Mössbauer Spectra of Soil Kaolins from South-Western Australia

Abstract

Abstract--Six well-characterized soil kaolins from widely separated sites in south-western Australia and four reference kaolins were studied by 57Fe M6ssbauer spectroscopy at room temperature after removal of non-structurally-bound iron with dithionite-citrate-bicarbonate solution. The soil kaolins and one of the reference kaolins were also studied at temperatures near 16 K. The soil kaolins were remarkably similar in crystal size, crystaUinity, dehydroxylation temperature, cation exchange capacity, surface area and iron content. M6ssbauer spectra of the soft kaolins at room temperature were also essentially identical consisting of a quadrupole-split doublet superimposed on a broad component which indicated that all of the iron was present as Fe(III) and that slow paramagnetic relaxation effects were present. Mean values for the chemical isomer shift and quadrupole splitting of the doublet for the soil kaolins were 0.33 and 0.55 mm/s respectively which indicates that the iron is in the octahedral sites of the kaolin lattice. The spectra of the soil kaolin samples at temperatures near 16 K showed a further slowing down of the paramagnetic relaxation and confirmed that no discrete iron oxide minerals were present.M6ssbauer spectra of the four reference kaolins at room temperature showed a doublet component similar to those for the soil kaolins. Three of them showed evidence for other spectral components including, in two cases, a component due to the presence of Fe(II).

Alteration of fossil-bearing shale (Autun Basin, France; Permian), part I: Characterizing iron speciation and its vulnerability to weathering by combined use of Mössbauer spectroscopy, X-ray diffraction, porosimetry and permeability measurements

“…Kaolinite was also highlighted. It is reported that this clay may contain some amount of iron (Murad, 2010;Saint Pierre et al, 1992;Stevens et al, 2005). Yet, this amount remains low as the substitution of Al by Fe is weak (<2%) to nil (Murad, 1998) whereas illite already contains from 1% to 8% of iron (Murad, 1998).…”

“…Paramètres Mössbauer mesurés sur les échantillons de schistes argileux et trouvés dans la littérature. Liste des références (Dyar et al, 2013 ;Ferrow, 2002 ;Huffman et Huggins, 1978 ;Loayza et al, 2011 ;Medina et al, 2006 ;Olowe et Genin, 1991 ;Pysh'yev et al, 2004 ;Saint Pierre et al, 1992 ;Stevens et al, 2005 ;Verma et Tripathi, 2000 ;Wagner et Wagner, 2004).…”

“…Several Mössbauer spectroscopy studies were dedicated to clay minerals (Ferrow, 2002;Loayza et al, 2011;Medina et al, 2006;Murad, 1998;Ruby et al, 1999;Saint Pierre et al, 1992;Stevens et al, 2005;Wagner and Wagner, 2004) showing a large dispersion and overlapping of MS signatures (Fig. 6).…”

Multimodal investigation of thermally induced changes in magnetic fabric and magnetic mineralogy

“…7a) [the firing product of kaolinite, metakaolin, is known to give very weak XRD peaks (Murad & Wagner 1991)]. The parameters of the high‐spin Fe(II) Mössbauer signal from the unheated sample are consistent with those for Fe(II) bound within the kaolinite lattice (Murad & Wagner 1991; Malden & Meads 1967; Cuttler 1980; St. Pierre et al . 1992).…”

Clay Minerals in Saprolite Overlying Hydrothermally Altered and Unaltered Rocks, Vera Epithermal Gold Deposit, Australia

“…Previous studies recognized differences in the morphology and composition of kaolinite in different environments. Large, well crystallized kaolinite occurs in epithermal and geothermal environments (Dill et al, 1997;Simpson et al, 2001;Tillick et al, 2001;Mas et al, 2003) and in saprolite underlying kaolin deposits (Varajão et al, 2001), whereas small crystals of disordered, Fe-substituted kaolinite occur in tropical soils (Herbillon et al, 1976;St Pierre et al, 1992;Hart et al, 2002Hart et al, , 2003. Both crystal morphology and composition were used by Dill et al (1997) to distinguish hypogene kaolinite associated with argillic alteration in an epithermal setting from supergene kaolinite formed by weathering, the former being more ordered and containing less Fe and Ti.…”