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Episodic and long-lasting Paleozoic felsic magmatism in the pre-Alpine basement of the Suretta nappe (eastern Swiss Alps)

Scheiber, T. ; Berndt, J. ; Heredia, B. ; Mezger, K. ; Pfiffner, O.

In: International Journal of Earth Sciences, 2013, vol. 102, no. 8, p. 2097-2115

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    Titre
    • Episodic and long-lasting Paleozoic felsic magmatism in the pre-Alpine basement of the Suretta nappe (eastern Swiss Alps)
    Auteur
    • Scheiber, T.. Institute of Geological Sciences, University of Bern, Baltzerstrasse 3, 3012, Bern, Switzerland
    • Berndt, J.. Institut für Mineralogie, Universität Münster, Corrensstraße 24, 48149, Münster, Germany
    • Heredia, B.. Institute of Geological Sciences, University of Bern, Baltzerstrasse 3, 3012, Bern, Switzerland
    • Mezger, K.. Institute of Geological Sciences, University of Bern, Baltzerstrasse 3, 3012, Bern, Switzerland
    • Pfiffner, O.. Institute of Geological Sciences, University of Bern, Baltzerstrasse 3, 3012, Bern, Switzerland
    Type de document
    • Postprint
    Langue
    • Anglais
    Publié dans
    • International Journal of Earth Sciences, 2013, vol. 102, no. 8, p. 2097-2115. Springer Berlin Heidelberg
    Autre version électronique
    Identifiant OAI-PMH
    • oai:doc.rero.ch:320338
    Summary
    The Suretta nappe of eastern Switzerland contains a series of meta-igneous rocks, with the Rofna Porphyry Complex (RPC) being the most prominent member. We present LA-ICP-MS U-Pb zircon data from 12 samples representing a broad spectrum of meta-igneous rocks within the Suretta nappe, in order to unravel the pre-Alpine magmatic history of this basement unit. Fine-grained porphyries and coarse-grained augengneisses from the RPC give crystallization ages between 284 and 271Ma, which either represent distinct magma pulses or long-lasting magmatic activity in a complex magma chamber. There is also evidence for an earlier Variscan magmatic event at ~320-310Ma. Mylonites at the base of the Suretta nappe are probably derived from either the RPC augengneisses or another unknown Carboniferous-Permian magmatic protolith with a crystallization age between 320 and 290Ma. Two polymetamorphic orthogneisses from the southern Suretta nappe yield crystallization ages of ~490Ma. Inherited zircon cores are mainly of late Neoproterozoic age, with minor Neo- to Paleoproterozoic sources. We interpret the Suretta nappe as mainly representing a Gondwana-derived crustal unit, which was subsequently intruded by minor Cambrian-Ordovician and major Carboniferous-Permian magmatic rocks. Finally, the Suretta nappe was thrust into its present position during the Alpine orogeny, which hardly affected the U-Pb system in zircon