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The 500 Ma-old Thyon metagranite; a new A-type granite occurrence in the western Penninic Alps (Wallis, Switzerland)

Francois Bussy, Marc-Henri Derron, Jerome Jacquod, Mario Sartori and Philippe Thelin
The 500 Ma-old Thyon metagranite; a new A-type granite occurrence in the western Penninic Alps (Wallis, Switzerland)
European Journal of Mineralogy (June 1996) 8 (3): 565-575

Abstract

The Thyon metagranite is in the frontal part of the Siviez-Mischabel nappe and is intrusive in a polymetamorphic banded volcanic complex as leucocratic concordant sills with pseudoaplitic rims. A distinct metamorphic schistosity is defined by dark-green Fe-rich biotite; abundant mesoperthites, chess-board albite and low microcline are presumably related to magmatic stages and/or greenschist-facies retrogressive metamorphism. Major, trace element and REE geochemistry, zircon typology, Y and Nb-bearing accessory minerals such as fergusonite and euxenite, all point to a metaluminous to peraluminous alkaline A-type granite. High-precision U-Pb zircon dating gave a subconcordant age of 500 (super +3) (sub -4 ) m.y. The Thyon metagranite is the third record of Cambro-Ordovician alkaline magmatic activity in the Alps. As A-type granite magmatism is common in post-orogenic to anorogenic extensional tectonic regimes, the Thyon intrusion could mark the transition between the Cadomian and the Caledonian orogenies.


ISSN: 0935-1221
Serial Title: European Journal of Mineralogy
Serial Volume: 8
Serial Issue: 3
Title: The 500 Ma-old Thyon metagranite; a new A-type granite occurrence in the western Penninic Alps (Wallis, Switzerland)
Affiliation: Royal Ontario Museum, Department of Geochronology, Toronto, ON, Canada
Pages: 565-575
Published: 199606
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 46
Accession Number: 1996-047204
Categories: Igneous and metamorphic petrologyGeochronology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables, geol. sketch map
N45°52'00" - N46°37'60", E06°47'60" - E08°28'00"
Secondary Affiliation: Universite Lausanne, CHE, Switzerland
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 199616
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