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High-pressure transformation behaviour of the cummingtonite-grunerite solid solution

Tiziana Boffa Ballaran, Ross J. Angel and Michael A. Carpenter
High-pressure transformation behaviour of the cummingtonite-grunerite solid solution
European Journal of Mineralogy (December 2000) 12 (6): 1195-1213

Abstract

The displacive C2/m<-->P2 (sub 1) /m phase transition that occurs with increasing pressure in cummingtonites has been investigated by means of X-ray single-crystal diffraction at different compositions and degrees of Mg/Fe (super 2+) order. Unit-cell parameters and a sub-set of intensity data of some "b" and "a" reflections were collected for four natural and two annealed samples as a function of pressure. The phase transition is close to second order in character, either with a significant contribution from the sixth order term of the Landau potential or with the fourth order coefficient depending on pressure via the bare elastic constants. The transition pressure, P (sub c) , obtained at the different compositions and degrees of order, displays a plateau at the grunerite end. The evolution of the spontaneous strain associated with the phase transition does not depend on the Mg/Fe (super 2+) substitution or ordering, but it is very sensitive to the impurity (Al, Na, Ca) content.


ISSN: 0935-1221
Serial Title: European Journal of Mineralogy
Serial Volume: 12
Serial Issue: 6
Title: High-pressure transformation behaviour of the cummingtonite-grunerite solid solution
Affiliation: University of Cambridge, Department of Earth Sciences, Cambridge, United Kingdom
Pages: 1195-1213
Published: 200012
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 44
Accession Number: 2001-040133
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 6 tables
Secondary Affiliation: Universitaet Bayreuth, DEU, Federal Republic of Germany
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2020, American Geosciences Institute.
Update Code: 200112
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