In:
Journal of Raman Spectroscopy, Wiley, Vol. 51, No. 9 ( 2020-09), p. 1530-1548
Abstract:
We present the results of a comprehensive study linking the crystal‐chemical formulae of amphiboles, a series of extremely complex silicates with the general formula (AB 2 C 5 T 8 O 22 W 2 , C 5 = M 1 2 M 2 2 M 3) to variations in the peak positions, widths, and intensities of the Raman‐active modes. To this purpose, we have analyzed the Raman scattering generated by the framework vibrations (15–1,215 cm −1 ) and by the OH‐stretching modes (3,000–4,000 cm −1 ) of 44 samples, spanning all six major subgroups. We show that, in addition to the information that can be derived from the OH‐stretching range (Leissner et al., Am. Mineral . 2015, 100, 2682), further important features of the amphibole structure, composition, and cationic site population can be directly extracted from the framework Raman spectrum, namely, (a) the distinction between the monoclinic and orthorhombic symmetries; (b) the estimation of T Al content, when T Al 〉 0.5 apfu; (c) the estimation of C Ti content, when C Ti 〉 0.3 apfu; (d) the estimation of C Li content, when C Li 〉 0.3 apfu; (e) the detection of C Al, when C Al 〉 0.7 apfu; (f) an estimate of C Mg; (g) the estimation of C Fe 3+ in the case of Na amphiboles; and (h) the estimation of the Fe 2+ content at the M 2 site in the case of Mg–Fe–Mn amphiboles. Additionally, we point out that the TO 4 ‐ring‐breathing mode near 670 cm −1 , which is commonly used to fingerprint various amphibole species, has to be handled with a great care, because it is sensitive to the site population at all crystallographic sites.
Type of Medium:
Online Resource
ISSN:
0377-0486
,
1097-4555
Language:
English
Publisher:
Wiley
Publication Date:
2020
detail.hit.zdb_id:
1481008-6
SSG:
11
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