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A high-pressure structural study of microcline (KAlSi (sub 3) O (sub 8) ) to 7 GPa

David R. Allan and Ross J. Angel
A high-pressure structural study of microcline (KAlSi (sub 3) O (sub 8) ) to 7 GPa (in EMPG-VI; Experimental mineralogy, petrology and geochemistry, E. A. J. Burke (editor), C. Chopin (editor), W. V. Maresch (editor), L. Ungaretti (editor) and C. Willaime (editor))
European Journal of Mineralogy (April 1997) 9 (2): 263-275

Abstract

Unit-cell parameters of a microcline of average composition Na (sub 0.01) K (sub 0.97) Si (sub 3.02) O (sub 4) were determined at 12 points from 1 atm to 7.1 GPa by single-crystal XRD in a diamond-anvil press. The angles alpha and beta show small changes in their variation with P at approximately 3.8 GPa, but with no measurable discontinuity in cell volume; the data are described by V (sub 0) = 719.8 Aa (super 3) , K (sub 0) = 58.3 GPa with K' fixed at 4. The crystal structure was refined to data collected at six pressures to a maximum P of 7.1 GPa; the symmetry remains Cl over this entire P range, the V compression being accommodated by flexing one of the T-O-T bond angles (by 15-18 degrees ) of the framework and shortening of the M-O distances. This flexing reduces the volume of the cage occupied by the M cation by 14 + or - 2% in this P range; at low P the M position moves in the [<$E 1 back 40 up 40 ->00] direction as P increases, but at higher P there is an additional component of displacement along [001].


ISSN: 0935-1221
Serial Title: European Journal of Mineralogy
Serial Volume: 9
Serial Issue: 2
Title: A high-pressure structural study of microcline (KAlSi (sub 3) O (sub 8) ) to 7 GPa
Title: EMPG-VI; Experimental mineralogy, petrology and geochemistry
Author(s): Allan, David R.Angel, Ross J.
Author(s): Burke, E. A. J.editor
Author(s): Chopin, C.editor
Author(s): Maresch, W. V.editor
Author(s): Ungaretti, L.editor
Author(s): Willaime, C.editor
Affiliation: Universitaet Bayreuth, Bayerisches Geoinstitut, Bayreuth, Federal Republic of Germany
Pages: 263-275
Published: 199704
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
Meeting name: Sixth international symposium on Experimental mineralogy, petrology and geochemistry
Meeting location: Bayreuth, DEU, Federal Republic of Germany
Meeting date: 19960410April 10-13, 1996
References: 31
Accession Number: 1997-036941
Categories: Mineralogy of silicates
Document Type: Serial Conference document
Bibliographic Level: Analytic
Illustration Description: 4 tables
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 199712
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