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排序方式: 共有215条查询结果,搜索用时 125 毫秒
1.
Takuya Matsumoto Masahiko Honda Ian McDougall Igor Yatsevich Suzanne Y. O'Reilly 《地学学报》2004,16(1):23-26
Using a Rayleigh distillation fractionation model, we calculate that the maximum isotope fractionation potentially achievable is less than 5% during the early stages of gas release from a sample. Our calculation corrects the erroneous conclusions of Gautheron and Moreira (2003), who re‐interpreted the plume‐like neon isotopic compositions found in metasomatic apatite from a south‐eastern Australian xenolith (Matsumoto et al., 1997) to be the result of Rayleigh‐type isotope fractionation of originally MORB‐type neon during stepheating gas extraction. We stress that the modelling of neon isotopic fractionation by Gautheron and Moreira (2003) is incorrect, and that the finding of a plume‐like neon isotopic composition in the apatite by Matsumoto et al. (1997) remains a quite valid and robust conclusion. 相似文献
2.
Toru?Iwata Keiko?Yoshikawa Katsutoshi?Nishimura Yoshihisa?Higuchi Takao?Yamashita Shigeru?Kato Eiji?OhtakiEmail author 《Journal of Oceanography》2004,60(6):995-1000
The measurements of the vertical transport of CO2 were carried out over the Sea of Japan using the specially designed pier of Kyoto University on September 20 to 22, 2000. CO2 fluxes were measured by the eddy correlation and aerodynamic techniques. Both techniques showed comparable CO2 fluxes during sea breeze conditions: −0.001 to −0.08 mg m−2s−1 with the mean of −0.05 mg m−2s−1. This means that the measuring site satisfies the fetch requirement for meteorological observations under sea breeze conditions. Moreover, the eddy diffusivity coefficient used in the aerodynamic technique is found to be consistent with the coefficient used in the eddy correlation technique. The present result leads us to conclude that the aerodynamic technique may be applicable to underway CO2 flux measurements over the ocean and may be used in place of the bulk technique. The important point is the need to maintain a measuring accuracy of CO2 concentration difference of the order of 0.1 ppmv on the research vessels or the buoys. 相似文献
3.
Horizontal and vertical distributions of mercury were determined in seawater in Minamata Bay and Yatsushiro Sea. The concentrations of total and particulate mercury respectively ranged from 56–285 ng l–1 and 2.1–506 ng l–1. They were both highest in the inner most part of Minamata Bay where the sediment was most heavily polluted, and decreased with increasing distance from there. Vertically, an evident increase in concentration was observed near the bottom. A good agreement was found between the mercury content in suspended matter and that in fine sediment particles.These facts show that the particulate mercury is supplied mostly from the bottom sediment, and that it is spreading offshore with dispersing in seawater. This process would eventually result in the pollution of sediment in Yatsushiro Sea. 相似文献
4.
Takuya Itaki Masashi Ito Hisashi Narita Naokazu Ahagon Hideo Sakai 《Deep Sea Research Part I: Oceanographic Research Papers》2003,50(12):1507
The depth distributions of the radiolarian fauna in the Chukchi and Beaufort Seas, marginal seas of the western Arctic Ocean, were examined quantitatively in depth-stratified plankton tows from 4 or 5 intervals above 500 m and in surface sediments from various depths between 163 and 2907 m. The radiolarian assemblage from the water column in September 2000 was dominated by Amphimelissa setosa and followed by the Actinomma boreale/leptoderma group, Pseudodictyophimus gracilipes and Spongotrochus glacialis. These species are related to the Arctic Surface Water shallower than 150 m. This assemblage is similar to that in the Greenland Sea relating to the ice edge, but did not contain typical Pacific radiolarians in spite of the flow of water of Pacific origin in this region. The living depth of Ceratocyrtis historicosa was restricted to the relatively warm water between 300 and 500 m corresponding to the upper Arctic Intermediate Water (AIW) originating from the Atlantic Ocean. Radiolarian assemblages in the surface sediments are similar to those in the plankton tows, except for common Cycladophora davisiana in sediment samples below 500 m. C. davisiana is probably a deep-water species adapted to the lower AIW or the Canadian Basin Deep Water ventilated from the shelves. 相似文献
5.
6.
Bacterial degradation of the hydrocarbons of lubricating oils was investigated by mass spectrometric analysis which gives
both total amount and the composition of hydrocarbon types of residual oil. An unused lubricating oil, which mainly consisted
of hydrocarbon types with only a small percentage ofn-alkanes, was degraded by marineBacillus sp. andPseudomonas sp. with 55 % and 25 % decreases in 10 days, respectively. Susceptibility of respective hydrocarbon types to biodegradation
was in the following order: alkanes > non-condensed cycloalkanes, mono-aromatics > condensed cycloalkanes. A used lubricating
oil of different brand showed a larger decrease than the unused oil. Both species of bacteria degraded large portions of alkane
fraction of Arabian light crude oil. 相似文献
7.
Masao Komazawa Hitoshi Morikawa Kajuro Nakamura Junpei Akamatsu Keiichi Nishimura Sumio Sawada Ayfer Erken Akin Onalp 《Soil Dynamics and Earthquake Engineering》2002,22(9-12):829-836
The 1999 Kocaeli earthquake brought serious damage to downtown of Adapazari. To study why strong motions were generated at the town, a bedrock structure was investigated on the basis of Bouguer gravity anomaly, and SPAC and H/V analyses of microseisms. It was revealed that, the basin consists of three narrow depressions of bedrock with very steep edges, extending in E–W or NE–SW directions along the North Anatolia faults, and the depth to bedrock reaches 1000 m or more. Downtown of Adapazari is located 1–2 km apart from the basin-edge. It is considered that, the specific configuration of bedrock amplifies ground motions at the downtown area by focusing of seismic waves and/or interference between incident S-waves and surface-waves secondarily generated at the basin-edge. Studying 3D bedrock structure is an urgent issue for microzoning an urban area in a sedimentary basin. 相似文献
8.
Abstract A southwest dipping Mesozoic accretionary complex, which consists of tectonically imbricated turbiditic mudstone and sandstone, hemipelagic siliceous mudstone, and bedded cherts and basaltic rocks of pelagic origin, is exposed in northern North Island, New Zealand. Interpillow limestone is sometimes contained in the basaltic rocks. The grade of subduction‐related metamorphism increases from northeast to southwest, indicating an inverted metamorphic gradient dip. Three metamorphic facies are recognized largely on the basis of mineral parageneses in sedimentary and basaltic rocks: zeolite, prehnite‐pumpellyite and pumpellyite‐actinolite. From the apparent interplanar spacing d002 data for carbonaceous material, which range from 3.642 to 3.564 Å, the highest grade of metamorphism is considered to have attained only the lowermost grade of the pumpellyite‐actinolite facies for which the highest temperature may be approximately 300°C. Metamorphic white mica K–Ar ages are reported for magnetic separates and <2 µm hydraulic elutriation separates from 27 pelitic and semipelitic samples. The age data obtained from elutriation separates are approximately 8 m.y. younger, on average, than those from magnetic separates. The age difference is attributed to the possible admixture of nonequilibrated detrital white mica in the magnetic separates, and the age of the elutriation separates is considered to be the age of metamorphism. If the concept, based on fossil evidence, of the subdivision of the Northland accretionary complex into north and south units is accepted, then the peak age of metamorphism in the north unit is likely to be 180–130 Ma; that is, earliest Middle Jurassic to early Early Cretaceous, whereas that in the south unit is 150–130 Ma; that is, late Late Jurassic to early Early Cretaceous. The age cluster for the north unit correlates with that of the Chrystalls Beach–Taieri Mouth section (uncertain terrane), while the age cluster for the south unit is older than that of the Younger Torlesse Subterrane in the Wellington area, and may be comparable with that of the Nelson and Marlborough areas (Caples and Waipapa terranes). 相似文献
9.
We report 26Mg excesses correlated with Al/Mg ratios in five chondrules from the primitive CO3.0 chondrite Yamato 81020 that yield a mean initial 26Al/27Al ratio of only (3.8 ± 0.7) × 10−6, about half that of ordinary chondrite (OC) chondrules. Even if asteroids formed immediately after chondrule formation, this ratio and the mean Al content of CO chondrites is only capable of raising the temperature of a well-insulated CO asteroid to 940 K, which is more than 560 K too low to produce differentiation. The same ratio combined with the higher Al content of CV chondrites results in a CV asteroid temperature of 1100 K. We calculate that the mean initial 26Al/27Al ratio of about 7.4 × 10−6 found in LL chondrules is only able to produce small amounts of melting, too little to produce differentiation. These results cast serious doubt on the viability of 26Al as the heat source responsible for asteroid differentiation. Inclusion of 60Fe raises temperatures about 160 K, but this increment is not enough to cause differentiation, even of an LL-chondrite asteroid. 相似文献
10.