Equation of state of hexagonal aluminous phase in basaltic composition to 63 GPa at 300 K     

S. Ono  K. Hirose  M. Isshiki  K. Mibe  Y. Saito 《Physics and Chemistry of Minerals》2002,29(8):527-531

A laser-heated diamond-anvil cell that is capable of operating up to a pressure of 63 GPa, with X-ray diffraction facilities using a synchrotron radiation source at the SPring-8, has been developed to observe the compressibility of a hexagonal aluminous phase, [K_0.15Na_1.66Ca_0.11Mg_1.29Fe²⁺ _0.86Al_3.13Ti_0.09Si_1.98] _Σ9.27O₁₂. The hexagonal aluminous phase is a potassium host mineral from the subducted oceanic crust in the Earth's lower mantle. A sample was heated using a YAG laser at each pressure increment to relax the deviatoric stress in the sample. X-ray diffraction measurements were carried out at 300 K using an angle-dispersive technique. Pressure was measured using an internal platinum pressure calibrant. The observed unit-cell volumes were used to obtain a third-order Birch–Murnaghan equation of state: unit-cell volume V _o=185.94(±16) ų, density ρ _o=4.145 g/cm³, and bulk modulus K _o=198(±3) GPa when the first pressure is derivative of the bulk modulus K ^′ _o is fixed to 4. The density of hexagonal aluminous phase is lower than that of coexisting Mg-perovskite in the subducted oceanic crust.  相似文献   

Compressibility of the calcium aluminosilicate, CAS, phase to 44 GPa     

Shigeaki Ono  Tsuyoshi Iizuka  Takumi Kikegawa 《Physics of the Earth and Planetary Interiors》2005,150(4):331-338

In situ X-ray diffraction measurements on a calcium aluminosilicate (CAS) phase have been carried out using a laser-heated diamond anvil cell up to a pressure of 44 GPa, employing a synchrotron radiation source. CAS is the major mineral formed from sediments subducted into the Earth's mantle. The sample was heated using a YAG laser after each pressure increment to relax the deviatoric stress in the sample. X-ray diffraction measurements were carried out at T = 300 K using an angle-dispersive technique. The pressure was calculated using an internal platinum metal pressure calibrant. The Birch–Murnaghan equation of state for the CAS phase obtained from the experimental unit cell parameters showed a density of ρ₀ = 3.888 g/cm³ and a bulk modulus of K₀ = 229 ± 9 GPa for K^′₀ = 4.7 ± 0.7. When the first pressure derivative of the bulk modulus was fixed at K^′₀ = 4, then the value of K₀ = 239 ± 2 GPa. From the experimental compressibility, the density of the CAS phase was observed to be lower than the density of co-existing Al-bearing stishovite, calcium perovskite, calcium ferrite-type phases, and (Fe,Al)-bearing Mg-perovskite in subducted sediments in the lower mantle. Therefore, the density of subducted sediments in the lower mantle decreases with increasing mineral proportion of the CAS phase.  相似文献   

Magnetic grain‐size distribution of the enhanced component in the loess–palaeosol sequences in the western Loess Plateau of China     

Toshiaki Mishima  Masayuki Torii  Hitoshi Fukusawa  Yugo Ono  Xiao-Min Fang  Bao-Tian Pan  Ji-Jun Li 《Geophysical Journal International》2001,145(2):499-504

  相似文献   

Accuracy of gravimetric deflections of the vertical and optimization of gravity networks     

S. Ono 《Journal of Geodesy》1985,59(3):275-288

In order to solve the problems of determining the shape of a part of the earth of national or continental extent, that is, of rigorous constituting and computing of the astrogeodetic network, it is required to determine gravimetric deflections of the vertical with an accuracy of, say, 0″.3. For this it is adequate to carry out additional gravity surveys in the neighborhoods of computation points, in addition to a given uniform gravity survey (normal density gravity survey). The study offers a method to determine the optimal distribution of gravity stations in such a gravity survey, which guarantees a given accuracy of computed gravimetric deflections of the vertical for a given statistical condition which characterizes the variation of the gravity field. The approach used here is based on the concept of the error of representation and the error propagation of Vening Meinesz integrals.  相似文献   

Unique deformation processes involving the recrystallization of chrysotile within serpentinite: implications for aseismic slip events within subduction zones     

Ken‐ichi Hirauchi  Haruka Yamaguchi 《地学学报》2007,19(6):454-461

Serpentinite bodies within the Franciscan Complex, a Mesozoic accretionary prism located in California, USA, display a unique form of deformation that involves the recrystallization of chrysotile and the formation of a block‐in‐matrix structure. The phacoidal‐shaped blocks have a preferred orientation, and result from the local replacement of serpentine minerals by chrysotile grains that are aligned parallel to ductile shear planes such as S–C foliation; ultimately, some of the rocks evolved into chrysotile schist. The relic blocks are also fragmented into multiple parts, with the spaces between fragments being infilled by recrystallized chrysotile. The low coefficient of friction of chrysotile means that this deformation process acts to suppress the frictional properties of the entire serpentinite body within the forearc mantle. This phenomenon can be attributed to the slip style that occurs in aseismic regions of subduction zones in areas shallower than the stability field of antigorite.  相似文献   

A new high-pressure phase of strontium carbonate     

Shigeaki Ono  Miki Shirasaka  Takumi Kikegawa  Yasuo Ohishi 《Physics and Chemistry of Minerals》2005,32(1):8-12

High-pressure and high-temperature experiments conducted in a laser-heated diamond-anvil cell with a synchrotron X-ray diffraction method have revealed a phase transformation in the aragonite-type SrCO₃ at pressures above 10 GPa. The new phase has an orthorhombic symmetry and was confirmed to remain stable to 32 GPa. The Birch-Murnaghan equation of state for new phase was determined from the experimental unit cell parameters, with K₀ = 101 (± 16) GPa, K₀ = 4 (constrained value), and V₀ = 111.9 (± 2.2). This transformation in SrCO₃ is different from that in BaCO₃ as reported in previous studies. After decompression at ambient pressure, the high-pressure phase transforms to a metastable structure, which has an orthorhombic symmetry. This result should also resolve a dispute regarding the stable high-pressure phases in BaCO₃, which is an analog material of CaCO₃ and SrCO₃.This revised version was published in February 2005 with corrections to the Introduction and to the References.  相似文献   

Comparison of Time-Dependent Tracer Ages in the Western North Pacific: Oceanic Background Levels of (SF6, CFC-11, CFC-12 and CFC-113     

Yutaka W. Watanabe  Akifumi Shimamoto  Tsuneo Ono 《Journal of Oceanography》2003,59(5):719-729

To verify the actual usefulness of time-dependent tracer dating techniques in the ocean, we simultaneously obtained two cross sections of sulfur hexafluoride (SF₆) and chlrofluoromethanes (CFC-11, trichlorofluoromethane; CFC-12, dichloro-difluromethane; CFC-113, trichlorotrifluoroethane) in the western North Pacific in 1998. The vertical distribution patterns of SF₆ and CFC-113 were similar in shape to those of CFC-11 and CFC-12. Maximum penetration depths of SF₆ and CFC-113 remained around 800 m in the subpolar region and 400 m in the tropical region, while the maximum penetration depths of CFC-11 and CFC-12 were still found below 1000 m depth. We also found all maximum contents of these tracers around 26.6−26.8σ_θ with a gradual decrease southward. This suggested that a new subsurface water mass in the subpolar region spread out over the entire North Pacific, which agrees closely with previous studies based on the salinity minimum. Moreover, we compared the tracer ages (the elapsed period of a water mass from when the water mass left from the ocean surface) using ten time-dependent tracer dating techniques, CFC-11, CFC-12, CFC-113, SF₆, CFC-11/CFC-12, CFC-113/CFC-11, CFC-113/CFC-12, SF₆/CFC-11, SF₆/CFC-12 and SF₆/CFC-113. This quantitative evaluation of multiple tracer dating techniques in the ocean was the first confirmation of its usefulness based on the observational data on the ocean basin-wide scale. We conclude that SF₆/CFC-11, SF₆/CFC-12, SF₆/CFC-113 and SF₆ dating techniques would be the most promising tools for determining the age of water mass not only just for the past several decades but for the future, too. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Reynolds-Number Dependence of Gas Dispersion Over a Wavy Wall     

Takenobu Michioka  Hiroshi Takimoto  Hiroki Ono  Ayumu Sato 《Boundary-Layer Meteorology》2017,162(3):401-426

Direct numerical simulations of an Ekman layer are performed to study flow evolution during the response of an initially neutral boundary layer to stable stratification. The Obukhov length, L, is varied among cases by imposing a range of stable buoyancy fluxes at the surface to mimic ground cooling. The imposition of constant surface buoyancy flux , i.e. constant-flux stability, leads to a buoyancy difference between the ground and background that tends to increase with time, unlike the constant-temperature stability case where a constant surface temperature is imposed. The initial collapse of turbulence in the surface layer owing to surface cooling that occurs over a time scale proportional to \(L/u_*\), where \(u_*\) is the friction velocity, is followed by turbulence recovery. The flow accelerates, and a “low-level jet” (LLJ) with inertial oscillations forms during the turbulence collapse. Turbulence statistics and budgets are examined to understand the recovery of turbulence. Vertical turbulence exchange, primarily by pressure transport, is found to initiate fluctuations in the surface layer and there is rebirth of turbulence through enhanced turbulence production as the LLJ shear increases. The turbulence recovery is not monotonic and exhibits temporal intermittency with several collapse/rebirth episodes. The boundary layer adjusts to an increase in the surface buoyancy flux by increased super-geostrophic velocity and surface stress such that the Obukhov length becomes similar among the cases and sufficiently large to allow fluctuations with sustained momentum and heat fluxes. The eventual state of fluctuations, achieved after about two inertial periods (\(ft \approx 4\pi \)), corresponds to global intermittency with turbulent patches in an otherwise quiescent background. Our simplified configuration is sufficient to identify turbulence collapse and rebirth, global and temporal intermittency, as well as formation of low-level jets, as in observations of the stratified atmospheric boundary layer.  相似文献   

First-principles simulation of high-pressure polymorphs in MgAl<Subscript>2</Subscript>O<Subscript>4</Subscript>     

Shigeaki Ono  John P. Brodholt  G. David Price 《Physics and Chemistry of Minerals》2008,35(7):381-386

We have used density functional theory to investigate the stability of MgAl₂O₄ polymorphs under pressure. Our results can reasonably explain the transition sequence of MgAl₂O₄ polymorphs observed in previous experiments. The spinel phase (stable at ambient conditions) dissociates into periclase and corundum at 14 GPa. With increasing pressure, a phase change from the two oxides to a calcium-ferrite phase occurs, and finally transforms to a calcium-titanate phase at 68 GPa. The calcium-titanate phase is stable up to at least 150 GPa, and we did not observe a stability field for a hexagonal phase or periclase + Rh₂O₃(II)-type Al₂O₃. The bulk moduli of the phases calculated in this study are in good agreement with those measured in high-pressure experiments. Our results differ from those of a previous study using similar methods. We attribute this inconsistency to an incomplete optimization of a cell shape and ionic positions at high pressures in the previous calculations.  相似文献   

High-pressure phase transformations of FeS: Novel phases at conditions of planetary cores     

Shigeaki Ono  Artem R. Oganov  John P. Brodholt  Lidunka Vo adlo  Ian G. Wood  Andriy Lyakhov  Colin W. Glass  Alexander S. Ct  G. David Price 《Earth and Planetary Science Letters》2008,272(1-2):481-487

Iron sulfide (FeS) was investigated using first-principles calculations up to a pressure of 400 GPa. A number of new phase transitions were found. An antiferromagnetic MnP-type structure, FeS II, was confirmed to be stable at low pressures, whereas at high pressures (40–135 GPa) we find a new stable phase, with a non-magnetic MnP-type structure, FeS VI. The observed first-order change in the cell shape between the two phases can be explained by the difference in magnetic configurations. The calculated cell parameters, atomic coordinates, and bulk modulus of non-magnetic MnP-type phase are consistent with those determined from experiment. The upper pressure limit of the stability of the non-magnetic MnP-type phase was calculated to be 135 GPa. A hitherto unsuspected phase transition from the non-magnetic MnP-type to a phase with Pmmn symmetry, FeS VII, was identified using the evolutionary crystal structure prediction (USPEX) method. The structure of the Pmmn phase has no known analogues, but can be described as a distortion of the NaCl-type structure. The Pmmn phase with the distorted NaCl-type structure is stable from 135 GPa at least up to 400 GPa. According to previous experiments and the present study, the transition sequence of FeS at low temperatures is as follows: troilite ➔ antiferromagnetic MnP-type phase ➔ monoclinic phase ➔ non-magnetic MnP-type phase ➔ Pmmn phase. The calculated volume reduction from the monoclinic to the non-magnetic MnP-type phase is 1.0% at 40 GPa, which is in good agreement with experimental observations. The calculated volume reduction from the non-magnetic MnP-type to the Pmmn phase is 3.7% at 135 GPa.  相似文献