HR: 15:16h
AN: MR23D-09    [Abstracts]
TI: Iron-carbon system at Earth's lower mantle conditions
AU: * Prakapenka, V
EM: prakapenka@cars.uchicago.edu
AF: CARS, University of Chicago, Buldg 434A, APS 9700 S.Cass Ave, Argonne, 60439, United States
AU: Rivers, M
EM: rivers@cars.uchicago.edu
AF: CARS, University of Chicago, Buldg 434A, APS 9700 S.Cass Ave, Argonne, 60439, United States
AU: Sutton, S
EM: sutton@cars.uchicago.edu
AF: CARS, University of Chicago, Buldg 434A, APS 9700 S.Cass Ave, Argonne, 60439, United States
AB: The abundance of the carbon near the surface of the Earth is significantly lower than that expected from a cosmochemical grounds. As was shown in recent studies (Shcheka, 2006) the solubility of carbon in the major mantle forming silicates is very low and other minor carbon-rich phases should dominate the carbon budget within the bulk Earth's mantle. One of the them, magnesite (MgCO3) doesn't undergo dissociation at lower mantle conditions (~115 GPa and ~2200 K) and can be one of the major hosts for carbon throughout most parts of the Earth's lower mantle (Isshiki, 2003). It is well known that presence even small amount of carbon can significantly change the path of multi elemental chemical reactions and thereby physical properties of the end products. Hence, the affect of carbon on the phase transformation, chemical reaction, partitioning, melting temperatures etc of the core-mantle forming elements can significantly change our understanding of Earth's lower mantle and the influence of carbon on evolution of Earth. In this work we have studied in-situ the chemical stability and physical properties of the iron-carbon system under appropriate Earth's lower mantle core conditions. The double-sided laser heating technique combined with high resolution angle-dispersive micro x-ray diffraction system at GSECARS (Sector 13, APS, Argonne) was used to characterize samples in the diamond anvil cell (DAC). Iron carbide was synthesized in-situ in DAC from a mixture of Fe and C powders at pressures above 6 GPa and temperature ~1500K. We did not found dissociation of iron carbide in the entire pressure-temperatures range studied: up to ~170 GPa and ~4000K. High pressure high temperature stability of iron carbide phases in the D'' layer, is essential for interpreting the observed seismic anomaly in that region and understanding of the early Earth differentiation. Implications of these results to the composition of the Earth's interior will be discussed.
DE: 1000 GEOCHEMISTRY
DE: 3600 MINERALOGY AND PETROLOGY
SC: Mineral and Rock Physics [MR]
MN: 2007 Fall Meeting