Located in the southern part of the Western Alps, the Argentera massif belongs to the paleo-European basement of the external domain. It experienced a polyphased deformation history, Hercynian and Alpine. The Alpine history is characterized by the development of a network of ductile shear zones. An 39Ar−40Ar study of single grains of Hercynian muscovites and Alpine phengites allowed to constrain various events. A muscovite cooling age at ca 296-299 Ma is proposed for the Argentera granite, clearly later than the estimated cooling age at ca 310-315 Ma for the low-pressure anatexis. Neocrystallized phengites collected within an Alpine shear zone (Frema Morte) crosscutting the late Hercynian Argentera granite yielded an age at 22.2 ± 0.3 Ma (1σ). This is one of the first unequivocal absolute age constraint of a late Alpine metamorphism in the external crystalline massifs of the Western Alps. Our P-T conditions estimates indicate a regional temperature at ca 350°C for pressure at 0.35-0.4 GPa for this Alpine metamorphism. These estimates imply a minimum burial of 14 km for the Argentera massif, which could result from the overloading imposed by the internal nappes emplacement, probably between 28 Ma and 22.2 Ma.
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Corsini et al. (2004) studied this question.