The deep magmatic system of the Campi Flegrei caldera (Italy).

Melt inclusions in phenocrysts of the Minopoli2 shoshonite and Fondo Riccio latite eruptive products (Campi Flegrei caldera; 10.2 to 9.5 ka BP) constrain the nature of deep Phlegraean magmatic fluids, their role in volcanism and give new insights into the magmatic plumbing system. The analyzed melt inclusions show that CO2 is an abundant gaseous species, confirming the results of geochemical studies on the magmatic gas fraction involved in present-day fumarolic emissions. Volatile concentrations within the melt inclusions require gas-melt equilibria between 8 and 9 km depth, and closed-system degassing in presence of ascending CO2-rich fluids of deep provenance. Magmas later re-equilibrate at depths up to 3–2 km, i.e. above the top of the carbonate basement. These observations correlate well with independent geophysical and geochemical evidence and are useful constraints for volcanic hazards assessment at Campi Flegrei.