掲載種別：研究論文（学術雑誌）   出版者・発行元：American Geophysical Union (AGU)  

DOI： 10.1029/2022gl098279

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Determination of the chemical composition of the Earth's mantle is of prime importance to understand the evolution, dynamics, and origin of the Earth. However, there is a lack of experimental data on sound velocity of iron-bearing Bridgmanite (Brd) under relevant high-pressure conditions of the whole mantle, which prevents constraints on the mineralogical model of the lower mantle. To uncover these issues, we have conducted sound-velocity measurement of iron-bearing Brd in a diamond-anvil cell (DAC) up to 124 GPa using Brillouin scattering spectroscopy. Here we show that the sound velocities of iron-bearing Brd throughout the whole pressure range of lower mantle exhibit an apparent linear reduction with the iron content. Our data fit remarkably with the seismic structure throughout the lower mantle with Fe2+-enriched Brd, indicating that the greater part of the lower mantle could be occupied by Fe2+-enriched Brd. Our lower-mantle model shows a distinctive Si-enriched composition with Mg/Si of 1.14 relative to the upper mantle (Mg/Si = 1.25), which implies that the mantle convection has been inefficient enough to chemically homogenize the Earth's whole mantle.

DOI： 10.1073/pnas.1917096117

PubMed

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

© 2019 Elsevier B.V. Phase relations, including the eutectic liquid composition in the Fe–C binary system, remain unclear under the core pressure range, which makes estimating the carbon budget in the Earth's core difficult. To explore this issue, we have conducted melting and subsolidus experiments on Fe–C alloys in a diamond-anvil cell up to 255 GPa. Textural and compositional characterizations of quenched samples show that carbon concentration in the eutectic liquid slightly decreases with increasing pressure and is about 3 wt.% at the inner core boundary (ICB) pressure. The solubility of carbon in solid Fe is found to be almost constant at ∼1.0 wt.%. In situ X-ray diffraction data indicate that Fe forms eutectic melting with Fe 3 C to 203 GPa and with Fe 7 C 3 at 255 GPa. Previous studies on liquid Fe–C alloys suggested that the density of the outer core is explained by liquid Fe containing 1.8 to 4.2 wt.% C. If the liquid core includes <3 wt.% C as a single light element, hexagonal close-packed (hcp) Fe crystallizes at the ICB. However, the carbon content in such solid Fe is ≤1 wt.%, less than that required to account for the inner core density deficit from pure iron. When the outer core includes ≥3 wt.% C, it forms Fe 7 C 3 at the ICB, whose density is too small for the inner core. Carbon is therefore not a primary light element in the core. Nevertheless, the outer core liquid can be Fe–C–Si, Fe–C–S, or Fe–C–H. Such core liquid crystallizes solid Fe with light elements including less than 1 wt.% C, which may explain the density and the sound velocities observed in the inner core.

DOI： 10.1016/j.epsl.2019.03.020

Web of Science

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER GEOPHYSICAL UNION  

©2016. American Geophysical Union. All Rights Reserved. Recent studies show that δ-AlOOH is stable up to the base of the mantle. This phase is, therefore, a possible carrier and host of water in the deep mantle. To uncover the physical properties of δ-AlOOH under deep mantle pressure conditions, we have conducted high-pressure acoustic wave velocity measurements of δ-AlOOH by using Brillouin spectroscopy combined with high-pressure Raman spectroscopic measurements in a diamond anvil cell up to pressures of 134 GPa. There is a precipitous increase by ∼14% in the acoustic velocities of δ-AlOOH from 6 to 15 GPa, which suggests that pressure-induced O-H bond symmetrization occurs in this pressure range. The best fit values for the high-pressure form of δ-AlOOH of K0 = 190 (2) (GPa), G0 = 160.0 (9) (GPa), (∂K/∂P)0 = K0′ = 3.7 (1), and (∂G/∂P)0 = G0′ = 1.32 (1) indicate that δ-AlOOH has a 20-30% higher VS value compared to those of the major constituent minerals in the mantle transition zone, such as wadsleyite, ringwoodite, and majorite. On the other hand, the VS of δ-AlOOH is ∼7% lower than that of Mg-bridgmanite under lowermost mantle pressure conditions because of the significantly lower value of the pressure derivative of the shear modulus. By comparing our results with seismic observations, we can infer that δ-AlOOH could be one of the potential causes of a positive VS anomaly observed at ∼600 km depth beneath the Korean peninsula and a negative VS jump near 2800 km depth near the northern margin of the large low-shear-velocity province beneath the Pacific.

DOI： 10.1002/2015JB012477

Web of Science

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掲載種別：研究論文（学術雑誌）  

© 2021 Author(s). Semiconductor-based heaters for diamond anvil cells (DACs) have advantages over metal wire heaters in terms of repeated use and the ability to reach higher temperatures. We introduce a cylindrical SiC heater for an externally heated DAC (EHDAC) that works satisfactorily at temperatures up to 1500 K and pressures around 90 GPa. The heater is reusable and inexpensive, and only slight modifications to the DAC are required to fit the heater. Experiments on melting of NaCl and gold are conducted at ambient pressure to test the temperature accuracy of the EHDAC system, and resistance measurements on iodine at high pressures and temperatures are performed to assess the heater assembly. These test runs show that a uniform and accurate temperature can be maintained by the EHDAC assembly, which has potential applications to a variety of transport property measurements.

DOI： 10.1063/5.0036551

Scopus

PubMed

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記述言語：英語   掲載種別：速報，短報，研究ノート等（大学，研究機関紀要）  

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記述言語：日本語   出版者・発行元：日本高圧力学会  

DOI： 10.4131/jshpreview.29.217

CiNii Article

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記述言語：日本語   出版者・発行元：日本惑星科学会  

CiNii Article

CiNii Books

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記述言語：日本語   出版者・発行元：一般社団法人日本鉱物科学会  

本研究では下部マントル圧力条件でのFe³⁺を含むMg-ペロブスカイトの状態方程式を求めることにより、鉄のスピン転移による影響の有無を調べることを目的とした。NaClおよびNe圧媒体を用いてX線回折実験を行った。NaCl圧媒体の実験では、各測定時にアニールはしていない。一方Ne圧媒体では各測定前にレーザーを用いて1800K程度で加熱アニールした。高圧でアニールをしていないNaCl圧媒体による測定は、Ne圧媒体を用いた測定とは一致せず、大きな格子体積を示した。この違いは、試料部の静水圧性の違い、アニーリングの有無によるFe²⁺/Fe³⁺の違いによる可能性もある。Ne圧媒体を用いたX線回折実験では、圧縮データは62GPaまでの圧力範囲では格子体積の圧縮挙動について不連続的な変化は見られなかったが、b/aについては、50GPa付近で不連続に見える変化が認められた。

DOI： 10.14824/jakoka.2012.0_136

CiNii Article

CiNii Books

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開催年月日： 2018年12月

記述言語：英語   会議種別：口頭発表（一般）  

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開催年月日： 2017年7月 - 2017年8月

記述言語：英語   会議種別：口頭発表（招待・特別）  

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記述言語：英語   会議種別：口頭発表（一般）  

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記述言語：英語   会議種別：口頭発表（一般）  

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開催年月日： 2022年5月22日 - 2022年6月3日

会議種別：ポスター発表  

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