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Crystal chemistry of Al-V-Cr oxy-tourmalines from Sludyanka Complex, Lake Baikal, Russia

Ferdinando Bosi, Leonid Reznitskii, Ulf Halenius and Henrik Skogby
Crystal chemistry of Al-V-Cr oxy-tourmalines from Sludyanka Complex, Lake Baikal, Russia
European Journal of Mineralogy (December 2016) 29 (3): 457-472

Abstract

Twelve Al-V-Cr oxy-tourmalines from the Sludyanka crystalline complex (Russia) were structurally and chemically characterized by single-crystal X-ray diffraction and electron microprobe analysis. Three samples were also optically characterized by optical absorption spectroscopy and refractive index measurements. The data obtained and those of fourteen earlier studied oxy-tourmalines from the same locality show a complete substitution series due to the replacement of Al <--> V (super 3+) <--> Cr (super 3+) . The cation site distribution results show that Mg has a strong preference for the Z site, whereas the trivalent cations have a preference for Y and Z controlled by their size: (super Y) V (super 3+) > (super Y) Cr >> (super Y) Al and (super Z) Al >> (super Z) Cr > (super Z) V (super 3+) . In accordance with the bond-valence theory, the observed increase of F content with increasing Cr content may be interpreted by the occurrence of the local arrangements (super O1) (F)- (super Y) (CrCrCr) and (super Z) [Cr(Cr,Mg)]- (super O3) (O (super 2-) )- (super Y) (Cr), while the incorporation of V (super 3+) into the oxy-tourmaline structure is controlled by the local arrangement (super O1) (O (super 2-) )- (super Y) (VVV). The unit-cell parameters (a and c) are strictly correlated to each other and can be expressed by a quadratic relation dependent on the mean-bond distances <Z-O> and <X-O>. A strong positive correlation between (V + Cr) content and mean refractive index is proposed as a reliable guide to derive the composition of Al-V-Cr oxy-tourmalines from refractive-index measurements.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 29
Serial Issue: 3
Title: Crystal chemistry of Al-V-Cr oxy-tourmalines from Sludyanka Complex, Lake Baikal, Russia
Affiliation: Sapienza Universita di Roma, Dipartimento di Scienze della Terra, Rome, Italy
Pages: 457-472
Published: 20161227
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Germany
References: 54
Accession Number: 2017-006183
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 5 tables
N52°00'00" - N56°00'00", E104°00'00" - E110°00'00"
Secondary Affiliation: Russian Academy of Science, Siberian Branch, Institute of the Earth's Crust, RUS, Russian FederationSwedish Museum of Natural History, SWE, Sweden
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Schweizerbart'sche Verlagsbuchhandlung. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201705
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