Titanochondrodite and titanoclinohumite derived from the upper mantle in the Buell Park Kimberlite,Arizona, USA   总被引：2，自引：0，他引：2  

Ken-ichiro Aoki  Kiyoshi Fujino  Masaki Akaogi 《Contributions to Mineralogy and Petrology》1976,56(3):243-253

Kimberlite from Buell Park, Arizona, which was intruded into Permian sediments about 30 m.y. ago, is characterized by the hydrous silicates titanochondrodite and titanoclinohumite. Titanochondrodite is the first finding in kimberlites. Optical properties, chemical compositions and cell dimensions of these two minerals are determined.Titanochondrodite and titanoclinohumite are considered to crystallize from kimberlite magma at a depth of about 100 km and at 1,000° C, on the basis of kimberlite mineralogy, petrography and high pressure experimental work. Although there is no direct evidence, the importance of these two minerals in peridotite wedges above sinking lithosphere at the continental margins is also discussed.  相似文献   

Longshot experiments to study velocity anisotropy in the oceanic lithosphere of the northwestern Pacific   总被引：1，自引：0，他引：1  

H. Shimamura  T. Asada  K. Suyehiro  T. Yamada  H. Inatani 《Physics of the Earth and Planetary Interiors》1983,31(4):348-362

Several long-range explosion seismology experiments have been conducted in the northwestern Pacific basin, where one of the oldest oceanic lithospheres is postulated to exist. The experiments were conducted from 1974 to 1980. Highly sensitive ocean-bottom seismographs which had been developed for longshot experiments were used. The lengths of the profiles ranged from 1000 to 1800 km, and the directions were chosen to provide wide azimuthal coverage. One of the aims of this series of experiments was to test the existence of velocity anisotropy on a large, regional scale.The results show that the oceanic lithosphere has anisotropy wherein the velocity changes by 4–7%. The anisotropy extends from a depth of at least 40 to 140 km beneath the sea bottom; however, the magnitude of the anisotropy may vary with depth. The azimuth of the maximum velocity is 150–160° clockwise from north, and coincides with the “fossil” direction of spreading of the Pacific plate, whereas it differs from the present direction of plate motion by ～ 30°. The azimuth does not seem to depend on depth. In the direction of maximum velocity, the lithosphere is basically two-layered: 8.0–8.2 and 8.6 km s^?1. The depth of the interface is 50–60 km beneath the sea floor.  相似文献   

Normal faulting of the Daiichi-Kashima Seamount in the Japan Trench revealed by the Kaiko I cruise, Leg 3     

Kazuo Kobayashi  Jean-Paul Cadet  Jean Aubouin  Jacques Boulgue  Jacques Dubois  Roland von Huene  Laurent Jolivet  Toshihiko Kanazawa  Junzo Kasahara  Kin-ichiro Koizumi  Serge Lallemand  Yasuo Nakamura  Guy Pautot  Kiyoshi Suyehiro  Shin Tani  Hidekazu Tokuyama  Toshitsugu Yamazaki 《Earth and Planetary Science Letters》1987,83(1-4)

A detailed topographic and geophysical survey of the Daiichi-Kashima Seamount area in the southern Japan Trench, northwestern Pacific margin, clearly defines a high-angle normal fault which splits the seamount into two halves. A fan-shaped zone was investigated along 2–4 km spaced, 100 km long subparallel tracks using narrow multi-beam (Seabeam) echo-sounder with simultaneous measurements of gravity, magnetic total field and single-channel seismic reflection records. Vertical displacement of the inboard half was clearly mapped and its normal fault origin was supported. The northern and southern extensions of the normal fault beyond the flank of the seamount were delineated. Materials on the landward trench slope are displaced upward and to sideways away from the colliding seamount. Canyons observed in the upper landward slope terminate at the mid-slope terrace which has been uplifted since start of subduction of the seamount. Most of the landward slope except for the landward walls aside the seamount comprises only a landslide topography in a manner similar to the northern Japan Trench wall. This survey was conducted on R/V “Jean Charcot” as a part of the Kaiko I cruise, Leg 3, in July–August 1984 under the auspices of the French-Japanese scientific cooperative program.  相似文献   

Spectroscopic properties of Cr-doped melilite crystals     

Akiko Sugimoto  Yukio Nobe  Takafumi Yamazaki  Yutaka Anzai  Kiyoshi Yamagishi  Yusaburo Segawa  Humihiko Takei 《Physics and Chemistry of Minerals》1997,24(5):326-332

 Four kinds of Cr-droped melilite crystals, Ca₂MgSi₂O₇ (akermanite), CaAl₂SiO₇ (gehlenite), CaGa₂SiO₇ (Ga-gehlenite) and CaGa₂GeO₇ (GaGe-gehlenite), with different sizes of the sites for Cr ions to substitute, were grown in series, using both the CZ and FZ techniques. Although Cr⁴⁺ is regarded as a major species in melilites, the existence of Cr⁶⁺ in gehlenite is also suggested from the change in absorption spectra by annealing, and the dependence of distribution coefficient of Cr ions on growth atmosphere. Spectral peak shifts are not obvious if the host crystal field is altered in melilites, because the local environment of the sites for Cr ion is possibly changed by reforming the packing features of the host lattice. Received February 7, 1996 / Revised, accepted September 20, 1996  相似文献   

Coda Q in two-layer random media     

Kiyoshi Yomogida  Keiiti Aki  Rafael Benites 《Geophysical Journal International》1997,128(2):425-433

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Plastic deformation of garnets: systematics and implications for the rheology of the mantle transition zone   总被引：14，自引：0，他引：14  

Shun-ichiro Karato  Zichao Wang  Bofa Liu  Kiyoshi Fujino 《Earth and Planetary Science Letters》1995,130(1-4):13-30

Plastic properties of materials with garnet structure have been studied under wide temperature conditions, ranging from room temperature to 95% of the melting temperatures, using uniaxial compression and hot microhardness tests. Garnets studied include single crystals of oxide garnets (Y₃Al₅O₁₂, Gd₃Ga₅O₁₂ and Y₃Fe₅O₁₂) and silicate garnets (various solid solutions, including grossular, almandine, andradite, pyrope, spessartine and uvarovite). Both uniaxial compression and hot hardness tests indicate that there is a general trend in the plasticity of garnets when the data are compared at normalized conditions (T/T_m andσ/μ), and that the resistance to plastic deformation in garnets is significantly higher than most of the other minerals in the Earth's mantle. Based on both stress-dip tests and microstructural observations, it is proposed that the creep strength of garnet is largely controlled by the resistance to dislocation glide rather than by recovery processes. This conclusion is consistent with the high Peierls stress inferred from the hot hardness tests. The high Peierls stress in garnets is, presumably, due to the large unit cell (i.e., long Burgers vectors) and/or the bcc packing, which are common to all garnets. We postulate, therefore, that the present results can be applied to the strength of high-pressure garnet (majorite) and suggest that garnet-rich layers in the Earth, such as subducted oceanic crust in the transition zone or a possibly garnet-rich (bottom part of the) transition zone, will be considerably stronger than surrounding regions.  相似文献   

Fate of carbonates within oceanic plates subducted to the lower mantle, and a possible mechanism of diamond formation     

Yusuke Seto  Daisuke Hamane  Takaya Nagai  Kiyoshi Fujino 《Physics and Chemistry of Minerals》2008,35(4):223-229

We report on high-pressure and high-temperature experiments involving carbonates and silicates at 30–80 GPa and 1,600–3,200 K, corresponding to depths within the Earth of approximately 800–2,200 km. The experiments are intended to represent the decomposition process of carbonates contained within oceanic plates subducted into the lower mantle. In basaltic composition, CaCO₃ (calcite and aragonite), the major carbonate phase in marine sediments, is altered into MgCO₃ (magnesite) via reactions with Mg-bearing silicates under conditions that are 200–300°C colder than the mantle geotherm. With increasing temperature and pressure, the magnesite decomposes into an assemblage of CO₂ + perovskite via reactions with SiO₂. Magnesite is not the only host phase for subducted carbon—solid CO₂ also carries carbon in the lower mantle. Furthermore, CO₂ itself breaks down to diamond and oxygen under geotherm conditions over 70 GPa, which might imply a possible mechanism for diamond formation in the lower mantle.  相似文献   

Intensity of radiation reflected by a vertically inhomogeneous medium through multiple scattering     

Kiyoshi Kawabata  Ryuko Hirata 《Astrophysics and Space Science》1985,109(2):345-356

To facilitate the computation of the radiative intensity reflected, upon multiple scattering, by a vertically inhomogeneous medium, an implicit formula for integrating the invariant imbedding equation for Fourier-decomposed reflection function is derived starting with the formal solution: the height variations of the single-scattering albedo and the phase function characterizing the degree of inhomogeneity are thereby approximated by piece-wise, but continuous, linear functions of optical height , while the reflection function is approximated by a piece-wise quadratic polynomial in over each integration step. Using these approximations, the integration involved in the formal solution is then carried out analytically, yielding a correctortype formula for finding the reflection function at each step of . It is expected that this formula is capable of handling general cases of inhomogeneous media where both single-scattering albedo and phase function are allowed to vary continuously with height.Similar, but explicit expressions are also derived for the single and the second-order scattering solutions, with which the higher-order Fourier terms of reflection function are to be approximated, thereby enabling us to avoid the iterative process.  相似文献   

Redox processes and occurrence of arsenic in a volcanic aquifer system of Kumamoto Area,Japan     

Shahadat Hossain  Takahiro Hosono  Kiyoshi Ide  Midori Matsunaga  Jun Shimada 《Environmental Earth Sciences》2016,75(9):740

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Economic implications of climate change impacts on human health through undernourishment     

Tomoko Hasegawa  Shinichiro Fujimori  Kiyoshi Takahashi  Tokuta Yokohata  Toshihiko Masui 《Climatic change》2016,136(2):189-202

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