Paleostress orientation from 3-D orientation distribution of microcracks in quartz from the Cretaceous granodiorite core samples drilled through the Nojima Fault, south-west Japan   总被引：1，自引：0，他引：1  

Toru Takeshita  Koshi Yagi 《Island Arc》2001,10(3-4):495-505

Abstract The orientations of both healed extension microcracks and microcracks in quartz grains sealed mostly by carbonate minerals were measured from Cretaceous granodiorite core samples drilled along the Nojima Fault, southwest Japan. The preferred orientations of both healed and sealed microcracks consist of approximately three orthogonal sets, (components) A, B and C, in which A strikes NS–NW-SE and dips vertically, B strikes EW–NE-SW and dips vertically, and C is subhorizontal. Both the healed and sealed microcracks were possibly formed by hydraulic fracturing, and the successive release of tensile stress due to pore fluid overpressure in the principal stress directions could have caused this microcracking in mutually orthogonal directions. The quartz grains are also very moderately plastically deformed, which is indicated by the occurrence of kink bands and undulose extinction. The association of healed microcracks and kink bands in the quartz suggests that these microstructures formed under subgreenschist facies conditions (≈300°C) during hydrothermal activity that could have occurred immediately after the emplacement of granodiorite during the Late Cretaceous period. Based on both the preferred orientation of microcracks, and c-axis fabrics of kinked and unkinked grains (so called kink method), it is inferred that the σ₁-and σ₃-axis were oriented horizontally in NS–NW-SE and EW–NE-SW directions, respectively. The inferred paleostress field does not conform to the east–west-trending compression during the Quaternary period, but to the activation of EW–NE-SW-trending, left–lateral strike–slip faults during the Late Cretaceous period in southwest Japan.  相似文献   

Crystallization of chondrules in ordinary chondrites     

Makoto Kimura  Kenzo Yagi 《Geochimica et cosmochimica acta》1980,44(4):589-602

The process of crystallization and the origin of chondrules are discussed, in terms of the phase relations of the minerals in chondrules in six ordinary chondrites of the Yamato-74 meteorites, especially the Yamato-74191 (L3).Chondrules are classified into six types. The bulk compositions of chondrules projected onto the MgO-FeO-SiO₂ system show that the compositions of chondrules vary widely. Investigations by means of the MgO-Al₂O₃-SiO₂ system indicate that porphyritic chondrules can be regarded as products of supercooling crystallization. The growth rates of crystals in porphyritic chondrules were fairly small. The difference between types of chondrules is interpreted in terms of the compositions of chondrules and the nucleation temperatures of the supercooled droplets.All these observations and estimations must be taken into account for discussing the origin of chondrules. The impact and dust fusion theories do not appear to be plausible. Molten droplets due to these mechanisms will be glassy spherules, or crystallize at equilibrium. Only a liquid condensation theory can well explain the characteristic features and the process of the crystallization of chondrules.  相似文献   

Crystal-field spectra for blue and green diopsides synthesized in the join CaMgSi2O6-CaCrAlSiO6     

Ko Ikeda  Kenzo Yagi 《Contributions to Mineralogy and Petrology》1982,81(2):113-118

Synthetic diopsides in the join CaMgSi₂O₆ CaCrAlSiO₆ have been studied by means of crystal-field theory. These diopsides are either blue or pale green in colour. The former forms at lower temperatures and the latter at higher temperatures. The optical spectra and colours can be unequivocally explained based on the assumption that Cr³⁺ions occupy both tetrahedral and octahedral sites in the diopsides. In the blue diopsides Cr³⁺ions are present in two kinds of spin state, i.e., tetrahedrally coordinated low spin and octahedrally coordinated high spin. On heating the blue diopsides, tetrahedral occupancy of chromium decreases sharply due to spin transformation from tetrahedral low spin to octahedral high spin. Above 1,160° C nearly all chromium ions are present in octahedral sites with high spin state and the diopsides become pale green in colour. Some petrogenetic applications of the resultes are discussed.  相似文献   

Experimental investigation on forsterite-grossularite incompatibility in presence of excess water     

A. K. Gupta  Kenzo Yagi 《Bulletin of Volcanology》1978,41(4):657-663

A mixture containing equal amounts of forsterite and grossularite by weight (Fo₅₀Gr₅₀) has been studied at temperatures between 750 and 1400°C under pressures ranging from 6 to 25 kbar in presence of excess water. The assemblages noted under low pressure (<8 kbar) are as follows: Diopside_ss+forsterite_ss+monticellite_ss+vapor and Diopside_ss+forsterite_ss+monticellite_ss+liquid+vapor. (ss denotes solid solution) Under intermediate pressures between 8 and 24 kbar following assemblages were noted in the order of increasing temperature: Diopside_ss+forsterite_ss+spinel+vapor, Diopside_ss+forsterite_ss+spinel+liquid+vapor, Diopside_ss+forsterite_ss+liquid+vapor, and Forsterite_ss+liquid+vapor. At pressures above 24 kbar the assemblages are as follows: Diopside_ss+forsterite_ss+garnet+vapor, Diopside_ss+forsterite_ss+garnet+liquid+vapor, Diopside_ss+forsterite_ss+liquid+vapor, and Forsterite_ss+liquid+vapor. Electron microprobe analyses of diopside and forsterite crystallized at 1050°C and 23 kbar, show that the former contains 6 to 6.5 wt % of Al₂O₃ as solid solution whereas the latter incorporates 1.3 wt % of monticellite in solid solution. The monticellite content of forsterite increases at low pressures at a given temperature to about 6 wt % at 1050°C and 6 kbar. The study indicates that forsteritic olivine does not coexist with pure grossularite in the studied temperature and pressure ranges, although the former is in equilibrium with pyrope-rich garnet, containing 23 mole % grossularite. The study supports the conclusion ofWerner andLuth (1973) that the solubility of monticellite in forsterite decreases with increasing pressure at a given temperature. The results of the investigation are also in agreement with the findings ofKushiro andYoder (1966), who noted that spinel peridotites found in folded belts and in alkalic basalts are produced under intermediate pressures, whereas garnet peridotite xenoliths found in kimberlite and in orogenic belts are formed at high pressures.  相似文献   

Natural water-purification system observed in a shallow coastal lagoon: Matsukawa-ura,Japan     

Kohata K  Hiwatari T  Hagiwara T 《Marine pollution bulletin》2003,47(1-6):148-154

Field surveys and in situ experiments were conducted in the shallow Matsukawa-ura in summer to evaluate the biological efficiencies of shallow-water areas for preserving coastal ecosystems. In Matsukawa-ura (5.8 km(2)), the suspension-feeding bivalves Ruditapes philippinarum and Crassostrea gigas were the dominant animals--their total biomasses (wet weight) were estimated to be 3.4 x 10(6) and 2.3 x 10(6) kg, respectively. Ulva sp. and Zostera marina were the dominant macrophyte species during the summer, with standing crops estimated to be 0.29 x 10(6) and 0.20 x 10(6) kg, respectively. The dissolved inorganic nitrogen (DIN) uptake rates for Ulva sp. and Z. marina were determined by in situ experiments. An ecological model calculated on the basis of the observed dataset showed that, in comparison with tidal exchange, a significant amount of particulate organic matter was removed by bivalve filtration and a considerable quantity of DIN was removed by macrophyte species.  相似文献   

Application of spectral decomposition algorithm for mapping water quality in a turbid lake (Lake Kasumigaura,Japan) from Landsat TM data     

Youichi Oyama  Bunkei Matsushita  Takehiko Fukushima  Kazuo Matsushige  Akio Imai 《ISPRS Journal of Photogrammetry and Remote Sensing》2009,64(1):73-85

The remote sensing of Case 2 water has been far less successful than that of Case 1 water, due mainly to the complex interactions among optically active substances (e.g., phytoplankton, suspended sediments, colored dissolved organic matter, and water) in the former. To address this problem, we developed a spectral decomposition algorithm (SDA), based on a spectral linear mixture modeling approach. Through a tank experiment, we found that the SDA-based models were superior to conventional empirical models (e.g. using single band, band ratio, or arithmetic calculation of band) for accurate estimates of water quality parameters. In this paper, we develop a method for applying the SDA to Landsat-5 TM data on Lake Kasumigaura, a eutrophic lake in Japan characterized by high concentrations of suspended sediment, for mapping chlorophyll-a (Chl-a) and non-phytoplankton suspended sediment (NPSS) distributions. The results show that the SDA-based estimation model can be obtained by a tank experiment. Moreover, by combining this estimation model with satellite-SRSs (standard reflectance spectra: i.e., spectral end-members) derived from bio-optical modeling, we can directly apply the model to a satellite image. The same SDA-based estimation model for Chl-a concentration was applied to two Landsat-5 TM images, one acquired in April 1994 and the other in February 2006. The average Chl-a estimation error between the two was 9.9%, a result that indicates the potential robustness of the SDA-based estimation model. The average estimation error of NPSS concentration from the 2006 Landsat-5 TM image was 15.9%. The key point for successfully applying the SDA-based estimation model to satellite data is the method used to obtain a suitable satellite-SRS for each end-member.  相似文献   

Discovery of a large-scale clumpy structure around the Lynx supercluster at z∼ 1.27     

Fumiaki Nakata  Tadayuki Kodama  Kazuhiro Shimasaku  Mamoru Doi  Hisanori Furusawa  Masaru Hamabe  Masahiko Kimura  Yutaka Komiyama  Satoshi Miyazaki  Sadanori Okamura  Masami Ouchi †  Maki Sekiguchi  Yoshihiro Ueda  Masafumi Yagi  Naoki Yasuda 《Monthly notices of the Royal Astronomical Society》2005,357(4):1357-1362

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Evolution of the colour–radius and morphology–radius relations in SDSS galaxy clusters     

Tomotsugu Goto †  Masafumi Yagi  Masayuki Tanaka  Sadanori Okamura 《Monthly notices of the Royal Astronomical Society》2004,348(2):515-518

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Reconnaissance report on landslide disasters in northeast Japan following the M 9 T��hoku earthquake     

Toyohiko Miyagi  Daisuke Higaki  Hiroshi Yagi  Shoji Doshida  Noriyuki Chiba  Jun Umemura  Go Satoh 《Landslides》2011,8(3):339-342

An earthquake of M_w 9.0 struck the Pacific coast in northeast Japan on March 11, 2011 and was followed by a hugely damaging tsunami along 500 km of the Japanese coastline. An inland aftershock of M. 7.0 occurred on April 11; during which, surface fault ruptures appeared on land. A large variety of landslide disasters resulted from these earthquakes in various parts of northeastern Honshu, Japan. The full extent of the landslides is still being determined. This brief report introduces some of the landslide phenomena so far investigated by the Japanese Landslide Society. These are (1) failure of a water reservoir embankment dam in Sukagawa, Fukushima prefecture, (2) landslides and surface seismic fault rupture from the April 11 aftershock in Iwaki, Fukushima, (3) a concentration of surface failures at Matsushima Bay in Miyagi prefecture, and (4) small landslides on modified slopes in residential areas around Sendai city.  相似文献   

Puzzling calcite-III dimorphism: crystallography,high-pressure behavior,and pathway of single-crystal transitions   总被引：1，自引：1，他引：0  

T. Pippinger  R. Miletich  M. Merlini  P. Lotti  P. Schouwink  T. Yagi  W. A. Crichton  M. Hanfland 《Physics and Chemistry of Minerals》2015,42(1):29-43

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