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51.
An unusual association of chromite and hornblende was found in the spessartites of andesite composition, occurring as a dike
swarm associated with a Cretaceous granite batholith. The spessartites are largely porphyritic with phenocrysts of either
hornblende or augite. One dike, comprising a finegrained spessartite, exhibits distinct chilled selvages of aphanitic facies.
The chromites in the fine-grained and augite-spessartites are significantly higher in Cr/ (Cr+Al) than those occurring rarely
as inclusions in the phenocrystic hornblendes in the hornblende spessartite, although both are similar in Mg/ (Mg+Fe), Fe2O3, and TiO2. The phenocrystic hornblendes are titaniferous pargasite with high Mg/ (Mg+Fe), and differ in their higher octahedral Al
from the groundmass hornblendes including those in the fine-grained spessartite. The crystallization sequence in the phenocrystic
hornblende-bearing spessartites is Al-rich chromite, phenocrystic hornblende, and plagioclase without pyroxene, suggesting
a high water content in the magma and the start of the crystallization at relatively high pressures. The finegrained spessartite
from which the porphyritic spessartites have been derived by fractionation of dominant mafic minerals, has the high Mg-value
and Cr content equivalent to those in primitive, undifferentiated basalts, although still andesitic in SiO2 content. Chemically similar magnesian andesites, although uncommon, found in some orogenic calc-alkalic suites may represent
a magma composition in equilibrium with mantle peridotite under the condition of high water pressures. 相似文献
52.
The accurate measurement of thermal expansion in spinel MgAl2O4 over a temperature range between 30° C and 900° C has revealed an anomalous behaviour indicating a possible presence of a second order phase transition at 660° C. 相似文献
53.
Nondimensionalization of variables enables us to treat experiment data much more simply and efficiently by decreasing the
number of variables. In some cases, trivial conclusions (which Kenney, 1982, called spurious self-correlation) result from
a formal application of dimensional analyses. In contrast, in some cases fully significant conclusions can be derived. We
first discuss how to construct nondimensional variables retaining the physical meanings of variables. We then propose simple
and efficient methods, especially the use of “spurious triangle (SpT)”, to discriminate between significant conclusions and
spurious self-correlations in the analysis of nondimensionalized variables. 相似文献
54.
Jun Takahashi Tatsuo Suzuki Igor V Polyakov Kohei Mizobata Moto Ikeda Fancois J.Saucier Markus Meier 《极地研究(英文版)》2008,19(2):159-167
This study investigates the Arctic Ocean warming episodes in the 20th century using both a high-resolution coupled global climate model and historical observations. The model, with no flux adjustment, reproduces well the Atlantic Water core temperature (AWCT) in the Arctic Ocean and shows that four largest decadalscale warming episodes occurred in the 1930s, 70s, 80s, and 90s, in agreement with the hydrographic observational data. The difference is that there was no pre-warming prior to the 1930s episode, while there were two pre-warming episodes in the 1970s and 80s prior to the 1990s, leading the 1990s into the largest and prolonged warming in the 20th century. Over the last century, the simulated heat transport via Fram Strait and the Barents Sea was estimated to be, on average, 31.32 TW and 14.82 TW, respectively, while the Bering Strait also provides 15.94 TW heat into the west- ern Arctic Ocean. Heat transport into the Arctic Ocean by the Atlantic Water via Fram Strait and the Barents Sea correlates significantly with AWCT ( C = 0.75 ) at 0- lag. The modeled North Atlantic Oscillation (NAO) index has a significant correlation with the heat transport ( C = 0.37 ). The observed AWCT has a significant correlation with both the modeled AWCT ( C =0.49) and the heat transport ( C =0.41 ). However, the modeled NAO index does not significantly correlate with either the observed AWCT ( C = 0.03 ) or modeled AWCT ( C = 0.16 ) at a zero-lag, indicating that the Arctic climate system is far more complex than expected. 相似文献
55.
A modified Rankine source panel method is presented for solving a linearized free-surface flow problem with respect to the double-body potential. The method of solution is based on the distribution of Rankine sources on the hull as well as its image and on the free surface. An iterative algorithm is used for determining the free surface and wave resistance using upstream finite difference operator. A verification of numerical modeling is made using the Wigley hull and the validity of the computer program is examined by comparing the details of wave profiles and wave making resistance with Series 60 model. 相似文献
56.
The structure of the cosmic ray electron halo of a starburst galaxy depends strongly on the nature of galactic wind and the
configuration of the magnetic field. We have investigated these dependencies by solving numerically the propagation of electrons
originating in starburst galaxies, most likely in supernova remnants. The calculations are made for several models for the
galactic winds and for the configuration of the magnetic fields for comparison with observations. Our simulation of a quasi-radio
halo reproduces both the extended structure of ∼9 kpc and the subtle hollow structure near the polar region of the radio halo
that are observed in the starburst galaxy NGC 253. These findings suggest the existence of strong galactic wind in NGC 253.
相似文献
57.
Besshi-type Cu deposits are strata-bound volcanogenic massive sulfide deposits usually associated with mafic volcanic rocks or their metamorphic equivalents. Although there are numerous Besshi-type deposits in the Sanbagawa metamorphic belt, Japan, their tectonic settings and depositional environments remain controversial because of a lack of depositional age constraints. We report Re-Os data for the Iimori deposit, one of the largest Besshi-type deposits in western Kii Peninsula, in order to examine the robustness of the Re-Os isotope system for dating sulfide minerals in the high-P/T metamorphic belt and to elucidate the primary depositional environment of the Iimori sulfide ores. An 11-point Re-Os isochron plot yields an age of 156.8 ± 3.6 Ma. As this Re-Os isochron age is significantly older than the timing of the Sanbagawa peak metamorphism (110-120 or ∼90 Ma) and a well-defined isochron was obtained, the Re-Os age determined here is most likely the primary depositional age. Despite high-grade metamorphism at up to 520 ± 25 °C and 8-9.5 kbar, the Re-Os isotope system of the Iimori sulfides was not disturbed. Hence, we consider that the whole-rock Re-Os closure temperature for the Iimori sulfide ores was probably higher than 500 °C. As the accretion age of the Sanbagawa metamorphic belt is considered to be 120-130 or 65-90 Ma on the basis of radiolarian and radiometric ages, we estimated the time from the Iimori sulfide deposition on the paleo-seafloor to its accretion at the convergent plate boundary to be greater than 25 Myr. Consequently, the depositional environment of the Iimori sulfide ores was not in the marginal sea, but was truly pelagic. 相似文献
58.
We performed a comprehensive metaproteomic analysis of the dissolved organic matter (DOM) in Japanese coastal waters using liquid chromatography–tandem mass spectrometry and demonstrated that these proteomes were characterized by proteins with various functions, including metabolic enzymes, membranes, and photosynthetic proteins. The protein sources included cyanobacteria, heterotrophic bacteria, and eukaryotic phytoplankton. Most of the components were similar among samples and also similar to pelagic components. We also observed differences in the compositions of the microbial communities of origin among the different dissolved protein samples and differences in the relative abundance of specific dissolved protein types (e.g., cytoskeletal proteins), possibly indicating potential dynamics in the coastal DOM pool. 相似文献
59.
Sohiko Kameyama Satoshi Yoshida Hiroshi Tanimoto Satoshi Inomata Koji Suzuki Hisayuki Yoshikawa-Inoue 《Journal of Oceanography》2014,70(3):225-239
We measured dissolved isoprene (2-methyl-1,3-butadiene; C5H8) concentrations in a broad area of the southern Indian Ocean and in the Indian sector of the Southern Ocean from 35°S to 64°S and from 37°E to 111°E during austral summer 2010–2011. Isoprene concentrations were continuously measured by use of a proton-transfer-reaction mass spectrometer combined with a bubbling-type equilibrator. Concentrations of isoprene and its emission flux throughout the study period ranged from 0.2 to 395 pmol L?1 and from 181 to 313 nmol m?2 day?1, respectively, the averages being generally higher than those of previous studies. Although we found a significant linear positive relationship between isoprene and chlorophyll-a concentrations (r 2 = 0.37, n = 36, P < 0.001), the correlation coefficient was lower than previously reported. In contrast, in the high-latitude area (>53°S) we identified a significant negative correlation (r 2 = 0.59, n = 1263, P < 0.001) between isoprene and the temperature-normalized partial pressure of carbon dioxide (n-pCO2), used as an indicator of net community production in this study. This suggests that residence times and factors controlling variations in isoprene and n-pCO2 are similar within a physically stable water column. 相似文献
60.
Toshihiro Yoshimura Atsushi Suzuki Yusuke Tamenori Hodaka Kawahata 《Geo-Marine Letters》2014,34(1):1-9
Micro-scale distributions of trace and minor elements in, for example, coral skeletons are crucial as geochemical tracers of past environmental conditions, because they have the inherent advantage of accounting for confounding diagenetic and physiological effects. To extract reproducible paleoceanographic records from coral skeletons, a selective measurement of specific ultrastructures at high spatial resolution is required. Compared to warm-water reef-building corals, such data are limited in cold-water corals and, to the best of the authors’ knowledge, the latter have to date not been examined by means of micro-X-ray fluorescence. This technique was used for micrometer-scale imaging of P, Mg, Sr, O, and Fe intensities (counts per unit time) in a fossil specimen (as yet unknown age) of the cold-water coral Desmophyllum sp. from surface sediments of the NW Pacific. Cross plots confirmed that the micro-XRF signals were associated with corresponding trends in elemental concentration (ppm). Two major structural components of the septum—centers of calcification (COCs) and the surrounding fibrous aragonite portion—differed in composition. The COCs were characterized by higher intensities of P and Mg (650 and 220 counts per 5 s, respectively), and lower intensities of Sr (2,800) and O (580; corresponding values for the fibrous aragonite are 370, 180, 3,300 and 620 counts per 5 s, respectively). Oxygen intensity values were mostly homogeneous, but slightly lower in COCs and substantially higher in a well-defined patch in the fibrous aragonite. The mostly homogeneous P signals in the fibrous aragonite confirm the utility of this structural component and of coral septa in general for tracer studies of oceanic P. Nevertheless, spot occurrences of elevated P (>950 counts per 5 s) spanning tens of micrometers in specific parts of the fibrous region of the septum would cause overestimates of oceanic P, and should evidently not be overlooked in future research. The distribution of Fe showed no correlation with P, indicating no significant contamination in the form of P-bearing diagenetic ferromanganese precipitates. Such hotspots plausibly reflect the presence of other mineral phases, such as crystalline hydroxylapatite inclusions or contamination with organic material. The P signal intensity was positively correlated with Mg (r=0.553, p<0.001), and negatively with Sr (r=–0.489, p<0.001) and O (r=–0.311, p<0.001). There was no discernible evidence of control by water temperature in the Sr distribution pattern. These findings establish micro-X-ray fluorescence as a highly suitable pre-screening tool in cold-water coral sclerochronology, which can serve to refine sampling strategies without sample damage, and complement other micrometer-scale spatial distribution analyses of elements (notably, Ca) based on well-known approaches involving micro-milling, electron microprobes, secondary ion mass spectrometry, and laser ablation. 相似文献