Résumé
In orogenic settings, complex fault networks accommodate crustal deformation during the different tectonic stages of build-up and dismantling of the mountain range. Most of the fault zones present multiphase activity in ductile and/or brittle conditions, which renders challenging their analysis in terms of kinematics, metamorphism, fluid circulation and temporal evolution, resulting in contrasting interpretations for their role during the orogenic cycle. Constraining the exhumation history in mountain ranges allows to interpret fault activity in terms of spatio-temporal changes in exhumation rates. The situation becomes more difficult when the studied orogen results from a poly-orogenic evolution and complex geomorphological evolution, such as the case of the Eastern part of the pyrenean Axial Zone. Here, we focus on the Tet and Py faults which are major NE-SW trending crustal faults in the Eastern Pyrenees that have accommodated the exhumation of Mont-Louis, Canigou and Caranca massifs. These faults are characterized by the presence of gouge zones with different phyllosilicate generations, and record deformation from slightly above the ductile-brittle transition to brittle conditions. (super 40) Ar/ (super 39) Ar illite/muscovite dating on fault gouge zones shows different activity phases at the brittle-ductile transition. New dates provide a polyphased scenario of fault motion between the early Eocene (Pyrenean building) to the early Miocene (Gulf of Lion opening). Periods of tectonic activity highlighted by (super 40) Ar/ (super 39) Ar dating are closely linked to massif exhumation periods recorded by low-temperature thermochronological data and cooling stages constrained from 1D thermal (QTQt) and 3D thermo-kinematic (Pecube) modelling. This study shows that a combined methodological approach, focusing on fault zones at different spatial scales, can be relevant to disentangle geomorphological and tectonic components in the upper-crust thermal evolution. Moreover, it can be a powerful tool to ascertain geological interpretations of low-temperature thermochronological data, peculiarly in terms of polyphased activity of complex fault networks.