Thermo-barometric constraints on the Mt. Etna 2015 eruptive event

The petrologic and thermobarometric study of volcanic products frequently emitted during short strombolian to lava fountaining events from the Mt. Etna Summit Craters allow us to constraint the T-P-XH 2 O phase stability, crystallization conditions and mixing processes along the main open-conduit feeding system. In this study, we discuss new petrologic, thermo-barometric data and related Rhyolite-MELTS modelling for the December 2015 eruptive activity that involved the concomitant activation of all Mt. Etna summit craters. The obtained results, in comparison with the previous paroxystic events of the 2011-2012, reinforce the model of a vertically extended feeding system and highlight that the activity at the New South East Crater was fed by a magma residing at significant shallower depth with respect to Central Craters (CC) and North East Crater (NEC), even if all conduits are fed by a common deep (P = 530- 440 MPa) basic magmatic refilling. Plagioclase stability model and recognized dissolution and resorption textures confirm its dependence on H 2 O content, thus suggesting that further studies on the effect that flushing from fluids with different H 2 O/CO 2 ratio are needed in order to understand the eruption triggering mechanisms of paroxystic fountaining.