Non thermal equilibrium two-phase flow of melt in a compacting matrix : insights on melt migration and dike initiation in the upper mantle

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The formation of oceanic and continental crust is tightly linked with the migration of liquids, called melts, from super-solidus regions, where they originate because of partial melting, to sub-solidus regions where they finally emplace and freeze as sills, plutons, or volcanic products. Melt migration in super- and sub-solidus regions has been successfully modeled respectively as two-phase porous flow of melt within a compacting matrix and as dikes propagating through the hosting solid rock. However, the evolution of melt transport processes at the transition from super- to sub-solidus regions remains poorly understood. While migrating towards the surface, melt pathways merge and widen, and melt transport conditions evolve from thermal equilibrium to disequilibrium. Although thermal disequilibrium development in super-solidus regions may be key for understanding melt transport evolution when approaching the transition to sub-solidus, it has never been considered in melt migration two-phase flow models. This project aims at evaluating the influence of thermal disequilibrium on melt segregation and transport in super-solidus regions, as well as on dikes initiation at the transition to sub-solidus. Using the formulation proposed by Schmeling et al. (2017) for thermal disequilibrium in a porous flow, we propose to develop a non thermal equilibrium two-phase flow model. From this new model we will evaluate and quantify the influence of thermal effects on melt segregation and transport. Results may provide interesting insights on dikes initiation processes. In collaboration with Herbert Wallner, Harro Schmeling and Eleonora Rivalta, we will then use these informations for developing a self-consistent numerical model for melt migration from the original melting area to final emplacement zones, that supports melt transport evolution at the super- to sub-solidus transition. This post-doctoral project will be held in the Goethe Universität in Frankfurt am Main, within the Geophysics research group, from which the researcher will especially collaborate with Harro Schmeling and Herbert Wallner.