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.
ASJC Scopus subject areas
- Geochemistry and Petrology