Paleomagnetic study of Cretaceous rocks of Peru, South America: Evidence for rotation of the Andes     

Kosuke Heki  Yozo Hamano  Hajimu Kinoshita  Asahiko Taira  Masaru Kono 《Tectonophysics》1984,108(3-4)

Paleomagnetic data for the Cretaceous volcanic and sedimentary rocks in the Andean region of Peru are given. Reliable paleomagnetic field directions were obtained for three Cretaceous (Albian to Cenomanian) formations from calcareous sediments in northern Peru. Stable remanent magnetization directions were also derived from twelve Cretaceous lava flows and dikes in coastal Peru. Paleomagnetic data of the same age from the stable areas of South America such as Brazil demonstrate that the paleomagnetic poles are nearly coincident with the present pole, but Peruvian paleomagnetic directions studied here showed several tens of degrees of counterclockwise declination shifts. This suggests counterclockwise tectonic rotation of an extensive block which includes the whole of Andean Peru.  相似文献   

On the stable growth of segregated ice in freezing soil under negligible overburden pressure     

Yoshisuke Nakano 《Advances in water resources》1986,9(4)

The stable growth condition of a segregated ice layer is studied by the use of the principle of mass and heat conservation. This condition evidently depends upon the properties of a thin transitional zone, which is believed to exist between the boundary of an ice layer and a 0[°C] isotherm. All probable models of the transitional zone are classified and the conditions for each model is derived. The effect of the small amount of soil minerals contained in an ice layer is also studied.  相似文献   

Transport of water in frozen soil: I: Experimental determination of soil-water diffusivity under isothermal conditions     

Yoshisuke Nakano  Allen Tice  Joseph Oliphant  Thomas Jenkins 《Advances in water resources》1982,5(4):221-226

A new experimental method for measuring the soil-water diffusivity of frozen soil under isothermal conditions is introduced. The theoretical justification of the method is presented and the feasibility of the method is demonstrated by experiments conducted using marine deposited clay. The measured values of the soil-water diffusivity are found comparable to reported experimental data.  相似文献   

Seepage and consolidation of bentonite saturated with pure- or salt-water by the method of unified molecular dynamics and homogenization analysis     

Y. Ichikawa  K. Kawamura  M. Nakano  K. Kitayama  T. Seiki  N. Theramast 《Engineering Geology》2001,60(1-4):127-138

Bentonite clay is a micro-inhomogeneous material, which consists of clay minerals (mainly montmorillonite), macro-grains (mainly quartz), water, air and others. Properties of the saturated bentonite clay are essentially characterized by the montmorillonite and water (i.e. montmorillonite hydrate). We analyze the molecular behavior of sodium montmorillonite hydrate Na_1/3Al₂[Si_11/3Al_1/3]O₁₀(OH)₂·nH₂O by applying a molecular dynamics (MD) simulation method. And by using the MD results we calculate the swelling property of the montmorillonite hydrate, and compare with an experimental result. Next, by using the same MD procedure we treat a montmorillonite mineral with a large number of external water molecules to check the properties of the water. Here we treat pure- and salt-water. Then we calculate the diffusivity and viscosity of water molecules and Na⁺ and Cl⁻ ions.

For extending the microscopic characteristics of constituent materials to a macroscopic seepage behavior of the micro-inhomogeneous material we apply a homogenization analysis (HA). That is, starting with the Navier–Stokes equation with distributed viscosity that is calculated by the former MD procedure we determine macroscopic permeability characteristics of bentonite for both cases of pure- and salt-water. Then, by using the permeability property we calculate long-term consolidation behavior of buffering clay, which is planed to be used for high-level radioactive waste (HLRW) management. Here the deformation is treated under the well-defined Cam clay model.  相似文献   

Mantled feldspars in alkali rhyolite from Oki-Dogo island,Japan     

Dr. S. Nakano  Prof. Dr. K. Suwa 《Mineralogy and Petrology》1995,54(3-4):277-289

Summary Feldspar phenocrysts in alkali rhyolite from Oki-Dogo island in the Sea of Japan show mantled textures with cores of anorthoclase and rims of sanidine. These feldspars were examined by electron microscopy, X-ray diffraction and X-ray microanalysis. Anorthoclase first crystallized, then was partially resorbed, and finally sanidine overgrew on the anorthoclase. Saw-tooth or comb-like interfaces between the cores and rims were likely formed at the magmatic stage of resorption and overgrowth. Optically perthitic intergrowths appear in thin sections cutting saw-tooth or comb-like interfaces of the mantled feldspars. The sanidine preserves primary cryptoperthitic textures of a periodicity smaller than 10 nm, which are considered to have been produced by subsolidus exsolution after the resorption event ended. The anorthoclase has no exsolution texture under an electron microscope.

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Feldspatkristalle in Alkali-Rhyolith von der Insel Oki-Dogo, Japan

Zusammenfassung Feldspatkristalle in Alkali-Rhyolith von der Oki-Dogo Insel im Japanischen Meer zeigen ummantelte Texturen mit Kernen von Anorthoklas und Rändern von Sanidin. Diese Feldspate wurden mit Elektronenmikroskopie, Röntgendiffraktion und Mikrosondenanalyse untersucht. Anorthoklas kristallisierte zuerst, wurde dann teilweise resorbiert und schließlich wuchs Sanidin über den Anorthoklas. Sägezahn- und Kamm-ähnliche Grenzen zwischen Kernen und Rändern wurden wahrscheinlich wahrend des magmatischen Stadiums von Resorption und Überwachsung gebildet. Unter dem Mikroskop erkennt man, daß perthitische Verwachsungen durch Sägezahn- oder Kamm-artige Grenzen der ummantelten Feldspäte hinwegsetzen. Der Sanidin erhellt primäre kryptoperthitische Texturen mit einer Periodizität von > 10 nm, die als Produkte einer Subsolidus-Entmischung nach der Resorption interpretiert werden. Anorthoklas läßt unter dem Elektronenmikroskop keine Entmischungstexturen erkennen.

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With 6 Figures  相似文献   

Transport of water in frozen soil IV. Analysis of experimental results on the effects of ice content     

Yoshisuke Nakano  Allen Tice  Joseph Oliphant 《Advances in water resources》1984,7(2):58-66

Effects of ice content on the transport of water in frozen soil are studied experimentally and theoretically under isothermal conditions. A physical law, that the flux of water in unsaturated frozen soil is proportional to the gradient of total water content is proposed. Theoretical justification is made by the use of the two-phase flow theory. The experimental results are shown to support the proposed physical law. The results of this study are presented in two parts and this is the second paper describing the theoretical aspects of the study.  相似文献   

Calcium distribution patterns in alkali feldspar in a quartz syenite from Oki-Dozen, southwest Japan     

S. Nakano 《Mineralogy and Petrology》1998,63(1-2):35-48

Summary Microscopically alkali feldspar in a quartz syenite from Oki-Dozen, Japan, consists of clear and turbid areas. Clear areas occur in the interiors of feldspar grains and are cryptoperthitic. Film microperthites are developed with turbidity in the rims, and mosaic microperthites are developed with turbidity in the interiors and in the rims. Turbidity is attributed to the presence of abundant micropores. The chemical compositions of pristine clear feldspars are around Or₃₃Ab₆₄An₃. The interior microperthitic feldspars have lower An content than the clear feldspars. Some areas of the clear and microperthitic feldspars in the interiors are poor in calcium. In contrast, the microperthitic rims contain almost no calcium. The zonal patterns of calcium-rich cores and calcium-poor rims are very distinct in almost all feldspar grains. The overall calcium distribution patterns suggest a secondary calcium-depletion from the feldspars during hydrothermal or deuteric reactions. The development of Or-rich veins transversing feldspar grains and rim albite is consistent with this model. Calcium distribution patterns in alkali feldspar provide new and useful information on processes during geologic events.

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Calcium-Verteilung in Alkalifeldspat eines Quarz-Syenites von Oki-Dozen, Südwest-Japan

Zusammenfassung Mikroskopisch zeigt Alkalifeldspat aus einem Quarz-Syenit von Oki-Dozen, Japan, klare und trübe Bereiche. Die klaren Bereiche treten in den inneren Zonen von Feldspatkörnern auf und sind kryptoperthitisch. Die getrübten Ränder sind Film-Mikroperthite während Mosaik-Perthite Trübung in Kern-und Randbereichen zeigen. Die Trübung ist auf die Anwesenheit zahlreicher Mikroporen zurückzuführen. Die chemische Zusammensetzung der ursprünglichen klaren Feldspäte ist etwa Or₃₃Ab₆₄An₃. Die Kerne der mikroperthitischen Feldspäte haben niedrigere An-Gehalte als die klaren Feldspäte. Im Unterschied führen die Mikroperthit-Ränder kein Kalzium. Die Zonierungsmuster, d.h. Ca-reiche Kerne und Ca-arme Ränder, sind sehr typisch für alle Feldspäte. Die generelle Ca-Verteilung weist auf eine sekundäre Ca-Verarmung der Feldspäte im Zuge hydrothermaler oder deuterischer Prozesse hin. Die Bildung Orreicher Gängehen, die die Feldspatkörner durchsetzen und von Albiträndern stimmen mit diesem Modell überein. Die Ca-Verteilungsmuster in Alkalifeldspat erlauben somit Einblicke in und geben nützliche Informationen über geologische Prozesse.

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With 7 Figures  相似文献   

软岩的强度—变形—时间之间关系的试验分析   总被引：6，自引：4，他引：2  

廖红建  赵树德 《岩土力学》1998,19(2):8-13

对软岩和有不连续面的软岩试样进行一系列固结不排水三轴压缩和蠕变试验,测定并分析了它们在正常固结和超固结状态下的应变软化性状、蠕变特性和残余强度的变化规律。探讨了软岩中存在的不连续面对应力－应变关系、残余强度特性和蠕变应变速率的影响。  相似文献   

Fast Oxidation Reaction of Nitrite by Dissolved Oxygen in the Freezing Process in the Tropospheric Aqueous Phase     

Norimichi Takenaka  Tohru Daimon  Akihiro Ueda  Keiichi Sato  Masaru Kitano  Hiroshi Bandow  Yasuaki Maeda 《Journal of Atmospheric Chemistry》1998,29(2):135-150

Nitrite oxidation in the tropospheric aqueous phase by freezing was evaluated by freezing a field sample. Nitrite oxidation by dissolved oxygen in the freezing process is much faster than by other oxidation processes, such as reactions with ozone, hydrogen peroxide or dissolved oxygen in an aqueous solution at pHs 3 to –6. At pH 4.5 and 25°C, the lifetime of nitrite in the aqueous phase is ca. 1 hr in oxidation by ozone (6×10^-10 mol dm^-3), ca. 10 hr in oxidation by H₂O₂ (2×10^-4 mol dm^-3), and 7.5 hr (Fischer and Warneck, 1996) in photodissociation at midday in summer. Under the same conditions at a temperature below 0°C, the lifetime of nitrite in the freezing process is estimated as ca. 2 sec when the droplets are frozen within a second. The reaction by freezing is affected by the presence of salts, such as NaCl or KCl, or orgnaic compounds, such as methanol or acetone. The results of freezing a field rain or fog sample showed that nitrite oxidation proceeds below pH 6, and the conversion ratio of nitrate from nitrite increases with decreasing pH. The oxidation of nitrite by freezing was also observed in freezing fog particles generated by an ultrasonic humidifier. The ratios of the concentrations of ions in the winter sample to those in the summer sample (or those in the fog sample) were almost the same values. However, the concentration of nitrite in the winter sample was lower than that estimated by the ratios of other ions. From the present study, it seems that the freezing process plays an important role in the nitrite sink process in the tropospheric aqueous phase.  相似文献   

地闪回击的微秒级辐射场特征及近地面连接过程分析   总被引：14，自引：6，他引：8  

郄秀书  郭昌明 《高原气象》1998,17(1):44-54

利用１μｓ时间分辨率的慢天线电场变化仪在甘肃中川地区雷暴过程中测量得到的大量地闪辐射波形地地闪回击辐射场特征及回击的慢前沿过程进行分析,发现１８次正地闪和８５次负地闪产在周前沿过程上升时间为１９．２μｓ和９．４μｓ,８４次负地闪继后回击的前沿过程为４．３ μｓ。ＹＹ ＵＤＡ Ｏ ３．１μ;  相似文献