Isotope geochemistry and FOZO mantle component of the alkaline-carbonatitic association of Fuerteventura, Canary Islands, Spain

Carbonatites are very rare in oceanic environments, where they have been reported only at the Canary and Cape Verde islands in the Atlantic Ocean. In the Canary archipelago, calciocarbonatites occur only on the island of Fuerteventura, in clear spatial and temporal association to alkaline silicate rocks, ranging from ultramafic to salic, and comprising alkaline clinopyroxenites, melteigites–ijolites–urtites, nepheline-bearing gabbros and nepheline–syenites, together with their volcanic equivalents. Selected isotopic (Sr, Nd and Pb) data from representative samples of this alkaline–carbonatitic association show a very estricted range of isotopic compositions, with those of the calciocarbonatites overlapping those of the alkaline silicate rocks. Despite the fact that all these rocks display cumulate textures and cover a wide range of SiO2 and Sr, Nd, Pb contents, initial isotopic compositions are approximately constant and mantle-like, indicating that evolution of the alkaline–carbonatitic association of Fuerteventura must have taken place in the absence of crustal contamination processes. Regarding the mantle source for the alkaline–carbonatitic association, its depleted initial Sr (87Sr/86Sr=0.7032–0.7036) and Nd (143Nd/144Nd=0.5128–0.5129) compositions, fall on the same trend as the East African young (