Stéphane Hourdez & Cédric Boulart
National
Flotte Océanographique Française
Start Date
14/05/2026
End Date
14/05/2026
The Southeast Indian Ridge (SEIR) remains one of the least explored ridges on Earth compared to other spreading systems, mostly because of the difficulty of access and the commonly difficult weather conditions in the Southern Indian Ocean. Yet, the diversity of geological and tectonic contexts due to the segmentation in some areas and the presence of hotspots (Amsterdam, Kerguelen), offer contrasted conditions for the establishment of a hydrothermal circulation in the seafloor. Evidence of hydrothermal plume signatures have been described along the whole ridge, from the Rodriguez Triple Junction to the Macquarie Ridge but active hydrothermal vents still remain to be confirmed and described. The SEIR is also a crossroads between the Indian, Pacific and Atlantic Oceans, and as such, constitutes a dispersal route for hydrothermal fauna. However, very few studies have focused on this system, which is characterised by numerous transform faults that can act as barriers to this dispersal.
The SPHINX (amSterdam saint Paul Hotspot INteraction and hydrothermal eXploration of the SEIR) cruise, led by Stéphane Hourdez (LECOB Banyuls) and Cédric Boulart (LEMAR Brest), aims to explore and study hydrothermal systems located on the SEIR, particularly around the Amsterdam-Saint Paul Plateau and Boomerang Seamount. This multidisciplinary project addresses fundamental questions about biodiversity, the biogeography of hydrothermal species, accretion processes on ocean ridges, the geochemistry of hydrothermal fluids, and biogeochemical fluxes in the Indian Ocean. It also seeks to understand the interactions between the St Paul-Amsterdam hotspot and the ridge, controlling hydrothermal circulation in a largely unexplored region. In line with national priorities (France 2030) and international collaborations (InterRidge, GEOTRACES), the project addresses important scientific and societal issues, particularly in relation to the management and conservation of the Deep Ocean.
The cruise will take place from 13 February to 28 March 2027 aboard the NO Pourquoi Pas ? of the French Oceanographic Fleet together with the manned submersible Nautile and an AUV.
Laboratory Members
Contributors
Stéphane Hourdez (LECOB Banyuls)
Anne Briais, Marcia Maia, Sidonie Révillon (Geo-Ocean)
Sophie Arnaud-Haond (Ifremer Sète )
GET Toulouse : Georges Ceuleneer, Valérie Chavagnac
Laure Corbari (MNHN)
Didier Jollivet, Thomas Broquet (AD2M Roscoff)
Sabine Gollner (NIOZ, Pays-Bas)
Andrea Rizzo (Univ. Milano, Italie)
Loic Michel (Univ. Liège, Belgique)
Céline Rommevaux (MIO Marseille)
