Géochronologie U-Pb sur zircon et monazite du massif composite de granite à deux micas hercynien de Cabeceiras de Basto (Nord-Portugal)

The zircon and monazite U-Pb minimum age of the Hercynian peraluminous two-mica composite granite pluton of Cabeceiras de Basto (Northern Portugal) is 311±1 Ma (2 σ). This age, well constrained by a concordant monazite of 311±4 Ma (2 σ), is in good agreement with the age suggested for the synkynematic, syn-D3, Iberian granites of the Hercynian orogeny (315–305; Pinto et al., 1987). The ( 87 Sr/ 86 sr), and ɛ Nd isotopic ratios, calculated for 311 Ma, suggest that the three granite units which constitute the massif may derive from an heterogeneous crustal source dated (upper intercept of the discordia) around 1 200 Ma.