The stability and equation of state for the cotunnite phase of TiO2 up to 70 GPa     

Daisuke Nishio-Hamane  Asa Shimizu  Ritsuko Nakahira  Ken Niwa  Asami Sano-Furukawa  Taku Okada  Takehiko Yagi  Takumi Kikegawa 《Physics and Chemistry of Minerals》2010,37(3):129-136

The stability and equation of state for the cotunnite phase in TiO₂ were investigated up to a pressure of about 70 GPa by high-pressure in situ X-ray diffraction measurements using a laser-heated diamond anvil cell. The transition sequence under high pressure was rutile → α-PbO₂ phase → baddeleyite phase → OI phase → cotunnite phase with increasing pressure. The cotunnite phase was the most stable phase at pressures from 40 GPa to at least 70 GPa. The equation of state parameters for the cotunnite phase were established on the platinum scale using the volume data at pressures of 37–68 GPa after laser annealing, in which the St value, an indicator of the magnitude of the uniaxial stress component in the samples, indicates that these measurements were performed under quasi-hydrostatic conditions. The third-order Birch-Murnaghan equation of state at K ₀′ = 4.25 yields V ₀ = 15.14(5) cm³/mol and K ₀ = 294(9), and the second-order Birch-Murnaghan equation of state yields V ₀ = 15.11(5) cm³/mol and K ₀ = 306(9). Therefore, we conclude that the bulk modulus for the cotunnite phase is not comparable to that of diamond.  相似文献   

Lawsonite-bearing eclogitic metabasites in the Cazadero area, northern California   总被引：5，自引：0，他引：5  

H. Shibakusa  H. Maekawa 《Mineralogy and Petrology》1997,61(1-4):163-180

Summary In the Cazadero area, northern California, Lawsonite-bearing eclogitic metabasites occur in association with glaucophane schists. Lawsonite-bearing eclogitic metabasites are coarse-grained, and characteristically lack albite. Representative mineral assemblages are; (1) garnet + omphacite + Lawsonite + epidote + glaucophane + chlorite + quartz, (2) garnet -F- omphacite + Lawsonite + pumpellyite + glaucophane + actinolite + quartz, (3) garnet + omphacite + Lawsonite + pumpellyite + epidote + glaucophane + quartz. They can be represented on an A1₂O₃-Fe₂O₃-MgO-Na₂O diagram in which all minerals are projected from quartz, Lawsonite, almandine garnet, and H₂O-predominant fluid. On the basis of the garnet-clinopyroxene geothermometry and phase relations, the metamorphic conditions for the formation of Lawsonite-bearing eclogitic metabasites are estimated at 360-445 °C and more than 9 ± 1 kbar. Lawsonite-bearing eclogitic metabasites formed near the univariant curve albite = jadeite +quartz. A petrogenetic grid constructed by Schreinemakers' method shows that the Lawsonite-bearing eclogitic metabasites in the Cazadero area formed under transitional P-T conditions between those of the garnet-bearing glaucophane schists in New Caledonia and lawsonitebearing eclogitic metabasites in Corsica.Zusammenfassung Im Gebiet um Cazadero, Nordkalifornien, kommen Lawsonit-führende eklogitische Metabasite in Assoziation mit Glaukophanschiefern vor. Den grobkörnigen Lawsonitführenden Metabasiten fehlt charakteristischerweise Albit. Repräsentative Mineralparagenesen sind: (1) Granat + Omphacit + Lawsonit + Epidot + Glaukophan + Chlorit + Quarz, (2) Granat + Omphacit + Lawsonit + Pumpellyit + Glaukophan + Aktinolith + Quarz, (3) Granat + Omphacit +Lawsonit + Pumpellyit + Epidot + Glaukophan + Quarz. Sie lassen sich in einem A1₂O₃-Fe₂O₃-MgO-Na₂O Diagramm, in dem alle Minerale von Quarz, Lawsonit, Almandin-reichem Granat und einem H₂O-dominierten Fluid projiziert werden, darstellen. Die Metamorphosebedingungen der Lawsonitführenden eklogitischen Metabasite werden auf Grund von Granat-Klinopyroxenthermometrie und der Phasenbeziehungen mit 360-445°C und mehr als 9 ± 1 kbar abgeschätzt. Die Lawsonit-führenden eklogitischen Metabasite bildeten sich nahe der univarianten Reaktion Albit = Jadeit +Quarz. Ein petrogenetisches Netz, konstruiert nach der Schreinemakers Methode, zeigt, daß die P-T Bedingungen der Lawsonitführenden eklogitischen Metabasite im Gebiet von Cazadero im übergangsbereich zwischen jenen von Granat-führenden Glaukophanschiefern in Neukaledonien und Lawsonit-führenden eklogitischen Metabasiten in Korsika liegen.

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Lawsonit-führende eklogitische Metabasite im Gebiet um Cazadero, Nordkalifornien

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With 9 Figures  相似文献   

Community structures of coral reefs around Peninsular Malaysia     

Tatsuki Toda  Tomoko Okashita  Takeshi Maekawa  Bin Abdul Adzis Kee Alfian  Mohd Kushairi Mohd Rajuddin  Ryota Nakajima  Wenxi Chen  Kunio T. Takahashi  Bin Haji Ross Othman  Makoto Terazaki 《Journal of Oceanography》2007,63(1):113-123

Coral community structures at eleven fringing reef sites were investigated along the coast of Peninsular Malaysia. Estimated coverage of coral communities is examined by applying quantitative digital image analysis to the line transect method. Four coral community types were characterized by dominant genera and lifeforms: Acropora branching community, Montipora-Acropora community, Porites massive community, and Heliopora community. Live coral coverage in all study sites ranged from 17.9% to 68.6%. Most reefs were in “fair” condition while some reefs were shown to be in “poor” condition. Coral community structures among the study sites were divided into the west coast of Peninsular Malaysia with a dominant Porites massive lifeform, and the east coast with a variety of lifeform categories of Montipora and Acropora. Physical effects such as the monsoon wind regime and sedimentation are likely to influence the formation of dominant coral communities around Peninsular Malaysia.  相似文献   

Development of density measurement for metals at high pressures and high temperatures using X-ray absorption imaging combined with externally heated diamond anvil cell     

Yusaku Takubo  Hidenori Terasaki  Tadashi Kondo  Shingo Mitai  Seiji Kamada  Takumi Kikegawa  Akihiko Machida 《Comptes Rendus Geoscience》2019,351(2-3):182-189

A technique for density measurement under high pressure and high temperature was developed using the X-ray absorption imaging method combined with an externally heated diamond anvil cell. The densities of solid and liquid In were measured in the pressure and temperature ranges of 3.2–18.6 GPa and 294–719 K. The densities obtained through the X-ray absorption imaging method were in good agreement (less than 2.0% difference) with those obtained through X-ray diffraction. Based on the measured density, the isothermal bulk modulus of solid In is determined as 48.0 ± 1.1?40.9 ± 0.8 GPa at 500 K, assuming K′ = 4 to 6. The compression curve of liquid In approaches that of solid In at higher pressures and does not cross over the solid compression curve in the measurement range. The present technique enables us to determine the densities of both solids and liquids precisely in a wide pressure and temperature range.  相似文献   

A numerical study of polar ionospheric currents     

Hiroshi Maeda  Koichiro Maekawa 《Planetary and Space Science》1973,21(8):1287-1300

Numerical calculations for the electric current in the polar ionosphere have been made by assuming some realistic distributions of the electric field and conductivity. Two dynamo actions are taken into account; one of which is induced by ionospheric winds and the other by the solar wind. For the solar wind dynamo action, it is found that the secondary polarization field caused by non-uniform distribution of ionospheric conductivity is much larger than the primary field induced by the solar wind, suggesting its important effect on charged particles in the magnetosphere, and that the irrotational current having a source and sink is of the same order of magnitude as the solenoidal current closing its circuit in the ionosphere. It is also found that the solar wind is, in general, more effective than the ionospheric winds in producing polar current systems such as DP 1 and 2, but in some cases the ionospheric winds have a significant effect on the current distribution.  相似文献   

Iron-water reaction at high pressure and temperature, and hydrogen transport into the core     

Eiji Ohtani  Naohisa Hirao  Tadashi Kondo  Masayoshi Ito  Takumi Kikegawa 《Physics and Chemistry of Minerals》2005,32(1):77-82

We observed a direct reaction of metallic iron with water to form iron hydride and iron oxide, 3Fe + H₂O–>2FeH_x + FeO, at pressures from 6 GPa to 84 GPa and temperatures above 1,000 K in diamond anvil cell (DAC). Iron hydride is dhcpFeH_x or -FeH_x, and iron oxide has the rhombohedral or B1 structure at pressures at least up to 37 GPa. The formation of an assembly composed of dhcpFeH_x and FeO with the B8 structure was observed at 84 GPa. In primordial Earth, water formed by dehydration of the low temperature primitive materials reacts with metallic iron in the high temperature component to form iron hydride FeH_x and iron oxide FeO. The former would be incorporated in the iron forming the core. Thus hydrogen could be an important element of the Earths core. This reaction would be essential for transport of hydrogen into the core in the accretion stage of the Earth.  相似文献   

Modelling the Mont Terri HE-D experiment for the Thermal–Hydraulic–Mechanical response of a bedded argillaceous formation to heating     

B. Garitte  T. S. Nguyen  J. D. Barnichon  B. J. Graupner  C. Lee  K. Maekawa  C. Manepally  G. Ofoegbu  B. Dasgupta  R. Fedors  P. Z. Pan  X. T. Feng  J. Rutqvist  F. Chen  Jens Birkholzer  Q. Wang  O. Kolditz  H. Shao 《Environmental Earth Sciences》2017,76(9):345

Coupled thermal–hydrological–mechanical (THM) processes in the near field of deep geological repositories can influence several safety features of the engineered and geological barriers. Among those features are: the possibility of damage in the host rock, the time for re-saturation of the bentonite, and the perturbations in the hydraulic regime in both the rock and engineered seals. Within the international cooperative code-validation project DECOVALEX-2015, eight research teams developed models to simulate an in situ heater experiment, called HE-D, in Opalinus Clay at the Mont Terri Underground Research Laboratory in Switzerland. The models were developed from the theory of poroelasticity in order to simulate the coupled THM processes that prevailed during the experiment and thereby to characterize the in situ THM properties of Opalinus Clay. The modelling results for the evolution of temperature, pore water pressure, and deformation at different points are consistent among the research teams and compare favourably with the experimental data in terms of trends and absolute values. The models were able to reproduce the main physical processes of the experiment. In particular, most teams simulated temperature and thermally induced pore water pressure well, including spatial variations caused by inherent anisotropy due to bedding.  相似文献