Diversity, dynamics and impact of the hydrothermal activity on ultramafic substracts at mid-oceanic ridges

Funding: ANR PRC, 450 000 € (reference ANR-23-CE01-0011-01)

Coordinator: Muriel Andreani

Host institution : Université Lyon 1

Partners :

  • ENS Paris
  • IPGP
  • Sorbonne Université

Duration : 2023 – 2026


Alteration of mantle rocks is a widespread process that enriches fluids with H2, producing unique environments for ecosystem development and abiotic chemical reactions involving redox-sensitive elements (e.g. C, S, metals). It has hitherto been neglected in ocean-lithosphere chemical exchanges, despite the fact that at least 25% of the ocean floor is composed of mantle rocks exhumed by detachment faults. These domains have revealed a great diversity of hydrothermal activity, manifested by fluid outflows of varying temperature and pH, focused or diffuse, associated with carbonates or sulfides. Estimating their impact on biogeochemical cycles requires extrapolating local observations to the global scale, and thus identifying the relative importance of these different types of activity. Their spatio-temporal (dis)continuity and longevity? Their links with the geological framework, ecosystems and the age of the lithosphere? DHYAM will address these questions by coupling available data on mantlesubstrate sites along the North MidAtlantic Ridge, with an exhaustive study of the Rainbow Massif, whose recent exploration (ArcEnSub campaign, 2022) has revealed an abundance of hydrothermal sites of both known and undescribed types, both active and ancient.

DHYAM proposes to i) characterize the nature, diversity and spatio-temporal distribution of these sites, in relation to past/current ecosystems and the structural and tectono-magmatic framework of the massif, and ii) use these data to improve numerical models of ocean accretion to predict the extent of hydrothermal activity within the massif. Extrapolated to other sites, these results will help build a general model of alteration from ultramafic domains to ridges for integration into global tectonic models (e.g. using G-Plates) including chemical balances.

Nouveaux sites hydrothermaux, actifs et fossiles, découverts lors de la campagne océanographique «Arc-en-sub » (mai 2022 – Pi M. Andreani & J. Escartin), Massif de Rainbow, 36°N le long de la dorsale Médio-Atlantique. Opérée par la Flotte océanographique française (FOF :


Lien vers Arc-en-sub

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