Long-lasting plutonism during orogenic cycles : incremental emplacement of the Variscan Bassiès Pluton (Central Pyrenees, France)

Abstract

Laser ablation U–Pb single zircon geochronology was applied to four peraluminous granite and granodiorite samples from the Bassiès pluton in the Central Pyrenees (France) yielding a wide range of concordant ages from early Carboniferous (Tournaisian, 351 Ma) to early Permian (Artinskian, 285 Ma). Emplacement of the Bassiès pluton occurred incrementally during the main Variscan deformation phase, with increased activities every 7–15 Myr and a peak at around 321 Ma. Evolution of the Bassiès pluton is more complex than the previously published single age of 312 Ma implied, underscoring the importance of synorogenic Variscan magmatism within the Axial Zone. Supported by geochronologic data from other plutons and gneiss domes, the notion that magmatism in the Axial Zone was confined to the late- to post-orogenic phase (315–295 Ma) is refuted. A possible thermal source for the long-lasting widespread plutonism in the Variscan crust is the TUZO mantle plume.