Edades 40 Ar-39 Ar del Complejo Basal de la isla de La Gomera

Résumé

This essay shows some new dating of the Basal Complex of La Gomera Island and among them, the first ones obtained using the 40Ar-39Ar methodology. Two of them are rocks of the Submarine Edifice. In the first one we obtain an age of 11,49 ± 0,66 Ma by the 40Ar-39Ar method, and in the second one 11,4 ± 1,6 Ma by the K-Ar method. These ages reveal that the volcanic activity of the NW outcroping Submarine Edifice is approximately 11,5 Ma in age, close to the beginning of the Lower Old Edifice activity. The third sample dated also by the 40Ar-39Ar method, is from the only syenitic rocks outcrop of La Gomera (Tamargada syenite); its age, 7,59 ± 0,81 Ma, confirms that these rocks represent the roots of one of the Old Edifice felsic episodes and that they do not belong to a felsic stage contemporary with the submarine growth of the island.