The timing of transition between the contractional and extensional regimes along the Pyrenean range remains debated. Compared to its central and western parts, the eastern part of the chain was significantly affected by extensional tectonics mostly related to the opening of the Gulf of Lion. The Têt normal fault is the best example of this tectonic activity, with topographic reliefs above 2,000 m in its footwall. In this study, we synthetized previous thermochronological data and performed new (U-Th)/He and fission-track dating in the Eastern Pyrenean massifs. Output apparent exhumation rate and thermal modeling in the hanging-wall of the Têt fault highlight a rapid exhumation (0.48 km/Ma) and cooling (~30°C/Ma) phase between 38 and 35 Ma, followed by slower exhumation/cooling afterwards. In the footwall, cooling subsequently propagated westward along the fault during Priabonian (35-32 Ma), upper Oligocene and lower Miocene (26-19 Ma), and Serravalian-Tortonian times (12-9 Ma). These data and modeling outcomes suggest that the exhumation of the Têt fault hanging-wall related to southward thrusting ended at 35 Ma, and was followed by different extensional stages, with a propagation of the deformation towards the West during the upper Miocene. We propose that the onset of extension in the Eastern Pyrenees occurred during the late Priabonian period, contemporaneously with the large-scale rifting episode recorded in Western Europe. After this event, the Têt fault activity and the westward propagation of the deformation appear mainly controlled by the opening of the Gulf of Lion.

The Crustal Fault Zones provides an interesting geological target for high temperature geothermal energy source in naturally deep-fractured basement areas. Field and laboratory studies have already shown the ability of these systems to let fluid flow down to Brittle-Ductile-Transition. However, several key questions about exploration still exist, in particular the fundamental effect of tectonic regimes on fluid flow in fractured basement domains. Based on poroelasticity assumption, we considered an idealized 3D geometry and realistic physical properties. We examined a model with no tectonic regime (benchmark experiment) and a model with different tectonic regimes applied. Compared to the benchmark experiment, the results suggest that different tectonic regimes cause pressure changes in the fault/basement system. The tectonic-induced pressure changes affect fluid patterns, onset of convection as well as the spatial extent of thermal plumes and the intensity of the temperature anomalies.