Contributions to the chronology of the Basal Complex of Fuerteventura, Canary Islands

K–Ar and Ar–Ar analyses of the Basal Complex of Fuerteventura confirm the early start of magmatism in the Late Cretaceous. Plateau ages of 63.1±0.8 Ma and 64.2±1.0 Ma have been obtained for the oldest syenite intrusions indicating the minimum age of these plutonics. The emplacement of carbonatites and syenites along ductile shear zones took place during a relatively short period of time between 23.2±1.0 and 22.1±0.9 Ma. This episode is synchronous all over the island. Younger plutons were intruded around 21.1±0.8 Ma ago and 20.7±0.9 Ma and are probably related to the building of Miocene subaerial edifices. Almost all the minerals and rocks of the Basal Complex show a clear effect of excess argon. Some was acquired during the hydrothermal stage but also some excess argon was trapped during the early crystallization stage of the magma. Moreover, only a part of the radiogenic Ar which had accumulated in pre-Miocene rocks was released during the Miocene magmatism.