Planet Formation

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

J. J. Roberts, J. H. Kinney, J. Siebert, and F. J. Ryerson

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 1019 m2 at the lowest concentration of melt (1% by volume), to 1013 m2 at higher concentrations (13% by volume). Permeability as a function of melt fraction is described by a relation of the form k = ad2fn 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.

Citation: Roberts, J. J., J. H. Kinney, J. Siebert, and F. J. Ryerson (2007), Fe-Ni-S melt permeability in olivine: Implications for planetary core formation, Geophys. Res. Lett., 34, L14306, doi:10.1029/2007GL030497.