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GEOREF RECORD

Microstructural variations in a natural cordierite from the Eifel volcanic field, Germany

Wolfgang F. Mueller and Werner Schreyer
Microstructural variations in a natural cordierite from the Eifel volcanic field, Germany
European Journal of Mineralogy (December 1991) 3 (6): 915-931

Abstract

A cordierite crystal (approx 3 mm) from a small metapelitic xenolith from the Bellerberg volcano, Eifel, was studied by TEM, which showed that the grain was subdivided into regions with different types of microstructure. These regions are a few mu m to 0.1 mm in size and range from metrically hexagonal to orthorhombic. They include: 1) modulated structures approx 100 (sub hex) and perpendicular it, i.e. approx the corresponding plane of type 120 (sub hex) ; 2)distinct lamellae with modulated structures sharing splitting of high order reflections <100> (super *) (sub orth) ; 3) lamellar and blocky twin domains of the mirror twin laws 110 (sub orth) and 110 (sub orth) , and 4) orthorhombic regions without modulated structures and twin domains. This variety of different but adjacent microstructures correlates with varying degrees of K + Al for Si substitution: regions (1) have the highest K contents (0.09-0.23 per formula unit with 18 O) whereas regions (2)-(4) have K <= 0.09 pfu. Thus, KAlSi (sub -1) is shown to stabilize the modulated structure, described here for the first time from a natural cordierite, and to hinder its transformation to orthorhombic cordierite.


ISSN: 0935-1221
Serial Title: European Journal of Mineralogy
Serial Volume: 3
Serial Issue: 6
Title: Microstructural variations in a natural cordierite from the Eifel volcanic field, Germany
Affiliation: Tech. Hochsch. Darmstadt, Inst. Mineral., Darmstadt, Federal Republic of Germany
Pages: 915-931
Published: 199112
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 1 p.
Accession Number: 1994-052619
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: 1 table
N50°00'00" - N50°30'00", E06°19'60" - E07°19'60"
N49°00'00" - N51°00'00", E06°10'00" - E08°30'00"
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: 199424
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