Assignment of the Far-Infrared Absorption Bands of K in Micas

Abstract

Abstract--To identify the far-infrared (FIR) absorption bands related to K cations in micas, spectra of muscovite, phlogopite, and biotite were compared with the spectra of pyrophyllite and talc, which have no compensating cations, and to the spectra of micas in which K is substituted by mono-and divalent cations. Dichroic experiments using single crystals of these micas showed that some of the bands or components related to K have a strong in-plane and out-of-plane dichroic character. These experimental data led to the assignment of the FIR bands at 110, 91, and 83 cm -~ for muscovite, phlogopite, and biotite, respectively, which have no in-plane and out-of-plane dichroic character, to the vibration of the double ring of oxygen atoms that constitutes the cage in which K is located (mode III).Bands at 146, t36, and 152 cm -I for muscovite, phlogopite, and biotite, respectively, which have a strong out-of-plane dichroic character, were assigned to the out-of-plane vibrations of K atoms (mode IV). Some of the components at 190, 158-153, and 145-124 cm l for muscovite, phlogopite, and biotite, respectively, which have a strong in-plane dichroic character, are possibly related to the in-plane vibrations of K atoms (modes I and II). The 165-cm ~ band of muscovite is a lattice mode of vibration. Frequencies of modes III and IV of the compensating cations of micas in which K was substituted by mono-and divalent cations exchanged as a function of ~ where Z is the charge and m the mass of the cation. Modes III and IV were well resolved and very sensitive to the crystallochemical properties of the structure (di-or trioctahedral character, Fe content, etc.). FIR spectroscopy may therefore be an important tool that uses compensating cations as probes to study the interactions between the cations and the structure of mica minerals.

Characterization and Assignment of Far Infrared Absorption Bands of K+ in Muscovite

“…DISCUSSION AND CONCLUSIONS Laperche and Prost (1991) showed that K § in muscovite produces absorption bands near 110 and 140 cm J. The present pleochroic study of the FIR absorption bands of K § in muscovite shows the existence of three dichroic bands at 107, 110, and 143 cm -~.…”

“…Schroeder (1990) and Prost and Laperche (1990) independently assigned the FIR absorption band near 100 cm -~ to K § in micas. Laperche (1991) and Laperche and Prost (1991) exchanged K § of micas by other cations and again assigned the FIR absorption bands near 100 and 140 cm -1 to the vibration of the compensating cations.…”

“…Fripiat (1981) also refers to the in-plane and out-of-plane vibrations of compensating cations. Laperche and Prost (1991) failed to properly assign the modes I and II described by Ishii et aL (1967). The aim of this paper is to determine the band assignments by the study of the in-plane and out-of-plane dichroic character of FIR absorption bands of K § in muscovite.…”

Far-infrared spectra of synthetic [4][(Al2-xGax)(Si2-yGey)](OH,OD,F)2-kinoshitalite: Characterization and assignment of interlayer Ba-Oinner and Ba-Oouter stretching bands

“…Tateyama et al (1977) were the first to assign the strong band near 100 cm -1 in the spectra of K-bearing micas to K-O inner stretching. Farmer (1974), Prost and Laperche (1990), Laperche and Prost (1991), and Diaz et al (2000) identified two in-plane modes at 107 and 110 cm -1 and one out-of-plane mode at 143 cm -1 involving K and two double trigonal rings in muscovite, with the maximum absorption directions near b-, a-, and c*-axis, respectively. Loh (1973), Velde (1978), Roth (1978), Velde and Couty (1985), Schroeder (1990), andBoukilli et al (2001) also reported FIR spectra of micas, and Beran (2002) and Fleet (2003) reviewed FTIR work on micas, including that in the mid-IR (MIR) and FIR regions.…”

Development of far-infrared attenuated total reflectance spectroscopy for the mineralogical analysis of shales

“…Peaks below 150 cm À1 are generally assigned to vibrations of the interlayer cations or in the case of kaolinite the band at 117 cm À1 can be attributed to a vibration of the distorted Si 2 O 5 layer [20,44]. Illite and smectite have bands occurring at 88 cm À1 and 92 cm À1 respectively which have been associated with vibrations of the interlayer potassium ions [45,46]. It is evident that the illite peak at 92 cm À1 is far more intense than nearby peaks in smectite or kaolinite, suggesting that it may be possible to identify and distinguish this mineral in a clay mixture.…”