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GEOREF RECORD

Crystal chemistry of narsarsukite

Christiane Wagner, Gian C. Parodi, Michel Semet, Jean L. Robert, Mohamed Berrahma and Danielle Velde
Crystal chemistry of narsarsukite
European Journal of Mineralogy (June 1991) 3 (3): 575-586

Abstract

The finding of Zr-rich narsarsukite in a peralkaline lava from Morocco prompted a re-evaluation of the crystal chemistry of this mineral. Microprobe analyses show that F is present in narsarsukite from all known occurrences. An examination of two specimens (from Narsarsuk and Montana) by Mossbauer spectroscopy indicates that most of the iron is present in the trivalent state. The infrared spectra of three specimens exhibit four absorption bands in the 4000-3000 cm (super -1) range. The assignment of these bands either to hydroxyls or water molecules is discussed, the latter hypothesis being favoured. Significantly larger unit-cell parameters in the Moroccan sample are compatible with the extensive replacement of Ti by Zr. The entry of F in the structure is coupled with the replacement of Ti by Fe (super 3+) , F substituting the underbonded apical oxygens of the TiO (sub 6) octahedra. These new results suggest that the general formula Na (sub 2) [(Ti,Zr) (sub (1-x)) Fe (sub x) (super 3+) ] O (sub (1-x)) F (sub x) Si (sub 4) O (sub 10-) (0-1/2)H (sub 2) O, with 0<x<1, may be proposed for narsarsukite.


ISSN: 0935-1221
Serial Title: European Journal of Mineralogy
Serial Volume: 3
Serial Issue: 3
Title: Crystal chemistry of narsarsukite
Affiliation: Univ. Paris, Lab. Petrol. Mineral., Paris, France
Pages: 575-586
Published: 199106
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
Accession Number: 1993-042670
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 5 tables, 10 anals.
N27°40'00" - N32°04'60", W13°15'00" - W02°00'00"
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Geoline, Bundesanstalt fur Geowissenschaften und Rohstoffe, Hanover, Germany
Update Code: 1993
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