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GEOREF RECORD

Experimental study of the composition and stabilities of synthetic nyboite and nyboite-glaucophane amphiboles

Alison R. Pawley
Experimental study of the composition and stabilities of synthetic nyboite and nyboite-glaucophane amphiboles
European Journal of Mineralogy (February 1992) 4 (1): 171-192

Abstract

Nyboite, Na (sub 3) Mg (sub 3) Al (sub 3) Si (sub 7) O (sub 22) (OH) (sub 2) , like glaucophane, cannot be synthesized from its own or any other bulk composition. Compositions close to nyboite, obtained in experiments on its own bulk composition are quaternary nyboite- glaucophane-katophorite-eckermannite compositions, with nyboite contents <= approx 70%. The eckermannite contents decrease with increasing T via the Tschermak's exchange, while with increasing P there is a filling of the A site. These amphiboles are stable to P > 32 kbar at 600-900 degrees C and in this T range they break down at < 15 kbar to albite + nepheline + sodium phlogopite. Amphiboles coexisting with quartz are ternary nyboite-glaucophane-katophorite solid solutions. The reaction interpreted by Ernst [A.M. 48-241] to be a polymorphic reaction between low- and high-P polymorphs of glaucophane is in fact the reaction amphibole + quartz = albite + talc (bracketed at 14.8-18.5 kbar, 700 degrees C to 18.2-19.5 kbar, 800 degrees C) above which amphiboles synthesized from the glaucophane bulk composition are ternary nyboite-glaucophane- katophorite solid solutions, and below which they arequarternary nyboite-glaucophane-katophorite-eckermannite solid solutions.


ISSN: 0935-1221
Serial Title: European Journal of Mineralogy
Serial Volume: 4
Serial Issue: 1
Title: Experimental study of the composition and stabilities of synthetic nyboite and nyboite-glaucophane amphiboles
Author(s): Pawley, Alison R.
Affiliation: Univ. Edinburgh, Dep. Geol. Geophys., Edinburgh, United Kingdom
Pages: 171-192
Published: 199202
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 2 p.
Accession Number: 1993-025697
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 5 tables
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom. Reference includes data from Geoline, Bundesanstalt fur Geowissenschaften und Rohstoffe, Hanover, Germany
Update Code: 1993
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