57Fe-Mössbauer investigation on garnets from Ivrea-Verbano zone

A Mossbauer 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 srructural characterisation of the local environmenr 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 ali the samples. Mossbauer resuLtsare in agreement with those obtained by XAS and Sh0W that, at least in the compositiooal range of the garnets examined (0.1-0.5 calcium atoms p.f.u.), the iron environment is not sìgnificantly modifìed by the ~arger ca1ciu~ cations sharit;tg the s~e dodecahedral site. I.tis confirmed that the Mossbauer technique ISmore sensìtive than XAS In detectmg low percentages of iron, especially when the cation is present in more than one oxidation state and coordination number.