Variation of rare earth concentrations in pigeonitic and hypersthenic rock series from Izu-Hakone region,Japan     

Toshihiko Yajima  Hideo Higuchi  Hiroshi Nagasawa 《Contributions to Mineralogy and Petrology》1972,35(3):235-244

The abundances of rare earth elements in 5 each of aphyric volcanic rocks of pigeonitic and hypersthenic rock series from Izu-Hakone region have been determined by neutron activation analysis. Pigeonitic rock series show rare earth patterns with relative depletion of lighter rare earths (low lanthanum type) and large increase in rare earth abundances with differentiation. Hypersthenic rock series show higher lanthanum abundances (high lanthanum type) compared with pigeonitic rock series. The differences in rare earth patterns between two rock series are compatible with the theory of independent magmatic generation of these two series. Variation of rare earth patterns in both series have been examined by a model of magmatic differentiation based on the observed rare earth partition coefficients.  相似文献   

Specimen-apparatus interaction during stick-slip in a tri axial compression machine: A decoupled two-degree-of-freedom model     

Toshihiko Shimamoto  John Handin  John M. Logan 《Tectonophysics》1980,67(3-4)

The stick-slip of frictional sliding depends not only on material properties but also on the elastic and inertial properties of the loading system. To compare data from different testing machines or to apply them to the problem of natural seismogenic faulting, one must account for the differences in stiffness and mass. We develop a simple mechanical model to describe the stick-slip oscillation during frictional sliding in a triaxial-compression machine. The experimental system, the loading frame and rock specimen with precut sliding surface, is divided into two subsystems across this surface. The model is based upon two key assumptions: the kinetic friction is constant regardless of the relative motion of the subsystems, and the elastic restoring force is uniform throughout each subsystem. The first assumption leads to the decoupling of the subsystems, and the behavior of each becomes mathematically analogous to that of a simple spring/mass/slider-block model, owing to the second assumption. The theory agrees well with the experimental data from the dynamic measurements of stick-slip. The displacement-time function is of cosine form, the rise time of stick-slip is constant, and the relation between force drop and average displacement rate is linear. From this model we argue that the differences in the frictional behavior of experimental fault-gouges may indeed be ascribed to differences in the material properties of their specimens because the elastic and inertial properties of a particular testing machine are little influenced by the specimen itself, so long as all specimens are of about the same size. However, interlaboratory correlations may well be invalid unless machine effects are properly accounted for.  相似文献   

Andradite and andradite-grossular solid solutions in very low-grade regionally metamorphosed rocks in Southern New Zealand     

D. S. Coombs  Y. Kawachi  B. F. Houghton  G. Hyden  I. J. Pringle  J. G. Williams 《Contributions to Mineralogy and Petrology》1977,63(3):229-246

Almost pure andradite and intermediate members of the andradite-grossular series (gros_40–49, and _47–54, py_0–3, alm_0–3, spess_0–2, hydrogarnet_0–3), often framboidal in habit, are widespread in metabasites including lavas, minor intrusions, and volcanic sandstones and breccias metamorphosed under prehnite-pumpellyite and pumpellyite-actinolite facies conditions, possibly extending into the zeolite facies. Coexisting phases include iron-rich epidotes (100 Fe*/Fe*+Al=22–34), pumpellyite, prehnite, actinolite, and chlorite, electron microprobe analyses of which are given, as well as quartz, albite, and calcite. Zoisite (100 Fe*/Fe*+Al=1–5) and iron-poor epidote (100 Fe*/Fe*+Al=11–18) occur in 2 rocks in pseudomorphs after plagioclase together with more iron-rich epidote, but not in close association with the garnets. Coexisting pumpellyite is iron-rich (FeO* 9–14%) in the prehnite-pumpellyite facies and iron-poor (FeO* 5%) in the pumpellyiteactinolite facies. Chlorites and actinolites vary widely and sympathetically in FeO/MgO+FeO ratio. Andradite is also described from a stilpnomelane-actinolite-hematite-bearing andradite quartzite of the pumpellyite-actinolite facies. Conditions of formation involved temperatures of 300 to 400 ° or less, at pressures up to a few kilobars. A wide range of oxygen fugacities is possible, but in the fluid phase was low. Grandite and chlorite are incompatible in the pumpellyite-actinolite and greenschist facies in the presence of quartz but the 2 minerals occur together in some pumpellyite-actinolite facies assemblages as a result of incomplete reaction and/or local deficiency in silica. In the greenschist facies the association is replaced by epidote-actinolite±hematite and sodic amphibole. Whereas at medium to high grades of metamorphism andradite and grandite are characteristic of skarns irrespective of , at very low grades they are found in mafic volcanic rocks and volcanogenic sediments as well as in certain cherty rocks of unusual composition, rodingites, and serpentinites, where was very low.  相似文献   

Three‐dimensional shapes and Fe contents of Stardust impact tracks: A track formation model and estimation of comet Wild 2 coma dust particle densities     

Yosuke IIDA  Akira TSUCHIYAMA  Toshihiko KADONO  Kanako SAKAMOTO  Tomoki NAKAMURA  Kentaro UESUGI  Tsukasa NAKANO  Michael E. ZOLENSKY 《Meteoritics & planetary science》2010,45(8):1302-1319

Abstract– We investigated three‐dimensional structures of comet Wild 2 coma particle impact tracks using synchrotron radiation (SR) X‐ray microtomography at SPring‐8 to elucidate the nature of comet Wild 2 coma dust particles captured in aerogel by understanding the capture process. All tracks have a similar entrance morphology, indicating a common track formation process near the entrance by impact shock propagation irrespective of impactor materials. Distributions of elements along the tracks were simultaneously measured using SR‐XRF. Iron is distributed throughout the tracks, but it tends to concentrate in the terminal grains and at the bottoms of bulbs. Based on these results, we propose an impact track formation process. We estimate the densities of cometary dust particles based on the hypothesis that the kinetic energy of impacting dust particles is proportional to the track volume. The density of 148 cometary dust particles we investigated ranges from 0.80 to 5.96 g cm^?3 with an average of 1.01 (±0.25) g cm^?3. Moreover, we suggest that less fragile crystalline particles account for approximately 5 vol% (20 wt%) of impacting particles. This value of crystalline particles corresponds to that of chondrules and CAIs, which were transported from the inner region of the solar system to the outer comet‐forming region. Our results also suggest the presence of volatile components, such as organic material and perhaps ice, in some bulbous tracks (type‐C).  相似文献   

Spatial heterogeneity in near surface aerosol characteristics across the Brahmaputra valley     

Binita Pathak  Arup Borgohain  Pradip Kumar Bhuyan  Shyam Sundar Kundu  S Sudhakar  Mukunda M Gogoi  Toshihiko Takemura 《Journal of Earth System Science》2014,123(4):651-663

In order to examine the spatial variability of the aerosol characteristics across the Brahmaputra valley, a land campaign was conducted during late winter (February 3–March 2) 2011. Measurements of particulate matter (PM, PM₁₀, PM_2.5) and black carbon (BC) concentrations were made onboard an interior redesigned vehicle. The length of the campaign trail stretched about 700 km, covering the longitude belt of 89.97°–95.55°E and latitude belt of 26.1°–27.6°N, comprising 13 measurement locations. The valley is divided into three sectors longitudinally: western sector (R1: 89.97°–91.75°E), middle sector (R2: 92.5°–94.01°E) and eastern sector (R3: 94.63°–95.55°E). Spatial heterogeneity in aerosol distribution has been observed with higher PM₁₀ and PM_2.5 concentrations at the western and middle sectors compared to the eastern sector. The locations in the western sector are found to be rich in BC compared to the other two sectors and there is a gradual decrease in BC concentrations from west to east of the Brahmaputra valley. Two hotspots within the western and middle sectors with high PM and BC concentrations have been identified. The associated physico-optical parameters of PM reveal abundance of PM_2.5 aerosols along the entire valley. High population density in the western and middle sectors, together with the contribution of remote aerosols, leads to higher anthropogenic aerosols over those regions. Spectral Radiation-Transport Model for Aerosol Species (SPRINTARS) slightly underestimates the measured PM₁₀ and PM_2.5 at the eastern sector while the model overestimates the measurements at a number of locations in the western sector. In general, BC is underestimated by the model. The variation of BC within the campaign trail has not been adequately captured by the model leading to higher variance in the western locations as compared to the middle and eastern locations.  相似文献   

Earthquake distribution in the subduction zone off eastern Hokkaido, Japan, deduced from ocean-bottom seismographic and land observations     

Takaya Iwasaki  Naoshi Hirata  Toshihiko Kanazawa  Taku Urabe  Yoshinobu Motoya  Hideki Shimamura 《Geophysical Journal International》1991,105(3):693-711

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Velocity of finer fragments from impact     

Akiko M. Nakamura  Akira Fujiwara  Toshihiko Kadono   《Planetary and Space Science》1994,42(12):1043-1052

We describe the method and the result of a new experiment to obtain velocity distribution of fine ejecta fragments, from a few to a hundred microns in size, produced from basalt targets by impacts of nylon projectiles at a velocity of 3.7 km s⁻¹. The size distribution of holes perforated by the ejecta fragments on thin films and foils placed around the targets was investigated, and the size-velocity relation was determined with the aid of an empirical formula for threshold penetration (McDonnell and Sullivan, Hypervelocity Impacts in Space, Unit for Space Sciences, University of Kent, 1992). The velocity of the fastest fragments, at a given size, is from the extrapolation of the size-velocity relation for 1–100 mm fragments (Nakamura and Fujiwara, Icarus92, 132–146, 1991; Nakamura et al, Icarus100, 127–135, 1992). The laboratory results are also compared with those obtained from the study of secondary craters around large lunar craters (Vickery, Icarus67, 224–236, 1986, Geophys. Res. Lett. 14, 726–729, 1987). All these data provide a smooth size-velocity relationship in the normalized fragment size range of four orders of magnitude.  相似文献   

Solar dust ring observation at the total solar eclipse in Mexico     

Syuzo Isobe  Toshihiko Tanabe  Motokazu Noguchi 《Celestial Mechanics and Dynamical Astronomy》1992,54(1-3):233-235

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Observations of microseismicity in the southern Kuril Trench area by arrays of ocean bottom seismometers     

Naoshi Hirata  Toshihiko Kanazawa  Kiyoshi Suyehiro  Takaya Iwasaki  Hideki Shimamura 《Geophysical Journal International》1989,98(1):55-68

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Far-infrared properties of metallic dust grains     

Toshihiko Tanabé  Takashi Onaka  Fumio Kamijo 《Astrophysics and Space Science》1984,98(2):323-342

Far-infrared properties of metallic particle are reinvestigated in detail. In the far-infrared region, absorption due to the eddy current generally dominates over that obtained by using the Rayleigh approximation erroneusly. The wavelength dependence of the eddy current term is examined carefully and shown to be less steep than that predicted by the Rayleigh approximation for dust grains larger than 100 nm in radius. It also depends more sensitively on the grain size. A wider temperature distribution is expected corresponding to a given size distribution and hence the emission spectrum becomes less steep than the preductions by the Rayleigh approximation. Iron and graphite particles are investigated as typical interstellar metallic grains. Effects of coating of dielectric materials are also examined. Comparisons with experimental results and with observations are discussed.  相似文献