Magma storage and ascent dynamics

The complex structure of stratovolcanoes makes magmas able to interact with the crust and differentiate at several levels of the feeding system during their ascent from the source zone towards the surface. Thus, it is often difficult to assess the relative role of evolutionary processes such as fractional crystallization, crustal assimilation and magma mixing between variously evolved magmas. Whole rock compositions that we study through classic geochemical approaches are potentially due to the superimposition of several of these processes, so that tracking magma evolution might become a hard task.

For this reason, we are dedicating during the last years endeavours in the field of in situ investigations primarily on phenocryst zoning patterns in volcanic rocks, which have been proved to be a powerful tool for deciphering the dynamics and timescales of volcanic processes within the plumbing system.

Minerals can be highly sensitive to gradual or sudden modifications of the volcanic system, and can record changes of thermodynamic equilibria in their textural and compositional zoning patterns, depending on the process they underwent. The growth history of crystals can therefore be interpreted in order to recognize which process drove the magmatic system towards new physical and chemical equilibrium conditions, such as recharging of fresh magma, volatile input/loss or ascent-related decompression.

 Several works have pointed out that textural and chemical zoning particularly of plagioclase may be an efficient tool for constraining the dynamics and kinetics of magmatic processes, chiefly due to its high sensitivity to changes in pressure and volatile contents of the system. Our recent researches in this field allowed us to constrain the modes of magma recharge and timescales of storage in the feeding system, the styles of magma ascent at the surface and the main eruption triggering mechanisms at Mount Etna. The same methodological approach is currently used for understanding the geometry and the working mechanisms of other active volcanoes on Earth.