16:45 〜 17:00
[SIT17-06] Density and Sound Velocity of Liquid Fe and FeO at High Pressure
キーワード：液体、密度、音速、高圧、核
The Earth's core is almost molten. While the dominant component of the core is believed to be iron, a large amount of lighter impurities can be dissolved into the core. Oxygen is a possible candidate for the light impurity in the liquid outer core. Seismological observations exhibit the presence of a low-velocity layer (LVL) at the top of the Earth's core, which might be attributed to the enrichment of oxygen [1,2]. Furthermore, the enrichment of the FeO component and/or partial melting are considered to be the origin of the ultra-low velocity zone (ULVZ) at the base of the lower mantle (e.g. [3]). Therefore, the density (ρ) and longitudinal sound velocity (VP) of Fe-O liquids under relevant high-pressure and -temperature conditions are of great importance to understand those seismological anomalies. Here we present those elastic properties of liquid Fe and FeO under high-pressure and -temperature (P-T) conditions.
We have determined the ρ of liquid Fe up to 116 GPa based on in-situ x-ray diffraction measurements at BL10XU, SPring-8, using a laser-heated diamond-anvil cell (LH-DAC) [4]. The VP of liquid Fe was obtained up to 45 GPa by inelastic x-ray scattering (IXS) measurements in the LH-DAC at BL43LXU, SPring-8 [5]. From these results combined with previous shock-wave data, we obtained the P–T–ρ–VP–γ relation for the Earth's entire outer core conditions [6]. Also, we determined the VP of liquid FeO up to 82 GPa using the IXS technique. The present results show that the VP of liquid FeO is faster than that of liquid Fe by ~15% at the condition of the Earth's core-mantle boundary (CMB). Since the FeO component increases the P-wave velocity of liquid iron alloy, the enrichment of FeO cannot be the origin of the low-velocity anomaly at the top of the outer core. On the other hand, the VP of liquid FeO is slower by ~35% relative to lower mantle minerals at the base of the lower mantle, so that the ULVZ can be attributed to a tiny amount of liquid FeO component.
[1] G. Helffrich and S. Kaneshima, Nature 468, 807 (2010).
[2] T. Komabayashi, J. Geophys. Res. Solid Earth 119, 4164 (2014).
[3] S. Labrosse, J. W. Hernlund, and N. Coltice, Nature 450, 866 (2007).
[4] N. Hirao, S. I. Kawaguchi, K. Hirose, K. Shimizu, E. Ohtani, and Y. Ohishi, Matter Radiat. Extrem. 5, 018403 (2020).
[5] A. Q. R. Baron, SPring-8 Inf. Newsl. 15, 14 (2010).
[6] Y. Kuwayama, G. Morard, Y. Nakajima, K. Hirose, A. Q. R. Baron, S. I. Kawaguchi, T. Tsuchiya, D. Ishikawa, N. Hirao, and Y. Ohishi, Phys. Rev. Lett. 124, 165701 (2020).
We have determined the ρ of liquid Fe up to 116 GPa based on in-situ x-ray diffraction measurements at BL10XU, SPring-8, using a laser-heated diamond-anvil cell (LH-DAC) [4]. The VP of liquid Fe was obtained up to 45 GPa by inelastic x-ray scattering (IXS) measurements in the LH-DAC at BL43LXU, SPring-8 [5]. From these results combined with previous shock-wave data, we obtained the P–T–ρ–VP–γ relation for the Earth's entire outer core conditions [6]. Also, we determined the VP of liquid FeO up to 82 GPa using the IXS technique. The present results show that the VP of liquid FeO is faster than that of liquid Fe by ~15% at the condition of the Earth's core-mantle boundary (CMB). Since the FeO component increases the P-wave velocity of liquid iron alloy, the enrichment of FeO cannot be the origin of the low-velocity anomaly at the top of the outer core. On the other hand, the VP of liquid FeO is slower by ~35% relative to lower mantle minerals at the base of the lower mantle, so that the ULVZ can be attributed to a tiny amount of liquid FeO component.
[1] G. Helffrich and S. Kaneshima, Nature 468, 807 (2010).
[2] T. Komabayashi, J. Geophys. Res. Solid Earth 119, 4164 (2014).
[3] S. Labrosse, J. W. Hernlund, and N. Coltice, Nature 450, 866 (2007).
[4] N. Hirao, S. I. Kawaguchi, K. Hirose, K. Shimizu, E. Ohtani, and Y. Ohishi, Matter Radiat. Extrem. 5, 018403 (2020).
[5] A. Q. R. Baron, SPring-8 Inf. Newsl. 15, 14 (2010).
[6] Y. Kuwayama, G. Morard, Y. Nakajima, K. Hirose, A. Q. R. Baron, S. I. Kawaguchi, T. Tsuchiya, D. Ishikawa, N. Hirao, and Y. Ohishi, Phys. Rev. Lett. 124, 165701 (2020).