Igneous processes governing the formation and evolution of MUSHy OCEANic reservoirs: melt interactions, transfers, and related kinematics – MUSH-OCEAN

Almost 2/3 of Earth's surface is covered by oceanic crust formed at mid-ocean ridges where >70% of the total magma flux is concentrated. In the last decades it has been shown that the magmatic system, which has long been seen as a melt-dominated system, is rather mushy: magmatic but with a high crystal fraction. This modifies the expected thermal regime, the modes of melt migration, and the igneous processes that give rise to the crust by differentiation and magma emplacement. Despite tremendous progress made over the last decades by a multidisciplinary marine geoscience community, our understanding of the oceanic magma plumbing architecture and of the related igneous processes at both fast- and slow-spreading ridges still needs to be refined and quantified. More specifically, the modes of differentiation that have been considered during decades to be governed by fractional crystallization (operating in crystal-poor mediums) are now revisited, and a yet poorly constrained reactive porous flow process is now widely proposed. The objective of MUSH-OCEAN is to make a breakthrough in our understanding of oceanic magmatic systems. With MUSH-OCEAN we will provide brand new constraints on 1/ the temporal (e.g., lifespan), spatial, and thermal relations between magma (s.s.) bodies (with <40 % crystals, thus mobilizable for e.g., seafloor eruptions), and mushy igneous reservoirs (>40 % crystals, thus not mobilizable), 2/ the kinematics of melt collection and migration in mushy reservoirs, and 3/ the igneous processes that govern mush evolution, and thus the overall differentiation of oceanic igneous reservoirs (reactive porous flow).
Finally, beyond allowing a major advance in our understanding of oceanic magmatic systems (>2/3 of magmatism on Earth), the understanding of the processes governing the evolution of magmatic mushes will allow a better understanding of the majority of igneous systems in other geodynamic contexts since these crystal-rich mediums seem to be dominant in general.