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Journal Articles

Deuterium content and site occupancy in iron sulfide at high pressure and temperature determined using in situ neutron diffraction measurements

Abeykoon, S.*; Howard, C.*; Dominijanni, S.*; Eberhard, L.*; Kurnosov, A.*; Frost, D. J.*; Boffa Ballaran, T.*; Terasaki, Hidenori*; Sakamaki, Tatsuya*; Suzuki, Akio*; et al.

Journal of Geophysical Research; Solid Earth, 128(9), p.e2023JB026710_1 - e2023JB026710_17, 2023/09

Small amounts of iron sulphide minerals are found in most rocks from the Earth's mantle and as inclusions trapped in natural diamonds. Hydrogen may dissolve into iron sulphide minerals under high pressures and temperature, but is most likely lost once pressure and temperature are removed. In this study, we determined deuterium contents in iron sulphide, held under high pressure and temperature conditions, using neutron diffraction measurements with 6-ram multi-anvil press at PLANET, J-PARC. Deuterium contents in iron sulphide were measured at high-P, up to 11.4 GPa and high-T to 1300 K in in situ neutron diffraction experiments. The total deuterium content increases with both P and T. The results are used to estimate hydrogen contents of iron sulphide minerals in the deep continental lithospheric mantle, which are found to be in the range 1700-2700 ppm. This corresponds to approximately 2-3 ppm of hydrogen in the bulk mantle.

Journal Articles

Interstitial hydrogen atoms in face-centered cubic iron in the Earth's core

Ikuta, Daijo*; Otani, Eiji*; Sano, Asami; Shibazaki, Yuki*; Terasaki, Hidenori*; Yuan, L.*; Hattori, Takanori

Scientific Reports (Internet), 9, p.7108_1 - 7108_8, 2019/05

 Times Cited Count:32 Percentile:92.34(Multidisciplinary Sciences)

Hydrogen is likely one of the light elements in the Earth's core. Despite its importance, no direct observation has been made of hydrogen in an iron lattice at high pressure. We made the first direct determination of site occupancy and volume of interstitial hydrogen in a face-centered cubic (fcc) iron lattice up to 12 GPa and 1200 K using the in situ neutron diffraction method. At pressures $$<$$ 5 GPa, the hydrogen content in the fcc iron hydride lattice (x) was small at x $$<$$ 0.3, but increased to x $$>$$ 0.8 with increasing pressure. Hydrogen atoms occupy both octahedral (O) and tetrahedral (T) sites; typically 0.870 in O-sites and 0.057 in T-sites at 12 GPa and 1200 K. The fcc lattice expanded approximately linearly at a rate of 2.22 $AA $^{3}$$ per hydrogen atom, which is higher than previously estimated (1.9 $AA $^{3}$$/H). The lattice expansion by hydrogen dissolution was negligibly dependent on pressure. The large lattice expansion by interstitial hydrogen reduced the estimated hydrogen content in the Earth's core that accounted for the density deficit of the core. The revised analyses indicate that whole core may contain hydrogen of 80 times of the ocean mass with 79 and 0.8 ocean mass for the outer and inner cores, respectively.

Journal Articles

Ponded melt at the boundary between the lithosphere and asthenosphere

Sakamaki, Tatsuya*; Suzuki, Akio*; Otani, Eiji*; Terasaki, Hidenori*; Urakawa, Satoru*; Katayama, Yoshinori; Funakoshi, Kenichi*; Wang, Y.*; Hernlund, J. W.*; Ballmer, M. D.*

Nature Geoscience, 6(12), p.1041 - 1044, 2013/12

 Times Cited Count:124 Percentile:96.55(Geosciences, Multidisciplinary)

The bounday between Earth's rigid lighosphere and the underlying, ductile ashenosphere is marked by a distinct siseismic discontinuity. We measure the density, viscosity and structure of basaltic magmas using high-pressure and high-temperature experiments and in situ X-ray analysis under pressure of up to 5.5 GPa. We find that the magmas rapidly become denser with increasing presure and show a viscosity minimum near 4 GPa. Magma mobility determined by the density and viscosity data exhibits a peak at pressures corresponding to depths of 120-150 km, within the asthenosphere. The diminishing mobility of magma in Earth's asthenosphere as the mlets ascend could lead to excessive melt accumulation at depths of 80-100 km, at the lithosphere-asthenosphere boundary. It is concluded that the observed seismic discontinuity at the lithosphere-asthenosphere boundary records this accumulation of melt.

Journal Articles

Density measurement of liquid FeS at high pressures using synchrotron X-ray absorption

Nishida, Keisuke*; Otani, Eiji*; Urakawa, Satoru*; Suzuki, Akio*; Sakamaki, Tatsuya*; Terasaki, Hidenori*; Katayama, Yoshinori

American Mineralogist, 96(5-6), p.864 - 868, 2011/05

 Times Cited Count:32 Percentile:69.54(Geochemistry & Geophysics)

The density of liquid iron sulfide (FeS) was measured up to 3.8 GPa and 1800 K using the X-ray absorption method. The compression curve of the liquid FeS can be fitted using the Vinet equation of state. Isothermal bulk modulus and its temperature and pressure derivatives were determined by a non-linear least squares fit. Liquid FeS is more compressible than Fe-rich Fe-S liquid.

Journal Articles

Density of carbonated peridotite magma at high pressure using an X-ray absorption method

Sakamaki, Tatsuya*; Otani, Eiji*; Urakawa, Satoru*; Terasaki, Hidenori*; Katayama, Yoshinori

American Mineralogist, 96(4), p.553 - 557, 2011/04

 Times Cited Count:29 Percentile:68.51(Geochemistry & Geophysics)

The density of carbonated peridotite magma was measured up to 3.8 GPa and 2100 K using an X-ray absorption method. The bulk modulus of carbonated peridotite magma is larger than that of hydrous peridotite magma. The partial molar volume of CO$$_{2}$$ in magma under high pressure and temperature conditions was calculated. Our results show that the partial molar volume of CO$$_{2}$$ is less compressible than that of H$$_{2}$$O, suggesting that, on an equal molar basis, CO$$_{2}$$ is more effective than H$$_{2}$$O in reducing peridotite melt density at high pressure.

Journal Articles

Phase relationships and equations of state for FeS at high pressures and temperatures and implications for the internal structure of Mars

Urakawa, Satoru*; Someya, Keiko*; Terasaki, Hidenori*; Katsura, Tomoo*; Yokoshi, Sho*; Funakoshi, Kenichi*; Utsumi, Wataru; Katayama, Yoshinori; Sueda, Yuichiro*; Irifune, Tetsuo*

Physics of the Earth and Planetary Interiors, 143-144, p.469 - 479, 2004/06

 Times Cited Count:61 Percentile:72.92(Geochemistry & Geophysics)

no abstracts in English

Journal Articles

Viscosity change and structural transition of molten Fe at 5 GPa

Terasaki, Hidenori*; Kato, Takumi*; Urakawa, Satoru*; Funakoshi, Kenichi*; Sato, Kiminori*; Suzuki, Akio*; Okada, Taku

Geophysical Research Letters, 29(8), p.68_1 - 68_3, 2002/05

The in situ viscosity measurements of the pure molten Fe under high pressures were made by falling sphere X-ray radiography method. Viscosity coefficients at about 2000 K were 15-24 mPa s at 2.7-5.0 GPa, and 4-9 mPa s at 5.0-7.0 GPa. Drastic decrease was found at around 5 GPa, at which stable solid phase below the melting temperatures change from delta (bcc) to gamma (fcc) phases. The observation indicates the possibility that the structural change in the molten Fe occurs in a narrow pressure interval (1 GPa) at the similar condition with the phase transformation in the solid.

Journal Articles

The Effect of temperature, pressure, and sulfur content on viscosity of the Fe-FeS melt

Terasaki, Hidenori*; Kato, Takumi*; Urakawa, Satoru*; Funakoshi, Kenichi*; Suzuki, Akio*; Okada, Taku; Maeda, Makoto*; Sato, Jin*; Kubo, Tomoaki*; Kasai, Shizu*

Earth and Planetary Science Letters, 190(1-2), p.93 - 101, 2001/07

 Times Cited Count:52 Percentile:68.67(Geochemistry & Geophysics)

The Fe-FeS melt is thought to be the major candidate of the outer core material. Its viscosity is one of the most important physical properties to study the dynamics of the convection in the outer core. We performed the in situ viscosity measurement of the Fe-FeS melt under high pressure using X-ray radiography falling sphere method with a novel sample assembly. Viscosity was measures in the temperature, pressure, and compositional conditions of 1233-1923 K, 1.5-6.9 GPa, and Fe-Fe $$_{72}$$ S $$_{28}$$ (wt %), respectively. The viscosity coefficients obtained by 17 measurements change systematically in the range of 0.008-0.036 Pa s. An activation energy of the viscous flow, 30 kJ/mol, and the activation volume, 1.5 cm $$^{3}$$ /mol, are determined as the temperature and pressure dependence, and the viscosity of the Fe $$_{72}$$ S $$_{28}$$ melt is found to be smaller than that of the Fe melt by 15 %. These tendencies can be well correlated with the structural variation of the Fe-FeS melt.

Journal Articles

High-pressure and high-temperature experiments using multi-anvil appratus; Recent results

Funakoshi, Kenichi*; Utsumi, Wataru; Otaka, Osamu*; Irifune, Tetsuo*; Inoue, Toru*; Ito, Eiji*; Katsura, Tomoo*; Kubo, Atsushi*; Hirose, Kei*; Ando, Junichi*; et al.

Ganseki Kobutsu Kagaku, 30(2), p.102 - 103, 2001/03

no abstracts in English

Oral presentation

In-situ observation of microstress and solid state transformation in low temperature transformation weld metal by synchrotron radiation X-rays

Zhang, S.; Terasaki, Hidenori*; Komizo, Yuichi*

no journal, , 

In weld metal, it is important to decrease the residual stress of the welded joints because residual stress generated by welding promotes brittle fracture, stress corrosion cracking. As one of a countermeasure to use a volume expansion of martensitic transformation during low temperature transformation (LTT) has been examined. Then to establish this examination, the interplay between a solid state transformation and a stress deformation is very important. In this colloquium, we will present in-situ observation of the relationship between the stress deformation and the martensitic transformation of LTT, by using synchrotron radiation X-rays.

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