Petrological monitoring of persistently active basaltic volcanoes: the case study of Stromboli (Aeolian Islands, Southern Italy)

Investigating the dynamics and timescales of magmatic processes in active volcanoes is crucial for understanding explosive eruptions and assessing volcanic hazards. In this context, we are currently conducting a petrological survey of the Stromboli volcano (Aeolian Islands, Southern Italy), whose persistent activity is characterized by periodic and mildly explosive Strombolian eruptions, alternating with episodic lava effusions and more violent eruptive events, namely major explosions and paroxysms. The plumbing system is characterized by a vertically-extended mush column in which the shallow magmatic reservoir (highly porphyritic or Hp-magma) is continuously refilled with mafic recharges (low porphyritic or Lp-magma) rising from depth. During the paroxysmal events, sustained injections of Lp-magmas produce ample and continuous H2O-rich gas phases that are released with great energy through the vent, together with ash, scoriaceous spatters, bombs and lithics traveling over long distances. With the final scope of deciphering mutual relationships between Hp- and Lp-magmas, as well as magma-mush interplay within the shallow plumbing system, we present in situ microchemical analyses of plagioclase phenocrysts from nineteen scoria clasts ejected during mild to violent explosions at Stromboli over a timespan of ~18 years, from 2003 to 2021. Major and trace element compositions, as well as Sr-isotopic data have been integrated with thermometric modeling and Mg-in-plagioclase diffusion chronometry to constrain the physicochemical changes within the plumbing system and the timescales of magmatic processes. Through this approach, a new eruptive cycle at Stromboli volcano has been identified, where more energetic open-conduit dynamics are associated with an increased intensity and frequency of eruptions due to mush disruption by sustained injections of mafic recharge magmas from depth.