Occurrence of calcite in Sanbagawa pelitic schists: implications for the formation of garnet, rutile, oligoclase, biotite and hornblende   总被引：2，自引：0，他引：2  

A. Goto  S. Banno  T. Higashino  C. Sakai 《Journal of Metamorphic Geology》2002,20(2):255-262

The frequency of occurrence of minerals in 1876 samples of Sanbagawa pelitic schist in central Shikoku is summarized on the basis of microscopic observation accompanied, in part, by use of an electron microprobe. All samples contain quartz, plagioclase, phengite, chlorite and graphite. More than 90% of samples contain clinozoisite, titanite and apatite. Garnet is present in 95% of samples from the garnet zone, and biotite is present in 64% of samples from the albite‐biotite zone. Calcite is found in about 40% of samples of the pelitic schist collected from outcrop, but occurs in 95% of the pelitic schist from drill cores. Calcite was apparently ubiquitous in the pelitic schist during the Sanbagawa metamorphism, but must have been dissolved recently by the action of surface or ground water. The mineral assemblages of the Sanbagawa pelitic schist have to be analyzed in the system with excess calcite, quartz, albite (or oligoclase), clinozoisite, graphite and fluid that is composed mainly of H₂O, CO₂ and CH₄. In the presence of calcite, reactions that produce garnet, rutile, oligoclase, biotite and hornblende, some of which define isograds of the metamorphic belt, should be written as mixed volatile equilibria that tend to take place at lower temperature than the dehydration reactions that have been proposed. The presence of calcite in pelitic schist suggests that fluid composition is a variable as important in determining mineral assemblages as pressure and temperature. Thus Ca‐bearing phases must be taken into account to analyze the phase relations of calcite‐bearing pelitic schist, even if CaO content of Sanbagawa pelitic schist is low. As calcite is a common phase, the mineral assemblages of the biotite zone pelitic schist may contravene the mineralogical phase rule and warrant further study.  相似文献   

Concentrations and isotope ratios of carbon,nitrogen and sulfur in ocean-floor basalts     

H. Sakai  D.J.Des Marais  A. Ueda  J.G. Moore 《Geochimica et cosmochimica acta》1984,48(12):2433-2441

Fresh submarine basalt glasses from Galapagos Ridge, FAMOUS area, Cayman Trough and Kilauea east rift contain 22 to 160 ppm carbon and 0.3 to 2.8 ppm nitrogen, respectively, as the sums of dissolved species and vesicle-filling gases (CO₂ and N₂). The large range of variation in carbon content is due to combined effect of depth-dependency of the solubility of carbon in basalt melt and varying extents of vapour loss during magma emplacement as well as in sample crushing. The isotopic ratios of indigenous carbon and nitrogen are in very narrow ranges,?6.2 ± 0.2% relative to PDB and +0.2 ± 0.6 %. relative to atmospheric nitrogen, respectively. In basalt samples from Juan de Fuca Ridge, however, isotopically light carbon (δ¹³C = around ?24%.) predominates over the indigenous carbon; no indigenous heavy carbon was found. Except for Galapagos Ridge samples, these ocean-floor basalts contain 670 to 1100 ppm sulfur, averaging 810 ppm, in the form of both sulfide and sulfate, whereas basalts from Galapagos Ridge are higher in both sulfur (1490 and 1570 ppm) and iron (11.08% total iron as FeO). The δ³⁴S values average +0.3 ± 0.5%. with average fractionation factor between sulfate and sulfide of +7.4 ± 1.6%.. The sulfate/sulfide ratios tend to increase with increasing water content of basalt, probably because the oxygen fugacity increases with increasing water content in basalt melt.  相似文献   

Fugacity-concentration relationship of dilute hydrogen in water at elevated temperature and pressure     

Noriaki Kishima  Hitoshi Sakai 《Earth and Planetary Science Letters》1984,67(1):79-86

The fugacity vs. concentration ratio(Y) of dilute hydrogen dissolved in water was determined at temperatures below 500°C and pressures below 1000 bar by measuring H₂ concentrations in magnetite-hematite-water and palladium hydride-water systems. Combining these results with reported solubility data of H₂ in water and with the Shaw's expression for the activity-composition relationship of H₂H₂O mixture at higher temperatures, theP-T-Y diagram was constructed over theP-T range below 900°C and 1000 bar.  相似文献   

Identification of constitutive androstane receptor cDNA in northern fur seal (Callorhinus ursinus)     

Sakai H  Iwata H  Kim EY  Tanabe S  Baba N 《Marine environmental research》2004,58(2-5):107-111

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Characterization of Fe(III) (hydr)oxides in arsenic contaminated soil under various redox conditions by XAFS and Mössbauer spectroscopies     

Satoshi Mitsunobu  Yoichi Sakai  Yoshio Takahashi 《Applied Geochemistry》2008

Characterization of Fe(III) (hydr)oxides in soils near the Ichinokawa mine was conducted using X-ray absorption fine structure (XAFS) and Mössbauer spectroscopies, and the structural changes were correlated with the release of As into pore-water. The Eh values decreased monotonically with depth. Iron is mainly present as poorly-ordered Fe(III) (hydr)oxides, such as ferrihydrite, over a wide redox range (from Eh = 360 to −140 mV). Structural details of the short-range order of these Fe(III) (hydr)oxides were examined using Mössbauer spectroscopy by comparing the soil phases with synthesized ferrihydrite samples having varying crystallinities. The crystallinity of the soil Fe (hydr)oxides decreased slightly with depth and Eh. Thus, within the redox range of this soil profile, ferrihydrite dominated, even under very reducing conditions, but the crystalline domain size, and, potentially, particle size, changed with the variation in Eh. In the soil–water system examined here, where As concentration and the As(III)/As(V) ratio in soil water increased with depth, ferrihydrite persisted and maintained or even enhanced its capacity for As retention with increased reducing conditions. Therefore, it is concluded that As release from these soils largely depends on the transformation of As(V) to As(III) rather than reductive dissolution of Fe(III) (hydr)oxide.  相似文献   

Prompt particle acceleration around moving X-point magnetic field during impulsive phase of solar flares     

Jun-Ichi Sakai 《Solar physics》1992,140(1):99-119

We present a model for high-energy solar flares to explain prompt proton and electron acceleration, which occurs around moving X-point magnetic fields during the implosion phase of the current sheet. We derive the electromagnetic fields during the strong implosion of the current sheet, which is driven by the converging flow toward the center of the magnetic arcade. We investigated a test particle motion in the strong electromagnetic fields derived from the MHD equations. It is shown that both protons and electrons can be promptly (within 1 s) accelerated to 70 and 200 MeV, respectively. This acceleration mechanism can be applicable for the impulsive phase of the gradual gamma-ray and proton flares (gradual GR/P flare), which have been called two-ribbon flares.  相似文献   

Classification of magnetic reconnection during two current-loop coalescence     

Jun-ichi Sakai  Shinji Koide 《Solar physics》1992,142(2):399-402

We present a classification of magnetic reconnection during two current loop coalescence, which may be quite important for the physical process of both solar flares and coronal loop heating in the solar active region. It is suggested that different kinds of the current loop coalescence processes could be identified from the soft X-ray telescope(SXT) of the Yohkoh satellite and the magnetic field data in the active region.  相似文献   

Earthquake simulation test of circular reinforced concrete bridge column under multidirectional seismic excitation     

Junichi Sakai Shigeki Unjoh 《地震工程与工程振动(英文版)》2006,5(1):103-110

1 Introduction Since the 1971 San Fernando earthquake, a signi?cant amount of research has been conducted on the ductility capacity of reinforced concrete bridge columns, resulting in signi?cant advances in the seismic design of bridges. Since most tests have been done in static or quasistatic conditions and unidirectional loading conditions, however, no method that properly evaluates the effect of multidirectional dynamic loading has been developed, and design recommendations on this effect a…  相似文献   

Measurement of Ocean Surface Currents by the CRL HF Ocean Surface Radar of FMCW Type. Part 2. Current Vector     

Akitsugu Nadai  Hiroshi Kuroiwa  Masafumi Mizutori  Shinnchi Sakai 《Journal of Oceanography》1999,55(1):13-30

The Communications Research Laboratory (CRL) has been developing high-frequency ocean surface radars (HFOSRs). The CRL dual-site HFOSR system can clarify the distribution of surface currents with a nominal range of 50 km. This paper presents a theoretical and experimental analysis of the measurement error of the current vector obtained by the CRL HFOSR system, using a comparison of instantaneous current vectors acquired by the HFOSR system and current meters moored at a depth of 2 m, taking account of the vertical current shear. The theoretical analysis shows that the probability distribution of the measurement error of the current vector forms concentric ellipses at a spatial scale that depends on the RMS measurement error of radial current velocity and with an aspect ratio that depends only on the azimuthal difference of the radar beams. When the azimuthal difference is a right angle, the measurement error of the current vector is at a minimum. A comparison between instantaneous current vectors measured by the CRL HFOSR system and moored current meters shows that the distribution of the difference vector between the radar current and the meter current agrees well with the theoretical measurement error of the current vector and that the RMS of difference vector length is about 10 cm s^–1 while the azimuthal difference between two radar beams is between 45 and 135 degrees. The accuracy of current measurement by the dual-site HFOSR system is therefore considered to be less than 10 cm s^–1 in this range of azimuthal difference. The theoretical analysis will be applicable for a wider range of the azimuthal difference of the radar beams.  相似文献   

THRUST PACKAGES OF 1.68 Ga INDIAN SUPRA-CRUSTAL ROCKS IN THE MIOCENE SIWALIK BELT,CENTRAL NEPAL HIMALAYAS     

Harutaka Sakai    Yutaka Takigami    B.N.Upreti    D.P.Adhikary  WT  ”BX 《地学前缘》2000,(Z1)

THRUST PACKAGES OF 1.68 Ga INDIAN SUPRA-CRUSTAL ROCKS IN THE MIOCENE SIWALIK BELT,CENTRAL NEPAL HIMALAYAS  相似文献