Control of source fertility on the eruptive activity of Piton de la Fournaise volcano, La Réunion

International audienceThe eruptive activity of basaltic hotspot volcanoes displays major fluctuations on times scales ofyears to decades. Theses fluctuations are thought to reflect changes in the rate of mantle melt supply.However, the crustal filter generally masks the mantle processes involved. Here, we show that thecyclic and generally increasing activity of the Piton de la Fournaise volcano (La Réunion) since the mid20th century is tightly linked to the fertility of its source, as recorded by 87Sr/86Sr and incompatibletrace elements ratios of lavas. We identify a twofold control of source fertility on eruptive activity: meltextraction from fertile, incompatible element-enriched veins initiates decadal-scale eruptive sequences,so that vein distribution in the plume source directly controls the cyclic activity. Indirectly, reactiveflow of enriched melts increases mantle porosity and promotes melts extraction from the peridotitematrix. This process is thought to have caused a fourfold increase in magma supply between 1998 and2014 at Piton de la Fournaise, and could also explain magma surges at other frequently active hotspotvolcanoes, such as Kilauea, Hawaii. The short-term eruptive activity of hotspot volcanoes appears to beultimately linked to the distribution and size of lithological heterogeneities in mantle plumes