Fe-Ni-S melt permeability in olivine: Implications for planetary core formation

Abstract

A controversial issue in models of planetary core formation concerns whether iron-sulfide melts in contact with silicate minerals at high temperature and pressure form permeable, percolating networks. We address this issue by determining interconnectivity and calculating the permeability of quenched olivine-iron-sulfide partial-melt samples synthesized at high temperature and pressure for a range of melt fractions and two melt compositions using 3D synchrotron radiation computed tomography and lattice-Boltzmann simulations. Permeability ranged from ∼10-19 m2 at the lowest concentration of melt (∼1% by volume), to ∼ 10-13 m2 at higher concentrations (∼13% by volume). Permeability as a function of melt fraction is described by a relation of the form k = αd2 φn with a scaling exponent n of 3.6. Our findings, considered a lower bound when compared to larger grained planetesimals, show percolation is a viable mechanism for the migration of FeS melt that may be applicable to models of planetary core formation. Copyright 2007 by the American Geophysical Union.