DI52A-06
Sound velocity of liquid Fe alloys at high pressure by inelastic X-ray scattering
Friday, 18 December 2015: 11:35
303 (Moscone South)
Yoichi Nakajima1,2, Saori Imada3, Tetsuya Komabayashi4, Kei Hirose5, Haruka Ozawa6, Shigehiko Tateno6, Yasuhiro Kuwayama7, Satoshi Tsutsui3 and Alfred Q. R. Baron2, (1)RIKEN SPring-8 Center, Hyogo, Japan, (2)RIKEN SPring-8 Center, Material Dynamics Laboratory, Hyogo, Japan, (3)Japan Synchrotron Radiation Research Institute, Hyogo, Japan, (4)University of Edinburgh, Edinburgh, EH9, United Kingdom, (5)Tokyo Institute of Technology, Earth-Life Science Institute, Tokyo, Japan, (6)Institute for Study of the Earth's Interior, Okayama University, Tottori, Japan, (7)Ehime University, Geodynamics Research Center, Matsuyama, Japan
Abstract:
The light elements in the Earth’s core have long been controversial. Sound velocity and density are important observational constraints on the chemical composition of the Earth’s core. While properties of solid iron alloying with possible lighter elements have been extensively examined by laboratory studies to core pressures, little is known for liquid alloys because of experimental difficulties. The core is predominantly molten, and therefore the longitudinal wave (P-wave) velocity of liquid alloy is the key to constrain its composition. We have performed inelastic X-ray scattering (IXS) measurements combined with laser-heated and external-heated diamond-anvil cells at the SPring-8 synchrotron facility, in order to investigate the sound velocities of liquid Fe–light-element alloys under high pressure and high temperature. We measured longitudinal acoustic phonon excitations of liquid iron alloying with possible components in the core such as Ni, C, Si, or S, and then determined their P-wave velocities to 70 GPa and 3000 K. The elastic parameters and equations of state for liquid iron alloys were also examined using the velocity data-set together with available thermodynamic parameters in literature, which enables us to estimate densities of liquid alloys as well as sound velocities under the core pressure and temperature conditions. Based on the comparison of sound velocity and density based on the present IXS measurements with seismological observations, we will discuss the role of lighter elements in the Earth’s outer core.
