation (Fe³⁺/ΣFe) in the rocks varies from 20-27% with the oxidized iron largely residing in the titanomagnetite.