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Si-deficient, OH-substituted, boron-bearing vesuvianite from Sakha-Yakutia, Russia; a combined single-crystal, 1H MAS-NMR and IR spectroscopic study

Taras L. Panikorovskii, Sergey V. Krivovichev, Evgeny V. Galuskin, Vladimir V. Shilovskikh, Anton S. Mazur and Ayya V. Bazai
Si-deficient, OH-substituted, boron-bearing vesuvianite from Sakha-Yakutia, Russia; a combined single-crystal, 1H MAS-NMR and IR spectroscopic study
European Journal of Mineralogy (December 2016) 28 (5): 931-941

Abstract

Single crystals of Si-deficient vesuvianite with significant degree of hydrogarnet-type (SiO (sub 4) ) (super 4-) -(O (sub 4) H (sub 4) ) (super 4-) substitution occur as epitactic overgrowth on the surface of large wiluite crystals from the Wiluy River, Sakha-Yakutia, Russia. Electron-microprobe analysis revealed considerable Si-deficiency, Si ranging from 16.30 to 17.50 apfu The crystal structure of the mineral has been refined in the P4/nnc space group, a = 15.5876(4), b = 11.8021(5) Aa to R (sub 1) = 0.028 for 1533 unique observed reflections. The refinement of the site-occupancy factors confirmed significant vacancy at the Z(1) and Z(2) sites (27 % and 10 %, respectively), with associated increase of the Z(1)-O and Z(2)-O bond lengths to 1.697 and 1.655 Aa, respectively. The increased size of the Z(1) tetrahedra results in the compression of the X(1) polyhedra, while the expansion of the Z(2) tetrahedra is compensated by the compression of the X(4) polyhedra. As a result, the significant degree of the hydrogarnet-type substitutions does not have an essential influence upon the unit-cell parameters compared to the usual defect-free vesuvianite. Thermogravimetric (TGA) and differential scanning calorimetry (DSC) curves indicated two steps of the weight loss in the temperature ranges of 600-900 degrees C (2.08 wt%) and 1014 degrees C (2.22 wt%). The total weight loss is estimated as 4.30 %, which is in good agreement with the total content of OH estimated as 13.72 apfu The (super 1) H solid state MAS-NMR demonstrates the presence of a strong additional line at 3.38 ppm compared to the usual vesuvianite, which is explained by the existence of the additional H(3) site. The infrared spectrum in the OH-stretching vibration region shows the additional (B') absorption band at 3618 cm (super -1) typical for a hydrogarnet-type substitution.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 28
Serial Issue: 5
Title: Si-deficient, OH-substituted, boron-bearing vesuvianite from Sakha-Yakutia, Russia; a combined single-crystal, 1H MAS-NMR and IR spectroscopic study
Affiliation: Saint-Petersburg State University, Department of Crystallography, St. Petersburg, Russian Federation
Pages: 931-941
Published: 201612
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Germany
References: 52
Accession Number: 2017-075614
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 6 tables
N63°01'00" - N63°01'00", E112°19'60" - E112°19'60"
Secondary Affiliation: University of Silesia, POL, PolandRussian Academy of Sciences, Kola Science Centre, Geological Institute, RUS, Russian Federation
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: 201740
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