Appel à manifestation d’intérêt – Expédition SPARC « CHEMS »: CHemical and Energy exchanges between the Mantle, magma and Seawater at mid-ocean ridges

Pour mieux comprendre la nature et l’origine des hétérogénéités lithologiques et géochimiques au niveaux de dorsales à expansion lente, l’expédition se propose de caractériser les processus de rétroactions complexes entre des processus magmatiques, des phénomènes de déformation et des interactions fluides-roches en réanalysant d’anciens échantillons issus de forages océaniques

Motivation scientifique (en anglais)

Formation, aging and recycling of oceanic lithosphere are fundamental components of plate tectonics, which drives global cycles of energy and matter on Earth. Mid-ocean ridges are dynamic environments in which magmatic processes, tectonic deformation and hydrothermal circulation are tightly intertwined. These processes are all influenced by the initial thermo-chemical heterogeneities of the sub-ridge mantle, and account for the largest fluxes of energy and matter from the deep Earth to the surface, with volcanism along ⁓60000 km of oceanic ridges representing their most evident manifestation. While high- to low-temperature processes driving the formation and evolution of oceanic lithosphere are often approached as separate entities, the lithological, geochemical and rheological heterogeneities formed during mantle melting and magmatic activity strongly influence deformation patterns, which in turn control melt focusing and hydrothermal fluid circulation within the oceanic lithosphere.

The CHEMS project aims to bridge the gap between these processes, by determining how initial mantle thermo-chemical heterogeneities and coupled magmatic, deformation and hydrothermal processes interact to shape the physical and chemical evolution of the oceanic lithosphere. It will focus on relatively magma-poor segments of a slow-spreading ridge where detachment faults exhume mantle and gabbroic rocks, and where magmatic and hydrothermal processes strongly interact with lithospheric deformation during exhumation.

CHEMS will use complementary ODP and IODP assets drilled along the Mid-Atlantic Ridge, namely the Atlantis Massif (30°N), the Kane Fracture Zone (23°N) and the Fifteen-Twenty Fracture Zone (15°20”N). Together, these legacy cores capture the strong architectural heterogeneity of slow-spreading oceanic lithosphere and encompass contrasting mantle thermo-chemical characteristics, allowing to determine how regional and local heterogeneities control feedback processes between magmatic processes, deformation and hydrothermal alteration.

This Expedition places particular emphasis on collaborative interdisciplinary sample characterisation and correlated mapping. This approach will provide centimetre-scale, pixel-by-pixel structural and chemical mapping of melt- and fluid-rock interactions, their relationship with deformation, and with the redistribution of elements during high- to low-temperature processes..

Logistique

Les candidatures pour participer à cette expédition seront ouvertes à la fin de l’année 2026. Toutefois, si vous souhaitez être parmi les premiers à recevoir des informations sur cette expédition passionnante, nous invitons les potentiels candidats à remplir le formulaire de manifestation d’intérêt ci-dessous.

Cette démarche n’est pas obligatoire, ne vous engage pas à postuler lors de l’appel principal, et le fait de ne pas remplir ce formulaire n’aura aucune incidence sur l’évaluation de votre candidature ultérieure. Nous vous encourageons toutefois vivement à remplir ce formulaire afin que nous puissions vous accompagner au mieux. Remplir le formulaire prend 2 minutes!