Faculty Profiles - TERASAKI Hidenori

Effect of structural transitions on properties of high-pressure silicate melts: Al-27 NMR, glass densities, and melt viscosities Reviewed

Jeffrey R. Allwardt, Jonathan F. Stebbins, Hidenori Terasaki, Lin-Shu Du, Daniel J. Frost, Anthony C. Withers, Marc M. Hirschmann, Akio Suzuki, Eiji Ohtani

AMERICAN MINERALOGIST 92 ( 7 ) 1093 - 1104 2007.7

Language：English Publishing type：Research paper (scientific journal) Publisher：MINERALOGICAL SOC AMER

The densities and viscosities of silicate melts depend strongly on pressure, in part because of potentially measurable structural rearrangements. In an attempt to further understand these changes and how they affect macroscopic properties, we have used Al-27 MAS NMR to determine the coordination of the Al cations in a series of alummosilicate glasses quenched from melts at pressures of 2 to 8 GPa, have measured the glass densities, and have applied an in-situ falling sphere method to measure melt viscosities at high pressure. Spectra from these four- and five-component glasses show increasing Al coordination with increasing pressure and with increasing average field strength of the modifier cation, as was previously reported for simpler compositions. These data also indicate that when multiple modifier cations are present (e.g., Ca and K), the Al coordination is lower than what would be expected from linear combinations of the appropriate alummosilicate end-members.
The viscosity of Ca3Al2Si6O18 melts, measured using a falling sphere method that combines multianvil techniques with synchrotron X-ray radiography, may reach a minimum at a pressure below 6 GPa. A quasi-thermodynamic approach using equilibrium constants for the reactions that generate high-coordinated Al suggests that this pressure may be related to a maximum in the concentration of five-coordinated Al. These results further support the concept that pressure-induced network structural transitions have direct implications for the macroscopic properties of high-pressure melts.

DOI： 10.2138/am.2007.2530

Interconnectivity of Fe-O-S liquid in polycrystalline silicate perovskite at lower mantle conditions Reviewed

Hidenori Terasaki, Daniel J. Frost, David C. Rubie, Falko Langenhorst

PHYSICS OF THE EARTH AND PLANETARY INTERIORS 161 ( 3-4 ) 170 - 176 2007.5

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

An important aspect of planetary core formation concerns whether interconnectivity of liquid metal can occur in crystalline silicates, which at low melt fractions requires that the dihedral angle between the two phases is < 60 degrees. [Shannon, M.C., Agee, C.B., 1998. Percolation of core melts at lower mantle conditions. Science 280, 1059-1061] previously reported that dihedral angles in mantle assemblages decrease from 108 degrees at upper mantle conditions to 71 degrees at lower mantle conditions as a result of mineral phase transformations. Furthermore [Terasaki, H., Frost, D.J., Rubie, D.C., Langenhorst, F., 2005. The effect of oxygen and sulphur on dihedral angle between Fe-O-S melt and solid silicates under high pressure: implications for Martian core formation. Earth Planet. Sci. Lett. 232, 379-392] observed that dihedral angles between Fe-O-S liquid and solid silicates (olivine and ringwoodite) decrease to 66 degrees at high oxygen and sulphur fugacities. Therefore, it may be possible for liquid metal to form an interconnected network at lower mantle conditions at high 0 and S fugacities. We have investigated the effects of the FeO content of perovskite, with Mg/(Mg + Fe) (Mg#) = 0.84-1.00, on the dihedral angle up to 23.5 GPa and 2223 K. Observed dihedral angles decrease significantly from 102 degrees to 79 degrees with increasing FeO content of the perovskite phase. This tendency is in good agreement with our previous dihedral angle results for olivine and ringwoodite. The dihedral angle is, however, still higher than the critical value of 60 degrees at pressures of the top of the lower mantle, i.e. at this depth efficient core-mantle differentiation is not possible by a percolation mechanism. (c) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.pepi.2007.01.011

Post-stishovite phase transformation in hydrous oceanic crust and seismic reflectors in the lower mantle

Litasov, K, Ohtani, E, Terasaki, H, Suzuki, A

Spring-8 User Experimental Report 2006B1230 2007.4

Determination of the phase boundary and the reaction kinetics of the post-spinel phase transition in the MgO-SiO2-H2O system

Ohtani E, Ghosh S, Suzuki A, Litasov K, Terasaki H, Ozawa S

Spring-8 User Experimental Report 2007A1701 2007.4

Reaction between metallic iron and elta-AlOOH at the core-mantle boundary

Ohtani, E, Kondo, T, Terasaki, H, Sano, A, Hirao, N

Spring-8 User Experimental Report 2006B1094 2007.4

In situ observation of liquid immiscibility of Fe-O-S liquid using X-ray radiography under high pressure

Terasaki, H, Ohtani, E, Suzuki, A, Tsuno, K, Asahara, Y, Sakamaki, T, Ozawa, S, Shibazaki, Y, Ghosh, S, Litasov, K, Nishida, K, Funakoshi, K

Spring-8 User Experimental Report 2007A1096 2007.4

Search for post delta-AlOOH at multi-megabar conditions

Ohtani E, Sano A, Terasaki H, Sakai T, Hirao N, Asanuma H

Spring-8 User Experimental Report 2007A2090 2007.4

Immiscible two-liquid regions in the Fe-O-S system at high pressure: Implications for planetary cores Reviewed

Kyusei Tsuno, Eiji Ohtani, Hidenori Terasaki

PHYSICS OF THE EARTH AND PLANETARY INTERIORS 160 ( 1 ) 75 - 85 2007.1

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

We have determined phase relations in the Fe-O and Fe-O-S systems in the range of 15-21 GPa and 1825-2300 degrees C. Below the liquidus temperatures, solid FeO and metallic liquids are observed in both the Fe-O and the Fe-O-S systems. An immiscible two-liquid region exists in the Fe-O binary system in the pressure range investigated, and the immiscibility gap between Fe-rich metallic liquid and FeO-rich ionic liquid does not greatly change with either pressure or temperature. On the other hand, an immiscible two-liquid region in the Fe-O-S ternary system narrows significantly with increasing pressure at constant temperature and vice versa, and it almost disappears at 21 GPa, and 2300 degrees C. Immiscible two-liquid regions are thus not expected to exist in the Fe-O-S system in the Earth's core, suggesting that both oxygen and sulfur can be incorporated into the core. Our results are consistent with a geochemical model for the core containing 5.8 wt.% oxygen and 1.9 wt.% sulfur as proposed by McDonough and Sun [McDonough, W.F., Sun, S.-S., 1995. The composition of the Earth. Chem. Geol. 120, 223-253]. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.pepi.2006.09.004

メガバール領域におけるFe-Ni合金と含水相δ-AlOOHの反応：コア-マントル境界における水素の行方

Terasaki, H, Ohtani, E, Sakai, T, Kamada, S, Asanuma, H, Sano, A, Hirao, N

Spring-8 User Experimental Report, 2007A1731 2007

Equation of state and phase relation of FeNiSi alloy to megabar pressure

Ohtani E, Asanuma H, Sakai T, Terasaki H, Kondo T, Hirao N

Spring-8 User Experimental Report 2007A1678 2007

In-situ determination of solvus in the Fe-FeO system at high temperatures and high pressures

Asahara, Y, Frost, D, Rubie, D, Terasaki, H, Tsuno, K, Nishida, K, Saikia, A, Ohtani, E

Spring-8 User Experimental Report 2006B1313 2007

Influence of water on phase transitions in forsterite and olivine compositions with implication to seismic discontinuities in the Earth's mantle

Litasov, K, Ohtani, E, Ghosh, S, Terasaki, H, Suzuki, A

Spring-8 User Experimental Report 2007A1701 2007

X-ray diffraction study of basaltic liquid at high pressure and high temperature

Sakamaki, T, Suzuki, A, Ohtani, E, Terasaki, H, Nishida

Spring-8 User Experimental Report 2007A1095 2007

Effect of pressure on the viscosity of Fe-S and Fe-C liquids up to 16 GPa Reviewed

H. Terasaki, A. Suzuki, E. Ohtani, K. Nishida, T. Sakamaki, K. Funakoshi

GEOPHYSICAL RESEARCH LETTERS 33 ( 22 ) L22307 - L22307 2006.11

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER GEOPHYSICAL UNION

The viscosity of liquid Fe78S22 was measured up to 16 GPa and 1723 K using a high-speed CCD camera system ( 125 frames/s maximum). In order to prevent a chemical reaction between the sample and a Re viscosity marker sphere, the Re spheres were coated with alumina to a thickness of 1 - 2 mu m. The measured viscosity coefficients were 3.2 - 8.5 mPa-s and the activation volume was estimated to be 1.46 cm(3)/mol. The viscosity of liquid Fe86C14 was also measured up to 4.5 GPa and 1843 K. The viscosity coefficients were 3.8 - 6.3 mPa-s. There was no large difference in viscosity coefficient and activation volume between the Fe-S and Fe-C eutectic liquids in the range of measurement. Viscosities of Fe-S and Fe-C eutectic liquids are likely to remain low in the planetary interior.

DOI： 10.1029/2006GL027147

Interaction between iron and post-perovskite at core-mantle boundary and core signature in plume source region Reviewed

Takeshi Sakai, Tadashi Kondo, Eiji Ohtani, Hidenori Terasaki, Noriaki Endo, Toshiko Kuba, Toshiaki Suzuki, Takumi Kikegawa

GEOPHYSICAL RESEARCH LETTERS 33 ( 15 ) 10.1029/2006GL026868- 2006.8

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER GEOPHYSICAL UNION

Interaction between the lower mantle and core is essential for understanding the nature of D '' layer at the core-mantle boundary (CMB). Here, we report the reaction between post-perovskite (PPv) and metallic iron under the condition of the CMB, for example, 139 GPa and 3000 Kelvin. Analytical transmission electron microscope ( ATEM) analysis revealed that significant amount of oxygen up to 6.3 weight percent (wt.%) and silicon up to 4.0 wt.% can be dissolved into molten iron. The dihedral angle between PPv and molten iron is 67 degrees. Thus, a small amount of core metal of about 2 volume percent (vol.%) can be trapped without separation in the PPv region at the CMB. The amount of core metal trapped by this mechanism can produce the isotopic signature of the outer core in the plume source at the base of the lower mantle.

DOI： 10.1029/2006GL026868

High-temperature viscosity measurements of hydrous albite liquid using in-situ falling-sphere viscometry at 2.5 GPa Reviewed

BT Poe, C Romano, C Liebske, DC Rubie, H Terasaki, A Suzuki, K Funakoshi

CHEMICAL GEOLOGY 229 ( 1-3 ) 2 - 9 2006.5

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

In-situ failing-sphere viscometry using shadow radiography in a multianvil apparatus was conducted on a series of samples along the NaAlSi3O8-H2O join up to 2.8 wt.% H2O at the Spring-8 synchrotron radiation facility (Hyogo, Japan). This allowed us to determine viscosities normally too low to be measured at ambient pressure for hydrous silicate melts at high temperatures due to rapid devolatilization. Pressure was fixed at 2.5 GPa for all experiments allowing us to gauge the effect of chemical composition on viscosity. In particular, the series of samples allowed us to vary the melt's degree of polymerization while maintaining a constant At to Si ratio. Our results show that, for all samples, viscosity decreases as a function of pressure between 1 atm and 2.5 GPa at 1550 degrees C, indicating that the pressure anomaly can still be observed as depolymerization of the melt increases from nominally 0 (dry albite liquid) to NBO/T=0.8 (assuming water speciation entirely as hydroxyl groups at experimental conditions). We also find that the magnitude of the decrease in viscosity over this pressure interval does not appear to be dependent on the amount of water in the melt (i.e., NBO/T). An explanation for this behavior might be that the molar volume, at least over this limited compositional range, is nearly constant and the effects of compression of these melts, though different in degree of polymerization, are similar. (c) 2006 Published by Elsevier B.V.

DOI： 10.1016/j.chemgeo.2006.01.010