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51.
52.
A Fourier analysis on galaxy number counts from redshift data of both the Sloan Digital Sky Survey and the 2dF Galaxy Redshift Survey indicates that galaxies have preferred periodic redshift spacings of Δz= 0.0102, 0.0246, and 0.0448 in the SDSS and strong agreement with the results from the 2dF GRS. The redshift spacings are confirmed by the mass density fluctuations, the power spectrum P(z) and N pairs calculations. Application of the Hubble law results in galaxies preferentially located on co-moving concentric shells with periodic spacings. The combined results from both surveys indicate regular co-moving radial distance spacings of 31.7±1.8 h?1?Mpc, 73.4±5.8 h?1?Mpc and 127±21 h?1? Mpc. The results are consistent with oscillations in the expansion rate of the universe over past epochs. 相似文献
53.
We investigated the structure and persistency of the dominant sea-surface temperature (SST) anomaly pattern in summer over
the North Pacific from 1960 to 2004, which has been attracting less attention than those in winter. The leading empirical
orthogonal functions (EOFs) for August and September, which can be treated as the summer patterns, rather resemble each other
in both spatial structure and time variations but are quite different from those of the other months. A lag correlation analysis
indicates that the summer patterns do not show significant persistency in the following winter and the summer of the next
year. An inappropriate definition of the summer season might obscure the characteristics of the dominant summer SST anomaly
pattern in the North Pacific. 相似文献
54.
We report Sr, Nd, and Pb isotopic data of young alkaline basalt lava from a new type of volcano (petit-spot) on the northwestern Pacific Plate. Petit-spot lavas show Dupal, or extremely EM-1-like, Sr-Nd-Pb isotopic compositions. The data cannot be explained by contamination of pelagic sediment, in spite of the prediction on the basis of geological observation. We thus consider that the geochemistry of petit-spot lava indicates the existence of recycled fertile plate materials, not only the Dupal isotopic signature, in the northern hemisphere Pacific upper mantle unrelated to one or more active plumes. In consideration of published experimental results for fertile plate materials, selective melting of recycled material is a process critical in generating petit-spot lava. Moreover, the small volume of the volcano and low degree of melting in the mantle source needed to form strongly alkalic lavas suggest that petit-spot volcanism is originated from small-scale heterogeneities of recycled material. This idea consistently explains the geochemistry and noble gas isotopic composition of petit-spot lava, and also suggests small-scale heterogeneity widespread in the upper mantle of the Pacific Ocean. Together with a revised view of upper mantle heterogeneity, we propose that gross upper mantle composition is controlled by abundances and scales of regions of recycled material that correspond to differences in the relative position to the Pangea supercontinent, suggesting the link to the tectonic origin of the global scale heterogeneity. 相似文献
55.
Atsushi Okamoto Hanae Saishu Nobuo Hirano Noriyoshi Tsuchiya 《Geochimica et cosmochimica acta》2010,74(13):3692-3706
We conducted hydrothermal flow-through experiments at 430 °C and 31 MPa to investigate the mechanism of silica precipitation on granite under crustal conditions. Two experiments were performed using different input solutions: a single-component Si solution, and a multi-component solution with minor Al, Na, and K. The degree of supersaturation with respect to quartz, Ω = CSi/CSi,Qtz,eq, where CSi and CSi,Qtz,eq indicate Si concentration in solutions and the solubility of quartz within water, respectively, decreased from 3-3.5 to <1.1 along the flow path. A variety of silica minerals formed during the experiments (opal-A, opal-C, chalcedony, and quartz), and their occurrences and modal abundances changed in response to Ω and the presence of additives in the solution.For near-equilibrium solutions (Ω < ∼1.2), silica precipitation occurred in a simple way in both experiments, being restricted to overgrowths on pre-existing quartz surfaces in the granite. At higher saturation levels (Ω > ∼1.2), silica minerals were deposited on other surfaces in addition to quartz. In the single-component experiment, the dominant silica minerals changed in the order of opal-A → opal-C → quartz with decreasing Si concentration along the flow path. In contrast, in the multi-component experiment, quartz and minor chalcedony formed throughout the entire reaction vessel. This finding indicates that impurities (Na, K, and Al) in the solutions inhibited the precipitation of opal and enhanced the direct nucleation of quartz. The systematic appearance of metastable silica minerals were examined by nucleation processes and macroscopic precipitation kinetics. Our experimental results indicate that different precipitation mechanisms yield contrasting textures, which in turn suggests that vein textures can be used as indicators of solution chemistry within the fracture. 相似文献
56.
Ayano Sofiya Akira Ishiwatari Naoto Hirano Tatsuki Tsujimori 《International Geology Review》2017,59(13):1621-1631
Serpentinites (massive and schistose) and listvenite occur as tectonic sheets and lenses within a calcareous metasedimentary mélange of the Tulu Dimtu, western Ethiopia. The massive serpentinite contains high-magnesian metamorphic olivine (forsterite [fo] ~96 mol%) and rare relict primary mantle olivine (Fo90–93). Both massive and schistose serpentinites contain zoned chromian spinel; the cores with the ferritchromite rims preserve a pristine Cr/(Cr+Al) atomic ratio (Cr# = 0.79–0.87), suggesting a highly depleted residual mantle peridotite, likely formed in a suprasubduction zone setting. Listvenite associated with serpentinites of smaller ultramafic lenses also contain relict chromian spinel having identical Cr# to those observed in serpentinites. However, the relict chromian spinel in listvenite has significantly higher Mg/(Mg+Fe2+) atomic ratios. This suggests that a nearly complete metasomatic replacement of ultramafic rocks by magnesite, talc, and quartz to prevent Mg–Fe2+ redistribution between relict chromian spinel and the host, that is, listvenite formation, took place prior to re-equilibration between chromian spinel and the surrounding mafic minerals in serpentinites. Considering together with the regional geological context, low-temperature CO2-rich hydrothermal fluids would have infiltrated into ultramafic rocks from host calcareous sedimentary rocks at a shallow level of accretionary prism before a continental collision to form the East African Orogen (EAO). 相似文献
57.
The sea surface heights (SSHs) observed by the TOPEX altimeter are compared with tide gauge data at Chichijima in Ogasawara (Bonin) Islands and hydrographic data taken around the islands, in order to quantitatively verify the altimeter observations and oceanic tide corrections by three tide models proposed by Cartwright and Ray (1991), Rayet al. (1994), and Maet al. (1994). First, performance of the new tide models is assessed by comparing tidal variations consisting of diurnal and semi-diurnal constituents with the tide gauge data at Chichijima. The tide model proposed by Rayet al. gives the smallest root-mean-squared (rms) difference of 2.61 cm. Errors in amplitude and phase in each tide model are evaluated by spectral analysis. The TOPEX SSHs corrected by the tide models are compared with sea level data at Chichijima. A long-term variation of a period of about 1 year is found in the residual between the SSHs and the Chichijima sea levels. This variation is also found in the difference between the dynamic height anomalies calculated from hydrographic data around the island and the Chichijima sea levels. By subtracting the long-term variation, the rms difference between the TOPEX SSHs and the Chichijima sea levels is reduced to about 4 cm and the slope of the regression line is improved to unity. The residual shows variations related to aliasing caused by incompleteness of the ocean tide correction with the repeat cycle of the altimeter observation. 相似文献
58.
We have collected 34 hot spring and mineral spring gases and waters in the Chugoku and Kansai districts, Southwestern Japan
and measured the 3He/4He and 4He/20Ne ratios by using a noble gas mass spectrometer. Observed 3He/4He and 4He/20Ne ratios range from 0.054 Ratm to 5.04 Ratm (where Ratm is the atmospheric 3He/4He ratio of 1.39 × 10−6) and from 0.25 to 36.8, respectively. They are well explained by a mixing of three components, mantle-derived, radiogenic,
and atmospheric helium dissolved in water. The 3He/4He ratios corrected for air contamination are low in the frontal arc and high in the volcanic arc regions, which are consistent
with data of subduction zones in the literature. The geographical contrast may provide a constraint on the position of the
volcanic front in the Chugoku district where it was not well defined by previous works. Taking into account the magma aging
effect, we cannot explain the high 3He/4He ratios of the volcanic arc region by the slab melting of the subducting Philippine Sea plate. The other source with pristine
mantle material may be required. More precisely, the highest and average 3He/4He ratios of 5.88 Ratm and 3.8±1.6 Ratm, respectively, in the narrow regions near the volcanic front of the Chugoku district are lower than those in Kyushu and Kinki
Spot in Southwestern Japan, but close to those in NE Japan. This suggests that the magma source of the former may be related
to the subduction of the Pacific plate, in addition to a slight component of melting of the Philippine Sea slab. 相似文献
59.
Yasushi Fukamachi Iori Tanaka Kay I. Ohshima Naoto Ebuchi Genta Mizuta Hideo Yoshida Shiro Takayanagi Masaaki Wakatsuchi 《Journal of Oceanography》2008,64(3):385-392
The vertical structure of the Soya Warm Current (SWC) was observed by a bottom-mounted acoustic Doppler current profiler (ADCP)
in the region of the SWC axis near the Soya Strait during a 1-year period from May 2004. The ADCP data revealed a marked seasonal
variability in the vertical structure, with positive (negative) vertical shear in summer and fall (winter and spring). The
volume transport of the SWC is estimated on the basis of both the vertical structure observed by the ADCP and horizontal structure
observed by the ocean radars near the strait. The transport estimates have a minimum in winter and a maximum in fall, with
the yearly-averaged values in the range of 0.94–1.04 Sv (1 Sv = 106 m3 s−1). These lie within a reasonable range in comparison to those through other straits in the Japan Sea. 相似文献
60.
The popularity of applying filtering theory in the environmental and hydrological sciences passed its first climax in the
1970s. Like so many other new mathematical methods it was simply the fashion at the time. The study of groundwater systems
was not immune to this fashion, but neither was it by any means a prominent area of application. The spatial-temporal characteristics
of groundwater flow are customarily described by analytical or, more frequently, numerical, physics-based models. Consequently,
the state-space representations associated with filtering must be of a high order, with an immediately apparent computational
over-burden. And therein lies part of the reason for the but modest interest there has been in applying Kalman filtering to
groundwater systems, as reviewed critically in this paper. Filtering theory may be used to address a variety of problems,
such as: state estimation and reconstruction, parameter estimation (including the study of uncertainty and its propagation),
combined state-parameter estimation, input estimation, estimation of the variance-covariance properties of stochastic disturbances,
the design of observation networks, and the analysis of parameter identifiability. A large proportion of previous studies
has dealt with the problem of parameter estimation in one form or another. This may well not remain the focus of attention
in the future. Instead, filtering theory may find wider application in the context of data assimilation, that is, in reconstructing
fields of flow and the migration of sub-surface contaminant plumes from relatively sparse observations.
Received: October 27, 1997 相似文献