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排序方式: 共有193条查询结果,搜索用时 31 毫秒
41.
东昆仑南缘早三叠世洪水川组的源区特征:来自碎屑组成、重矿物和岩石地球化学的证据 总被引:6,自引:3,他引:3
分布于东昆仑南缘的早三叠世洪水川组系一套由砾岩、砂岩、页岩和鲕粒灰岩等浅海相和河流相沉积物构成的弧前盆地沉积组合.砂岩碎屑组成、重矿物组合、岩石地球化学和古水流综合研究结果表明,洪水川组砂岩物源主要来自于北侧的岛弧带,同时南侧的阿尼玛卿蛇绿混杂带也为其形成提供了部分物源;源区主要出露长英质岩石、变质岩和硅质岩. 相似文献
42.
Kiseleva Yu. V. Gektin Yu. M. Zaytsev A. A. Kuharsky A. V. Rublev A. N. Uspensky A. B. 《Izvestiya Atmospheric and Oceanic Physics》2016,52(9):1181-1190
Izvestiya, Atmospheric and Oceanic Physics - A new intercalibration technique for infrared channels of the MSU-GS imager on the Elektro-L no. 1 Russian geostationary meteorological satellites is... 相似文献
43.
The Stockholm archipelago spans roughly a semicircular area with a radius of approximately 60 km, traditionally partitioned into three parts: the inner, the middle and the outer archipelago. This subdivision coincides with differing water exchange regimes. The inner and middle archipelagos are characterised by comparatively larger basins which are interconnected by a limited number of straits. This configuration is well suited for a discrete basin (DB-) model approach by partitioning the area into a set of sub-basins that are only resolved vertically. The advantage of this approach over 3D-models is the possibility for enhanced vertical resolution and improved strait exchange formulation, outweighing the disadvantage of neglected horizontal gradients within the basins. In the inner archipelago the dominating exchange process is estuarine circulation, induced by the marked freshwater discharge and the vertical mixing. In the outer and middle archipelagos the density fluctuations due to Ekman pumping along the Baltic boundary interface produce another type of baroclinic process that clearly dominates. Measurements to adequately resolve these density variations do not exist. Missing forcing data are provided by linking the middle archipelago's boundary straits to a 3D-model of the Baltic with a grid resolution of 0.5 nautical miles (n.m.). This fine resolution model (FR-domain) is in turn driven by the atmospheric forcing and the density variation at the rectangular boundary of the FR-domain which acceptably resolves both the interfacial straits and the outer archipelago's complex hypsography. Massive computing resources would be demanded if the FR-domain were extended to comprise the entire Baltic. The FR-domain is thus interfaced with an existing coarse resolution model of the entire Baltic (CR-domain) with a grid size of 5 n.m., the open boundary of which is located in the Kattegat. This 3-fold model set-up has been run for one whole year (1992) with a one-year spin-up time to make up for the lack of initial data. The model concept is at this stage to be regarded as a framework for further development in anticipation of improved formulations, particularly for the strait exchange formulation. Therefore only primary validation experiments and a few sensitivity analyses have been performed. 相似文献
44.
Changing seas in the Early–Middle Miocene of Central Europe: a Mediterranean approach to Paratethyan stratigraphy
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The Miocene palaeogeographic evolution of the Paratethys Sea is still poorly constrained. Here, we use modern Mediterranean biochronology to provide an up‐to‐date overview of changing seas in Central Europe. Instead of a Paratethys that waxed and waned with fluctuating global sea levels, we show that the development of different seas was mainly controlled by tectonic phases. The Early Miocene “Ottnangian Sea” (~18 Ma) was connected to the Mediterranean via the Rhône valley, while the “Karpatian Sea” (~16.5 Ma) was initiated by a tectonically induced marine transgression through the Trans‐Tethyan gateway. In most Central European basins, the establishment of the “Badenian Sea” (<15.2 Ma), triggered by subduction‐related processes in the Pannonian and Carpathian domain, is significantly younger (by ~1 Myr) than usually estimated. The updated palaeogeographic reconstructions provide a better understanding of the concepts of basin dynamics, land–sea distribution and palaeoenvironmental change in the Miocene of Central Europe. 相似文献
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Forward dissolution rates of Na-Montmorillonite (Wyoming) SWy-2 smectite (Ca0.06Na0.56)[Al3.08Fe(III)0.38Mg0.54] [Si7.93 Al0.07]O20(OH)4 were measured at 25 °C in a mixed-flow reactor equipped with interior dialysis compartment (6-8 kDa membrane) as a function of pH (1-12), dissolved carbonate (0.5-10 mM), phosphate (10−5 to 0.03 M), and nine organic ligands (acetate, oxalate, citrate, EDTA, alginate, glucuronic acid, 3,4-dihydroxybenzoic acid, gluconate, and glucosamine) in the concentration range from 10−5 to 0.03 M. In organic-free solutions, the Si-based rates decrease with increasing pH at 1 ? pH ? 8 with a slope close to −0.2. At 9 ? pH ? 12, the Si-based rates increase with a slope of ∼0.3. In contrast, non-stoichiometric Mg release weakly depends on pH at 1 ? pH ? 12 and decreases with increasing pH. The empirical expression describing Si-release rates [R, mol/cm2/s] obtained in the present study at 25 °C, I = 0.01 M is given by
48.
Linear features dubbed “tiger stripes” in the south polar region of Enceladus have anomalously high heat fluxes and are the apparent source of the observed plume. Several explanations for the observed activity have been proposed, including venting from a subsurface reservoir of liquid water, sublimation of surface ice, dissociation of clathrates, and shear heating. Thermal modeling presented in this work, coupled with observations from the Cassini Composite Infrared Spectrometer (CIRS) instrument, seeks to elucidate the underlying physical mechanism by constraining vent temperatures and thermal emission sources, using a model in which the observed thermal signature results primarily from conductive heating of the surface by warm subsurface fractures. The fractures feed surface vents, which may themselves contribute to the observed thermal emission. Model variables include vent temperature, presence of a surface insulating layer, vent width, time-variable heat input, and heat sources other than the central vent. Results indicate that CIRS spectra are best fitted with a model in which the surface is heated by narrow vents at temperatures as high as 223 K. Although equally good fits can be obtained for vent temperatures in the range of 130 to 155 K if the vents are wider (180 m and 22 m respectively) and dominate the emission spectrum, these models are probably less realistic because vents with these temperatures and widths cannot supply the observed H2O vapor flux. The lack of emission angle dependence of the thermal emission when July 2005 and November 2006 CIRS observations are compared also argues against thermal emission being dominated by the vents themselves. Thus, results favor high-temperature models, possibly venting from a subsurface liquid water reservoir. However, a fracture filled with liquid water near the surface would produce significantly higher radiances than were detected unless masked by a thermally insulating surface layer. Models that best match the CIRS data are characterized by small fractions of the surface at high temperatures, which strengthens the case for the vents and/or their conductively-heated margins being the primary heat source. Models where the thermal emission is dominated by conductive heating of the surface from below by a laterally-extensive buried heat source cannot reproduce the observed spectrum. Models with a 10 cm thick upper insulating layer produce a poor match to the CIRS spectra, suggesting high thermal inertias near the tiger stripes. Finally, tiger stripe thermal emission measured by CIRS varied by less than 15% over the 16 month period from July 2005 to November 2006. 相似文献
49.
Rosanna Sordo Antonella Vallenari Rosaria Tantalo France Allard Ronny Blomme Jean-Claud Bouret Ines Brott Yves Fremat Christophe Martayan Yassine Damerdji Bengt Edvardsson Eric Josselin Bertrand Plez Oleg Kochukhov Mary Kontizas Ulisse Munari Tenay Saguner Jean Zorec Andreas Schweitzer Paraskevi Tsalmantza 《Astrophysics and Space Science》2010,328(1-2):331-335
ESA’s Gaia mission will collect low resolution spectroscopy in the optical range for ~109 objects. Complete and up-to-date libraries of synthetic stellar spectra are needed to built algorithms aimed to automatically derive the classification and the parametrization of this huge amount of data. In addition, libraries of stellar spectra are one of the main ingredients of stellar population synthesis models, aiming to derive the properties of unresolved stellar populations from their integrated light. We present (a) the newly computed libraries of synthetic spectra built by the Gaia community, covering the whole optical range (300–1100 nm) at medium-high resolution of (0.3 nm) for stars spanning the most different types, from M to O, from A-peculiar to Emission lines to White Dwarfs, and (b) the implementation of those libraries in our SSP code (Tantalo in The Initial Mass Function 50 Years Later, 327:235 2005), exploring different stellar evolution models. 相似文献
50.
Abstract— Large impact events like the one that formed the Chicxulub crater deliver significant amounts of heat that subsequently drive hydrothermal activity. We report on numerical modeling of Chicxulub crater cooling with and without the presence of water. The model inputs are constrained by data from borehole samples and seismic, magnetic, and gravity surveys. Model results indicate that initial hydrothermal activity was concentrated beneath the annular trough as well as in the permeable breccias overlying the melt. As the system evolved, the melt gradually cooled and became permeable, shifting the bulk of the hydrothermal activity to the center of the crater. The temperatures and fluxes of fluid and vapor derived from the model are consistent with alteration patterns observed in the available borehole samples. The lifetime of the hydrothermal system ranges from 1.5 to 2.3 Myr depending on assumed permeability. The long lifetimes are due to conduction being the dominant mechanism of heat transport in most of the crater, and significant amounts of heat being delivered to the near‐surface by hydrothermal upwellings. The long duration of the hydrothermal system at Chicxulub should have provided ample time for colonization by thermophiles and/or hyperthermophiles. Because habitable conditions should have persisted for longer time in the central regions of the crater than on the periphery, a search for prospective biomarkers is most likely to be fruitful in samples from that region. 相似文献