Mineralogía y geoquímica de las sienitas nefelínicas de Montaña Blanca-Esquinzo, NO de Fuerteventura (Islas Canarias)

Abstract

Nepheline-syenites from the northern, Montaña Blanca-Esquinzo sector of the Basal Complex in the island of Fuerteventura (Canary Islands) are the most differentiated rocks belonging to the alkaline-carbonatitic association in this area. These nepheline-syenites are peculiar when compared with their counterparts in other alkaline-carbonatitic bodies, due to their lack of hydrous minerals (amphiboles, micas) and their strong depletions in incompatible elements. In this work, we present both mineralógica! and geochemical data on these rocks in order to obtain information about their origin and relationship with the ultramafic and mafic terms (clinopyroxenites and melteigites-ijolites) of the alkaline silicate rocks belonging to this association of the Basal Complex. These data suggest that the Montaña Blanca-Esquinzo nepheline-syenites are the products of extensive fractionation + accumulation of the same magma that gave rise to the clinopyroxenites and melteigites-ijolites.