In-situ U–Pb SIMS dating and trace element (EMPA) composition of zircon from a granodiorite porphyry in the Wushan copper deposit, China     

X. Ding  S.-Y. Jiang  K.-D. Zhao  E. Nakamura  K. Kobayashi  P. Ni  L-X. Gu  Y.-H. Jiang 《Mineralogy and Petrology》2006,86(1-2):29-44

Summary Zircons from a granodiorite porphyry at the Wushan copper deposit in the Lower Changjiang Metallogenic Belt, east central China, were dated using a Cameca IMS 1270 secondary ion mass spectrometer (SIMS); their chemical compositions and Hf isotopes were analyzed using a JEOL JX A8800 electron microprobe (EMPA) and a Neptune LA-MC-ICP-MS, respectively. The U–Pb dating of zircon reveals two age groups for the granodiorite porphyry; i.e. 144.6 ± 3.9 Ma and 121.0 ± 2.5 Ma. Zircons of the two age populations display distinct chemical compositional characteristics with respect to UO₂/HfO₂ ratios, and show a negative correlation of (UO₂ + Y₂O₃ + ThO₂) and HfO₂. The older age group of ∼145 Ma, defined by the majority of the zircons, is interpreted as the magmatic emplacement age, whereas the younger age group of ∼121 Ma is interpreted as rejuvenation due to subsequent thermal or hydrothermal events. Other interpretations such as presence of two distinct magmatic crystallization stages or inheritance of the older zircons are also discussed in the paper. The ∼145 Ma magmatism at Wushan is consistent with the ages of most of the granitods in the Lower Changjiang Metallogenic Belt. The Hf isotope composition of zircons (ɛ_Hf = −2.1 and −7.0; T_DM^Hf ages = 0.87 and 1.05 Ga), together with other available geochemical and Sr–Nd isotope data suggest that the granodioritic magma was derived from mixing of juvenile mantle with older crustal material. Due to the close spatial and temporal relationship of the granodiorite porphyry and the skarn mineralization at Wushan, the magamatic hydrothermal mineralization likely took place between 145 Ma and 121 Ma, likely around 121 Ma.  相似文献   

Change in seismic activity in the Tokai region related to weakening and strengthening of the interplate coupling     

Akio Yoshida  Kohji Hososno  Toshimitsu Tsukakoshi  Akio Kobayashi  Hiromi Takayama  Stefan Wiemer 《Tectonophysics》2006,417(1-2):17

We investigate the relationship between changes in seismicity and crustal deformations in the Tokai region. We describe how seismicity in the subducted slab increased remarkably in the fall of 2000 and decreased in the fall of 2001, while in contrast, the crust seismicity decreased in the fall of 2000 and increased in the fall of 2001. We note that the trend of horizontal displacement at GPS stations changed coincidentally and we propose interpreting the increase and decrease in seismic activities and the changes in crustal deformations in a unified way based on changes in the state of the interplate coupling, i.e., the back-slip rate was reduced in the fall of 2000 and was partially restored in the fall of 2001. We explain why reduction of the back-slip rate increases seismogenic stress in the slab and decreases stress in the crust. We also describe the substantial positive dilatation observed in the region around Mt. Fuji in the fall of 2000 and suggest that the remarkable increase of low-frequency earthquakes beneath Mt. Fuji in October 2000 may have been caused by deceleration of the converging motion of the Izu micro-plate with the Eurasian plate. The decrease of the subduction velocity of the Izu micro-plate on the Suruga Trough in late 2000 would also have contributed to weakening of the interplate coupling beneath the Tokai region, since reduction of the relative velocity between overriding and subducting plates produces the same effect on the plate interface as a diminishing back-slip rate. However, subduction of the Izu micro-plate on the Suruga Trough was accelerated in early 2003, which may have caused increases in both slab and crust seismicities in that period.  相似文献   

Electrical conductivity measurement of gneiss under mid- to lower crustal P–T conditions     

Kiyoshi Fuji-ta  Tomoo Katsura  Takuya Matsuzaki  Masahiro Ichiki  Tomoyuki Kobayashi 《Tectonophysics》2007,434(1-4):93-101

We conducted electrical conductivity measurements perpendicular and parallel to mineral foliation in dry gneiss at up to 1000 K and a constant pressure of 1 GPa. The analyzed gneisses were obtained from the Higo metamorphic belt, Kyushu, Japan. As the metamorphic conditions of these rocks have been well determined by previous studies, we were able to select samples that were representative of the middle to lower crust. Prior to the conductivity measurements, the samples were maintained at the maximum temperature for a long period, until the electrical conductivity had stabilized. Our experiment results reveal linear and reproducible conductivity data between temperatures of 600 and 1000 K. Conductivity measured perpendicular and parallel to foliation differ by an order of magnitude over the same temperature window. A plausible explanation for this discrepancy in conductivity is the contrasting configuration of minerals in the two sample orientations, as observed by backscattered electron image (BEI) and electron probe microanalysis (EPMA). We evaluated the conductivity and computed activation energy for each of the samples and compared the results with those of previous studies; our results are consistent with the conductivity values reported for other types of rocks. We also compared the experiment results with data derived from electromagnetic (EM) soundings. Electrical conductivity measurements undertaken perpendicular to foliation can account for the subsurface conductivity structure beneath central Kyushu, Japan.  相似文献   

Fine structure in photoluminescence spectrum of S<Subscript>2</Subscript><Superscript>−</Superscript> center in sodalite     

Aierken Sidike  Alifu Sawuti  Xiang-Ming Wang  Heng-Jiang Zhu  S. Kobayashi  I. Kusachi  N. Yamashita 《Physics and Chemistry of Minerals》2007,34(7):477-484

The photoluminescence and excitation spectra of sodalites from Greenland, Canada and Xinjiang (China) are observed at 300 and 10 K in detail. The features of the emission and excitation spectra of the orange-yellow fluorescence of these sodalites are independent of the locality. The emission spectra at 300 and 10 K consist of a broad band with a series of peaks and a maximum peak at 648 and 645.9 nm, respectively. The excitation spectra obtained by monitoring the orange-yellow fluorescence at 300 and 10 K consist of a main band with a peak at 392 nm. The luminescence efficiency of the heat-treated sodalite from Xinjiang is about seven times as high as that of untreated natural sodalite. The emission spectrum of the S₂ ⁻ center in sodalite at 10 K consists of a band with a clearly resolved structure with a series of maxima spaced about 560 cm⁻¹ (20–25 nm) apart. Each narrow band at 10 K shows a fine structure consisting of a small peak due to the stretching vibration of the isotopic species of ³²S³⁴S⁻, a main peak due to that of the isotopic species of ³²S₂ ⁻ and five peaks due to phonon sidebands of the main peak.  相似文献   

Alteration of the equal settling ratio of fine particles by vertically-oscillating water     

Tatsuya Oki  Mikio Kobayashi  Shuji Owada  Daiki Matsuura 《International Journal of Mineral Processing》2007

An equal settling ratio is an important factor in estimating particle separation accuracy. However, this factor is often calculated using the settling velocity in stationary water, there are no examples of calculation of the equal settling ratio in an actual separator. This is difficult because particle movement in a separator is very complicated, and even simple periodic motions, such as the oscillation field used with many separators, are ignored in many cases. The authors have previously reported on the relation between the equal settling ratio and the oscillation frequency by analysis of particle movement in vertically oscillating water, using spherical particles of glass (average size 435 μm) and zirconia (202 μm) which have the same settling velocity in stationary water. In this study, the influence of particle diameter on the change in the settling velocity in oscillating water was experimentally investigated for three pairs of glass and zirconia particles having different sizes under 0.5 mm, which have the same settling velocity in stationary water. The settling velocities of different-sized particles decreased at different rates in oscillating water, indicating that the equal settling ratio is reduced by water oscillation. We conclude that water oscillation improves the accuracy of size separation for glass particles over 300 μm and zirconia particles over 150 μm when glass and zirconia particles are separated from each other with the difference of these settling velocities.  相似文献   

Multiple-Scattering Formulation of Pulsed Beam Waves in Hydrometeors and Its Application to Millimeter-Wave Weather Radar     

Ito  S. Kobayashi  S. Oguchi  T. 《Geoscience and Remote Sensing Letters, IEEE》2007,4(1):13-17

This letter deals with the backscattering of millimeter pulsed beam waves from hydrometeors. A new approach is presented for a solution of time-dependent three-dimensional vector radiative transfer equation for the Stokes vectors to study the multiple-scattering effects of beam waves on radar echoes. General solutions for beam waves are derived in an integral form without any approximation. They are given in numerically tractable forms representing the scattering process in the space and time domain. Time-dependent second-order solutions for radar echoes of pulsed beam waves are straightforwardly obtained to predict multiple-scattering effects depending on the variation of an incident beam size. It is shown that the inhomogeneity of the radial direction of beam waves causes the mode coupling of waves between the azimuth directions in the scattering matrix, and that the mode coupling depends on the ratio of the incident beam size to the total mean free path length of the medium  相似文献   

A new high-pressure and high-temperature polymorph of FeS     

Hiroaki Ohfuji  Nagayoshi Sata  Hisao Kobayashi  Yasuo Ohishi  Kei Hirose  Tetsuo Irifune 《Physics and Chemistry of Minerals》2007,34(5):335-343

A new polymorph of FeS has been observed at pressures above 30 GPa at 1,300 K by in situ synchrotron X-ray diffraction measurements in a laser-heated diamond anvil cell. It is stable up to, at least, 170 GPa at 1,300 K. The new phase (here called FeS VI) has an orthorhombic unit cell with lattice parameters a = 4.8322 (17) Å, b = 3.0321 (6) Å, and c = 5.0209 (8) Å at 85 GPa and 300 K. Its topological framework is based on the NiAs-type structure as is the case for the other reported polymorphs (FeS I-V). The unit cell of FeS VI is, however, more distorted (contracted) along the [010] direction of the original NiAs-type cell. For example, the c/b axial ratio is ～1.66 at 85 GPa and 300 K, which is considerably smaller than that of orthorhombic FeS II (～1.72) and NiAs-type hexagonal FeS V (=√3 ≈ 1.73). The phase boundary between FeS IV and VI is expected to be located around 30 GPa at 1,300 K. The phase transition is accompanied by gradual and continuous changes in volume and axial ratios and may be second order. At room temperature, FeS VI becomes stable over FeS III at pressures above 36 GPa. It is, therefore, suggested that the phase boundary of FeS III–VI and/or FeS IV–VI has negative pressure dependence.  相似文献   

The role of an extreme flood disturbance on macrophyte assemblages in a Neotropical floodplain     

André Andrian Padial  Priscilla Carvalho  Sidinei Magela Thomaz  Solana Meneghel Boschilia  Roberta Becker Rodrigues  Josilaine Taeco Kobayashi 《Aquatic Sciences - Research Across Boundaries》2009,71(4):389-398

Aquatic macrophytes produce large amounts of organic matter and have an essential structuring role in floodplains. This process highlights the importance of this community to aquatic biodiversity maintenance. We investigated the role of a flood disturbance on the response of macrophyte assemblages in regional and local structuring in the Upper Paraná River floodplain. Plant species were recorded before (November 2006) and after (March 2007) an uncommon increase in water level caused by the El Niño South Oscillation, which is considered a disturbance. Samples were taken in lakes and backwaters located in the floodplain and connected to three distinct rivers (that differentiate three sub-systems). Species richness and the assemblage structure of macrophyte patches underwent significant changes after the flood disturbance, depending on the specific sub-system (rivers) to which the lakes were connected. In addition, flood disturbance had a strong impact on community organization at the local scale. However, regionalization with respect to sub-systems remained significant after the flood disturbance. Our results emphasize the importance of connection to the river on macrophyte community composition and richness, and suggest that flood events in the Upper Paraná River floodplain disrupt community organization only at fine (local) scales.  相似文献   

Purification of seawater contaminated with undegradable aromatic ring compounds using ozonolysis followed by titanium dioxide treatment   总被引：1，自引：0，他引：1  

Nakamura Y  Kobayashi F  Daidai M  Kurosumi A 《Marine pollution bulletin》2008,57(1-5):53-58

Treatment of aromatic ring compounds, 2,4-dichlorophenoxy acetic acid (2,4-D), 2,4,5-trichloro-phenoxy acetic acid (2,4,5-T), and bisphenol A, in the artificial seawater, i.e. Allen seawater, was carried out by ozonation and titanium dioxide (TiO2) photocatalyst treatment. Each compound was degraded and varnished within 30 min by only ozonolysis at pH 9.0 and at 20 degrees C, while the TOC value of each compound decreased gradually but reached almost constant value, i.e. about 70-80% of the initial value, at even 30 min of ozonation time. Ozonolysis (30 min of ozonation time) followed by TiO2 photocatalyst treatment (50h of reaction time) was a very effective method for decreasing the TOC values of aromatic ring compounds in the artificial seawater. In consequence, TOC values of 2,4-D, 2,4,5-T, and bisphenol A could be reduced to about 28, 21, and 34% of their initial values, respectively.  相似文献   

The XUV Doppler Telescope (XDT)     

Sakao  T.  Tsuneta  S.  Hara  H.  Shimizu  T.  Kano  R.  Kumagai  K.  Yoshida  T.  Nagata  S.  Kobayashi  K. 《Solar physics》1999,187(2):303-333

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