HR: 1340h
AN: MR13A-0073    [Abstracts]
TI: Permeability of Olivine-FeS Partial-Melts Based on Tomographic X-ray Imaging
AU: * Roberts, J
EM: roberts17@llnl.gov
AF: Lawrence Livermore National Lab, 7000 East Avenue, Livermore, CA 94551 United States
AU: Kinney, J
EM: kinney3@llnl.gov
AF: Lawrence Livermore National Lab, 7000 East Avenue, Livermore, CA 94551 United States
AU: Siebert, J
EM: siebert2@llnl.gov
AF: Lawrence Livermore National Lab, 7000 East Avenue, Livermore, CA 94551 United States
AU: Ryerson, F J
EM: ryerson1@llnl.gov
AF: Lawrence Livermore National Lab, 7000 East Avenue, Livermore, CA 94551 United States
AB: The permeability of olivine-FeS partial melts is important for a number of geophysical problems such as models of planetary core formation that depend on the interconnectness of molten iron-sulfides in contact with silicates at high temperature and pressure. Yet in spite of its importance, permeability has not been measured directly in this system. Instead, permeability has been inferred from estimates of the interconnectivity and tortuosity of the melt phase, or by measurement of the electrical conductivity of the bulk material. This approach has led to great uncertainty in the permeability, with reported values differing by several orders of magnitude at the FeS concentrations of interest. Here, we provide a more direct determination of the permeability of these systems by synthesizing materials, performing microtomographic imaging and using a lattice-Boltzmann solver to calculate permeability. We have synthesized olivine-sulfide partial-melts containing 0, 3, 4, 6, 8, 10, and 12% by volume iron-sulfide of two compositions: (FeS and Fe_92.5Ni_7.5)S in a San Carlos olivine matrix (Fo₉₁). Samples were synthesized in a piston cylinder apparatus at 1300° C and 1 GPa for 24 hours. Samples are characterized using x-ray microtomographic imaging performed at the Advanced Light Source to 1.6 micron spatial resolution using energies between 14 and 25 keV. Lattice-Boltzmann simulations were performed on reconstructed 3-D volumes to estimate permeability. Results indicate little difference between the two compositions above approximately 8% FeS melt (volume). The permeabilities as a function of melt fraction follow a trend near that predicted by Faul (1997). At 12% volume fraction melt we estimate permeabilities on the order of 10^-14 m². The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. This work was performed under the auspices of the U.S. Department of Energy by the University of California Lawrence Livermore National Laboratory under contract W-7405-ENG-48 and supported specifically by Laboratory Directed Research and Development funding.
DE: 3947 Surfaces and interfaces
DE: 5112 Microstructure
DE: 5114 Permeability and porosity
DE: 5460 Physical properties of materials
DE: 8125 Evolution of the Earth (0325)
SC: Mineral and Rock Physics [MR]
MN: Fall Meeting 2005