Thermobaric structure of the Kokchetav ultrahigh-pressure–high-pressure massif deduced from a north–south transect in the Kulet and Saldat–Kol regions, northern Kazakhstan     

Tsutomu Ota  Masaru Terabayashi  Christopher D. Parkinson and  Hideki Masago 《Island Arc》2000,9(3):328-357

Abstract To investigate the regional thermobaric structure of the diamondiferous Kokchetav ultrahigh‐pressure and high‐pressure (UHP–HP) massif and adjacent units, eclogite and other metabasites in the Kulet and Saldat–Kol regions, northern Kazakhstan, were examined. The UHP–HP massif is subdivided into four units, bounded by subhorizontal faults. Unit I is situated at the lowest level of the massif and consists of garnet–amphibolite and acidic gneiss with minor pelitic schist and orthogneiss. Unit II, which structurally overlies Unit I, is composed mainly of pelitic schist and gneiss, and whiteschist locally with abundant eclogite blocks. The primary minerals observed in Kulet and Saldat–Kol eclogites are omphacite, sodic augite, garnet, quartz, rutile and minor barroisite, hornblende, zoisite, clinozoisite and phengite. Rare kyanite occurs as inclusions in garnet. Coesite inclusions occur in garnet porphyroblasts in whiteschist from Kulet, which are closely associated with eclogite masses. Unit III consists of alternating orthogneiss and amphibolite with local eclogite masses. The structurally highest unit, Unit IV, is composed of quartzitic schist with minor pelitic, calcareous, and basic schist intercalations. Mineral assemblages and compositions, and occurrences of polymorphs of SiO₂ (quartz or coesite) in metabasites and associated rocks in the Kulet and Saldat–Kol regions indicate that the metamorphic grades correspond to epidote–amphibolite, through high‐pressure amphibolite and quartz–eclogite, to coesite–eclogite facies conditions. Based on estimations by several geothermobarometers, eclogite from Unit II yielded the highest peak pressure and temperature conditions in the UHP–HP massif, with metamorphic pressure and temperature decreasing towards the upper and lower structural units. The observed thermobaric structure is subhorizontal. The UHP–HP massif is overlain by a weakly metamorphosed unit to the north and is underlain by the low‐pressure Daulet Suite to the south; boundaries are subhorizontal faults. There is a distinct pressure gap across these boundaries. These suggest that the highest grade unit, Unit II, has been selectively extruded from the greatest depths within the UHP–HP unit during the exhumation process, and that all of the UHP–HP unit has been tectonically intruded and juxtaposed into the adjacent lower grade units at shallower depths of about 10 km.  相似文献   

Analyses Of Jovian Decametric Radiation -Bursts Interacting With N-Bursts     

Oya  Masaru  Oya  Hiroshi  Ono  Takayuki  Iizima  Masahide 《Earth, Moon, and Planets》2000,88(4):187-209

Dynamic spectra of S-bursts of Jovian decametric radiations are obtained by using a high time resolution radio spectrograph which has a time resolutionof 2 msec and the bandwidth of 2 MHz.Within occurrence of 65 S-burst events observed in the period from 1983 to 1999, 26 events have been identified as the S-N burst events, which are characterized by the interaction between the S-burst emissions and the Narrow band emissions. In the dynamic spectra of the S-N burst, the trend of emissions with negative and slower frequency drift named as “Trailing Edge Emission” are often observed shortly after the appearance of the S-burst.Detailed analyses of these phenomena revealed that the Trailing Edge Emission is not a manifestation of S-burst with slower drift rate but a variation ofN-burst. The results suggested that S-burst and the associated Trailing Edge Emission are formed simultaneously started from a common region with different drift rates. It has been further suggested that the appearance of the S-burstsis not controlled by the geometrical effect between the source region and theobserver, but directly reflects the generation of the source region widelydistributed in an altitude range from a few thousands km to 30,000 km, alongthe Io flux tube. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Bulk density effects on soil hydrologic and thermal characteristics: A numerical investigation          下载免费PDF全文

Yuki Kojima  Joshua L. Heitman  Masaru Sakai  Chihiro Kato  Robert Horton 《水文研究》2018,32(14):2203-2216

Soil bulk density (ρ_b) is commonly treated as static in studies of land surface dynamics. Magnitudes of errors associated with this assumption are largely unknown. Our objectives were to (a) quantify ρ_b effects on soil hydrologic and thermal properties and (b) evaluate effects of ρ_b on surface energy balance and heat and water transfer. We evaluated 6 soil properties, volumetric heat capacity, thermal conductivity, soil thermal diffusivity, water retention characteristics, hydraulic conductivity, and vapour diffusivity, over a range of ρ_b, using a combination of 6 models. Thermal conductivity, water retention, hydraulic conductivity, and vapour diffusivity were most sensitive to ρ_b, each changing by fractions greater than the associated fractional changes in ρ_b. A 10% change in ρ_b led to 10–11% change in thermal conductivity, 6–11% change in saturated and residual water content, 49–54% change in saturated hydraulic conductivity, and 80% change in vapour diffusivity. Subsequently, 3 field seasons were simulated with a numerical model (HYDRUS‐1D) for a range of ρ_b values. When ρ_b increased 25% (from 1.2 to 1.5 Mg m^?3), soil temperature variation decreased by 2.1 °C in shallow layers and increased by 1 °C in subsurface layers. Surface water content differed by 0.02 m³ m^?3 for various ρ_b values during drying events but differences mostly disappeared in the subsurface. Matric potential varied by >100 m of water. Surface energy balance showed clear trends with ρ_b. Latent heat flux decreased 6%, sensible heat flux increased 9%, and magnitude of ground heat flux varied by 18% (with a 25% ρ_b increase). Transient ρ_b impacted surface conditions and fluxes, and clearly, it warrants consideration in field and modelling investigations.  相似文献   

Large but variable particulate flux in the Antarctic Ocean and its significance for the chemistry of Antarctic water     

Shizuo Tsunogai  Shinichiro Noriki  Koh Harada  Taro Kurosaki  Yasunori Watanabe  Masaru Maedaa 《Journal of Oceanography》1986,42(2):83-90

Settling particles were collected at 1,460 m and 3,760 m depth in the Antarctic Ocean with sediment traps of time series type. The total deployment period of 40 days was divided into four terms of 10 days each. Seawater samples were collected both at deployment and retrieval of the traps at each site. During the 42 days the concentration of silicate in the surface water decreased by 32%, whereas those of nitrate and phosphate decreased by only 4–5%. The total particulate flux in the Antarctic Ocean is the largest among those hitherto observed in the world ocean. The time variation of the particulate flux at 1,460 m depth almost coincided with that at 3,760 m. The settling particles were comprised roughly of 80% biogenic silica, 15% organic matter and 5% other substances including sea salt. The clay fraction was only 0.05% at 1,460 m depth. The settling flux of biogenic silica agrees fairly well with the calculated rate of change in the concentration of silicate in the surface 100 m. Thus it is concluded that preferential propagation of diatoms reduces the concentration of silicate prior to other nutrients in the Antarctic Ocean.  相似文献   

The uranium content and the activity ratio234U/238U in marine organisms and sea water in the western North Pacific     

Yasuo Miyake  Yukio Sugimura  Masaru Mayeda 《Journal of Oceanography》1970,26(3):123-129

The uranium content and activity ratio A²³⁴U/A²³⁸U were determined in open ocean water, marine plankton, marine algae and sea water in the environment in which plankton and algae live. The average uranium content of 3.34±0.28×10⁻⁶ g/l and the average activity ratio of 1.13±0.04 were obtained in open ocean water. The uranium contents in plankton and algae were respectively from 1.7 to 7.8×10⁻⁷ g/g and 0.4 to 23.5×10⁻⁷ g/g on dry basis with the respective concentration factors of 48 to 260 and 10 to 733. The activity ratio in plankton and algae ranged from 1.07 to 1.18 which coincided well with those in the environmental sea water.  相似文献   

The H i content of star-forming galaxies at z= 0.24     

Philip Lah  Jayaram N. Chengalur  Frank H. Briggs  Matthew Colless  Roberto De Propris  Michael B. Pracy  W. J. G. de Blok  Shinobu S. Fujita  Masaru Ajiki  Yasuhiro Shioya  Tohru Nagao  Takashi Murayama  Yoshiaki Taniguchi  Masafumi Yagi  Sadanori Okamura 《Monthly notices of the Royal Astronomical Society》2007,376(3):1357-1366

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Urban albedo as a function of the urban structure — A two-dimensional numerical simulation   总被引：4，自引：0，他引：4  

Masaru Aida  Kiyoshi Gotoh 《Boundary-Layer Meteorology》1982,23(4):415-424

Urban albedo change as a function of urban geometrical structure has been examined by using a two-dimensional urban block-canyon array model. The complex multiple reflections of incident photons in the urban canyon are simulated by using a Monte-Carlo method. The photons are tracked until they leave the canyon or are completely absorbed. In the model, the direct and diffuse components of incident solar radiation are introduced and the specular and isotropic reflection characteristics are considered for the relevant urban surfaces. The result shows that the urban albedo decreases as the urban irregularity increases as indicated by the model experiment of Aida (1982). The dependence of albedo on the incident solar zenith angle observed in the experiment is also confirmed for various urban models.As an application, some actual urban structures in the Marunouchi area in Tokyo are examined. Urban planning for absorption and reflection of solar radiation in urban areas is also discussed based on the analysis of the change in albedo with canyon dimensions and solar zenith angle.  相似文献   

Urban albedo as a function of the urban structure — A model experiment   总被引：4，自引：0，他引：4  

Masaru Aida 《Boundary-Layer Meteorology》1982,23(4):405-413

A model experiment has been carried out in order to examine the effect of surface irregularity of an urban structure on the anomalous absorption of incident solar radiation. Several models of an urban structure resembling buildings and canyons were constructed by using concrete blocks in cubic form. By building and dismantling the urban models, the albedo change as a function of solar zenith angle was observed throughout the year. The result shows that the absorption increment originating from the irregular urban structure amounts to about 20% as compared with the absorption by a flat surface of the same material. The amount of additional absorption depends on the relative area occupied by canyons in the model.  相似文献   

Observations of Atmospheric Downward Radiation in the Tokyo Area     

Masaru Aida  Masataka Yaji 《Boundary-Layer Meteorology》1979,16(3):453-465

The size and variation of the urban increase of atmospheric downward radiation have been observed in the Tokyo area. Downward radiation flux, air temperature and humidity were observed by automobile traverses along the expressways across the greater Tokyo area from the Kanagawa (southwest) to the Chiba (east) sides. The observations were carried out on clear and rather calm nights in the winters of 1975–1978. The results show that Tokyo receives increased downward radiation in comparison with the amount received in the surrounding rural areas. The area of increased downward flux extends about 40 km at its widest along the observation route when the winds are weak, and the rural-urban increase of downward radiation becomes about 8% on the Kanagawa side and about 10% on the Chiba side. The area of increased downward flux is close to that of the urban heat island, where an urban decrease of water vapour content is also observed. The present analysis shows that the large urban increase of radiation flux is due to the difference between the vertical temperature profiles over the urban and rural regions. The development of a surface temperature inversion over the rural area and the urban decrease in water vapour content provide a rather smaller rural-urban difference in downward radiation compared with the development of a heat island.  相似文献   

Characteristic frequencies for earthquake families and their tectonic implications: Evidence from earthquake swarms in the kanto district,Japan     

Masaru Tsujiura 《Pure and Applied Geophysics》1983,121(4):573-600

Through the analyses of waveform and spectrum for two swarm sequences in the Kanto District, including the results from 15 earthquake swarsm obtained previously, the mechanism of the faulting process in earthquake swarms is clarified in more detail. Earthquakes occurring in short time intervals consist mainly of events with similar waveforms andS-P times. These are called “earthquake families,” and many families are observed during a swarm sequence (70–80 percent); for example, 15 families were observed in the 1983 Izu Peninsula earthquake swarm. The source spectra of earthquake families share the same corner frequency, even though their low-frequency levels may differ by a factor as great as 1000, and the value of the corner frequency depends on the size of the largest event in the family. Local variations of corner frequencies within a factor of 25 are found among the earthquake swarms in the Kanto District. These observations suggest the existence of a characteristic fault length depending on the swarm area, and its length may be responsible for the size of the largest event in the family. The characteristic fault length is about 100 m for Ashio, about 400 m for the Izu Peninsula and about 2.5 km for areas off the Chiba Prefecture, and the magnitudes of the largest events expected from these fault lengths are about 2.5, 4, and 6, respectively.  相似文献