57Fe-Mössbauer Investigation on Garnets from the Ivrea-Verbano Zone

Simona Quartieri, Gilberto Artioli*, Antonio Deriu, Pier Paolo Lottici and Gianni Antonioli
Istituto di Mineralogia e Petrologia, Università di Modena, via S. Eufemia 19, 1-41100 Modena, Italy
Dipartimento di Fisica, Università di Parma, Viale delle Scienze, 1-43100 Parma, Italy
*Present address: Dipartimento di Scienze della Terra, Sez. Mineralogia, Universitā di Milano, Milano, Italy.

Abstract: A Mössbauer investigation has been carried out on garnets from the Ivrea-Verbano zone and the results are compared with those obtained on the same samples by X-ray absorption spectroscopy (XAS). The problem addressed is the precise structural characterisation of the local environment of iron in garnets with Fe/Ca ratio variable between ∼3.0 and ∼18.0. Ferric iron is octahedrally coordinated and ferrous iron is in the dodecahedral site in all the samples. Mössbauer results are in agreement with those obtained by XAS and show that, at least in the compositional range of the garnets examined (0.1–0.5 calcium atoms p.f.u.), the iron environment is not significantly modified by the larger calcium cations sharing the same dodecahedral site. It is confirmed that the Mössbauer technique is more sensitive than XAS in detecting low percentages of iron, especially when the cation is present in more than one oxidation state and coordination number.

Keywords: Mössbauer spectra • garnets • crystal chemistry • Ivrea-Verbano zone

Mineralogical Magazine; December 1993 v. 57; no. 389; p. 671-676; DOI: 10.1180/minmag.1993.057.389.11
© 1993, The Mineralogical Society
Mineralogical Society (www.minersoc.org)