Refined Relationships between Chemical Composition of Dioctahedral Fine-Grained Micaceous Minerals and Their Infrared Spectra Within the OH Stretching Region. Part II: The Main Factors Affecting OH Vibrations and Quantitative Analysis

Abstract

Abstract--A new model for the interpretation of dioctahedral mica infrared (IR) spectra in the OH stretching vibration region is proposed. It is based on the analysis of the main factors responsible for the observed sequence of the OH frequencies. In terms of this model, the simple analytical dependence between the OH frequencies and the mass and valency of cations bonded to OH groups has been found. The specific character of the interaction between octahedral A1 and OH groups in the mica structures is assumed.Integrated optical densities of the OH bands determined by the decomposition of the studied mica IR spectra are used for the quantitative analysis, that is, for the determination of a number of each type of octahedral cations per unit cell of the sample under study. A good agreement between the octahedral cation contents of 2:1 layers found from the IR spectra decomposition and the chemical analysis has shown that this technique may be used to study the local order-disorder of isomorphous cation distribution in mica structures.The essential result obtained by the quantitative analysis of the mica IR spectra is the determination of Fe 3+ cations in the tetrahedral sites of some samples. This means that the conventional presentation of structural formulae for Al-Fe3+-containing 2:1 layer silicates is unacceptable without consideration of tetrahedral Fe 3 ~ by spectroscopic techniques and by the quantitative analysis of the IR spectra, in particular.

Refined Relationships between Chemical Composition of Dioctahedral Fine-Grained Mica Minerals and Their Infrared Spectra within the OH Stretching Region. Part I: Identification of the OH Stretching Bands

“…Slonimskaya et al (1986) and Russell (1987) also observed a band at 3578-3580 cm -~ in the IR spectra of samples containing relatively high contents of AI and Fe 2+. However, according to our interpretation, the A1-Fe 2 § and Mg-Fe 3 § bands locate at the same positions (3559 --3 cm 1), whereas the band at 3573 ---3 cm ~ corresponds to A1-Fe 3 § Discussion of these new correlations will be given in the section on factors responsible for the regularities observed in the OH-stretching region (Besson and Drits 1997).…”

Characterization of Octahedral Substitutions in Kaolinites Using Near Infrared Spectroscopy

“…In the spectra of clay minerals other than kaolinite with various chemical compositions due to numerous cation substitutions, the vibrations of the OH groups are almost fully understood and have been found to be sensitive indicators of the hydroxyl environment (Robert and Kodama 1988;Madejov~i et al 1994;Besson and Drits 1997). Each definite type of cation bonded to an OH group is determined by a definite position of the corresponding OH band.…”

Partial Stabilization of Fe(II) in Reduced Ferruginous Smectite by Li Fixation

“…However, Rouxhet (1970) found that within the same type of minerals the absorption coefficient per OH group was about the same and did not depend appreciably on either the chemical composition or the orientation of the oscillator. This assumption was used effectively as a basis for the determination of the octahedral cation content (Slonimskaya et al, 1986;Madejov~ et al, 1996;Besson and Drits, 1997b). Thus, areas shown in Table 2 Wavenumbers (cm-1) Figure 5.…”