V043-03
The 2018-ongoing Mayotte submarine eruption: magma migration imaged by petrological monitoring
Wednesday, 16 December 2020: 11:38
Virtual
Carole Berthod1, Etienne Médard1, Patrick Bachelery1, Lucia Gurioli1, Andrea Di Muro2, Aline Peltier3, Jean-Christophe Komorowski4, Mhammed Benbakkar1, Jean-Luc Devidal1, Jessica Langlade5, Pascale Besson4, Georges Boudon4, Estelle F Rose-Koga1, Christine Deplus6, Anne Le Friant7, Manon Bickert4, Sophie Nowak8, Isabelle Thinon9, Pierre Burckel4, Samia Hidalgo4, Stephan Jorry10, Yves Fouquet10 and Nathalie Feuillet4, (1)Université Clermont Auvergne, CNRS, IRD, OPGC, Laboratoire Magmas et Volcans, Aubiere, France, (2)Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Université Paris Diderot, Observatoire Volcanologique du Piton de la Fournaise, Bourg Murat, France, (3)Université de Paris, Institut de Physique du Globe de Paris (IPGP), UMR 7154, Paris, France, (4)Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Université Paris Diderot, Paris, France, (5)IUEM Institut Universitaire Européen de la Mer, Plouzané, France, (6)IPGP & CNRS, Paris Cedex 05, France, (7)Université de Paris,, Institut de physique du globe de Paris, CNRS,, Paris, France, (8)Sorbonne Paris Cité, Université Paris Diderot, Paris, France, (9)BRGM - French geological survey, Orléans, France, (10)IFREMER, Plouzané, France
Abstract:
Following an intense seismic crisis in May 2018, a large submarine effusive eruption offshore the island of Mayotte (SW Indian Ocean) has extruded at least 6.4 km
3 of magma, making it the largest witnessed submarine eruption as well as the largest effusive eruption since Iceland’s 1783 Laki eruption. We present a detailed petrological and geochemical description of the erupted lavas sampled by the Mayobs 1, 2, and 4 cruises between May and July 2019 in order to image and track the entire deep magmatic system and its dynamics from the source to the surface. These cruises provide an exceptional time-series of bathymetric, textural, petrological, and geochemical data for the 2018-2019 eruptive period, thus bringing an invaluable opportunity to better constrain the evolution of magma storage and transfer processes during a long-lived submarine eruption.
Integrating the petrological signatures of dredged lavas with geophysical data, we show that the crystal-poor and gas-rich evolved basanitic magma was stored at mantle depth in a large (>9 km3) reservoir, experiencing extensive crystallization (~50% of cumulates). Fast magma ascent resulted in the eruption of crystal-poor, gas-rich lavas with typical textures indicating rapid crystal growth. During the eruption, magma ascent switched to a different pathway, sampling a small shallower magma batch close to the Moho. Given the differentiation timescales, that shallower magma batch likely evolved from a previous recent activity, implying the existence of recent submarine volcanic activity prior to the current crisis. Magma transfer from the deep mantle reservoir is syn-eruptive, as indicated by transfer times much shorter than the total eruption duration, estimated from diffusion in zoned olivine crystals.
Our study demonstrates that petrology of erupted products is a key tool for near-real-time monitoring of extreme events even if occurring in poorly accessible environments.
