A Mössbauer Investigation of Glauconite and its Geological Significance

Abstract

Ahstraet--M6ssbauer spectra of 9 glauconite samples from Upper Cretaceous and Lower Tertiary strata in the South Island of New Zealand contain a broad shoulder due to low intensity absorption continuous between 1.0 and 2.5 mm/sec when the absorber is at room temperature; the shoulder is absent, and sharp peaks are apparent in spectra taken with the absorber at 80~ The data suggest that electron transfer occurs between adjacent Fe 3+ and Fe z+ ions at room temperature. The low temperature spectra indicate that all Fe in the glauconites is in octahedral coordination. Fe z+ and Fe z+ ions occur in both cis and trans sites; Fe z+ shows a strong preference for cis sites whereas Fe 2+ shows an even stronger preference for trans sites.The partially variable oxidation state of Fe in glauconite is interpreted in terms of a geochemical model for glauconitization of a degraded or incomplete progenitor phyllosilicate. The model involves exchange of Fe ~+ for other cations which temporarily stabilize the progenitor, followed by FeZ § 3+ charge transfer reactions. Each reaction results from the system's tendency towards equilibrium. The model is supported by the observation that artificially leached glauconite increases both its Fe z+ and its Fe z+ content when placed in a solution containing Fe 2+ as the only Fe ion present.

Iron Substitution in Montmorillonite, Illite, and Glauconite by 57Fe Mössbauer Spectroscopy

“…The M6ssbauer spectra of illite and glauconite have also been reported by a number of workers (Rolf et al, 1977;Rozenson and Heller-Kallai, 1978;McConchie et al, 1979;Ross and Longworth, 1980;Kotlicki et al, 1981;De Grave et al, 1985). In general, these spectra show the presence of both Fe 2+ and Fe 3+ in the structure, and most spectra have been resolved into two Fe 3+ and two Fe 2+ doublets (e.g., De Grave et aL, 1985).…”

“…A controversy exists, however, in assigning the Fe 2+ doublets. Rolfet al (1977), Rozenson and Heller-Kallai (1978), Kotlicki et al (1981), andDe Grave et al (1985) considered that the Fe 2+ doublet having the larger quadrupole interaction arises from Fe 2+ in cis-OH sites, whereas McConchie et al (1979) and Ross and Longworth (1980) assigned this doublet to Fe 2+ in trans-OH sites.…”

Interpretation of Mössbauer Spectra of Nontronite, Celadonite, and Glauconite

“…Spectra of one type are somewhat better resolved and characterized by a relatively smaller total width compared with the spectra of the other type. Relatively wider and more poorly resolved spectra were interpreted conventionally, as described previously (Rozenson and Heller-Kallai, 1978;Govaert et al, 1979;McConchie et al, 1979). The spectra of the first type are approximated by a single doublet with broadened components (Annersten, 1975;Kotlicky et al, 1981), and the corresponding glauconites are considered "ordered", i.e., having only cis-positions occupied by cations.…”

“…Most workers have treated the spectra of celadonite (Malysheva et al, 1976), nontronite (Goodman et al, 1976;Heller-Kallai and Rozenson, 198 I), glauconites (Rozenson and Heller-Kallai, 1978;McConchie et al, 1979;Govaert et al, 1979;Kotlicki et al, 1981) as the superposition of two doublets related to Fe 3+ ions in cis-and trans-octahedra. According to X-ray and electron diffraction data, trans-octahedral sites of the 2:1 layers of these minerals are vacant (Tsipursky et al, 1978;Daynyak et al, 1981a;Besson et al, 1983; Tsipursky and Tsipursky et al, 1985).…”

Critical review of analytical applications of Mössbauer spectroscopy illustrated by mineralogical and geological examples (IUPAC Technical Report)

“…In the case of the four-doublet fits, one of the interpretation assigns the doublets with isomer shifts and quadrupole splitting δ = 1.14 mm/s, ∆ = 2.60 mm/s and δ = 0.35 mm/s, ∆ = 0.47 mm/s to Fe 2+ and Fe 3+ in cis position, respectively, while the doublet with δ = 1.05 mm/s, ∆ = 2.15 mm/s and δ = 0.56 mm/s, ∆ = 0.88 mm/s to Fe 2+ and Fe 3+ in trans position, respectively [60]. Based on this site assignment, geological conclusion was drawn on the evolution of glauconite-bearing strata [61]. However, this site assignment for the glauconite, which is analogous to that used for trioctahedral micas, gives contradictory results concerning the temperature dependence of Mössbauer parameters.…”