Localization of Melt Transport at Mid-Ocean Ridges

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Seismic experiments and seafloor morphology indicate that the region of crustal accretion, where melts reaches the base of the crust, has a half width of ~ 2 km, whereas the zone of melt production by decompression melting is much broader. Somehow, melt becomes focused by a factor of ~ 50 as it ascends, yet no single mechanism that has been proposed fully explains this focusing. Under this award, the PI will follow several lines of investigation, to: 1) Improve the treatment of crystallization and melt-rock reactions in steady-state one-dimensional columns to better understand the permeability structure at the base of the thermal boundary layer 2) Explore the effects of lateral variations in the crystallization function and the viscosity field, due to the thermal structure at the base of the lithosphere 3) Revisit the large-scale flow models to include non-Newtonian rheology and the effect of porosity variations on viscosity.