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41.
EPMA analyses and K-Ar age determinations were carried out on phengite in pelitic schist from the Sanbagawa metamorphic belt of the Kanto Mountains, Central Japan.
Phengite from the Sanbagawa pelitic schist in the Kanto Mountains generally occurs as aggregates of fine-grained crystals. It is extremely fine-grained in domains adjacent to relatively rigid garnet and albite porphyroblasts. This suggests that deformation-induced grain-size reduction took place in phengite during the ductile deformation accompanying the exhumation of the host schists. EPMA analysis shows that phengite is chemically heterogeneous at the thin-section scale, suggesting that it formed during retrograde metamorphism in restricted equilibrium domains. The retrograde chemical reaction was promoted by the ductile deformation.
K-Ar ages of phengite get younger from the Southern Unit (82 Ma) to the Northern Unit (58 Ma) in the Kanto Mountains. The age range is similar to that in Central Shikoku. The older schists occur in the higher metamorphic grade zone in Central Shikoku and in the lower-grade zone in the Kanto Mountains. The thermal structures in Central Shikoku are inverted, so that the highest-grade zone occurs in the upper or middle parts of the apparent stratigraphic succession. In contrast, the Kanto Mountains have a normal thermal structure: the higher-grade zone is in the lower part of the apparent stratigraphic succession. The different tectonic features in exhumation produced the two contrasting age-temperature-structure relations at the western side of Sanbagawa belt in Central Shikoku and the eastern end of the Sanbagawa belt in the Kanto Mountains that are 800 km distant from each other. Namely, the western Sanbagawa belt in Central Shikoku underwent longer ductile deformation during the exhumation than the eastern Sanbagawa belt in the Kanto Mountains. 相似文献
42.
Hiroshi?IshidaEmail author Yuji?Watanabe Tatsuo?Fukuhara Sho?Kaneko Kazushi?Furusawa Yoshihisa?Shirayama 《Journal of Oceanography》2005,61(5):835-843
In order to evaluate the environmental impact associated with sequestration of carbon dioxide in the deep sea, a free fall
type field experimental device, the benthic chamber, was developed. In situ experiments to expose deep-sea communities to elevated concentrations of carbon dioxide (average of 20,000 ppm, 5,000 ppm
and control) were carried out using this device 3 times, viz., in the winter of 2002 and in the spring and the summer of 2003,
in the Kumano Trough at a depth of 2,000 m. In the long-term experiments (about two weeks in winter of 2002 and summer of
2003), the abundance of meiobenthos declined whereas that of bacteria increased under the condition of 20,000 ppm carbon dioxide
compared with the control. Among meiofauna, the abundance of foraminifers at the same concentration of carbon dioxide became
less than the control even in the short-term (3 days in spring of 2003) experiment, suggesting that organisms with a calcium
carbonate exoskeleton are more sensitive to the raised concentration of carbon dioxide. The respiration rate of the benthic
community exposed to 20,000 ppm was lower in the early stage of the experiment than in the latter half, whereas it was opposite
under the condition of 5,000 ppm. The increase of biological activity in the 20,000 ppm exposure group is probably due to
an increase of bacteria adapted to high carbon dioxide concentrations. The present results suggest that the influence of carbon
dioxide on the deep-sea benthic ecosystem does not follow a simple, linear relationship with concentration. 相似文献
43.
To understand the effects of temperature, pH and mechanical stress on the pressure dissolution of quartz, two experiments using monocrystalline quartz samples were conducted. The first was a closed-fluid experiment to investigate the effect of pH, and the second was a flow-through experiment to investigate stress and temperature effects. To initiate the pressure dissolution, a pair of samples was immersed in a solution with a prescribed pH. The samples were stressed mechanically by pressing one sample against the other. In the closed-fluid experiments, the pH of the solution was fixed to 7, 9, 11 and 13, the applied stress was approximately 200 MPa and temperature 25°C. The flow-through experiments were conducted at three different temperatures (35, 50 and 75°C) at the same pH 11.7. The value of the applied stress was 7.32, 13.72, 21.42 or 25.27 MPa. During each of these dissolution tests, the solution was regularly sampled and analyzed by an Inductively Coupled Plasma-Atomic Emission Spectrometry technique to measure Si-concentration. With the measured Si-concentration, a dissolution rate constant was computed the different pH, stress and temperature conditions. The rate constant is proportional to pH, stress and temperature, as indicated in the literature. It should be noted that the rate constant for the highest stress (200 MPa) was considerably greater than for the other cases. In addition, island-channel patterns characterized by micro-cracks a few nanometers in length were seen on the dissolved parts of the samples. The findings and the measured data in this paper may be useful for the future development of theoretical models for pressure dissolution and its validation. 相似文献
44.
Mauro de Melo Júnior Leonardo K. Miyashita Naira J. Silva Salvador A. Gaeta Rubens M. Lopes 《Marine Ecology》2013,34(3):363-372
We investigated the reproductive biology of the planktonic harpacticoid copepod Euterpina acutifrons, including morphometric data, egg production rates (EPR) and viability, and weight‐specific egg production. Experiments were carried out during 1 year in an inner‐shelf area off Ubatuba (SE Brazil), a site seasonally influenced by bottom intrusions of the relatively cold and nutrient‐rich South Atlantic Central Water (SACW). We hypothesized that E. acutifrons attain higher reproductive rates when SACW penetrates in this region. Live females were incubated individually in cell culture plates during two periods of 24 h each, under controlled temperature and light conditions. Euterpina acutifrons carried on average 16.9 ± 6.9 eggs·sac?1, ranging between 10.8 ± 5.7 and 30.8 ± 7.4 eggs·sac?1. Estimated EPRs ranged from 6.3 ± 3.4 to 13.6 ± 4.2 eggs·female?1·day?1, with mean weight‐specific egg production rates of 0.06 ± 0.04 and 0.17 ± 0.08 per day. Euterpina acutifrons was not directly influenced by SACW intrusions, but body length and clutch size were positively related to temperature and chlorophyll content. Egg hatching time was clearly dependent on water temperature, as a 2 °C increase resulted in a decrease of 15 h in egg hatching time. This shows that even a small variation in temperature may considerably affect E. acutifrons population dynamics. Reproductive traits of this pelagic harpacticoid seem, therefore, to be controlled by the trade‐offs between increased food supply and the metabolic demands at low temperatures associated with SACW bottom intrusions toward this coastal area. 相似文献
45.
Hiroyasu Ando Takeshi Noguchi Masao Nakagiri Akihiko Miyashita Yasumasa Yamashita Kyoji Nariai Hiroyoshi Tanabe 《Astrophysics and Space Science》1989,160(1-2):183-189
Two steps have been taken to decide at what place and altitude to set up the JNLT on Mauna Kea. First, the wind tunnel experiment has been made in collaboration with the Institute of Meteorology using the two models of summit area with the reduced scales of 1/1000 and 1/5000. This study tells us that the north-west cone is suitable for JNLT. Secondly, we have done the measurement of the microthermal activities in this area with a 30 m tower, which was continued for about 4 months in collaboration with the University of Hawaii. This experiment has given the mean vertical profile ofC
T
2
over 4 months and its scale height in the boundayr layer on our site. By use of these measurements, the contribution of the boundary layer to seeing is estimated. The behaviour ofC
T
2
under strong winds can be explained very well by topographic effects, which is in fairly good agreement with the results of our wind tunnel experiment.Paper presented at the Symposium on the JNLT and Related Engineering Developments, Tokyo, November 29–December 2, 1988. 相似文献
46.
47.
Toshio Kataoka Eiji Yunoki Mitsuo Shimizu Tadashige Mori Osamu Tsukamoto Satoshi Takahashi Hironori Fudeyasu Yukitaka Ohashi Ken Sahashi Toshihiko Maitani Koh'ichi Miyashita Toru Iwata Takayuki Sasaki Yoko Fujikawa Akira Kudo Roger H. Shaw 《Boundary-Layer Meteorology》2003,107(1):219-249
Atmospheric activity concentrations of 212Pb and short-lived 222Rndaughters, together with meteorological elements, have been observed continuously atthree sites at Kamisaibara Village in Japan. In addition, atmospheric activity concentrationof 222Rn, equilibrium-equivalent concentration of 222Rn and conditionsof the lower atmosphere were observed for three intensive observation periods at Akawase,one of the three sites in Kamisaibara Village. The equilibrium-equivalent concentration of222Rn is almost the same as the atmospheric activity concentration of short-lived222Rn daughters.The activity concentrations of 212Pb and the short-lived 222Rn daughtersand their ratio were low in the daytime owing to convective mixing, and high at nightowing to the surface-based inversion during periods of no precipitation. Their variationshave several patterns corresponding to the scale of the drainage wind or weak mixing.Mechanical mixing due to strong winds through both day and night during the first andsecond observation periods made the atmospheric activity concentrations of 212Pb and the short-lived 222Rn daughters continuously low. However, their ratios werecontinuously high during the first period yet continuously low during the second period.This difference can be explained by the effect ofextraction of 220Rn and 222Rndue to strong winds and snow cover. There were also cases in which the ratio of theatmospheric activity concentration of 212Pb to that of the short-lived 222Rndaughters at night was equal to or less than the ratio in the daytime. Thisinverse trend, asin the periods of no precipitation mentioned above, is considered to be due to near-neutralconditions on these nights.We find a difference in the ratio of the equilibrium-equivalent concentration of222Rn (the activity concentration of short-lived 222Rn daughters) tothe activity concentration of 222Rn during the first observation period and thatduring the second. The difference can be explained by snow cover on the ground. Wealso find differences among the ratios of the activity concentration of the short-lived222Rn daughters to that of 222Rn during the three observation periods.These differences can be explained by the submergence of paddy fields. 相似文献
48.
Summary The Upper Cretaceous oceanic and island-arc terranes of Northeastern Kamchatka (Russia) are intruded by numerous ultramafic and mafic to intermediate plutons. Ultramafic plutons north of Epilchik Lake show a concentric structure: dunites in the core pass progressively outwards into wehrlites and pyroxenites and into gabbros along the rim which are occasionally phlogopite- and amphibole-bearing. Compositional layering and mineral orientations marked by spinel clusters in the dunites and by acicular amphiboles in the marginal gabbros are parallel to the contacts. The mafic to intermediate plutons studied in the Machevna area show similar concentric structure with a dioritic core and a gabbroic rim. Magmatic flow lines are near-vertical in the central part of the plutons. These internal structures and general geometry of the plutons suggest vertical magma intrusion into mega-tension gashes developed initially at a high angle to the subduction zone.Olivine, pyroxenes, and plagioclase have primitive compositions. Al-rich, highpressure amphiboles are followed by Al-poor, low-pressure hornblendes. A two stage model of pluton crystallization and emplacement is proposed: initial crystallization and seggregation at the Moho level below the intraoceanic island are (approximately 22–25 km depth) and final emplacement followed by partial recycling of primary ultramafic cumulates and solidification at upper crustal levels (approximately 8–10 km depth). Emplacement of the arc plutons was accompanied by epidote amphibolite-facies contact metamorphism of host volcanic and pyroclastic rocks.Major- and trace-element analyses of plutonic rocks indicate calc-alkaline affinities and emplacement in a primitive arc setting. The tectonic setting, age, and emplacement structures suggest that these plutons mark the change of geodynamic conditions from arc-related compression to local extension probably related to the initial stages of opening of the proto-Komandorsky basin. A two stage model for the crustal growth in magmatic arcs is proposed based on northeastern Kamchatka plutons. During stage I, primitive basaltic melts were emplaced along the crust-mantle boundary below the arc. Continuous fractionation and accumulation of olivine-rich cumulate rocks at the base of the growing island-arc crust resulted in production of evolved melt which was further emplaced in the upper arc crust. Crystal fractionation of a shallow, stage II magmatic reservoir below the active arc volcanoes resulted in formation of a significant amount of plutonic rocks and eruption of mafic to intermediate calc-alkaline lavas at the surface.
Zonierte kalk-alkalische Plutone im nardöstlichen Kamchatka, Russland: Hinweise auf Krusten Wachstum inmagmatischen Bögen
Zusammenfassung Zahlreiche ultramafische, Bowie mafische bis intermediäre Plutone intrudieren die oberkretazischen ozeanischen und Inselbogen-Terrains in Nordost-Kamchatka (Russland). Ultramafische Plutone nördlich des Epilchik Lake zeigen eine konzentrische Struktur: Dunite im Kern gehen graduell in Wehrlite und Pyroxenite, und schließlich am Rand in Gabbros über, die gelegentlich Phlogopit und Amphibol führen. Lagenbau und Orientierung von Mineralkörnern sind durch Spinell-Kluster in den Duniten und durch nadelige Amphibole in den randlichen Gabbros gekennzeichnet und liegen parallel zu den Kontakten. Die mafischen bis intermediären Plutone in dem Machevna-Gebiet zeigen ähnliche konzentrische Strukturen mit einem dioritischen Kern und einem gabbroischen Rand. Magmatische Flußlinien Bind fast vertikal in den zentralen Teilen der Plutone. Diese internen Strukturen und die allgemeine Geometrie der Plutone legen es nahe, daß es sich hier um vertikale Magmen-Intrusion in Mega-Strukturen handelt, die sich ursprünglich in einem hohen Winkel zur Subduktionszone gebildet haben.Olivine, Pyroxene und Plagioklase haben primitive Zusammensetzungen. Auf Alreiche Hochdruck-Amphibole folgen Al-arme Tiefdruck-Hornblenden. Ein Modell, das zwei Stadien der Pluton-Kristallisation und Platznahme vorsieht, wird vorgeschlagen: Ursprüngliche Kristallisation und Segregation im Moho-Niveau zwischen dem intraozeanischen Inselbogen (ungefähr 22–25 km Tiefe) und schließliche Platznahme gefolgt von teilweise Recycling primärer ultramafischer Kumulate und Verfestigung in oberen Krustenniveaus (ungefähr 8–10 km Tiefe). Die Platznahme der Bogen-Plutone war von Epidot-Amphibolit-Fazies Kontaktmetamorphose der intrudierten Vulkanite und Pyroklastite begleitet.Haupt- und Spurenelement-Analysen der plutonischen Gesteine weisen auf kalkalkalischen Charakter und eine Platznahme in einem primitiven Insenbogensetting hin. Die tektonische Situation, das Alter und die Strukturen der Platznahme lassen erkennen, daß these Plutone den Wechsel in geodynamischen Bedingungen von Inselbogenbezogener Kompression zu lokaler Extension repräsentieren, Vorgänge die mit den initialen Stadien der Öffnung des proto-Komandorsky Beckens zusammenhängen. Auf der Basis der Plutone des nordöstlichen Kamchatka wird ein Modell des Krustenwachstums in magmatischen Bögen vorgeschlagen, das auf zwei Stadien beruht. Während des ersten Stadiums werden primitive basaltische Schmelzen längs der Kruste-MantelGrenze unter dem Bogen intrudiert. Andauernde Fraktionicrung und Akkumulation Olivin-reicher Kumulatgesteine an der Basis der wachsenden Inselbogenkruste resultiert dann in der Produktion einer entwickelten Schmelze die spdter in der Kruste des oberen Bogens Platz genommen hat. Kristallfraktionierung eines seichten magmatischen Reservoirs des zweiten Stadiums unter den aktiven Vulkanen des Bogens führte dann zur Bildung signifikanter Mengen plutonischer Gesteine und zur Eruption von mafischen bis intermediären kalk-alkalischen Laven an der Oberfläche.相似文献
49.
Anil Bhardwaj Stas Barabash Yoshifumi Futaana Yoichi Kazama Kazushi Asamura David McCann R. Sridharan Mats Holmstrom Peter Wurz Rickard Lundin 《Journal of Earth System Science》2005,114(6):749-760
This paper reports on the Sub-keV Atom Reflecting Analyzer (SARA) experiment that will be flown on the first Indian lunar
mission Chandrayaan-1. The SARA is a low energy neutral atom (LENA) imaging mass spectrometer, which will perform remote sensing
of the lunar surface via detection of neutral atoms in the energy range from 10 eV to 3 keV from a 100km polar orbit. In this
report we present the basic design of the SARA experiment and discuss various scientific issues that will be addressed. The
SARA instrument consists of three major subsystems: a LENA sensor (CENA), a solar wind monitor (SWIM), and a digital processing
unit (DPU). SARA will be used to image the solar wind-surface interaction to study primarily the surface composition and surface
magnetic anomalies and associated mini-magnetospheres. Studies of lunar exosphere sources and space weathering on the Moon
will also be attempted. SARA is the first LENA imaging mass spectrometer of its kind to be flown on a space mission. A replica
of SARA is planned to fly to Mercury onboard the BepiColombo mission. 相似文献