Tarèse, Romain; Poujol, Marc; Ruffet, Gilles; Boulvais, Philippe; Yamato, Philippe and Košler, Jan
New U-Pb zircon and 40Ar/39Ar muscovite age constraints on the emplacement of the Lizio syn-tectonic granite (Armorican Massif, France).
Comptes Rendus Geosciences, 343(7),
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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 308.2 Ma. Muscovite chemistry is typical of primary magmatic muscovite, which precludes a late fluidsinduced 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.
||2011 Académie des sciences
||CNRS-INSU (‘‘3F’’ and ‘‘Action incitative’’ programs)
||40Ar/39Ar dating; Armorican Massif; Lizio granite; South Armorican Shear Zone; U-Pb dating; France
||Science > Physical Sciences
||30 Jan 2012 12:11
||23 Oct 2012 14:23
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