Las rocas ultramáficas alcalinas del Jable de las Salinas, Fuerteventura, Islas Canarias

Abstract

In this paper the geological, petrological and geochemical features of the alkaline pyroxenites and anphibololites of an ultramafic-carbonatite complex are studied. These rocks crop out in the SW coast of Fuerteventura (Canary Islands), in the area known as Amanay Massif. This subvolcanic complex was emplaced at the same time as the late basaltic dyke swarms of the Basal Complex and was intruded by a dense net-work mainly feldspathic and in some places also carbonatitic. Rocks related to fenitization processes are also present. The ultramafic rocks are pyroxenites and amphibololites composed mainly by: salite, kaersutite, apatite, magnetite and ilmenite. One of their most significant characteristics is the modal abundance of apatite and Fe-Ti oxides and the total Iack of olivine, feldspars and feldspathoids. Geochemically they present an alkaline and subsaturate trend with very low contents of SiO2 and high values of total Fe, TiO2 and P2O5. The textural, mineralogical and chemical character of the rocks indicate that they were probably formed by liquid inmiscibility processes.