Skip to content

What controls the compositions and eruptability of magmas in subduction zones? The Case of the Aegina Magmatic Province (Greece) from inception to extinction

Michelle Müller , Razvan-Gabriel Popa, Sophie Schierscher, Marcel Guillong, Olivier Bachmann

Abstract

The Aegina Magmatic Province, situated within the South Aegean Volcanic Arc, offers insights into the evolution of a magmatic system in a subduction zone. This study investigates its complete volcanic life cycle from inception to extinction, leveraging zircon U-Pb geochronology and extensive geochemical data to unravel the factors controlling magma compositions, reservoir evolution, and eruptability during the magmatic activity in the area. The system was active for ~2.8 My with volcanic eruptions beginning at approximately 4.3 Ma following a prolonged (>500 kyrs) phase of magma reservoir nucleation and growth in the crust (without eruption), discernable only by zircon crystallization. The volcanic history includes two eruptive phases with varying eruption frequencies. Mineral chemistry reveals stable upper-crustal storage conditions throughout Aegina's lifespan, with significant temperature and water content variations linked to magma recharge events. Initially, the recharge consisted of hydrous, volatile-rich magmas, which fostered crustal magma storage, differentiation to andesitic/dacite composition, and intermittent eruptions of such intermediate compositions. Over time, the influx of drier magmas increased, leading to more frequent eruptions progressively diluting the volatiles in the upper-crustal reservoir. The increase of dry magma persisted into the final phase, causing the system to lose its capacity for long-term magma storage and differentiation, leading to the end of volcanic activity at ~2.1 Ma with dry basaltic andesites. The introduction of dry magmas correlates with significant changes in εHf in zircon crystals, suggesting variable amounts of crustal contamination with time, likely happening dominantly in the mantle wedge by sediment addition.