HR: 17:00h
AN: DI24A-05    [Abstracts]
TI: A New Thermal Equation of State for Iron at Megabar Pressure
AU: * Fiquet, G
EM: guillaume.fiquet@impmc.jussieu.fr
AF: Institut de Mineralogie et de Physique des Milieux Condenses - CNRS Institut de Physique du Globe de Paris, 140 rue de Lourmel, Paris, 75015, France
AU: Badro, J
EM: james.badro@impmc.jussieu.fr
AF: Institut de Mineralogie et de Physique des Milieux Condenses - CNRS Institut de Physique du Globe de Paris, 140 rue de Lourmel, Paris, 75015, France
AU: Auzende, A
EM: anne-line.auzende@impmc.jussieu.fr
AF: Institut de Mineralogie et de Physique des Milieux Condenses - CNRS Institut de Physique du Globe de Paris, 140 rue de Lourmel, Paris, 75015, France
AU: Gregoryanz, E
EM: e.gregoryanz@ed.ac.uk
AF: School of Physics - CSEC University of Edinburgh, Erskine Williamson Building Mayfield Road, Edinburgh, EH9 3JZ, United Kingdom
AU: Siebert, J
EM: siebert2@llnl.gov
AF: Department of Energy & Environment Experimental Geophysic LLNL, LLNL - University of California 7000 East Avenue, Livermore, CA 94550, United States
AU: Matas, J
EM: jan.matas@ens-lyon.fr
AF: Laboratoire de Sciences de la Terre Ecole Normale Supérieure de Lyon, 46, allée d'Italie, Lyon, 69364, France
AU: Guignot, N
EM: nicolas.guignot@synchrotron-soleil.fr
AF: Synchrotron Soleil Ligne Haute Pression, L'Orme des Merisiers Saint-Aubin, Gif-sur-Yvette, 91192, France
AB: Because the core is composed primarily of iron alloyed with light elements, the physics of iron must be well understood to assess the effect of impurities on the properties the real core material could be made of. The structure of iron at inner core conditions is still an open issue, since some theoretical calculations ( e.g. Belonoshko et al. Nature 424, 1032, 2003) or a recent experimental observation on a nickel-iron alloy (Dubrovinsky et al. Science 316, 1880, 2007) indicate that a body centered cubic one could be more appropriate. It is however still reasonable to envisage that iron adopts the hexagonal close packed structure (hcp) at Earth's inner core conditions. In this report, the high-pressure and high-temperature behavior of iron has been investigated to 140 GPa and 3400 K with in situ synchrotron X-ray diffraction at ESRF (Grenoble). We present series of experiments carried out on hot-pressed samples of iron and periclase in a laser-heated diamond-anvil cell, that were combined with ATEM examination of recovered samples. Among all structures proposed so far, hcp-iron only is found to be present at the highest pressure and temperature investigated. In addition, these experiments allow us to better bracket the triple point between the fcc and hcp phases and the liquid, and to address the evolution of the c/a ratio with pressure and temperature and the related elastic anisotropy of iron at core conditions. Finally, we propose a new thermal equation of state for iron at megabar pressures, which put tighter constraints on the light element content of the inner core.
DE: 1015 Composition of the core
DE: 3919 Equations of state
DE: 3924 High-pressure behavior
DE: 8124 Earth's interior: composition and state (1212, 7207, 7208, 8105)
DE: 8147 Planetary interiors (5430, 5724, 6024)
SC: Study of the Earth's Deep Interior [DI]
MN: 2007 Fall Meeting