<abstract xml:lang="en" xmlns="http://www.w3.org/1999/xhtml">Two granite complexes in Egypt, a sodic type and an aluminous type are characterized by Mössbauer spectroscopy. Mössbauer spectra (MS) of the sodic granite show a major doublet of ferric (Fe3+) iron that is attributable to octahedral coordination (M1) sites plus/minus a tetrahedron Fe3+ doublet plus/minus a doublet of ferrous (Fe2+) iron on the M1 sites plus/ minus another Fe2+ (M1) doublet and a sextet of Fe3+. The sextet is attributed to α-Fe2O3 (hematite) and the other Fe components are due to NaCaFeSi2O6 (aegirine-augite) plus/minus minor contributions from (Ca2(Mg, Fe)5(Si, Al)8O22(OH)2 (magnesium-hornblende). Changes in the quadrupole splitting and width line of Fe2+ ions are likely composition-related. The MS of the aluminous-type granite, on the other hand, shows evidence only of single doublets containing Fe2+ or Fe3+ in the octahedral M1 sites, with parameters that remain almost constant. This consistency implies that the existing minerals - K(Mg, Fe2+)3 (Al, Fe3+)Si3O10(OH, F)2 (biotite), (Mg, Fe)6(Si, Al)4O10(OH)8 (clinochlore), (Na, K)Ca2(Fe, Mg)5(Al, Si)8O22(OH)2 (ferrohornblende and magnesiohornblende) - have similar iron positions. The intensity of iron oxidized (Fe3+/ΣFe) for the sodic granite is 79.1 to 100% and for the aluminous granite, 28.4 to 38.2%. The observed Fe3+/ΣFe differences between the two granites are source-related and consistent with distributions of other redox-sensitive elements.</abstract>

Two granite complexes in Egypt, a sodic type and an aluminous type are characterized by Mössbauer spectroscopy. Mössbauer spectra (MS) of the sodic granite show a major doublet of ferric (Fe3+) iron that is attributable to octahedral coordination (M1) sites plus/minus a tetrahedron Fe3+ doublet plus/minus a doublet of ferrous (Fe2+) iron on the M1 sites plus/ minus another Fe2+ (M1) doublet and a sextet of Fe3+. The sextet is attributed to α-Fe2O3 (hematite) and the other Fe components are due to NaCaFeSi2O6 (aegirine-augite) plus/minus minor contributions from (Ca2(Mg, Fe)5(Si, Al)8O22(OH)2 (magnesium-hornblende). Changes in the quadrupole splitting and width line of Fe2+ ions are likely composition-related. The MS of the aluminous-type granite, on the other hand, shows evidence only of single doublets containing Fe2+ or Fe3+ in the octahedral M1 sites, with parameters that remain almost constant. This consistency implies that the existing minerals - K(Mg, Fe2+)3 (Al, Fe3+)Si3O10(OH, F)2 (biotite), (Mg, Fe)6(Si, Al)4O10(OH)8 (clinochlore), (Na, K)Ca2(Fe, Mg)5(Al, Si)8O22(OH)2 (ferrohornblende and magnesiohornblende) - have similar iron positions. The intensity of iron oxidized (Fe3+/ΣFe) for the sodic granite is 79.1 to 100% and for the aluminous granite, 28.4 to 38.2%. The observed Fe3+/ΣFe differences between the two granites are source-related and consistent with distributions of other redox-sensitive elements.

Characterization of granites by 57Fe Mössbauer spectroscopy

Nuclear Materials Authority, P.O. Box 530, Maadi, Cairo, Egypt

Mineralogia

Characterization of granites by Fe Mössbauer spectroscopy

Two granite complexes in Egypt, a sodic type and an aluminous type are characterized by Mössbauer spectroscopy. Mössbauer spectra (MS) of the sodic granite...

Characterization of granites by ⁵⁷Fe Mössbauer spectroscopy

Publié en ligne: 04 mai 2010

Pages: 95 - 106

DOI: https://doi.org/10.2478/v10002-009-0008-x

Mots clés
granitic types, clinopyroxene, mica, amphibole, Mössbauer spectroscopy, oxygen fugacity, Western Desert

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