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Water in Zr-bearing synthetic and natural glasses

Francois Farges and Stephanie Rossano
Water in Zr-bearing synthetic and natural glasses (in Fluid/mineral interactions in the crust, Anonymous)
European Journal of Mineralogy (December 2000) 12 (6): 1093-1107

Abstract

The local environment of approximately 1400 ppm Zr in hydrous synthetic glasses (sodium trisilicate and albitic) has been probed at the Zr K-edge by X-ray Absorption Fine Structure (XAFS) spectroscopy and compared to that for natural glasses (volcanic and tektites). In most glasses (anhydrous and hydrous), Zr is found to be 6-coordinated by oxygen, with Zr-O distances of approximately 2.08 Aa. However, in anhydrous albite glass, the Zr-O distance increases to 2.12 Aa, related to the presence of highly-coordinated Zr-environments (7,8) in the glass. Network-forming, next-nearest neighbour T (T = Si/Al) contributions are measured near 3.6 Aa, suggesting corner-sharing ZrO (sub 6) -TO (sub 4) polyhedra. We observed no large effect due to the presence of water in these glasses, suggesting that molecular water and hydroxyls are not likely to complex Zr in these compositions. However, a slight structural relaxation of the tetrahedral framework (increased network fragility with a small production of NBO's) is observed around Zr in albitic compositions with more than 1 wt.% water. Then, no strong evidence for deploymerization induced by water is observed around Zr (Zr being used in that study as a probe for trace amounts of NBO's). By comparison with transition elements (Fe and Ni), Zr appears to be much less affected by the introduction of water. The conclusions for Zr are likely to be extrapolated to natural magmas, as the natural glasses probed show similar environments around Zr. Then, oxygen appears the most efficient anion to "complex" Zr, as compared to water, hydroxyls, halogens, CO (sub 2) or S.


ISSN: 0935-1221
Serial Title: European Journal of Mineralogy
Serial Volume: 12
Serial Issue: 6
Title: Water in Zr-bearing synthetic and natural glasses
Title: Fluid/mineral interactions in the crust
Author(s): Farges, FrancoisRossano, Stephanie
Author(s): Anonymous
Affiliation: Universite de Marne-la-Vallee, France
Pages: 1093-1107
Published: 200012
Text Language: English
Summary Language: French
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
Meeting name: Fluid/mineral interactions in the crust
Meeting location: Paris, FRA, France
Meeting date: 19991014Oct. 14-15, 1999
References: 53
Accession Number: 2001-040125
Categories: General mineralogy
Document Type: Serial Conference document
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables
Secondary Affiliation: Institut Universitaire de France, FRA, France
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 200112
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