CHIME age dating of monazites from metamorphic rocks and granitic rocks of the Ryoke belt in the Iwakuni area, Southwest Japan   总被引：2，自引：0，他引：2  

Kazuhiro  Suzuki  Mamoru  Adachi Terukazu  Nureki 《Island Arc》1996,5(1):43-55

Abstract CHIME (chemical Th-U-total Pb isochron method) ages were determined for monazite from gneisses and granitoids of the Ryoke belt in the Iwakuni area. The CHIME monazite ages are 99.6 ± 2.4, 98.9 ± 2.1 and 98.2 ± 5.7 Ma for the Ryoke gneiss, 90.7 ± 2.2, 89.7 ± 2.0 and 89.3 ± 2.2 Ma for the Tajiri Granite, 91.0 ± 3.2, 90.6 ± 3.2 and 89.9 ± 3.2 Ma for the Namera Granite, 89.3 ±3.3 and 88.6 ± 5.6 Ma for a small stock at Shimizu, and 87.3 ± 1.6 and 86.6 ± 2.1 Ma for the post-tectonic Shimokuhara Granite. The CHIME monazite ages, interpreted as the time of the first attainment at the amphibolite facies conditions for the gneisses and as the time of emplacement for the granites, respectively, agree with the field intrusive sequence. The present dating documented that the Ryoke metamorphism in the Iwakuni area reached the amphibolite facies conditions at ∼98 Ma, was complete at -87 Ma, the time of emplacement of the post-tectonic Shimokuhara Granite.  相似文献   

Precipitation of heavy metals in produced water: influence on contaminant transport and toxicity   总被引：1，自引：0，他引：1  

Azetsu-Scott K  Yeats P  Wohlgeschaffen G  Dalziel J  Niven S  Lee K 《Marine environmental research》2007,63(2):146-167

Produced water undergoes changes in its physical chemistry including precipitation of heavy metals after being discharged and mixed with ambient seawater. Potential impacts of the precipitation of heavy metals on their transport and toxicity were studied using samples from offshore oil production sites on the Scotian Shelf off eastern Canada. Concentrations of aluminum, cadmium, chromium, cobalt, copper, iron, lead, manganese, nickel and zinc were measured in total, particulate and dissolved fractions together with Microtox tests for assessment of toxicity. Heavy metals in produced water were transformed from dissolved to particulate phase in a period of hours under oxygenated conditions, and aggregated to larger particles that settle rapidly (>100 m/day) over a few days. In addition, there was production of buoyant particles comprised of heavy metal precipitates sequestered onto oil droplets that were transported to the surface. The particulate fraction was generally more toxic than the dissolved fraction. This was evident at the mixing interface between produced water and seawater where elevated particulate and toxicity levels were observed. Laboratory studies suggest an increase in the toxicity of discharged produced water over time. Time-series experiments showed a sustained toxic response for more than a week following the oxidation of freshly discharged produced water that initially elicited little or no toxic response in the Microtox test. Chemical processes identified in this study, namely precipitation of heavy metals and consequent settling and rising fluxes of particles, will influence the toxicity, the fate and the transport of potential contaminants in the produced water. Therefore, these processes need to be considered in assessment of the environmental impact associated with offshore oil and gas operations.  相似文献   

Stability Dependence and Diurnal Change of Large-Scale Turbulence Structures in the Near-Neutral Atmospheric Boundary Layer Observed from a Meteorological Tower     

Mitsuaki Horiguchi  Taiichi Hayashi  Ahoro Adachi  Shigeru Onogi 《Boundary-Layer Meteorology》2014,151(2):221-237

Based on the analysis of observations from a 213-m tall meteorological tower at Tsukuba, Japan, we have investigated the favourable conditions for the predominant existence of large-scale turbulence structures in the near-neutral atmospheric boundary layer (ABL). From the wavelet variance spectrum for the streamwise velocity component ( $u$ ) measured by a sonic anemometer-thermometer at the highest level (200 m), large-scale structures (time-scale range of 100–300 s) predominantly exist under slightly unstable and close to neutral conditions. The emergence of large-scale structures also can be related to the diurnal evolution of the ABL. The large-scale structures play an important role in the overall flow structure of the lower boundary layer. For example, $u$ velocity components at the 200-m and 50-m levels show relatively high correlation with the existence of large-scale structures. Under slightly unstable (near-neutral) conditions, a low-speed region in advance of the high-speed structure shows a positive deviation of temperature and appears as the plume structure that is forced by buoyancy in the heated lower layer. In spite of the difference in buoyancy effects between the near-neutral and unstable cases, large-scale structures are frequently observed in both cases and the same vertical correlation of $u$ components is indicated. However, the vertical wind shear is smaller in the unstable cases. On the other hand, in near-neutral cases, the transport efficiency of momentum at the higher level and the flux contribution of sweep motions are larger than those in the unstable cases.  相似文献   

Self‐similar solution of a plane‐strain fracture driven by a power‐law fluid     

J. I. Adachi  E. Detournay 《国际地质力学数值与分析法杂志》2002,26(6):579-604

This paper analyses the problem of a hydraulically driven fracture, propagating in an impermeable, linear elastic medium. The fracture is driven by injection of an incompressible, viscous fluid with power‐law rheology and behaviour index n?0. The opening of the fracture and the internal fluid pressure are related through the elastic singular integral equation, and the flow of fluid inside the crack is modelled using the lubrication theory. Under the additional assumptions of negligible toughness and no lag between the fluid front and the crack tip, the problem is reduced to self‐similar form. A solution that describes the crack length evolution, the fracture opening, the net fluid pressure and the fluid flow rate inside the crack is presented. This self‐similar solution is obtained by expanding the fracture opening in a series of Gegenbauer polynomials, with the series coefficients calculated using a numerical minimization procedure. The influence of the fluid index n in the crack propagation is also analysed. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Compilation method for 1 km grid data of monthly mean air temperature for quantitative assessments of climate change impacts   总被引：1，自引：0，他引：1  

Hideki Ueyama  Sachiho Adachi  Fujio Kimura 《Theoretical and Applied Climatology》2010,101(3-4):421-431

A new method is proposed to compile 1 km grid data of monthly mean air temperature by dynamically downscaling general circulation model (GCM) data with a regional climate model (RCM). The downscaling method used is a technique referred to as the pseudoglobal warming method to reduce GCM bias. For the grid data, RCM data were corrected with data from an existing meteorological network. The correction model for the RCM bias was developed by stepwise multiple regression analysis using the difference in the monthly mean air temperatures between the observation and RCM output as a dependent variable and the geographical factors as independent variables. Our method corrected the RCM bias from 1.69°C to 0.58°C for the month of August in the 1990s (1990–1999).  相似文献   

Instability of gradient dependent elasto-viscoplasticity for clay     

E. C. Aifantis  F. Oka  A. Yashima  T. Adachi 《国际地质力学数值与分析法杂志》1999,23(10):973-994

A gradient-dependent viscoplastic constitutive model for water saturated clay is proposed to describe the strain localization phenomena and pattern formation during deformation. Second- and fourth-order gradients of volumetric viscoplastic strain are introduced into the constitutive equations to account for the non-local effects due to the motion of microstructures. A linear perturbation analysis is applied to this model. The instability of the government equations (i.e. the constitutive equations and the equations of motion for the clay skeleton and pore water) is discussed for both the one-dimensional and the two-dimensional situations. In addition, issues concerned with the formulation of boundary value problems by finite element analysis in relation to the formulation and the boundary conditions are presented. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

Effect of ocean acidification on coastal phytoplankton composition and accompanying organic nitrogen production     

Takeo Hama  Shoko Kawashima  Koichi Shimotori  Yuhi Satoh  Yuko Omori  Shigeki Wada  Taiki Adachi  Shun Hasegawa  Takashi Midorikawa  Masao Ishii  Shu Saito  Daisuke Sasano  Hiroko Endo  Tsuyoshi Nakayama  Isao Inouye 《Journal of Oceanography》2012,68(1):183-194

The effect of ocean acidification, caused by the increase in pCO₂ in seawater, on phytoplankton population and on related organic nitrogen production was experimentally examined by use of a natural coastal microbial population. pCO₂ and pH were controlled by aeration with air in which pCO₂ was at the current level (control), for which ambient air was used, and with air in which pCO₂ was ??800?? and ??1200?? ppm, in 500-L culture vessels. The experiment was continued for 15?days after addition of the inorganic nutrients such as nitrate, phosphate, and silicate. During most of the experimental period, a minor increase in phytoplankton biomass was noted, probably because of low irradiance, an increase in phytoplankton biomass was observed at the end of the experiment. Flow cytometric and microscopic observations revealed that this increase was because of Chrysochromulina sp. (Haptophyceae). The growth of Chrysochromulina sp. was most obvious in the control vessel, and tended to be obscured by increasing pCO₂ (decrease in pH), indicating the possibility that ocean acidification inhibits the growth of specific phytoplankton groups, for example Chrysochromulina sp. Production of particulate organic nitrogen (PON), determined by the ¹⁵N tracer method, also diminished under acidified conditions compared with that at the current level.  相似文献   

Ductile deformation and development of andalusite microstructures in the Hongusan area: Constraints on the metamorphism and tectonics of the Ryoke Belt     

Yoko  Adachi  Simon  Wallis 《Island Arc》2008,17(1):41-56

Abstract   The main mesoscopic features of the ductile deformation in the Hongusan region of the Ryoke Belt can be explained in terms of a single deformation phase, Dm . The associated stretching lineation is roughly east–west and has an associated top-to-the-west sense of shear. This information fills an important gap in our knowledge about the deformational history of the Ryoke metamorphic belt. Andalusite porphyroblasts are well-developed in the Hongusan area and their microstructure can be used to link the deformational history with the metamorphism. However, the andalusite porphyroblasts show both intertectonic and post-tectonic microstructures. Some porphyroblasts have an intertectonic core and post-tectonic rim. Analysis of associated metamorphic minerals and bulk-rock chemistry suggests that the distinct types of microstructure can be explained in terms of distinct formation reactions related to regional and contact metamorphism. The intertectonic microstructure shows the presence of a deformation pre-dating Dm , referred to as Dc . These two deformation stages are sufficient to account for all the main deformation features. The distribution of post-tectonic andalusite growth shows a very broad thermal effect around an intrusion in the area. This can help place constraints on the thermal history of the Ryoke metamorphic belt.  相似文献   

Distribution of nano-phytoplankton including fragile flagellates in the subtropical northwestern Philippine Sea     

Takashi Tsuji  Rokuro Adachi 《Journal of Oceanography》1979,35(3-4):173-178

Distribution of nano-phytoplankton was studied during May–June 1971 in the subtropical northwestern Philippine Sea. Plankton samples were collected at various depths between 0 and 200 m. A gentle gravity filtration technique was employed to concentrate the samples. They were then examined without fixation under a microscope. The average cell number of total nano-phytoplankton was 1×10⁴2×10⁴/l, and nano-flagellate cell number often accounted for more than 90% of the total cell number of nano-phytoplankton, consisting mainly ofGymnodinium lacustre, Amphidinium sp., and unidentified small nano-flagellates. The distribution of nano-phytoplankton did not correlate with vertical profiles of chlorophylla.  相似文献   

The identification, counting, and measurement of phytoplankton by an image-processing system     

Ishii  T.; Adachi  R.; Omori  M.; Shimizu  U.; Irie  H. 《ICES Journal of Marine Science》1987,43(3):253-260

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