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ABSTRACT. Ultramafic xenoliths enclosed in Plio-Quaternary alkali basalts from Tallante near Cartagne (southern Spain) are composed mainly of spinel herzo-lites which are probably upper mantle residues. In many xenoliths, the spinel herzolite is cut by pyroxenite or gabbroic anorthosite veinlets generally 0.2-3 cm thick. The clinopyroxenite veinlets were formed by high-pressure crystal-liquid segregation from alkali basalt magmas formed earlier than the host basalts, whereas mantle metasomatism played a role in the genesis of gabbroic anorthosites. Close to the contact with the veinlets, the spinel lherzolites are enriched in Ca, Fe, and some incompatible elements including light REE due to the migration of a fluid from the veinlets into the surrounding lherzolites. The host alkali basalts were derived from a heterogeneous, incompatible lement-enriched upper-mantle source probably similar in composition and nature to the composite xenoliths, but were formed in a garnet stability field