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41.
Yasuhiro Kuwayama Kei Hirose Nagayoshi Sata Yasuo Ohishi 《Earth and Planetary Science Letters》2008,273(3-4):379-385
We have investigated the phase relations of iron and iron–nickel alloys with 18 to 50 wt.% Ni up to over 300 GPa using a laser-heated diamond-anvil cell. The synchrotron X-ray diffraction measurements show the wide stability of hcp-iron up to 301 GPa and 2000 K and 319 GPa and 300 K without phase transition to dhcp, orthorhombic, or bcc phases. On the other hand, the incorporation of nickel has a remarkable effect on expanding the stability field of fcc phase. The geometry of the temperature–composition phase diagram of iron–nickel alloys suggests that the hcp–fcc–liquid triple point is located at 10 to 20 wt.% Ni at the pressure of the inner core boundary. The fcc phase could crystallize depending on the nickel and silicon contents in the Earth's core, both of which are fcc stabilizer. 相似文献
42.
Takanobu OBA 《Journal of Earth System Science》1990,99(1):81-90
The join tremolite (Tr)-pargasite (Pa) was studied at temperatures between 800 and 1150°C under water vapour pressure of 10 kbar. The results show a continuous solid solution of amphibole between the composition Tr80Pa20 and Pa100 at 800°C and 10kb. Pargasite melts incongruently and breaks down at high temperature to clinopyroxene+forsterite+spinel+L+V. A single phase amphibole with composition lying between Tr80Pa20 and nearly pure Pa, breaks down to amphibole of different composition plus other phases. The stability fields of amphibole spread toward higher temperature side with increasing pargasite content, and pargasite itself has the widest stability field. At subliquidus, the composition of amphibole coexisting with other phases becomes more pargasitic with increasing temperature. The compositions of liquid, which are formed by partial melting of amphibole of Tr40Pa60 composition (Fo-normative) under water vapour pressure of 10 kbar, are alumina-rich and Qz-normative. 相似文献
43.
Richard D. Brodeur Joseph P. Fisher Yasuhiro Ueno Kazuya Nagasawa William G. Pearcy 《Journal of Oceanography》2003,59(4):415-434
During the 1980s and 1990s, scientific research cruises were conducted in both the eastern and western boundary regions of
the North Pacific Ocean. The main purpose of these cruises was to examine the abundance and distribution patterns of juvenile
salmon in coastal waters. These studies created one of the most extensive databases ever collected on the species composition
of coastal Transition Zone epipelagic nekton in the North Pacific Ocean. Catch data from two purse seine and two surface trawl
surveys (one each from off northern Japan and eastern Russia and off the West Coast of the U.S.) were examined using multivariate
techniques to analyze the community structure of nektonic cephalopods, elasmobranchs, and teleosts in the coastal zone during
the summer and autumn months. Juvenile salmonids are generally among the most common species caught, but in terms of overall
abundance, other potential competitors with juvenile salmon, such as small squids and clupeoid fishes predominated the catches.
Species diversity and dominance varied among areas and gear types. Distinct assemblages were found in each area, but the two
regions had closely related species occupying similar ecological positions in each habitat.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
44.
An Ecosystem Model Including Nitrogen Isotopes: Perspectives on a Study of the Marine Nitrogen Cycle
Chisato?YoshikawaEmail author Yasuhiro?Yamanaka Takeshi?Nakatsuka 《Journal of Oceanography》2005,61(5):921-942
We have developed an ecosystem model including two nitrogen isotopes (14N and 15N), and validated this model using an actual data set. A study of nitrogen isotopic ratios (δ15N) using a marine ecosystem model is thought to be most helpful in quantitatively understanding the marine nitrogen cycle.
Moreover, the model study may indicate a new potential of δ15N as a tracer. This model has six compartments: phytoplankton, zooplankton, particulate organic nitrogen, dissolved organic
nitrogen, nitrate and ammonium in a two-box model, and has biological processes with/without isotopic fractionation. We have
applied this model to the Sea of Okhotsk and successfully reproduced the δ15N of nitrate measured in seawater and the seasonal variations in δ15N of sinking particles obtained from sediment trap experiments. Simulated δ15N of phytoplankton are determined by δ 15N of nitrate and ammonium, and the nitrogen f-ratio, defined as the ratio of nitrate assimilation by phytoplankton to total nitrogenous nutrient assimilation. Detailed
considerations of biological processes in the spring and autumn blooms have demonstrated that there is a significant difference
between simulated δ15N values of phytoplankton, which assimilates only nitrate, and only ammonium, respectively. We suggest that observations of
δ 15N values of phytoplankton, nitrate and ammonium in the spring and autumn blooms may indicate the ratios of nutrient selectivity
by phytoplankton. In winter, most of the simulated biogeochemical fluxes decrease rapidly, but nitrification flux decreases
much more slowly than the other biogeochemical fluxes. Therefore, simulated δ15N values and concentrations of ammonium reflect almost only nitrification. We suggest that the nitrification rate can be parameterized
with observations of δ15N of ammonium in winter and a sensitive study varying the parameter of nitrification rate. 相似文献
45.
46.
47.
Philip Lah Jayaram N. Chengalur Frank H. Briggs Matthew Colless Roberto De Propris Michael B. Pracy W. J. G. de Blok Shinobu S. Fujita Masaru Ajiki Yasuhiro Shioya Tohru Nagao Takashi Murayama Yoshiaki Taniguchi Masafumi Yagi Sadanori Okamura 《Monthly notices of the Royal Astronomical Society》2007,376(3):1357-1366
48.
49.
Takamoto Okudaira Yasutaka Hayasaka Osamu Himeno Koichiro Watanabe Yasuhiro Sakurai Yukiko Ohtomo 《Island Arc》2001,10(2):98-115
Abstract The Ryoke metamorphic belt in south-west Japan consists mainly of I-type granitoids and associated low-pressure/high-temperature metamorphic rocks. In the Yanai district, it has been divided into three structural units: northern, central and southern units. In this study, we measured the Rb–Sr whole-rock–mineral isochron ages and fission-track ages of the gneissose granodiorite in the central structural unit. Four Rb–Sr ages fall in a range of ca 89–87 Ma. The fission-track ages of zircon and apatite are 68.9 ± 2.6 Ma and 57.4 ± 2.5 Ma (1σ error), respectively. Combining the newly obtained ages with previously reported (Th–)U–Pb ages from the same unit, thermochronologic study revealed two distinctive cooling stages; 1) a rapid cooling (> 40°C/Myr) for a period (~7 Myr) soon after the peak metamorphism (~ 95 Ma) and 2) the subsequent slow cooling stage (~ 5°C/Myr) after ca 88 Ma. The first rapid cooling stage corresponds to thermal relaxation of the intruded granodiorite magma and its associated metamorphic rocks, and to the uplift by a displacement along low-angle faults which initiated soon after the intrusion of the magma. Uplift by the later stage deformation having formed large-scale upright folds resulted in progress of the exhumation during the first stage. The average exhumation velocity of the stage is ≥ 2 mm/yr. During the second stage, the rocks were not accompanied by ductile deformation and were exhumed with the rate of 0.1–0.2 mm/yr. The difference in the exhumation velocity between the first and second cooling stages resulted from the difference in the thickness of the crust and in the activity of ductile deformation between the early and later stages of the orogenesis. 相似文献
50.
Bokuichiro Takano Yasuhiro Asano Kunihiko Watanuki 《Contributions to Mineralogy and Petrology》1980,72(2):197-203
The mode of incorporation of sulfate ion in travertine was discussed on the basis of chemical compositions, i.r. and laser Raman spectra. These data strongly suggest that most of the sulfate ions in the calcitic travertine replace carbonate ions. This conclusion is in good harmony with the facts that calcite incorporates more sulfate ions than aragonite does and that the sulfate content of manganoan calcite decreases with increasing manganese content (Takano et al. 1977). Based on this conclusion, retarding effect of sulfate ion on the precipitation of calcite from solution was discussed. 相似文献