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31.
Tsutomu Ota Katsura Kobayashi Takuya Kunihiro Eizo Nakamura 《Geochimica et cosmochimica acta》2008,72(14):3531-3541
Subduction of lithosphere, involving surficial materials, into the deep mantle is fundamental to the chemical evolution of the Earth. However, the chemical evolution of the lithosphere during subduction to depth remains equivocal. In order to identify materials subjected to geological processes near the surface and at depths in subduction zones, we examined B and Li isotopes behavior in a unique diamondiferous, K-rich tourmaline (K-tourmaline) from the Kokchetav ultrahigh-pressure metamorphic belt. The K-tourmaline, which includes microdiamonds in its core, is enriched in 11B relative to 10B (δ11B = −1.2 to +7.7) and 7Li relative to 6Li (δ7Li = −1.1 to +3.1). It is suggested that the K-tourmaline crystallized at high-pressure in the diamond stability field from a silicate melt generated at high-pressure and temperature conditions of the Kokchetav peak metamorphism. The heavy isotope signature of this K-tourmaline differs from that of ordinary Na-tourmalines in crustal rocks, enriched in the light B isotope (δ11B = −16.6 to −2.3), which experienced isotope fractionation through metamorphic dehydration reactions. A possible source of the heavy B-isotope signature is serpentine in the subducted lithospheric mantle. Serpentinization of the lithospheric mantle, with enrichment of heavy B-isotope, can be produced by normal faulting at trench-outer rise or trench slope regions, followed by penetration of seawater into the lithospheric mantle. Serpentine breakdown in the lithospheric mantle subducted in subarc regions likely provided fluids with the heavy B-isotope signature, which was acquired during the serpentinization prior to subduction. The fluids could ascend and cause partial melting of the overlying crustal layer, and the resultant silicate melt could inherit the heavy B-isotope signature. The subducting lithospheric mantle is a key repository for modeling the flux of fluids and associated elements acquired at a near the surface into the deep mantle. 相似文献
32.
33.
Norihiro Kobayashi Tomomi Eriguchi Kisaburo Nakata Shigeki Masunaga Fumio Horiguchi Junko Nakanishi 《Estuarine, Coastal and Shelf Science》2006,70(4):621
A 3-D chemical fate prediction model (FATE3D) was applied to predict the dioxin concentrations in the seawater of Tokyo Bay, Japan. The simulations were carried out for a period of one year (from September 2002 to August 2003). Parameters such as meteorological data, flow field conditions, concentrations and sinking rates of organic particulate matter, initial and boundary conditions, and loading fluxes and physico-chemical properties of dioxins were used as the model inputs.The simulation results compared favorably with the field measurements of dioxin concentrations in the bay for both the particulate and dissolved phases, indicating the validity and predictive capability of the model. Furthermore, the differences in the seasonal cycles and distributions between the particulate- and dissolved-phase dioxins in the bay were estimated from the simulation results.However, the particulate-phase dioxin concentrations in the bottom layers (+1 m from the bottom) were underestimated, probably because the resuspension process was not taken into account in the model. The improvement of the model's predictive capability, including the resuspension process, shall be the focus of our next study. 相似文献
34.
35.
Alamgir Md. Shah Furuya Jun Kobayashi Shintaro Mostafiz Rubaiya Binte Ahmed Md. Rashid 《GeoJournal》2021,86(6):2861-2885
GeoJournal - This paper examines the farm income differences, income inequality of farm households, parameters of income variability that ascertain vulnerability levels, and cost-income variability... 相似文献
36.
C. M. Copperwheat I. A. Steele R. M. Barnsley S. D. Bates D. Bersier M. F. Bode D. Carter N. R. Clay C. A. Collins M. J. Darnley C. J. Davis C. M. Gutierrez D. J. Harman P. A. James J. H. Knapen S. Kobayashi J. M. Marchant P. A. Mazzali C. J. Mottram C. G. Mundell A. Newsam A. Oscoz E. Palle A. Piascik R. Rebolo R. J. Smith 《Experimental Astronomy》2015,39(1):119-165
37.
Wavenumber spectra of the martian atmosphere covering zonal wavenumbers s=1-6 were obtained as a function of latitude and season for the first time from the temperatures measured by the Thermal Emission Spectrometer onboard the Mars Global Surveyor. The stationary component tends to peak at s=2, where the martian topography has large amplitude, and drops rapidly at higher wavenumbers. The transient component in the middle and high latitudes tends to peak at s=1, which is lower than the most unstable wavenumber based on linear theories, and exhibits spectral slopes much flatter than the stationary component. In the equatorial region, the spectra of the transient component are almost flat, indicating that the organization of large-scale structures is less efficient in this region. The spectral shapes are similar between the 0.5 and 2.2 hPa surfaces, except that the slopes are slightly steeper at 0.5 than at 2.2 hPa, probably due to selective vertical transmission at low wavenumbers. The seasonal variation is relatively large in the middle and high latitudes, where the maximum power occurs in winter and the minimum occurs in summer, with an exception that the transient component is maximum in spring in the southern hemisphere. Intensification of s=1 transient waves is observed around the period of the initiation of global dust storms. 相似文献
38.
R. Yamada I. Yamada S. Tanaka N. Kobayashi Y. Ishihara K. Yomogida A. Fujimura 《Planetary and Space Science》2009,57(7):751-763
We developed a seismometer system for a hard landing “penetrator” probe in the course of the former Japanese LUNAR-A project to deploy new seismic stations on the Moon. The penetrator seismometer system (PSS) consists of two short-period sensor components, a two-axis gimbal mechanism for orientation, and measurement electronics. To carry out seismic observations on the Moon using the penetrator, the seismometer system has to function properly in a lunar environment after a hard landing (impact acceleration of about 8000 G), and requires a signal-to-noise ratio to detect lunar seismic events. We evaluated whether the PSS could satisfactorily observe seismic events on the Moon by investigating the frequency response, noise level, and response to ground motion of our instrument in a simulated lunar environment after a simulated impact test. Our results indicate that the newly developed seismometer system can function properly after impact and is sensitive enough to detect seismic events on the Moon. Using this PSS, new seismic data from the Moon can be obtained during future lunar missions. 相似文献
39.
Aierken Sidike S. Kobayashi Heng-Jiang Zhu I. Kusachi N. Yamashita 《Physics and Chemistry of Minerals》2010,37(10):705-710
The photoluminescence (PL) and optical excitation spectra of baratovite in aegirine syenite from Dara-i-Pioz, Tien Shan Mts.,
Tajikistan and katayamalite in aegirine syenite from Iwagi Islet, Ehime, Japan were obtained at 300 and 80 K. Under short
wave (253.7 nm) ultraviolet light, baratovite and katayamalite exhibited bright blue-white luminescence. The PL spectrum of
baratovite at 300 K consisted of a wide band with a peak at approximately 406 nm and a full width at half maximum (FWHM) of
approximately 6.32k cm−1. The excitation spectrum of the blue-white luminescence from baratovite at 300 K consisted of a prominent band with a peak
at approximately 250 nm. The PL and excitation spectra of katayamalite were similar to those of baratovite. The luminescence
from these minerals was attributed to the intrinsic luminescence from the TiO6 center. 相似文献
40.
Mass depletion of bodies through successive collisional disruptions (i.e., collision cascade) is one of the most important processes in the studies of the asteroids belt, the Edgeworth-Kuiper belt, debris disks, and planetary formation. The collisional disruption is divided into two types, i.e., catastrophic disruption and cratering. Although some studies of the collision cascades neglected the effect of cratering, it is unclear which type of disruption makes a dominant contribution to the collision cascades. In the present study, we construct a simple outcome model describing both catastrophic disruption and cratering, which has some parameters characterizing the total ejecta mass, the mass of the largest fragment, and the power-law exponent of the size distribution of fragments. Using this simple outcome model with parameters, we examine the model dependence of the mass depletion time in collision cascades for neglect of coalescence of colliding bodies due to high collisional velocities. We find the cratering collisions are much more effective in collision cascades than collisions with catastrophic disruption in a wide region of the model parameters. It is also found that the mass depletion time in collision cascades is mainly governed by the total ejecta mass and almost insensitive to the mass of the largest fragment and the power-law exponent of fragments for a realistic parameter region. The total ejecta mass is usually determined by the ratio of the impact energy divided by the target mass (i.e. Q-value) to its threshold value for catastrophic disruption, as well as in our simple model. We derive a mass depletion time in collision cascades, which is determined by of the high-mass end of collision cascades. The mass depletion time derived with our model would be applicable to debris disks and planetary formation. 相似文献