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Chemical deviation from ideal form of plagioclase; study using the microprobe

Hans Schwander and Eduard Wenk
Chemische Abweichungen von der Idealformel bei Plagioklas, eine Studie mit der Mikrosonde
European Journal of Mineralogy (August 1992) 4 (4): 757-766

Abstract

Measures to decrease the analytical errors of EPMA are discussed. Plagioclases were analysed from different metamorphic rocks of the Central Alps and some volcanic rocks; deviation from the theoretical/stoichiometric compositions were calculated (DELTA Al, DELTA Si). As a result of loss of Na, deviations from the ideal formula of albitic plagioclases were larger than in anorthitic compositions, where the Ca loss is smaller. All the analysed metamorphic anorthites and several pure albites show almost perfect stoichiometry, but oligoclase-labradorite compositions show a distinct excess of Si in relation to Al (DELTA Si: DELTA Al approx 3:1). Plagioclases from volcanic rocks agree well with the theoretical composition, in spite of strong zoning.


ISSN: 0935-1221
Serial Title: European Journal of Mineralogy
Serial Volume: 4
Serial Issue: 4
Title: Chemische Abweichungen von der Idealformel bei Plagioklas, eine Studie mit der Mikrosonde
Translated Title: Chemical deviation from ideal form of plagioclase; study using the microprobe
Affiliation: Universitaet Basel, Mineralogisch-Petrographisches Institut, Basel, Switzerland
Pages: 757-766
Published: 199208
Text Language: German
Summary Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 10
Accession Number: 1995-056296
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: 2 tables
N46°00'00" - N47°00'00", E09°00'00" - E11°30'00"
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 199520
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