U–Pb Shrimp-RG zircon ages of Variscan igneous rocks from the Guilleries massif (NE Iberia pre-Mesozoic basement). Geological implications

One diorite sheet, syntectonic with the dominant D2 foliation in the Guilleries massif, 50 km south of the Variscan Pyrenean axial zone, has provided an U–Pb age of 323.6 ± 2.8 Ma, one of the oldest in that part of the Variscan basement. This age seems to be the same as that of the sillimanite-grade syn-D2 metamorphism in the deepest part of the massif; it is clearly separated from that obtained in three syn-extensional D3 leucogranite veins (305.3 ± 1.9; 301.5 ± 1.7; 299.0 ± 2.3 Ma) and the coeval biotite granites (305.9 ± 1.5 Ma). The leucogranites are 20 Ma younger than the syn-D2 diorite and the sillimanite-grade metamorphism. They are considered the melting-induced products in the host rocks, at a deeper level than that of the present outcropping of the mantle-related biotite granites during the extensional collapse (D3) of the chain in the Lower Stephanian.