High resolution electron microscopy of tourmaline crystals     

Dr. S. Iijima  Prof. J. M. Cowley  Prof. Gabrielle Donnay 《Mineralogy and Petrology》1973,20(3):216-224

Summary High resolution electron micrographs have been obtained from crystals of two types of tourmaline, aligned in a goniometer stage so that the electron beam is parallel to thec axis. Images having a resolution of about 3 Å taken out of focus show direct indications of the atomic arrangement; they suggest medium-range ordering of the metal atoms in buergerite and unexpectedh31l symmetry in elbaite-schorl solid solution. The appearance of ordering is tentatively explained in terms of electron-irradiation effects.

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Hochauflösende Elektronenmikroskopie von Turmalinkristallen

Zusammenfassung Hochauflösende Elektronen-Mikrographien wurden von zwei Typen von Turmalinkristallen, die auf einer Goniometereinrichtung so orientiert waren, daß der Elektronenstrahl parallel zurc-Achse verlief, erhalten. Bilder mit einer 3 Å-Auflösung, die entfokusiert aufgenommen wurden, geben direkte Hinweise auf die Atomanordnung; sie deuten auf Ordnung mittlerer Reichweite der Metallatome in Buergerit und zeigen unerwarteterweiseh31l-Symmetrie bei Elbait-Schörl-Mischkristallen. Das Auftreten von Ordnung wird als vermutlicher Elektronenbestrahlungseffekt gedeutet.

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With 3 Figures  相似文献   

Phase and group velocities and Q of mantle Love and Rayleigh waves of the first two modes and their azimuthal dependences for the 1963 Kurile Islands earthquake     

Yoshio Fukao  Minoru Kobayashi 《Physics of the Earth and Planetary Interiors》1983,32(1):4-35

Phase and group velocities and Q of mantle Love and Rayleigh waves from the 1963 Kurile Islands earthquake (M_w = 8.5) were determined over 37 great circle paths by a time variable filtering technique, in a period range 100–500 s for the fundamental modes and 100–275 s for the first higher modes. The preliminary reference Earth model (PREM) explains reasonably well the average dispersion results for the fundamental Love and Rayleigh waves. There exists a small, but significant inconsistency between the observation and the model for the first higher Love and Rayleigh waves. The Q structure of PREM is inconsistent with the observation for the fundamental Love waves, but explains other observations reasonably well. The dispersion of each mode shows a clear azimuthal dependence from which the four azimuthal windows were established. The phase and group velocity measurements for each window were, in general, shown to be mutually consistent. The azimuthal variations are largest for the first higher Rayleigh waves, indicating strong lateral heterogeneity in the structure of the low velocity zone. The first of the four windows is characterized by the largest fraction of Precambrian shields and the second window by the largest fraction of normal oceans. A comparison of these two windows may give some insight into deep lateral heterogeneity between continents and oceans. The observed phase and group velocities of the first window are systematically higher than those of the second window for the fundamental Love and Rayleigh waves at periods up to 400 s, and for the first higher Love and Rayleigh waves up to 175 s. Their differences are greatest for the first higher Rayleigh waves and least for the fundamental Rayleigh waves. Although the fundamental Rayleigh waves show the least velocity differences, their persistence up to a period of longer than 300 s is in striking contrast with some of the pure path phase velocities derived earlier for continents and oceans. A set of models for continents and oceans. PEM-C and PEM-O are not consistent with our observation. The third azimuthal window is characterized by trench-marginal seas and the fourth window by mountainous areas, typically the Asian high plateaus from northern China to the Middle East through Tibet. A comparison of these two windows gives some information about deep structural differences between subduction zones and continental collision zones, both belonging to plate convergence zones. For the fundamental and the first higher Love waves, the phase and group velocities for the third window are markedly low, whereas those for the fourth window are somewhat comparable to those for the second window. Slow Rayleigh waves are evident for two windows, with the fourth window apparently being the slowest for the fundamental Rayleigh above 200 s and for the first higher Rayleigh. For the fundamental Rayleigh waves, the third window is very slow below 200 s, but becomes progressively fast as the period increases and tends to be the fastest window around 400 s, suggesting a deep seated high velocity anomaly beneath trench-marginal seas. The dispersion characteristics of the fourth window indicate a thick high velocity lid with an extensive low velocity zone beneath it. The shield-like lithosphere, coupled with an extensive low velocity zone, may be a characteristic feature of continental collision zones. The particle motion of the fundamental Love waves was found not to be purely transverse to a great-circle connecting the epicenter to a station. The departure from the purely transverse motion is systematic among different periods, different G arrivals (G₂, G₃,…) and different stations, which may be interpreted as being due to lateral refraction.  相似文献   

Effects of a plastic deformation on the remanent magnetization of a Cu-Co alloy     

Minoru Ozima 《Earth and Planetary Science Letters》1980,47(1):121-123

Compressional plastic deformation of a Cu-Co alloy in which Co particles (submicron to a few tens of microns in diameter) were precipitated in a Cu matrix resulted in a systematic rotation of remanent magnetization (IRM atH = 1000Oe) away from the axis of compression with increasing degree of the deformation.  相似文献   

²⁴¹Pu and²⁴¹Am in sediments from coastal basins off California and Mexico     

Minoru Koide  Edward D. Goldberg  Vernon F. Hodge 《Earth and Planetary Science Letters》1980,48(2):250-256

In sediments deposited in the coastal basins off the western North American continent since the early 1960's, there is more²⁴¹Am activity than one would predict if its presence was solely due to the decay of²⁴¹Pu that was produced during the testing of weapons in 1961–1962 (taken as July 1, 1962 for calculations). This excess can be accounted for by the decay of²⁴¹Pu, if pre-1962 fallout (fallout from the pre-moratorium testing) has been continuously introduced into the recent sediments along with fallout from post-moratorium testing. This hypothesis is supported by the plutonium depth profiles which do not reflect direct fallout from the atmosphere, as characterized by two peaks corresponding to the two major weapons testing periods, but continuously increasing plutonium and americium concentrations from 1954 to 1974. Thus, the nuclides may be coming from a large reservoir that has accumulated and mixed fallout since 1952. Such a concentration gradient for all of the nuclides requires their immobilization in the sediment after deposition.  相似文献   

Marine geochronology withPb     

Minoru KoideAndrew Soutar  Edward D. Goldberg 《Earth and Planetary Science Letters》1972

The application of²¹⁰Pb dating to an inshore marine deposit off the California coast has been successful. The amounts of unsupported²¹⁰Pb annually accumulated in the Santa Barbara sediments are much greater than those from lake and glacial deposits and than the amount produced through the decay of radium in the overlying water column.  相似文献   

Dependence of the effective attachment coefficient of small ions upon the size of condensation nuclei     

Yukimasa Ikebe  Minoru Kawano 《Pure and Applied Geophysics》1970,83(1):120-130

Summary To clarify the ionization equilibrium near the ground, simultaneous measurements of the rate of ion pair production (q), the concentrations of small ions (n) and condensation nuclei (Z), and the diffusion coefficient of condensation nuclei (D) were carried out at several stations in the central area of Japan. The total rate of ion pair production (q) was estimated fromq=q(Rn)+q(Tn)+q()+q(+CR). The value ofq was estimated as 10J to 20J. The mean life () and the effective attachment coefficient () of small ions were also estimated at each station. Correlations amongn, Z, q, andD were also studied. If we take the variation ofD into consideration, the correlation was expressed by the simple formula;q=n Z. The dependence of upon size of nuclei (2r) were also measured, and was found to correlate well withD orr.  相似文献   

Study of the effect of water-soluble fractions of heavy-oil on coastal marine organisms using enclosed ecosystems,mesocosms   总被引：1，自引：0，他引：1  

Ohwada K  Nishimura M  Wada M  Nomura H  Shibata A  Okamoto K  Toyoda K  Yoshida A  Takada H  Yamada M 《Marine pollution bulletin》2003,47(1-6):78-84

Mesocosm facilities composed of 4 experimental and 2 reservoir tanks (1.5 m in diameter, 3.0 m in depth and 5 tons in capacity) made of FRP plastics, were constructed in the concrete fish rearing pond in the Fisheries Laboratory, The University of Tokyo. The water-soluble fraction of Rank A heavy residual oil was formed by mixing 500 g of the oil with 10 l of seawater, which was introduced to the 5000 l-capacity tanks. Experimental Run 4 was conducted from May 31 to June 7, 2000. Oil concentrations in the tanks were 4.5 microg/l called LOW, and 13.5 microg/l, called HIGH tank. Bacterial growth rates very quickly accelerated in the HIGH tank just after the loading of oil which corresponded with a high increase of bacterial cells in the same tank after 2 days. Later, bacterial numbers in HIGH tank rapidly decreased, corresponding with the rapid increase of heterotrophic nano-flagellates and virus numbers on the same day. Sediment traps were deployed at the bottom of the experimental tanks, and were periodically retrieved. These samples were observed both under light microscope and epi-fluorescent microscope with UV-excitation. It was observed that the main components of the vertical flux were amorphous suspended matter, mostly originating from dead phytoplankton and living diatoms. It was further observed from the pictures that vertical transport of oil emulsions were probably conducted after adsorption to amorphous suspended matter and living diatoms, and were settling in the sediment traps at the bottom of the tanks. This means that the main force which drives the soluble fraction of oil into bottom sediment would be vertical flux of such amorphous suspended particles and phytoplankton. Further incubation of the samples revealed that the oil emulsions were degraded by the activity of autochtonous bacteria in the sediment in aerobic condition.  相似文献   

Laumontization and Secondary Pores of Sandstones in the Paleogene and Upper Cretaceous Coal Measures, off Northeast Honshu, Japan     

Yutaka Yanagimoto  Azuma Iijima 《Resource Geology》2004,54(4):465-476

Abstract. Sandstones with high reservoir quality occur in the Paleogene and Upper Cretaceous coal measures off Sanriku and Sohma in the Pacific coast of northeast Honshu. The sandstone porosity was generally produced by the dissolution of calcite cement and clastic grains such as feldspar and glassy volcanics. The most probable cause of dissolution is the organic acids generated from the maturation of coal and coaly matter in the deeply subsiding source area prior to thermogenic hydrocarbon generation. The pore fluid including organic acids dissolved calcite and clastic silicates to form a small amount of laumontite and kaolinite at around 60C. The acidic and not neutralized pore fluid was responsible for the formation of kaoli-nite. On the other hand, laumontite was formed when the acidic pore fluid was neutralized and then made alkaline after the reaction with minerals such as plagioclase, glassy volcanics and calcite cement. Therefore, laumontite and kaolinite generally occur separately. Laumontite is 0.6–4.6 % by volume, whereas kaolinite is 0.6–9.8 % and the sandstone porosity remains from 10 to 22 %. This type of laumontization after the secondary pore formation might not give a severe damage to the reservoir property of the Paleogene and Upper Cretaceous coal measures in the Pacific coast of northeast Honshu and indicates further exploration possibility.  相似文献   

Improvement of seismological earth models by using data weighting in waveform inversion     

Nozomu Takeuchi  Minoru Kobayashi 《Geophysical Journal International》2004,158(2):681-694

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Geology of the summit limestone of Mount Qomolangma (Everest) and cooling history of the Yellow Band under the Qomolangma detachment     

Harutaka  Sakai  Minoru  Sawada  Yutaka  Takigami  Yuji  Orihashi  Tohru  Danhara  Hideki  Iwano  Yoshihiro  Kuwahara  Qi  Dong  Huawei  Cai  Jianguo  Li 《Island Arc》2005,14(4):297-310

Abstract   Newly discovered peloidal limestone from the summit of Mount Qomolangma (Mount Everest) contains skeletal fragments of trilobites, ostracods and crinoids. They are small pebble-sized debris interbedded in micritic bedded limestone of the Qomolangma Formation, and are interpreted to have been derived from a bank margin and redeposited in peri-platform environments. An exposure of the Qomolangma detachment at the base of the first step (8520 m), on the northern slope of Mount Qomolangma was also found. Non-metamorphosed, strongly fractured Ordovician limestone is separated from underlying metamorphosed Yellow Band by a sharp fault with a breccia zone. The ⁴⁰Ar–³⁹Ar ages of muscovite from the Yellow Band show two-phase metamorphic events of approximately 33.3 and 24.5 Ma. The older age represents the peak of a Barrovian-type Eo-Himalayan metamorphic event and the younger age records a decompressional high-temperature Neo-Himalayan metamorphic event. A muscovite whole-rock ⁸⁷Rb–⁸⁶Sr isochron of the Yellow Band yielded 40.06 ± 0.81 Ma, which suggests a Pre-Himalayan metamorphism, probably caused by tectonic stacking of the Tibetan Tethys sediments in the leading margin of the Indian subcontinent. Zircon and apatite grains, separated from the Yellow Band, gave pooled fission-track ages of 14.4 ± 0.9 and 14.4 ± 1.4 Ma, respectively. These new chronologic data indicate rapid cooling of the hanging wall of the Qomolangma detachment from approximately 350°C to 130°C during a short period (15.5–14.4 Ma).  相似文献