Studies of the orthoamphiboles. I. The Mössbauer and infrared spectra of holmquistite

Abstract

Un échantillon de l'orthoamphibole lithique holmquistite a été examiné par spectroscopic Mössbauer, et son spectre infrarouge dans l'intervalle d'absorption d'hydroxyle (3 800-3 500 cm⁻¹) a été déterminé. Les résultats qualitatifs et quantitatifs sont présentés, et les occupations des sites sont confrontées à celles de précédentes mesures aux rayons X.

Raman microscopic study of the Li amphibole holmquistite, from the Martin Marietta Quarry, Bessemer City, NC, USA

“…The OH-stretching region Figure 2 shows the OH-stretching region between 3600 and 3680 cm 1 of the Raman spectrum of holmquistite. Clearly recognizable are four sharp bands,~15 cm 1 apart at 3661, 3646, 3634 and 3614 cm 1 , similar to previously reported IR spectra (Wilkins et al, 1970;Law and Whittaker, 1981) although at slightly different frequencies as the vibrations are in-phase rather than out-ofphase stretching modes (Table 2). Similar bands have also been observed in the Raman spectra of several monoclinic amphiboles like cummingtonite and glaucophane (Wang et al, 1988a).…”

“…Such minor bands can be expected when small amounts of another cation such as Al 3+ or Fe 3+ are present. Law and Whittaker (1981) (Burns and Strens, 1966;Wilkinson et al, 1970). This leads to the following relationship for the relative intensities of the hydroxyl bands at 3661 and 3646 cm 1 :…”

“…The Fe 2+ distribution in holmquistite differs from other Fe-Mg-Mn amphiboles in that Fe 2+ shows a site preference for the M 3 site above M 1 and almost no Fe 2+ is found on the M 2 and M 4 sites (Hawthorne, 1981a). This is strongly re ected in the hydroxylstretching region of the infrared (IR) spectrum as reported by Wilkins et al (1970) which clearly show four bands and by Mössbauer spectroscopy (Law, 1973;Law and Whittaker, 1981).…”

“…H O L M Q U I S T I T E , L i 2 (M g , F e 2+ ) 3 (A l , Fe 3 + ) 2 (Si,Al) 8 O 22 (OH) 2 , named after the Swedish petrologist Per Holmquist, is a unique Li-rich member of the orthorhombic (space group Pnma (Law and Whittaker, 1981)) Mn-Mg-Fe-Liamphibole group. It typically occurs at the contact of Li-rich pegmatites with surrounding rocks and is associated with metasomatic processes (Wilkins et al, 1970;Gorelov et al, 1983;Frost and Tsambourakis, 1987;Lagache and Quéméneur;.…”

Ferro-ferri-holmquistite, □Li2(Fe2+3Fe3+2)Si8O22(OH)2, Fe2+Fe3+ analogue of holmquistite, from the Iwagi islet, Ehime, Japan

“…The full width at half maximum heights are roughly equal for all components, 10.1-10.4 cm −1 . Based on the OH-stretching IR bands in orthorhombic Pnma amphiboles such as holmquistite and the anthophyllite-gedrite series (Ishida and Hawthorne, 2003;Kloprogge et al, 2001;Law, , 1982Law and Whittaker, 1981;Burns and Law, 1970;Wilkins et al, 1970), the four main bands, labeled A, B, C and D, are assigned to local configurations M1M1M3-O3H-A, where A = ( , Na) and M1M1M3 = MgMgMg, MgMgFe (including MgFeMg and FeMgMg), MgFeFe (including FeMgFe and FeFeMg) 3.223(3) * <λ> and σ θ 2 are bond-length distortion and angle variance, respectively (Robinson et al, 1971).…”