Gas and heat fluxes during multiple effusive eruptions of Piton de la Fournaise (Réunion) and their implications for magmatic processes

Piton de la Fournaise (La Réunion, France) is one of the most active volcanoes in the world, producing frequent effusive basaltic eruptions of varying duration. These eruptions are accompanied by strong thermal infrared (TIR) signals and significant sulfur dioxide (SO₂) emissions detected by satellite instruments. The high frequency of eruptions provides an extensive dataset, which allows us to explore the relationships between eruptive heat, mass and gas fluxes. Five eruptions with different temporal trends of erupted mass flux have been selected for this study: April 2007, May 2015, August-October 2015, February 2019 and April 2020. For each of them, we estimated SO₂ emission from three ultraviolet satellite instruments (the Ozone Monitoring Instrument OMI, the Ozone Mapping and Profiler Suite OMPS and the Tropospheric Monitoring Instrument TROPOMI). The total SO₂ emission for each eruption has been estimated for an extensive range of sulfur (S) content within melt inclusions and the matrix using a petrological approach and the erupted magma masses obtained from MODIS TIR satellite data. Preliminary results show that, assuming the estimated SO₂ emission falls within the 30% error of the SO₂ mass detected by each satellite instrument, the implied magmatic sulfur contents are in good agreement with expected values for basaltic eruptions. Given pre-eruptive S contents between 200 and 750 ppm, estimated SO₂ emissions for the May 2015 eruption are consistent with an eruption largely fed by degassed magma. However, for the February 2019 eruption, there is a discrepancy between the three satellite sensors. Whereas the TROPOMI and the OMI instruments provide almost the same range of magmatic sulfur content (300-1100 ppm), the OMPS gives a higher range (700 to 1900 ppm) suggesting that fresh, undegassed magma was also involved in this eruption. Petrologic analysis of the pre-eruptive sulfur content will allow us to validate the satellite data and, in turn, to validate the ground-based SO₂ data from the NOVAC network operated by the Observatoire Volcanologique du Piton de la Fournaise (OVPF). Our approach yields insights into the characteristics of the magma reservoir supplying effusive events (e.g., eruptive degassing processes and the ratio of intrusive to extrusive magma) from space-based sensors.