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

Abstract

Olivine basalts from southern Egypt were studied by 57 Fe Mössbauer spectroscopy at 297 and 77 K, and by optical microscopy and X-ray diffraction. The 57 Fe Mössbauer spectra show three-magnetic sextets, three doublets of ferrous (Fe 2+ ), and a weak ferric (Fe 3+ ) doublet that is attributable to a nanophase oxide (npOx). The magnetic sextets relate to titanomagnetite and the Fe 2+ 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 (Fe 3+ /ΣFe) in the rocks varies from 20-27% with the oxidized iron largely residing in the titanomagnetite.