On the role of surface tension in the migration of melts and fluids

Abstract

It is shown that surface tension can cause redistribution of melt in a partially molten medium, in accordance with a non-linear diffusion equation for the melt fraction. The associated diffusivity D depends on the surface energy and is positive (stable) for dihedral angle <60° and negative (unstable) for dihedral angle >60°. In the more likely stable case, D ∼ 10^(−7) cm^2 .s^(−1) is typical for mantle melts, but a value as high as 10^(−1) cm^2 .s^(−1) is conceivable for volatile-rich fluids. Surface tension may play an important role in creating pathways for meta-somatizing fluids in the Earth, but does not appear likely to affect substantially the existing estimates of large scale melt migration (e.g., beneath mid-ocean ridges).