Beneath ocean ridges, the divergence of lithospheric plates causes hot mantle peridotite to ascend and induces partial melting. The buoyant melt formed by this process rises through the mantle, is focused towards the ridge axis, and forms new oceanic crust. Because the chemical and physical properties of the upper mantle and lower crust are strongly influenced by the amount of melt present, better understanding of permeability of partially molten rocks is crucial.
The goal of this project is to place better constraints on rates of melt migration and melt extraction within the partially molten regions at depth. An approach that integrates state-of-the-art micro-tomography, FIB/SEM CrossBeam imaging techniques, high temperature and pressure laboratory experiments, and numerical models will be used to quantify three-dimensional (3-D) melt distribution in partially molten mantle peridotite. With the experimentally determined 3-D melt distributions as input data, permeability of partially molten rocks with different compositions and melt fractions will be determined. Empirical relations between permeability, melt fraction, and pyroxene content will be derived. Permeability anisotropy for sheared samples with stress-driven melt bands will also be calculated. This study will produce the most reliable results to date on melt distribution and permeability of partially molten rocks. These results will lead to a better understanding of the geochemical and geophysical processes at mid-ocean ridges.
