Ti-rich hydroandradites from the Sanbagawa metamorphic rocks of the Shibukawa area,central Japan     

Hitoshi Onuki  Masahide Akasaka  Takeyoshi Yoshida  Munetomo Nedachi 《Contributions to Mineralogy and Petrology》1982,80(2):183-188

Ti-rich hydroandradite often occurs, though usually as a minor constituent, in serpentinized ultramafic rocks and associated gabbroic rocks of the Sanbagawa metamorphic belt. The chemistry of the host rocks is commonly characterized by undersaturation with SiO₂. Two Ti-rich hydroandradites from metasomatized gabbroic rocks of the Shibukawa area have been chemically analysed by the wet method. Mössbauer experiments indicate the presence of Fe³⁺ and Fe²⁺ in the octahedral sites of these Ti-rich hydroandradites. Wet chemical analyses for total reducing capacity of the present garnets by two different methods together with Mössbauer data imply the presence of octahedral Ti³⁺ in their structure. Ti-rich hydroandratites, apart from their hydrous property, have a similar crystal chemistry to natural Ti-rich andradites. Ti-rich hydroandradites were probably formed in rocks with unusual chemical compositions within a P-T region of 300–400° C and 4–7 kb under limited conditions of relatively low oxygen fugacity and low μCO₂.  相似文献   

Upscaling Permeability Measurements Within Complex Heterolithic Tidal Sandstones   总被引：2，自引：0，他引：2  

Matthew D. Jackson  Ann H. Muggeridge  Shuji Yoshida  Howard D. Johnson 《Mathematical Geology》2003,35(5):499-520

We investigate numerically the effect of sample volume on the effective single-phase permeability of heterolithic tidal sandstones, using three-dimensional models reconstructed directly from large rock specimens measuring 45 × 30 × 15 cm. We find that both individual and averaged effective permeability values vary as a function of sample volume, which indicates that permeability data obtained from core-plugs will not be representative at the scale of a reservoir model grid-block regardless of the number of measurements taken. However, the error introduced by averaged data may be minimized using the appropriate averaging scheme for a given facies type and flow direction.  相似文献   

Study of the effect of water-soluble fractions of heavy-oil on coastal marine organisms using enclosed ecosystems,mesocosms   总被引：1，自引：0，他引：1  

Ohwada K  Nishimura M  Wada M  Nomura H  Shibata A  Okamoto K  Toyoda K  Yoshida A  Takada H  Yamada M 《Marine pollution bulletin》2003,47(1-6):78-84

Mesocosm facilities composed of 4 experimental and 2 reservoir tanks (1.5 m in diameter, 3.0 m in depth and 5 tons in capacity) made of FRP plastics, were constructed in the concrete fish rearing pond in the Fisheries Laboratory, The University of Tokyo. The water-soluble fraction of Rank A heavy residual oil was formed by mixing 500 g of the oil with 10 l of seawater, which was introduced to the 5000 l-capacity tanks. Experimental Run 4 was conducted from May 31 to June 7, 2000. Oil concentrations in the tanks were 4.5 microg/l called LOW, and 13.5 microg/l, called HIGH tank. Bacterial growth rates very quickly accelerated in the HIGH tank just after the loading of oil which corresponded with a high increase of bacterial cells in the same tank after 2 days. Later, bacterial numbers in HIGH tank rapidly decreased, corresponding with the rapid increase of heterotrophic nano-flagellates and virus numbers on the same day. Sediment traps were deployed at the bottom of the experimental tanks, and were periodically retrieved. These samples were observed both under light microscope and epi-fluorescent microscope with UV-excitation. It was observed that the main components of the vertical flux were amorphous suspended matter, mostly originating from dead phytoplankton and living diatoms. It was further observed from the pictures that vertical transport of oil emulsions were probably conducted after adsorption to amorphous suspended matter and living diatoms, and were settling in the sediment traps at the bottom of the tanks. This means that the main force which drives the soluble fraction of oil into bottom sediment would be vertical flux of such amorphous suspended particles and phytoplankton. Further incubation of the samples revealed that the oil emulsions were degraded by the activity of autochtonous bacteria in the sediment in aerobic condition.  相似文献   

Effects of deposit feeder Stichopus japonicus on algal bloom and organic matter contents of bottom sediments of the enclosed sea   总被引：4，自引：0，他引：4  

Michio K  Kengo K  Yasunori K  Hitoshi M  Takayuki Y  Hideaki Y  Hiroshi S 《Marine pollution bulletin》2003,47(1-6):118-125

Algae growing in an enclosed sea may inhibit eutrophication because they absorb nutrients in the water. However, dead algae often cause anaerobic conditions in the water just above and on sediment after they are deposited on the bottom. We found that Stichopus japonicus inhibited the anaerobic processes coupling water sulfite production in sediment. The present study investigates whether S. japonicus inhibits algal flourish and influences sediment properties such as organic matter contents. Aquarium experiments were carried out at Komatsushima port in Tokushima Prefecture, western Japan. The aquaria used in the experiments were supplied with water directly from the adjacent sea (6 L/min), laid with sand of 10 cm depths, and lighted at 12 h intervals. Six aquaria each containing a sea cucumber from Komatsushima port and six aquaria without any were used in the experiments. Water temperature ranged between 9 and 15 degrees C during December 2000 and April 2001. Salinity ranged between 32 per thousand and 34 per thousand. Algae began to cover the bottom of the aquaria without S. japonicus after 2 weeks, whereas no growth was evident in the aquaria containing sea cucumbers. Chlorophyll a concentration in the surface sediment of the aquaria with S. japonicus (6.1+/-3.6 microg/g, mean S.D.+/-standard deviation) was significantly lower than that without it (60+/-17 microg/g, U-test, p<0.05). Phaeophytin concentration in the surface sediment of the aquaria with S. japonicus (0.9+/-0.09 microg/g) was also significantly lower than that without it (4.5+/-1.0 microg/g, U-test, p<0.05). TOC concentration in the surface sediment of the aquaria with S. japonicus (2.6+/-1.3 microg/g) was slightly lower than that without it (4.0+/-1.2 microg/g). These results showed that algal biomass and organic matter concentration of the bottom were decreased in the presence of S. japonicus. Therefore, S. japonicus inhibits algal bloom and decrease the contents of organic matter deposited on the bottom of enclosed sea areas.  相似文献   

International Seminar on Disaster Mitigation in Nepal, Kathmandu, November, 2003     

Vishnu Dangol  M. Yoshida 《Gondwana Research》2004,7(2):644-645

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Where and why do large shallow intraslab earthquakes occur?     

Tetsuzo Seno  Masaki Yoshida 《Physics of the Earth and Planetary Interiors》2004,141(3):183-206

We try to find how often, and in what regions large earthquakes (M≥7.0) occur within the shallow portion (20-60 km depth) of a subducting slab. Searching for events in published individual studies and the Harvard University centroid moment tensor catalogue, we find twenty such events in E. Hokkaido, Kyushu-SW, Japan, S. Mariana, Manila, Sumatra, Vanuatu, N. Chile, C. Peru, El Salvador, Mexico, N. Cascadia and Alaska. Slab stresses revealed from the mechanism solutions of these large intraslab events and nearby smaller events are almost always down-dip tensional. Except for E. Hokkaido, Manila, and Sumatra, the upper plate shows horizontal stress gradient in the arc-perpendicular direction. We infer that shear tractions are operating at the base of the upper plate in this direction to produce the observed gradient and compression in the outer fore-arc, balancing the down-dip tensional stress of the slab. This tectonic situation in the subduction zone might be realized as part of the convection system with some conditions, as shown by previous numerical simulations.  相似文献   

The Dependence of Constitutive Properties on Temperature and Effective Normal Stress in Seismogenic Environments     

Aitaro Kato  Shingo Yoshida  Mitiyasu Ohnaka  Hiromine Mochizuki 《Pure and Applied Geophysics》2004,161(9-10):1895-1913

— We have evaluated how the parameters prescribing the slip-dependent constitutive law are affected by temperature and effective normal stress, by conducting the triaxial fracture experiments on Tsukuba-granite samples in seismogenic environments, which correspond to a depth range to 15 km. The normalized critical slip displacement D _c almost remains constant below 300^oC (insensitive to both temperature and effective normal stress σ _n ^eff); D _c increases with increasing temperature above 300 °C, and the rate of D _c increase with temperature tends to be largest at higher σ _n ^eff. The breakdown stress drop Δτ _b for the granite at constant σ _n ^eff is roughly 80 MPa below 300 °C, and does not depend on σ _n ^eff. Above 300 °C, Δτ _b decreases gradually with increasing temperature, and the rate of Δτ _b reduction with temperature increases at higher σ _n ^eff. The peak shear strength τ _p increases nearly linearly with increasing σ _n ^eff below 300 °C. However, τ _p becomes lower above 300 °C, deviating from the linear relation extrapolated from below 300 °C. This is consistent with the onset of crystal plastic deformation mechanisms of Tsukuba granite.  相似文献   

Prof. Henri Ali Basira Kampunzu     

Jacques L.H. Cailteux  Franois R.T. Lubala  Masaru Yoshida 《Gondwana Research》2005,8(2):289-291

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Interactions of uranium with bacteria and kaolinite clay     

Toshihiko Ohnuki  Takahiro Yoshida  Takuo Ozaki  Mohamad Samadfam  Naofumi Kozai  Kunio Yubuta  Toshiaki Mitsugashira  Takeshi Kasama  Arokiasamy J. Francis 《Chemical Geology》2005,220(3-4):237-243

We assessed the accumulation of uranium (VI) by a bacterium, Bacillus subtilis, suspended in a slurry of kaolinite clay, to elucidate the role of microbes on the mobility of U(VI). Various mixtures of bacteria and the koalinite were exposed to solutions of 8 × 10^− 6 M- and 4 × 10^− 4 M-U(VI) in 0.01 M NaCl at pH 4.7. After 48 h, the mixtures were separated from the solutions by centrifugation, and treated with a 1 M CH₃COOK for 24 h to determine the associations of U within the mixture. The mixture exposed to 4 × 10^− 4 M U was analyzed by transmission electron microscope (TEM) equipped with EDS. The accumulation of U by the mixture increased with an increase in the amount of B. subtilis cells present at both U concentrations. Treatment of kaolinite with CH₃COOK, removed approximately 80% of the associated uranium. However, in the presence of B. subtilis the amount of U removed was much less. TEM–EDS analysis confirmed that most of the U removed from solution was associated with B. subtilis. XANES analysis of the oxidation state of uranium associated with B. subtilis, kaolinite, and with the mixture containing both revealed that it was present as U(VI). These results suggest that the bacteria have a higher affinity for U than the kaolinite clay mineral under the experimental conditions tested, and that they can immobilize significant amount of uranium.  相似文献   

Chemistry and Sulfur Isotopes of the Chert-Clastic Sequence Surrounding the Kajika Massive Sulfide Ores at the Ashio Copper Mine, Ashio Terrane, Central Japan     

Kosei Komuro    Masanori Yoshida  Yoshimichi Kajiwara 《Resource Geology》2006,56(4):433-445

Abstract. Chemical and sulfur isotopic compositions were obtained for a series of rocks within the chert‐clastic sequence surrounding the Kajika massive sulfide ore horizon at Shibukawasawa in the Ashio copper‐mining district, Ashio Terrane, central Japan. The sequence is lithologically classified into three units: chert, siliceous shale with basic volcanics, and sandstone‐shale, in ascending stratigraphic order. The Kajika ore horizon corresponds to the lowermost part of the unit that contains siliceous shale with basic volcanics. The rocks around the Kajika ore horizon are enriched in P₂O₅ (max. 0.22 %), Ba (max. 2400 ppm), Cu (595 ppm), V (323 ppm), Pb (168 ppm), Zn (124 ppm), and Mo (24 ppm) in siliceous shale; and Ba (4220 ppm), Zr (974 ppm), Cr (718 ppm), Ni (492 ppm), V (362 ppm), Zn (232 ppm), Nb (231 ppm), and Co (71 ppm) in the basic volcanics. The siliceous shale is enriched in a number of redox‐sensitive elements such as Cu, V, Pb, Zn, and Mo, which are known to be enriched in black shale and anoxic and hydrothermal sediments. The δ³⁴S values of sulfides in the chert and sandstone‐shale lie in the range of 0±2 %, and those in the siliceous shale range from ‐5 to ‐14 %. The measured δ³⁴S values in the basic volcanics are ‐0.3, ‐2.7, and ‐31.5 %. These heavier δ³⁴S signatures (around 0 %) recorded throughout the sequence indicate that the rocks formed under anoxic bottom‐water conditions. Slightly lighter δ³⁴S values recorded in siliceous shale might reflect significant mixing of sulfides that formed by sulfate‐reducing bacteria in an overlying oxic environment. The long‐term duration of anoxic conditions indicated by the heavier δ³⁴S signature is considered to have played an important role in protecting the Kajika sulfide ores from oxidative decomposition and preserving the ores in sedimentary accumulations.  相似文献