Multiple mush generations provide insight into the longevity of open-conduit basaltic volcanoes

Investigating the dynamics and timescales of magmatic processes in open-conduit basaltic volcanoes is crucial for improving our understanding of explosive eruptions and better assessing volcanic hazards. Among these processes, the role of mush disaggregation and remobilisation within the plumbing system remains rather underexplored. This study examines the longevity and dynamics of the mush system beneath Stromboli volcano (Aeolian Islands, Southern Italy), whose persistent activity results from variable degrees of interaction between different magmatic components. The complex zoning patterns of plagioclase phenocrysts from 2003 to 2021 eruptions have been interrogated by combining in-situ Sr isotope compositions, thermometric modelling, and Mg diffusion chronometry. Our findings shed new light on the physicochemical changes within the plumbing system, the timescales of crystal residence in the shallow reservoir, and the timing of magma recharge events. Timescales of mafic recharges and mush remobilisations recorded by plagioclase suggest rapid magma-mush dynamics during violent explosions but more sluggish during normal activity. Sr isotope heterogeneities in plagioclase reveal that multiple mush generations at Stromboli have been active over millennia, with remobilisation events and crystal recycling driven by mafic magma recharges from depth. This is further supported by a complementary in-situ investigation of clinopyroxene phenocryst cores. A previously unseen, prehistoric, highly radiogenic mush has been actively remobilised in recent years, pointing out that older components of open-conduit basaltic systems may persist longer than previously hypothesised.