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Raman and FTIR spectroscopy of synthetic amphiboles; 1, The OH librational bands and the determination of the OH-F content of richterites via Raman spectroscopy

Giancarlo Della Ventura, Frank C. Hawthorne, Boriana Mihailova and Armida Sodo
Raman and FTIR spectroscopy of synthetic amphiboles; 1, The OH librational bands and the determination of the OH-F content of richterites via Raman spectroscopy
The Canadian Mineralogist (December 2020) Pre-Issue Publication

Abstract

Unpolarized FTIR and Raman spectra were collected in the regions 4000-4600 cm (super -1) (NIR) and 100-4000 cm (super -1) from previously synthesized and characterized amphiboles in the systems richterite-fluoro-richterite, potassic-richterite-potassic-fluoro-richterite, rubidium-richterite-rubidium-fluoro-richterite, and potassic-richterite-deuterated potassic-richterite. The NIR spectra of Na-, K-, and Rb-richterites have peaks at 4325, 4210 cm (super -1) , and 3735-3730 cm (super -1) . All three peaks decrease in intensity with increasing F content, indicating that the higher-energy peaks are combination bands involving the principal OH-stretch at 3735-3730 cm (super -1) and two OH-libration modes, the frequencies of which can be calculated from the relation omega combination approximately omega OH + omega libration; these are 590 and 475 cm (super -1) , respectively. The FTIR spectra of the richterite-fluoro-richterite and potassic-richterite-potassic-fluoro-richterite series show decreasing intensity and eventual disappearance of the band at approximately 600 cm (super -1) with increasing F in accord with the assignment of this band as due to OH-libration. Raman spectra of the potassic-richterite-deuterated potassic-richterite amphiboles in the low-energy region show the disappearance of two peaks at 585 and 473 cm-1 that we have assigned to OH-libration modes. Collectively, these spectroscopic results indicate that there are two OH-libration modes at approximately 590 and approximately 475 cm (super -1) in these synthetic richterites and, by implication, in all monoclinic OH-bearing amphiboles with filled A sites. Similarly to FTIR, the relative intensities of the stretching modes associated with OH-A-OH and OH-A-F local configurations in the Raman spectra provide a reliable estimation of the F content in these A site-filled amphiboles.


ISSN: 0008-4476
EISSN: 1499-1276
Coden: CAMIA6
Serial Title: The Canadian Mineralogist
Serial Volume: Pre-Issue Publication
Title: Raman and FTIR spectroscopy of synthetic amphiboles; 1, The OH librational bands and the determination of the OH-F content of richterites via Raman spectroscopy
Affiliation: Universita di Roma Tre, Dipartimento di Scienze, Rome, Italy
Published: 20201208
Text Language: English
Publisher: Mineralogical Association of Canada, Ottawa, ON, Canada
References: 33
Accession Number: 2021-006897
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. table
Secondary Affiliation: University of Manitoba, CAN, CanadaUniversitaet Hamburg, DEU, Germany
Country of Publication: Canada
Secondary Affiliation: GeoRef, Copyright 2021, American Geosciences Institute. Abstract, copyright, Mineralogical Association of Canada. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 202105
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