Abstract
The formation and alteration of the oceanic lithosphere represent one of the main processes for energy and chemical exchanges between the deep Earth and its outer envelopes. However, the steep thermal gradients characterizing these environments, especially at the main thermal and lithological interfaces along mid-ocean accretion zones (Fig. 1), mean that the physical and chemical mechanisms controlling these exchanges remain poorly understood. Yet, these interfaces are the main transitions for the physical and rheological properties of rocks, such as permeability and viscosity, that control melt focussing and transport from the partially molten mantle to the surface, as well as deformation mechanisms and the influx of seawater into the cooling oceanic lithosphere. These processes also give rise to hydrothermal systems that produce economically valuable ore-deposits and play a major role in the global chemical budget. Some hydrothermal reactions produce hydrogen and abiotic hydrocarbon, hence these extreme environments sustain life and they are potentially implicated in its origin. Finally, these processes determine the architecture and composition of the lithosphere plunging into the deep Earth along subduction zones, and contribute to a broad range of mechanisms driving arc magmatism and localization of earthquakes in these regions.