Rapid differentiation in a sill-like magma reservoir: a case study from the campi flegrei caldera

In recent decades, geophysical investigations have detected wide magma reservoirs beneath quiescent
calderas. However, the discovery of partially melted horizons inside the crust is not sufficient to put
constraints on capability of reservoirs to supply cataclysmic eruptions, which strictly depends on the
chemical-physical properties of magmas (composition, viscosity, gas content etc.), and thus on their
differentiation histories. In this study, by using geochemical, isotopic and textural records of rocks erupted
from the high-risk Campi Flegrei caldera, we show that the alkaline magmas have evolved toward a critical
state of explosive behaviour over a time span shorter than the repose time of most volcanic systems and that
these magmas have risen rapidly toward the surface. Moreover, similar results on the depth and timescale of
magma storage were previously obtained for the neighbouring Somma-Vesuvius volcano. This consistency
suggests that there might be a unique long-lived magma pool beneath the whole Neapolitan area.

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