Composition ranges from shoshonite basalt to shoshonite, and latite.
Sr-isotope composition is always more radiogenic in separated clinopyroxenes and plagioclases, relative to both matrix and whole rock. As regards the rocks from Ventotene, petrographic and mineralogical data indicate equilibrium between phenocrysts and groundmass. The restricted chemical variations within each group of samples are generally explained in terms of fractional crystallization of the observed mineral phases. Sr and degree of chemical evolution, which strongly suggest that open-system processes were operating during evolution. Petrographic and geochemical data suggest interaction between distinct batches of magmas with different degree of chemical evolution and Sr-isotope composition.