HR: 0830h
AN: V51A-09    [Abstracts]
TI: Electrical Conductivity and Tomographic Imaging of Olivine-FeS Partial-Melts
AU: * Roberts, J
EM: roberts17@llnl.gov
AF: Lawrence Livermore National Laboratory, 7000 East Avenue PO Box 808, L-201, Livermore, CA 94551 United States
AU: Mei, S
EM: meixx002@unm.edu
AF: University of Minnesota, 310 Pillsbury Dr. SE, Minneapolis, MN 55455 United States
AU: Ryerson, R
EM: ryerson1@llnl.gov
AF: Lawrence Livermore National Laboratory, 7000 East Avenue PO Box 808, L-201, Livermore, CA 94551 United States
AU: Kinney, J
EM: kinney3@llnl.gov
AF: Lawrence Livermore National Laboratory, 7000 East Avenue PO Box 808, L-201, Livermore, CA 94551 United States
AB: The presence, distribution, and composition of melt affect the physical properties of polycrystalline ultramafic rock and are important to our interpretation of the Earth's lower crust and upper mantle, and to our understanding of planetary core formation via liquid-metal segregation. A key issue in models of planetary core formation is the interconnectness of molten iron-sulfides in contact with silicates at high temperature and pressure. Olivine-FeS partial-melts are also considered to be possible explanations for anomalously high conductivity regions beneath mountain ranges such as the Pyrenees and Andes. The interconnectivity and tortuosity of the melt phase, in combination with the properties of the individual melt and crystal phases, have bearing on the extractability of the melt, and on the rheology, and electrical conductivity of the bulk material. We have begun an integrated study of the electrical conductivity-texture-permeability relationships of olivine-sulfide partial-melt samples. Olivine-sulfide partial-melts containing 0, 1, 3, 6, and 10% by weight non-wetting compositions (Fe64S36) and wetting compositions (Fe34S19Ni47+O2) in a San Carlos olivine matrix (Fo91) have been synthesized in a piston cylinder apparatus at 1250 C and 1 to 2 GPa. Electrical conductivity measurements of the partial-melt and the individual melt and crystalline phases have been performed in a 1-atmosphere gas-mixing furnace up to 1400 C. Additional measurements in solid medium-pressure apparatus (D-DIA, piston cylinder) have begun. Samples are characterized using X-ray microtomographic (XRCT) performed at the Advanced Light Source with spatial resolution approaching 2 microns. Determination of the 3-D structure and interconnectedness of the melt phase, combined with the electrical conductivity measurements have been used to estimate the permeability of the mixtures at various experimental conditions. Results indicate sulfur fugacity is an important parameter controlling the wettability and interconnectivity of the melt phase. 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: 5109 Magnetic and electrical properties
DE: 5114 Permeability and porosity
DE: 5139 Transport properties
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2005 Joint Assembly