Mössbauer characteristics of glauconitisation

Abstract

57 Fe Mössbauer spectroscopy, X-ray diffraction and local (WDX, EDX) and bulk chemical methods (ICP-AES complemented with Fe 2+ titration) were used to study glauconites originating from three sandstone samples (NY1, NY3 and EWT) of the Upper Oligocene Eger Formation (Northern Hungary). The, during glauconitisation, increasing aggregate density and magnetic susceptibility offered a unique possibility to separate grains of different evolutionary stage from the same glauconite population. 57 Fe Mössbauer spectra of both structurally and chemically well characterised glauconite fractions were decomposed into four doublets. Twotwo of the doublets were assigned to octahedral Fe 2+ and octahedral Fe 3+ . Fe 2+ /Fe values determined by Mössbauer measurements were used for the calculation of the chemical formula of glauconite samples [including octahedral occupancy (B O ) E. Kuzmann et al. and octahedral charge (X O ) as well]. The gradual increase of Fe 2+ /Fe was documented with the increase of aggregate density in correlation with the foregoing of glauconitisation. Our results give a quantitative demonstration that octahedral occupancy (B O ) decrease and the substitution of octahedral Al by Fe 2+ are the major processes allowing the interlayer K incorporation during glauconitisation. The systematic crystalchemical evolution as reflected in the systematic changes of the Mössbauer data are discussed in terms of the subsequent steps of glauconitisation.

Revisiting the identification of commercial and historical green earth pigments

“…Doublets a and b are assigned to ferric sites. Similar parameters were previously reported in the literature for glauconites [48,54] and celadonites [45,52].…”

“…Velocity (mm s -1 ) The spectra of Glau_Vil and Cel_Mon are reproduced in Figures S2 and S3, respectively. As expected, that of Glau_Vil is reminiscent of those previously reported for glauconite [46][47][48][49][50], whereas that of Cel_Mon is very similar to those recorded for celadonite [51][52][53]. The spectra of GE_Boh and GE_Cyp are reproduced in Figure 9.…”

Mineralogical characteristics and geological significance of Albian (Early Cretaceous) glauconite in Zanda, southwestern Tibet, China

“…XRF spectroscopy and oxidation-reduction titration analyses of glauconite grains from sandstone sample XL34 show Fe 2 O 3 concentrations of 12.6% and FeO concentrations of 4.4%. The Fe 2+ /TFe ratio of 31% is higher than usual (10À15%; Kuzmann et al, 2008).…”

“…The colour of glauconite grains is one of the most reliable indicators of glauconite maturity. During progressive glauconitization, the colour of glauconite changes from light green to dark green, induced by the enrichment of octahedrally coordinated Fe 2+ relative to Fe 3+ (Kuzmann et al, 2008;Sánchez-Navas et al, 2008). The high Fe 2+ /TFe ratio (31%) in the glauconite from sample XL34 also indicates that the glauconite grains are highly evolved, as do their morphological characteristics.…”

Mössbauer study of transformation of Fe cations during thermal treatment of glauconite in air

“…A number of intrinsic glauconites have been studied by Mössbauer spectroscopy [8][9][10][11][12][13][14][15][16][17]; nevertheless, study of thermal glauconite transformation has been presented only in two papers [18][19][20] employing XRD and differential thermal analysis (DTA) without Mössbauer spectroscopy application.…”