Two phase flow in the dynamic Earth: Implications for melt flux and chemical differentiation

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In the lower parts of the Earth's crust, a mixture of crystalline solid and molten rock may exist simultaneously. This system will develop flow instabilities in response to different forcings, specifically to density contrasts or tectonic forcing. Three fundamental situations can be envisaged: melt is either "squeezed out", "fluxed through" or "accumulated in" interstitial pores between crystals, the parameter space that these situations "occupy" will differ with different forcings, force combinations and melt-rock ratios. The student will focus on addressing the pure fluid-mechanical phenomena relating to understanding the flux of the viscous phase from deep to shallow, which drives rapid melt transport and chemical differentiation within Earth. The student will aim to establish the characteristics and governing parameters of melt transport at different forcing scenarios both in theory and in different geologically relevant situations. To reach this aim, the student will apply first-principles fluid-mechanical modelling of two-phase flow under different forcings and explore these thoroughly over a dimensionless parameter space. In particular, the student will perform a comprehensive study of the effects of differential flow through a heterogeneous porous media driven by gravity and/or tectonic forcing. Potential generalizations of the theory include the implications of melt flux predictions through the Earths' crust for chemical effects.