HR: 09:00h
AN: U41A-05    [PDF]
TI: Chemical Reaction Between Silicate Perovskite and Liquid Iron up to 79 GPa
AU: * Takafuji, N
EM: takafuji@geo.titech.ac.jp
AF: Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo, 152-8551 Japan
AU: Hirose, K
EM: kei@geo.titech.ac.jp
AF: Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo, 152-8551 Japan
AU: Mitome, M
EM: MITOME.Masanori@nims.go.jp
AF: National Institute for material science, 1-2-1 Tukubax, Ibaragi, 152-8551 Japan
AU: Bando, Y
EM: BANDO.Yoshio@nims.go.jp
AF: National Institute for material science, 1-2-1 Tukubax, Ibaragi, 152-8551 Japan
AB: We investigated chemical reaction between silicate perovskite and liquid iron on the basis of high pressure and temperature experiments up to 79 GPa and 3150 K. A total of 30 runs were made in a Kawai-type apparatus and a laser-heated diamond-anvil cell. Mixtures of iron (99.9 % purity) and gel powder with compositions of Mg0.9Fe0.1SiO3 or Mg0.8Fe0.2SiO3 were used as starting materials (8:92 in weight). Textural observations and chemical analyses on the recovered samples were performed with an analytical transmission electron microscopy (ATEM) equipped with energy dispersive spectroscope (EDS) and electron energy loss spectroscope (EELS). Results demonstrated that dissolution both of oxygen and silicon from silicate perovskite into molten iron was significantly enhanced with increasing pressure and temperature. In contrast, FeO content in perovskite decreased with increasing pressure and temperature. The liquid iron in contact with perovskite quenched from 3100 K at 72 GPa includes 4.3(0.8) wt% oxygen and 3.1(0.7) wt% silicon. It also includes trace amount of magnesium content (0.3 wt%). In all the experiments, no reaction products other than metallic iron and perovskite were observed. This observation together with the fact that Si/O ratios in quenched liquid iron are close to 1/3 suggests that FeSiO3 component in perovskite dissolved into liquid iron without forming any reaction products. The oxygen and silicon contents in molten iron chemically reacted with silicate perovskite at 72 GPa and 3100 K can already account for a 7% density deficit in the outer core, according to Anderson and Isaak (2002, PEPI). It is therefore expected that oxygen and silicon are currently dissolving from the mantle into the core by the consequence of chemical reaction at the core-mantle boundary.
DE: 1015 Composition of the core
DE: 3924 High-pressure behavior
DE: 7207 Core and mantle
DE: 8124 Earth's interior--composition and state (old 8105)
SC: U
MN: 2003 Fall Meeting