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

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     

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

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.     

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

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     

Similarity solutions of the Cauchy problem of horizontal flow of water through porous media for experimental determination of diffusivity

An experimental method for determining diffusivity is studied by using similarity solutions of the Cauchy problem of horizontal flow of water through homogeneous porous media. The theoretical justification of the method is presented by applying a mathematical theorem recently derived by Van Duyn. Some important aspects of data analysis are discussed by using actual experimental data.     

The role of sticky interstellar organic material in the formation of asteroids

Abstract— Collision experiments and measurements of viscoelastic properties were performed involving an interstellar organic material analogue to investigate the growth of organic grains in the protosolar nebula. The organic material was found to be stickiest at a radius of between 2.3 and 3.0 AU, with a maximum sticking velocity of 5 m s^?1 for millimeter‐size organic grains. This stickiness is considered to have resulted in the very rapid coagulation of organic grain aggregates and subsequent formation of planetesimals in the early stage of the turbulent accretion disk. The planetesimals formed in this region appear to be represent achondrite parent bodies. In contrast, the formation of planetesimals at <2.1 and >3.0 AU begins with the establishment of a passive disk because silicate and ice grains are not as sticky as organic grains.     

Particular solutions to the problem of vertical flow of water and air through porous media near a water table

Particular solutions to the problem of vertical flow of water and air through homogeneous porous media are derived and the regularity properties of the solutions are presented. It is found that under certain conditions a singularity occurs in the solutions at the water table, though it is not certain whether or not a singularity always occurs. Effects of air flow on water flow are discussed.     

Determination of Zirconium, Niobium, Hafnium and Tantalum at ng g-1 Levels in Geological Materials by Direct Nebulisation of Sample HF Solution into FI-ICP-MS

We have developed a rapid and accurate method to determine Zr, Nb, Hf and Ta (denoted as HFSE) in geological samples by inductively coupled plasma-mass spectrometry fitted with a flow injection system (FI-ICP-MS). The method involves sample decomposition by HF followed by HF dissolution of HFSE coprecipitated with insoluble M and Ca fluoride residues formed during the initial HF attack. This HF solution was directly nebulized into an ICP mass spectrometer. An external calibration curve method and an isotope dilution method (ID) were applied for the determination of Nb and Ta, and of Zr and Hf, respectively. Recovery yields of HFSE were > 96% for peridotite, basalt and andesite compositions, apart from Zr and Hf for peridotite (> 85%). No matrix effects for either signal intensities of HFSE or isotope ratios of Zr and Hf were observed in basalt, andesite and peridotite solutions down to a dilution factor of 100. Detection limits in silicate rocks were 40, 2, 1 and 0.1 ng g-1 for Zr, Nb, Hf and Ta, respectively. This technique required only 0.1 ml of sample solution, and thus is suitable for analysing small and/or precious samples such as meteorites, mantle peridotites and their mineral separates. We also present newly determined data for the Zr, Nb, Hf and Ta concentrations in USGS silicate reference materials DTS-1, PCC-1, BCR-1, BHVO-1 and AGV-1, GSJ reference materials JB-1, -2, -3, JA-1, -2 and -3, and the Smithsonian reference Allende powder.     

Development of a 2-km resolution ocean model covering the coastal seas around Japan for operational application

Ocean Dynamics - In order to expand the coastal ocean monitoring and forecasting system of the Japan Meteorological Agency from the Seto Inland Sea to the entire coastal seas of Japan, a 2-km...