Mafic and ultramafic enclaves in Ustica Island lavas: Inferences on composition of lower crust and deep magmatic processes

Abstract Ustica Island, southern Tyrrhenian Sea, is constituted of Quaternary alkaline volcanics. A variety of enclaves representative of deep to supra-crustal settings were recently found in a hawaiitic lava flow. Enclaves consist of: (i) Ultramafic meta-cumulates, i.e. clinopyroxenites and wherlites characterized by variably deformed porphyroclastic to granoblastic textures. (ii) Mafic cumulates, i.e. gabbros (± amphibole) and troctolites, the first often characterized by frequent amphibole breakdown coronas (olivine + Ti-augite + plagioclase + magnetite + ilmenite + rhonite) in response to an H 2 O decrease during the ascent, while the troctolites interpreted as meta-cumulates. (iii) Mic…