Rare Earth element distribution on the Fuerteventura Basal Complex (Canary Islands, Spain): a geochemical and mineralogical approach

Abstract. The Fuerteventura Basal Complex comprises Oligocene and Miocene ultra-alkaline-carbonatitic magmatic pulses with outcrops that extend across kilometer-scale areas in some specific sectors of this oceanic island. Additionally, there is evidence of associated weathering materials that affect these magmatic lithologies. These alkaline magmatic rocks (including trachytes, phonolites, syenites, melteigites, and ijolites), carbonatites, and their associated weathering products underwent a preliminary evaluation of rare Earth element (REE) contents based on mineralogical and geochemical studies. REE concentrations in carbonatites of about 10 300 ppm REY (REEs plus yttrium) have been detected in volumes comparable to other locations hosting significant deposits of these critical elements worldwide. Conversely, alkaline magmatic rocks and the resulting weathering products display limited REE contents. Notably, REEs in carbonatites are associated with primary accessory phases such as REE-bearing pyrochlore and britholite and secondary monazite. The results obtained in the carbonatites of Fuerteventura underscore the interest in studying the concentrations of critical elements, such as REEs, within a non-conventional geological setting like oceanic islands. However, due to intricate structural attributes, the irregular distribution of these mineralizations, and possible land use and environmental constraints, additional future detailed investigations are imperative to ascertain the real potential of these REE concentrations.