New U-Pb zircon and 40Ar/39Ar muscovite age constraints on the emplacement of the Lizio syn-tectonic granite (Armorican Massif, France)

Romain Tartèse, Marc Poujol, Gilles Ruffet, Philippe Boulvais, Philippe Yamato, Jan Košler

    Research output: Contribution to journalArticlepeer-review

    Abstract

    LA-ICP-MS U-Pb analyses performed on zircon grains from the Lizio granite yielded an emplacement age of 316±6 Ma. Typical S-C structures show that the Lizio granite was emplaced contemporaneously with dextral shearing along the northern branch of the South Armorican Shear Zone and that it was therefore active at that time. 40Ar/39Ar analyses performed on muscovite grains yielded plateau dates ranging between 311.5 and 308.2Ma. Muscovite chemistry is typical of primary magmatic muscovite, which precludes a late fluids-induced resetting of the K-Ar isotopic system. 40Ar/39Ar dates thus likely correspond to the cooling ages below the argon closure temperature. Considering the uncertainties on the measured ages, we can propose that either the Lizio granite cooled down quickly in less than a million of years or that it remained in a hot environment for several millions of years after its emplacement. This latter scenario could have been sustained by shear heating during dextral shearing along the northern branch of the South Armorican Shear Zone.

    Original languageEnglish
    Pages (from-to)443-453
    Number of pages11
    JournalAcadémie des Sciences. Comptes Rendus. Geoscience
    Volume343
    Issue number7
    DOIs
    Publication statusPublished - Jul 2011

    Keywords

    • Ar/Ar dating
    • Armorican Massif
    • France
    • Lizio granite
    • South Armorican Shear Zone
    • U-Pb dating

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