Deformation-Controlled Fluid Migration During Late Cretaceous Rift Inversion and Paleogene Alpine Convergence in the Northeastern Pyrenees Constrained by 40Ar/ 39Ar Stepwise Crushing of K-feldspar

Deformation-Controlled Fluid Migration During Late Cretaceous Rift Inversion and Paleogene Alpine Convergence in the Northeastern Pyrenees Constrained by 40Ar/ 39Ar Stepwise Crushing of K-feldspar Key Points: Dating by stepwise crushing of K-feldspar yields clustered maximum apparent ages at ~82–74 Ma, ~56–54 Ma, and ~40 Ma, reflecting deformation- and fluid-assisted argon mobility during Late Cretaceous–Paleogene tectonic reactivation in the northeastern Pyrenees. These ages reflect heterogeneous argon retention and episodic argon mobility within lattice and non-lattice reservoirs associated with deformation-related microstructures in K-feldspar. Maximum apparent ages define a southward younging trend, with older ages (~82–74 Ma) occurring near the North Pyrenean Fault (NPF), and younger ages (~56–54 Ma and ~40 Ma) spatially associated with the Têt deformation zone.