Petrogenesis of trachyte and rhyolite magmas on Ponza Island (Italy) and its relationship to the Campanian magmatism

Magmatism on Ponza island (Italy) has been reviewed, considering both new and literature data, and compared with the Campanian Volcanic District (CVD) rocks. Different origins have been inferred for the two main rock types (trachyte and rhyolite). The trachytes were formed by fractional crystallization (FC) processes coupled with minor upper crustal contamination from magmas similar to the least evolved magma erupted into CVD. The rhyolites formed by partial melting of a lower crust component. The two lithotypes evolved through intra-suite FC, and they are correlated with the volcanic rocks of the CVD by major element, trace element and isotope data, extending the Campanian compositional spectrum. To explain the FC and the melting processes, a tectonic model is developed in which most of the FC for the CVD occurred in the lower-intermediate crust where magma rises from the upper mantle and is stored in a process of magma accumulation and fractionation. These processes have produced enough heat to melt the crust and cause several rhyolite episodes in Ponza Island. A subduction-related setting must be inferred to explain the origin of the Ponza trachytes and rhyolites and the rest of the CVD volcanism.