HR: 1340h
AN: MR43A-0879    [Abstracts]
TI: Experimental Partitioning of U Between Liquid Iron Sulfide and Liquid Silicate: Implications for Radioactivity in the Core
AU: * Wheeler, K
EM: kwheeler@ldeo.columbia.edu
AF: Lamont Doherty Earth Observatory and Department of Earth and Environmental Sciences, Columbia University, Rt 9 W, Palisades, NY 10964 United States
AU: Walker, D
AF: Lamont Doherty Earth Observatory and Department of Earth and Environmental Sciences, Columbia University, Rt 9 W, Palisades, NY 10964 United States
AU: Fei, Y
AF: Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Road NW, Washington, DC 20015 United States
AU: Minarik, W
AF: McGill University, McGill University, Montr‚al, QC H3A 2A7 Canada
AB: The prodigious affinity of U for oxygen suggests that it may be difficult for U to be incorporated in a core formed from silicate mantle with residual partially oxidized Fe. If U is reduced enough to join the metal of the core, then Fe should be effectively completely reduced. We explored the ability for initially native U metal to be retained within polymetallic sulfide liquid solutions \{Fe+FeS\} in equilibrium with plausible mantle silicate liquids \{peridotite KLB-1\} and excess carbon. We found no conditions from 2-10 GPa, 1750-$2100\deg$C, and 0-28 wt% S in the metallic liquid where sufficient U could be retained in the metallic liquid to be interesting in the context of U-derived heat sources in Earth's core. We do find interesting structure to the variations of DU\{sulfide/silicate\}, which was always a very small number. Typical DU ranged from a minimum of $<$1.3\times10$^{-5}$ to a maximum of 0.001. A possible weak increase in DU with temperature was observed. Increasing pressure also may cause a weak increase in DU. Sulfur content in the Fe sulfide was the largest influence on DU indicating some degree of U chalchophility. Typical DU values increased an order of magnitude when S content in the sulfide increased from 7 to 28 wt%. It is important to note that even wild extrapolation of the most favorable data did not yield significant U in the sulfide at core conditions. Therefore, it is our conclusion that if there is U in the core, it most likely did not get there during core formation in a partially oxidized magma ocean scenario.
DE: 5430 Interiors (8147)
DE: 3630 Experimental mineralogy and petrology
DE: 3672 Planetary mineralogy and petrology (5410)
DE: 1015 Composition of the core
SC: Mineral and Rock Physics [MR]
MN: 2004 AGU Fall Meeting