Abstract
Clay minerals from different Cretaceous stratigraphic successions of Egypt were investigated using XRD, DTA, dissolution analysis (DCB), IR, Mossbauer and X-ray Electron Spin Resonance (ESR) spectroscopes. The purity of the samples and the degree of their structural order were determined by XRD. The location of Fe in the octahedral sheet is characterized by absorption bands at ∼875cm−1 assigned as Al-OH-Fe which persist after chemical dissolution of free iron. The Mossbauer spectra of these clays show two doublets with isomer shift and quadrupole splitting typical of octahedrally coordinated Fe3+, in addition to third doublet with hyperfine parameter typical of Fe2+ in the spectra of Abu-Had kaolinite (H) sample. Six-lines magnetic hyperfine components which are consistent with those of hematite are confirmed in the spectra of both Isel and Rish kaolinite samples. Goethite was confirmed by both IR and DTA. Multiple nature of ESR of these clays suggested structural Fe in distorted octahedral symmetry as well as non-structural Fe.
Published Version
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