Diverse mineralogical and oxygen isotopic signatures recorded in CV3 carbonaceous chondrites     

Hatsumi Ishida  Tomoki Nakamura  Hitoshi Miura  Yuki Kakazu 《Polar Science》2012,6(3-4):252-262

We describe the petrography and mineralogy of six CV3 carbonaceous chondrites. LAP02206, LAP02228, LAP04843, and GRA06101 are classified as oxidized Allende-like chondrites (CV3_oxA). RBT04143 and QUE97186 are classified as members of the reduced subtype (CV3_red). Chondrules in the CV3_oxA chondrites show extensive Fe–Mg zoning. Fe-rich olivine in the rims of the CV3_oxA chondrules are ¹⁶O-poor relative to Mg-rich olivine in the cores, suggesting that in addition to Fe and Mg, oxygen was exchanged between chondrules and matrix during weak thermal metamorphism. The CV3_red chondrites appear to have formed through various processes. QUE97186 shows chondrule flattening with a preferred orientation, which is interpreted to have resulted from shock impact at a pressure of ～20 GPa. The post-shock residual heat (～1000 °C) is likely to be responsible for the restricted Fe/Mg ratios of matrix olivine. Based on the degree of Fe–Mg homogenization of matrix olivines, we estimate the spatial scale of the shock-heated region to be ～1 m. RBT04143 is a breccia containing many clasts of two types of lithologies: reduced-type material and very weakly altered material.  相似文献   

Geochemical characteristics of pelagic chert sequences across the Permian-Triassic boundary in southwest Japan   总被引：1，自引：0，他引：1  

Hroaki  Ishiga  Kotaro  Ishida  Kaori  Dozen Makoto  Musashino 《Island Arc》1996,5(2):180-180

Abstract Geochemical characteristics, mainly of major and trace elements and REE (rare earth elements) of bedded chert and shale/mudstone sequences, across the Permian/Triassic boundary in southwest Japan are examined. The boundary is characterized by the disappearance of bedded cherts, and the interval between the Upper Permian cherts and Lower Triassic (probably Smithian) cherts comprises siliceous shales and organic black mudstones. Bedded cherts are characterized by a gradual depletion of chemical elements from Middle to Upper Permian. However, overlying siliceous shales exhibit a clear enrichment in some elements, especially alkaline metals (such as K, Rb and Cs) and Ti, Th, Y, P₂O₅, and REE in comparison with elements of the PAAS (post Archean Australian shales). This indicates that average components of the upper continental crust were transported in the boundary interval, possibly caused by volcanic activity. Ce-negative shifting in NASC (North American Shales Composite)-normalized REE patterns is characteristic of this interval, and could be related to the deposition of siliceous rocks in Ce-depleted seawater. This was probably caused by an invasion of water mass with a Ce-negative anomaly into the previously existing water mass of the Paleo-Tethys. Weak negative Eu-anomalies in this interval are suggestive of plagioclase fractionation caused by acid volcanisms and the LREE/HREE ratios in the interval show a slightly light-REE enrichment. Organic black mudstones are characteristically intercalated in the interval. These rocks are usually regarded as a product of oceanic deterioration, but in pelagic conditions, organic materials were formed by high primary production that resulted from the active upwelling of ocean floor water currents with rich nutrients. This may have been caused by the inferred mixing of water masses of the Paleo-Tethys and of the Panthalassa in Early Triassic time which was regarded as an event synchronous with an increase in volcanic activity on highly matured island arcs and/or continents.  相似文献   

Radiolarian-bearing conglomerate from the Hayang Group, the Kyongsang Supergroup, southeastern Korea   总被引：1，自引：0，他引：1  

T. Mitsugi  K. Ishida  B. -G. Woo  K. -H. Chang  S. -O. Park  H. Hirano 《Journal of Asian Earth Sciences》2001,19(6):87

The non-marine Cretaceous Kyongsang Supergroup, which is divided into the Sindong, the Hayang and the Yuchon groups, is widely distributed in southeastern Korea. Radiolarian-bearing pebbles are collected from the conglomerates of the Kumidong and the Kisadong formations of the Hayang Group. The age of radiolarian fossils range from Late Permian to Middle Jurassic. In Korea, Permian to Middle Jurassic marine chert beds are not exposed. The directions of paleocurrents of the Kumidong and the Kisadong formations are mainly from the northeast to southwest. During Cretaceous time, the Mino-Tamba Belt, within which Permian to Middle Jurassic chert beds are exposed, is suggested to have been located northeast of the Kyongsang Basin. The radiolarian faunas of the Hayang Group are similar to those of the Mino-Tamba Belt and other associated Mesozoic accretionary belts in Japan (e.g. the Ashio Belt). The provenance of the radiolarian-bearing pebbles collected from the Kumidong and the Kisadong formations is interpreted to be the Mino-Tamba Belt and other associated Mesozoic accretionary belts in Japan.  相似文献   

Measurements of the effective attachment coefficient between RaA ions and condensation nuclei     

Yukimasa Ikebe  Michikuni Shimo  Minoru Kawano 《Pure and Applied Geophysics》1970,83(1):131-141

Summary To clarify the interaction between RaA ions and condensation nuclei, simultaneous measurements of the concentration of RaA ions (n _A), radon-222, and condensation nuclei (Z) were carried out at several stations. In some occasions, the diffusion coefficients of nuclei (D) were also measured. It was found that the correlation among them may be well expressed by the simple formula;q _A = _A n_A Z. The correlation between _A andD (or radius of nuclei) was also obtained.The effective attachment coefficient of RaA ions was compared with that of small ordinary ions, and it was presumed that about one fourth of RaA atoms formed on the decay of radon-222 is positively charged, and the rest is neutral.  相似文献   

Cosmic ray sidereal diurnal variation of galactic origin observed by neutron monitors     

K. Nagashima  Y. Ishida  S. Mori  I. Morishita 《Planetary and Space Science》1983,31(11):1269-1278

We have analyzed the sidereal diurnal variation of cosmic rays, using 620 station-years of neutron monitor data during the period 1958–1979. The sidereal variation averaged over the period for all the stations in the Northern Hemisphere is different from the corresponding variation in the Southern Hemisphere. The difference is statistically significant and can be identified with the spurious sidereal variation produced from the stationary anisotropy of solar origin, responsible for the solar semi-diurnal variation. The variation common to both hemispheres is also exceptionally significant from the statistical point of view and could be regarded as being due to a uni-directional galactic anisotropy. This variation has an amplitude of 0.0204 ± 0.0015% and a phase of 6.8 ± 0.3 h and is clearly different from that ( ～ 0.05%, 0 ～ 3 h) observed in the high rigidity region (500 ～ 10⁴ GV). The physical meaning of the variation is discussed from the standpoint of the heliomagnetospheric modulation of galactic anisotropy.  相似文献   

Determination of Multiple Trace Element Compositions in Thin (> 30 μm) Layers of NIST SRM 614 and 616 Using Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS)     

Tomoaki Morishita  Yoshito Ishida  Shoji Arai  Miki Shirasaka 《Geostandards and Geoanalytical Research》2005,29(1):107-122

To understand and/or avoid small-scale chemical heterogeneities within geological materials prepared as normal thin sections, in situ multiple trace element determination coupled with the simultaneous microscopic observation of the sample during analysis is preferable. We have examined fifty trace elements in thin (< 30 μm) layers of the NIST SRM 614 and 616 glass reference materials by LA-ICP-MS using different pit diameters and internal standard elements (Ca and Si). Compositional heterogeneities of Tl, Bi, As and Cd were found in NIST SRM 614 and 616 at the spatial resolution of ca. 10 0 μm. Except for these elements, the RSDs of six determinations for most elements were better than 10% in NIST SRM 614 when ablation diameters were < 50 μm. The measured concentrations for most elements in NIST SRM 614 and 616 agree with previous values in the literature at the 95% confidence level with the exception of W and Bi. New LA-ICP-MS data for K, As and Cd are also reported. The results support the view that the latest LA-ICP-MS is a powerful and flexible analytical technique for the determination of multiple ultra-trace element compositions in geological materials prepared as normal thin sections of the type that has been used for polarising optical microscopic observations since the end of the 19th century.  相似文献   

Observation of core discing and in situ stress measurements; Stress criteria causing core discing     

Dr. T. Ishida  T. Saito 《Rock Mechanics and Rock Engineering》1995,28(3):167-182

Summary Core discing was typically observed in cores recovered from near horizontal holes drilled in Palaeogene sandstones at a depth of 1055 m in the Horonai colliery, Hokkaido, Japan. We have observed disc- and ring-like cores and measured in situ stress where they were recovered. We compared the measured stress state with an empirical criterion of core discing based on Obert and Stephenson (1965) and a theoretical criterion based on Sugawara et al. (1978) and Ishida and Saito (1989). Consequently, we found that disc-like cores were recovered under lower stress state than predicted by both criteria. The stress state where ring-like cores were recovered satisfied the empirical criterion, however, it was below the critical stress state according to the theoretical criterion. These discrepancies indicate that existing stress criteria are not satisfactory and that further experimental, theoretical and field investigations are needed.  相似文献   

The effects of mesoscale convective cells on the surface wind field over the ocean     

Hiroshi Ishida  Wayne V. Burt  Yasushi Mitsuta 《Boundary-Layer Meteorology》1984,29(1):75-84

Near-surface wind velocities were measured on an array of anchored spar buoys in the East China Sea in February 1975 as a part of the Japanese AMTEX '75 (Air Mass Transformation Experiment), a subprogram of GARP. These data were used to determine the effects of atmospheric convection associated with mesoscale convective cells (MCC) on near-surface winds over the ocean. When MCC were present, a peak occurred in the near-surface wind spectrum in the so-called spectral gap.  相似文献   

Melting and Multi-stage Metasomatism in the Mantle Wedge beneath a Frontal Arc Inferred from Highly Depleted Peridotite Xenoliths from the Avacha Volcano, Southern Kamchatka   总被引：3，自引：0，他引：3  

Ishimaru  Satoko; Arai  Shoji; Ishida  Yoshito; Shirasaka  Miki; Okrugin  Victor M. 《Journal of Petrology》2007,48(2):395-433

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Simultaneous In Situ Analysis of Carbon and Nitrogen Isotope Ratios in Organic Matter by Secondary Ion Mass Spectrometry          下载免费PDF全文

Akizumi Ishida  Kouki Kitajima  Kenneth H. Williford  Michael L. Tuite  Takeshi Kakegawa  John W. Valley 《Geostandards and Geoanalytical Research》2018,42(2):189-203

An in situ measurement method for simultaneous determination of carbon and nitrogen isotope ratios in organic matter was developed by secondary ion mass spectrometry with a spatial resolution of ~ 12 μm. Secondary ion intensities of ¹²C^?₂, ¹²C¹³C^?, ¹²C¹⁴N^? and ¹²C¹⁵N^? were simultaneously measured by three Faraday cups and one electron multiplier. Ions of ¹²C₂H^? were measured to monitor hydride interferences and to correct for mass bias. The analytical precisions of δ¹³C and δ¹⁵N values of a reference material (UWLA‐1 anthracite) were 0.16‰ and 0.56‰, respectively (2s). A negative correlation was observed between the mass bias of carbon and ¹²C₂H^?/¹²C^?₂ ratios of examined reference materials. In contrast, there was no correlation between mass bias and hydrogen concentration for nitrogen. The δ¹³C_VPDB and δ¹⁵N_Air values of twenty‐two individual globules of organic matter, found in carbonate rock of the 1878 Ma Gunflint Formation, were determined by the new procedure, ranging from ?33.8‰ to ?33.3‰ and +4.2‰ to 5.8‰, respectively. Means of δ¹³C_VPDB and δ¹⁵N_Air values, ?33.5 ± 0.25‰ and +5.2 ± 0.81‰, are consistent with reported values from bulk sample analysis within analytical precision.  相似文献