Large-scale chaotically mixed sedimentary body within the Late Pliocene to Pleistocene Chikura Group, Central Japan     

Yuzuru  Yamamoto  Yujiro  Ogawa  Takayuki  Uchino  Satoru  Muraoka  Tae  Chiba 《Island Arc》2007,16(4):505-507

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Simultaneous boninitic and arc-tholeiitic volcanisms in the Izu forearc region during early arc volcanism, based on ODP Leg 125 Site 786     

Satoru Haraguchi  Teruaki Ishii 《Contributions to Mineralogy and Petrology》2007,153(5):509-531

Early arc volcanism during Eocene to Oligocene in the Izu forearc region was investigated during ODP Legs 125 and 126 in 1989, and effusive and intrusive volcanics were recovered from Leg 125 Site 786. These rocks were all classified into boninites and associated rocks by Leg 125 Shipboard Scientific Party, and they concluded that boninitic volcanism had occurred before 40 Ma, and arc tholeiitic volcanism began after 40 Ma. In this study, lava flows and breccias that classified into boninite series are divided into two groups, tholeiite and boninite, based on petrographical and petrological properties. Both series are also distinguished by bulk rock composition. It is considered that the sources of both rock types have similar depleted compositions because of their similar, very low bulk HFSE concentrations. We suggest that boninitic and tholeiitic volcanism occurred closely in time and space, and reflected different temperature and water condition.  相似文献   

Diffusivity anisotropy in a rhyolite and its relation to pore structure     

Tadashi Yokoyama  Satoru Nakashima 《Engineering Geology》2005,80(3-4):328-335

The diffusivity anisotropy of ions through rock pore water was evaluated quantitatively by through-diffusion experiments on a rhyolite rock having anisotropic pore structure. The rhyolite has planar flow structure with elongated pore shapes to the flow direction (X–Y plane). Diffusion coefficients of K⁺ ions for the direction perpendicular to this flow structure (Z-direction) were about 5–9 times smaller than those for the orthogonal parallel directions (X- and Y-direction). Pore geometrical analyses on backscattered electron microscopic images indicated that the pore length ratios among the X-, Y-, and Z-direction were roughly 2 : 2 : 1. This shorter pore length for the Z-direction appears to reduce pore connectivity, causing larger tortuosity and smaller diffusivity for this direction. This diffusivity anisotropy needs to be taken into account for precise modeling of diffusion-limited geological processes such as contaminant transport and rock deformation.  相似文献   

Formation of a void and galaxies in a neutrino-dominated universe     

Masayuki Umemura  Satoru Ikeuchi 《Astrophysics and Space Science》1986,119(1):243-245

The recent discovery of the large honeycomb structure of the Universe has triggered many models of the Universe dominated by dark matter. The neutrino-dominated universe is a favorable model for explaining the size of the large-scale structure and the dark matter of the larger scale than the galactic one. Our calculations on the evolution of density perturbations in a two-component universe composed of neutrinos and dissipative gas on a spherically-symmetric model have shown that the galactic scale does correlate the scale of a void of galaxies: if a neutrino has the mass of some tens eV, galaxies of the typical size form surrounding a typical void.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.  相似文献   

Calcium-alkalinity-nitrate relationship in the north pacific and the Japan Sea     

Hisashi Ikegami  Satoru Kanamori 《Journal of Oceanography》1983,39(1):9-14

When biogenic particles of calcium carbonate and organic matter are formed or decomposed in sea water, calcium concentration, alkalinity and nitrate concentration are changed according to the following equation: ΔCa=0.5 ΔTA+0.63 ΔNO ₃, where ΔCa, ΔTA and ΔNO ₃ are the differences in calcium, alkalinity and nitrate concentration, respectively, between two waters. This relationship was pointed out in a previous paper of ours, and it holds well for data obtained from the North Pacific and the Japan Sea. Furthermore, in sea water containing little or no nutrients, the variations in calcium concentration and alkalinity are consistent with the variations expected from the formation and dissolution of calcium carbonate alone.  相似文献   

The determination of Mn,Fe, Ni,Cu and Zn in seawater by atomic absorption spectrometry after coprecipitation with lanthanum hydroxide     

Yoshimasa Toyota  Shiro Okabe  Satoru Kanamori  Yasushi Kitano 《Journal of Oceanography》1983,38(6):357-361

A simple and rapid coprecipitation method for the determination of several trace metals in seawater is presented. These metals are coprecipitated with lanthanum hydroxide, the precipitate is dissolved, and then the metals are determined by atomic absorption spectrometry. Lanthanum hydroxide was chosen as a coprecipitant for the following reasons, (a) lanthanum hydroxide has a sufficiently low solubility and forms an easily filterable flocculate at about 80C, and (b) lanthanum has an absorption wavelength that is sufficiently separated from those of the other elements to be analysed, i.e., Mn, Fe, Ni, Cu and Zn. Experimental results show that these metals are coprecipitated by the present method with excellent recoveries.  相似文献   

Early tholeiitic and calc-alkaline arc magmatism of middle to Late Eocene Age in the southern Ogasawara (Bonin) forearc     

Satoru Haraguchi  Teruaki Ishii  Jun-Ichi Kimura 《Contributions to Mineralogy and Petrology》2008,155(5):593-618

Analysis of middle and upper Eocene rocks from the IBM forearc, including the Ogasawara and Mariana Islands, help illuminate early arc volcanism of the proto-IBM arc. Dredged volcanic rocks from the forearc are two-pyroxene basalt to andesite, and may be divided into two groups, tholeiite and calc-alkaline, on the basis of mineralogy, petrography, and bulk chemistry. Tholeiites are characterized by high HFSE contents, high crystallization temperatures, and low water contents. In contrast, the calc-alkaline rocks are characterized by low HFSE contents, low crystallization temperatures, and higher water contents. These characteristics indicate that magma genesis for the two series differed. The tholeiites resulted from high degrees of partial melting of slightly depleted mantle under anhydrous conditions, whereas the calc-alkaline rocks were generated by low degrees of melting of depleted mantle under hydrous conditions. We believe that differences in mantle depletion arose from compositional layering and fluid zonations caused by MORB volcanism and slab dehydration, respectively. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

Sequential explosions of supernovae in an ob association and formation of a superbubble     

Kohji Tomisaka  Asao Habe  Satoru Ikeuchi 《Astrophysics and Space Science》1981,78(2):273-285

From the standpoint of view that the early type stars are formed sequentially at an OB association, it is expected that the supernova explosions will also occur sequentially. We study the expansion law of a supernova remnant, which is formed by sequential explosions of supernovae. The superbubbles and supershells with the radii 2001000 pc are naturally explained by this model. Assuming that the sequential explosion of supernovae occurs at every OB association, we deduce the star formation rate in our Galaxy.  相似文献   

Time evolution of hydraulic and electrokinetic parameters around the Nojima fault, Japan, estimated by an electrokinetic method     

Hideki Murakami  Naoto Oshiman  Satoru Yamaguchi  Takeshi Hashimoto  Ryokei Yoshimura 《Tectonophysics》2007,443(3-4):200

The Nojima Fault Zone Probe was designed to study the properties and healing processes of the Nojima fault, which is the surface fault rupture of the Hyogo-ken Nanbu earthquake (M7.2) of 1995 (1995 Kobe earthquake). In this project, water injection experiments were conducted in a borehole of 1800 m depth at the Nojima fault. We set up electrodes around the borehole and observed self-potential variations to investigate the magnitude of electrokinetic and hydraulic parameters around the Nojima fault zone. In the 1997 experiment, self-potential variations were in the range of a few to about 20 mV across 320–450 m electrode dipoles with hydraulic pressure variations from 3.5 to 4 MPa. In the 2000 experiment, self-potential variations were in the range of a few to about 85 mV across 160–260 m electrode dipoles with the hydraulic pressure variations from 3 to 4.5 MPa. In the 2003 experiment, self-potential variations were in the range of a few to about 30 mV across 20–80 m electrode dipoles with hydraulic pressure of 4 MPa. These observed self-potential variations were explained well with an electrokinetic effect due to the underground flow of the injected water. From the observed results, we estimated that the ratio of hydraulic parameters (permeability, porosity, and tortuosity) to electrokinetic parameters (zeta potential and dielectric constant) decreased approximately 40% during eight years after the earthquake. This result suggests that the healing process around the fault zone progress.  相似文献   

Water content in natural eclogite and implication for water transport into the deep upper mantle   总被引：14，自引：0，他引：14  

Ikuo Katayama  Satoru Nakashima  Hisayoshi Yurimoto 《Lithos》2006,86(3-4):245-259

Infrared spectroscopy and ion micro-probe measurements showed that the major constituent minerals of eclogites from the Kokchetav massif, which have been subducted to 180 km depths, contain significant amounts of water up to 870 ppm H₂O (by weight) in omphacite, 130 ppm H₂O in garnet and 740 ppm H₂O in rutile. Omphacite shows three hydroxyl absorption bands at 3440–3460, 3500–3530 and 3600–3625 cm^− 1, garnet has a single band at 3580–3630 cm^− 1 and rutile has a single sharp band at 3280 cm^− 1. The hydroxyl absorbance at these wavenumbers changes with the crystal orientation in polarized infrared radiation, indicating that the water is structurally incorporated in these minerals. The water contents in omphacite and garnet increase systematically with the metamorphic pressure of the host eclogites. The partitioning coefficient of the water content between coexisting garnet and omphacite is similar in different eclogites, D^Grt/Omp0.1–0.2, but decreases slightly at high pressure. Based on the mineral proportions of the eclogites, we estimate bulk-rock water content in the eclogites ranging from 3070 to 300 ppm H₂O (by weight). Although hydrous minerals are absent in the diamond-grade eclogite (60 kbar and 1000 °C), trace amounts of water are incorporated in the nominally anhydrous minerals such as omphacite and garnet. The presence of significant water in these minerals implies that the subducting oceanic crust can transport considerable amounts of water into the deep upper mantle beyond the stability of hydrous minerals. Such water may be stored in the deep upper mantle and have an important influence on dynamics in the Earth's interior.  相似文献