HR: 1330h
AN: T42A-0272    [PDF]
TI: Connectivity of molten Fe alloy in mantle peridotite based on in situ electrical conductivity measurements
AU: * Yoshino, T
AF: Institute for Study of the Earth's Interior, 827 Yamada, Misasa, Tottori, 682-0193 Japan
AU: Walter, M J
AF: Institute for Study of the Earth's Interior, 827 Yamada, Misasa, Tottori, 682-0193 Japan
AU: Katsura, T
AF: Institute for Study of the Earth's Interior, 827 Yamada, Misasa, Tottori, 682-0193 Japan
AB: The connectivity of molten Fe-S in peridotite has been experimentally investigated by means of in situ electrical conductivity measurements at high temperatures and 1GPa. Starting materials were powdered mixtures of peridotite KLB-1 with various amounts (0, 3, 6, 13, 19, 24 volume percent) of the 1 GPa eutectic composition in the Fe-FeS binary system. At temperatures above the eutectic point in the Fe-FeS system (1253K) and below the solidus of KLB1 (1473K), molten Fe-S in a solid silicate matrix interconnects when the volume fraction is over 5 percent. Conductivity-temperature paths indicate that in the presence of partial silicate melting the connectivity of molten Fe-S in a peridotite matrix is inhibited. Based on observations of retrieved samples, the percolation threshold of Fe-S melts in the presence of low to moderate degrees of silicate melt is estimated at approximately 13 volume percent. These results indicate that if the volume fraction of Fe-alloy in a planetesimal was initially greater than 5 percent, and if early heating by decay of radionuclides raised the temperature of the interior above the Fe-alloy melting point, initial metal segregation was controlled by permeable flow of molten iron alloy melt in a solid silicate matrix. These conditions were likely met by many terrestrial objects in the early nebula. Efficient removal of residual Fe-alloy (5 volume percent) from silicate requires high-degree melting of silicate so that metal can segregate as droplets. Giant impacts during the final stage of accretion of large planetary objects could supply the energy required for high-degrees of melting. Alternatively, if initial metal segregation were delayed until a planetery object grew to large size (approximately 1000 km in diameter), release of gravitational potential energy due to metal segregation could contribute enough heat to form a magma ocean.
DE: 1749 Volcanology, geochemistry, and petrology
DE: 3914 Electrical properties
DE: 5112 Microstructure
DE: 5114 Permeability and porosity
DE: 5139 Transport properties
SC: Tectonophysics [T]
MN: 2003 Fall Meeting