Rare earth minerals in carbonatites of basal complex of Fuerteventura (Canary Islands, Spain)

Abstract

The Fuerteventura calciocarbonatites appear in the Basal Complex as veins, breccias and shear bands along the coastline between Puerto de la Pena and Cueva de Lobos, and in the area around the Barranco of Esquinzo. These carbonatites are essentially made up of calcite and to a lesser extent apatite, aegirine-augite, albite, orthoclase-sanidine, biotite, ore minerals and epidote with accessory minerals such as sphene, zircon, garnet, celestite, barite, britholite, allanite, pyrochlore and monazite. Geochemical analysis of these carbonatites show high values of REE of between 511 and 7,372 ppm with a high relation of LREE/HREE. Microprobe studies reveal that these elements are mainly associated with phosphates (britholite, monazite, and apatite), silicates (allanite and titanite), oxides (pyrochlore), carbonates (bastnaesite) and sulphates (barite). The carbonatites were generated in the last magmatic-hydrothermal crystallization phases of the alkaline intrusive complexes of Fuerteventura and some of them were emplaced along shear zones showing important plastic deformation structures.