Skip to content

A Voluminous Melt-rich Magmatic Reservoir Beneath Mayotte Island

Pierre Wawrzyniak1, Fabrice Gaillard2, Sophie Hautot3, Juan Andujar1, Pascal Tarits4, Laurent Arbaret2, Samuel Guegan2 , David Sifré2, Jean-François D'Eu5, Sheldon Warden6, Frédéric Dubois1, Jacques Deparis1, Anne Lemoine1, Isabelle Thinon1

  • Affiliations:  1BRGM, Bureau des Recherches Géologiques et Minières, 3 av. Claude-Guillemin, BP 36009, 45060 Orléans Cedex 2, France ; 2Institut des Sciences de la Terre d'Orléans, CNRS-INSU/Université d'Orléans/Université de Tours, 1a rue de la Férollerie 45071, Orléans cedex 2,  France; 3IMAGIR Sarl, Tech-Iroise, ZA de Mespaol 2, 1 rue des Ateliers, 29290 Saint Renan,  France; 4IUEM, Institut Universitaire Européen de la Mer, LGO, UMR 6538 - IUEM/UBO, Place Nicolas Copernic, Plouzané, 29280,  France; 5MAPPEM Geophysics SAS, Marine Electromagnetic Investigation, Batiment Tech-Iroise, 1 rue des Ateliers, Zone de Mespaol, 29290 Saint-Renan,  France; 6Hyperion Geophysics, France 

  • Presentation type: Poster

  • Presentation time: Friday 16:30 - 18:00, Room Poster Hall

  • Poster Board Number: 19

  • Programme No: 1.5.26

  • Theme 1 > Session 5

Abstract

The exact nature of crustal magmatic reservoirs is elusive since they cannot be sampled in situ. The traditional view that magma chambers contain essentially molten material has recently been replaced by the transcrustal magmatic system (TCMS), in which reservoirs are mostly composed of immobile magmatic crystals with a minute fraction of more mobile melt, creating a "magmatic mush". Eruptions are possible if a significant portion of melt segregates into melt lenses within the mush reservoirs. The TCMS concept is however a default model essentially justified by the absence of clear geophysical signatures of melt-rich magma chambers, and by the rare and tentative estimates of the melt fraction in the crustal storage zones based on geochemical and textural analysis of eruptive products. Here, we image a bright electrical conductor at 23±1 km b.s.l. beneath Mayotte island that we interpret as a magmatic reservoir, based on laboratory measurements of Mayotte's melt conductivity. This large magmatic reservoir (> 200 km3) contains a high melt fraction (22-42%). Such a crystal to liquid ratio matches the reconstructed differentiation paths conducive to the basanite to phonolite melts that recently erupted at Mayotte. This reservoir is possibly connected to the system that fed the large submarine eruption of Fani Maoré in 2018-2019.