Abstract

Partial melting of the mantle beneath mid-ocean ridges, subduction zone arcs, and hotspot volcanoes produces new igneous crust and is the primary mechanism of chemical differentiation on Earth. Magmas are extracted to the surface through viscous compaction of the mantle residue, and via brittle fractures in the cold tectonic plates. Holistic modelling of magma transport in Earth’s interior requires consistent coupling of the thermodynamics of melting and melt-rock reaction, and the fluid dynamics of melt extraction from a deformable medium. However, the high dimensionality of such coupled problems presents a major theoretical and computational challenge. In this talk I will present a new thermodynamically consistent and tractable framework for integrating multicomponent thermodynamics and multiphase geodynamics. Globally oceanic crust is observed to have a basaltic composition, presenting a conundrum as it is not in chemical equilibrium with the uppermost mantle. I will apply the framework to explore how emergent reactive channelisation beneath midocean ridges permit this geochemical disequilibrium to be sustained.