Paroxysmal volcanic eruptions predicted by temporal variations in helium isotopes

As Piton de la Fournaise is one of the most active and closely monitored volcanoes in the world, its eruptive products are sampled and analysed at each eruption. The chemical and isotopic composition of gaseous emissions (thermal springs rich in_CO2) located near deep seismogenic zones is also regularly characterised.

The data obtained show a significant enrichment in ³He within the volcanic gases and fluid inclusions in the magmas that led to the most voluminous eruptions and caldera collapses. Modelling of these data suggests a correspondence with the deep signature of a primordial pole of the mantle source. A significant change in fluid composition is also detected during long-lasting eruptions whose magmatic products are chemically zoned and whose intensity of activity increases with the depth of the magmas emitted.

The results of this study highlight the effectiveness of using helium isotopes to detect early the increase in deep magma input to the surface magma system. This process can modulate the rate of magmatic extrusion and thus determine major events such as the caldera collapses observed at Piton de la Fournaise in 2007 and Kilauea in 2018.