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排序方式: 共有77条查询结果,搜索用时 15 毫秒
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Organized bacterial assemblies in manganese nodules: evidence for a role of S-layers in metal deposition 总被引:1,自引:0,他引:1
Xiaohong Wang Heinz C. Schröder Ute Schloßmacher Werner E. G. Müller 《Geo-Marine Letters》2009,29(2):85-91
Polymetallic/ferro-manganese nodules (Mn-nodules) reach sizes of up to 10 cm in diameter and are abundantly found on the seabed.
To date, the origin of Mn-nodules remains unclear, and both abiogenic and biogenic origins have been proposed. In search of
evidence for a contribution of microbial processes to the formation of Mn-nodules, we analyzed those spherical nodules which
contain a concentrically banded texture in their interior. The Mn-nodules were collected at a depth of 5,152 m from the Clarion-Clipperton
Zone. Our high-resolution scanning electron microscopy analyses reveal first published evidence that endolithic microorganisms
exist and are arranged in a highly organized manner on plane mineral surfaces within the nodules. These microorganisms are
adorned on their surfaces with S-layers, which are indicative for bacteria. Moreover, the data suggest that these S-layers
are the crystallization seeds for the mineralization process. We conclude that the mineral material of the Mn-nodule has a
biogenic origin, and hope that these data will contribute to the development of biotechnological approaches to concentrate
metals from seawater using bacteria in bioreactors. 相似文献
3.
Ansgar Greshake Richard Wirth Jörg Fritz Tomasz Jakubowski Ute Böttger 《Meteoritics & planetary science》2018,53(3):467-481
Libyan Desert Glass (LDG) is a SiO2-rich natural glass whose origin, formation mechanism, and target material are highly debated. We here report on the finding of a lens-shaped whitish inclusion within LDG. The object is dominantly composed of siliceous glass and separated from the surrounding LDG by numerous cristobalite grains. Within cristobalite, several regions rich in mullite often associated with ilmenite were detected. Mineral assemblage, chemical composition, and grain morphologies suggest that mullite was formed by thermal decomposition of kaolinitic clay at atmospheric pressure and T ≥ 1600 °C and also attested to high cooling rates under nonequilibrium conditions. Cristobalite contains concentric and irregular internal cracks and is intensely twinned, indicating that first crystallized β-cristobalite inverted to α-cristobalite during cooling of the SiO2-rich melt. The accompanied volume reduction of 4% induced the high density of defects. The whitish inclusion also contains several partly molten rutile grains evidencing that at least locally the LDG melt was at T ≥ 1800 °C. Based on these observations, it is concluded that LDG was formed by high-temperature melting of kaolinitic clay-, rutile-, and ilmenite-bearing Cenozoic sandstone or sand very likely during an asteroid or comet impact onto Earth. While melting and ejection occurred at high pressures, the melt solidified quickly at atmospheric pressure. 相似文献
4.
A quantitative map comparison/integration technique to aid in petroleum exploration was applied to an area in south-central Kansas. The visual comparison and integration of maps has become increasingly difficult with the large number and different types of maps necessary to interpret the geology and assess the petroleum potential of an area; therefore, it is desirable to quantify these relationships. The algebraic algorithm used in this application is based on a point-by-point comparison of any number and type of spatial data represented in map form. Ten geological and geophysical maps were compared and integrated, utilizing data from 900 wells located in a nine-township area on the Pratt Anticline in Pratt County, Kansas. Five structure maps, including top of the Lansing Group (Pennsylvanian), Mississippian chert, Mississippian limestone, Viola Limestone (Ordovician), and Arbuckle Group (Cambro-Ordovician), two isopachous maps from top of Mississippian chert to Viola and Lansing to Arbuckle, a Mississippian chert porosity map, Bouguer gravity map, and an aeromagnetic map were processed and interpreted. Before processing, each map was standardized and assigned a relative degree of importance, depending on knowledge of the geology of the area. Once a combination of weights was obtained that most closely resembled the pattern of proved oil fields (target map), a favorability map was constructed based on a coincidence of similarity values and of geological properties of petroleum reservoirs. The resulting favorability maps for the study area indicate location of likely Mississippian chert and lower Paleozoic production. 相似文献
5.
Bathymetric, gravity, and magnetic data from Antarctic expeditions with RV POLARSTERN and satellite altimeter data from the Geosat Geodetic Mission are analysed using methods from geostatistics and geophysical inverse theory.The Explora Escarpment represents the edge between the Antarctic Continental Shelf and the Weddell Abyssal Plain. It is an important link in the reconstruction of Gondwana breakup, but a feature as large as the 2000 m deep Wegener Canyon was only discovered in 1984, when extensive bathymetric, gravimetric, and magnetic surveys with RV POLARSTERN began.Geostatistics, the theory of regionalized variables, is applied to integrate dense surveys of Wegener Canyon and sparse observations in adjacent areas into maps with full coverage of the 230 km by 330 km area at 10°–20° W/70°–72° S. The resultant highresolution bathymetric and gravity maps reveal detailed structures of the Explora Escarpment. Using geophysical inversion, the gravity terrain effect is calculated. Satellite data are used for their better coverage, but have much lower resolution. Nevertheless, the structures of Wegener Canyon and other more prominent features appear with surprisingly good correlation also in the Geosat altimeter data. While it was initially supposed that Wegener Canyon is purely an erosional structure, the magnetic map now provides evidence of the canyon's tectonic origin. 相似文献
6.
7.
Is the ocean floor a fractal? 总被引:1,自引:0,他引:1
The topographic structure of the ocean bottom is investigated at different scales of resolution to answer the question: Can the seafloor be described as a fractal process? Methods from geostatistics, the theory of regionalized variables, are used to analyze the spatial structure of the ocean floor at different scales of resolution. The key to the analysis is the variogram criterion: Self-similarity of a stochastic process implies self-similarity of its variogram. The criterion is derived and proved here: it also is valid for special cases of self-affinity (in a sense adequate for topography). It has been proposed that seafloor topography can be simulated as a fractal (an object of Hausdorff dimension strictly larger than its topological dimension), having scaling properties (self-similarity or self-affinity). The objective of this study is to compare the implications of these concepts with observations of the seafloor. The analyses are based on SEABEAM bathymetric data from the East Pacific Rise at 13°N/104°W and at 9°N/104°W and use tracks that run both across the ridge crest and along the ridge flank. In the geostatistical evaluation, the data are considered as a stochastic process. The spatial continuity of this process is described by variograms that are calculated for different scales and directions. Applications of the variogram criterion to scale-dependent variogram models yields the following results: Although the seafloor may be a fractal in the sense of the definition involving the Hausdorff dimension, it is not self-similar, nor self-affine (in the given sense). Mathematical models of scale-dependent spatial structures are presented, and their relationship to geologic processes such as ridge evolution, crust formation, and sedimentation is discussed. 相似文献
8.
Taro Takahashi Stewart C. Sutherland Rik Wanninkhof Colm Sweeney Richard A. Feely David W. Chipman Burke Hales Gernot Friederich Francisco Chavez Christopher Sabine Andrew Watson Dorothee C.E. Bakker Ute Schuster Nicolas Metzl Hisayuki Yoshikawa-Inoue Masao Ishii Takashi Midorikawa Yukihiro Nojiri Arne Krtzinger Tobias Steinhoff Mario Hoppema Jon Olafsson Thorarinn S. Arnarson Bronte Tilbrook Truls Johannessen Are Olsen Richard Bellerby C.S. Wong Bruno Delille N.R. Bates Hein J.W. de Baar 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(11):2075-2076
9.
Geostatistics for Compositional Data: An Overview 总被引:1,自引:0,他引:1
Tolosana-Delgado Raimon Mueller Ute van den Boogaart K. Gerald 《Mathematical Geosciences》2019,51(4):485-526
Mathematical Geosciences - This paper presents an overview of results for the geostatistical analysis of collocated multivariate data sets, whose variables form a composition, where the components... 相似文献
10.
Liquid Fe metal-liquid silicate partition coefficients for the lithophile and weakly-siderophile elements Ta, Nb, V, Cr, Si, Mn, Ga, In and Zn have been measured in multianvil experiments performed from 2 to 24 GPa, 2023-2873 K and at oxygen fugacities of −1.3 to −4.2 log units relative to the iron-wüstite buffer. Compositional effects of light elements dissolved in the metal liquid (S, C) have been examined and experiments were performed in both graphite and MgO capsules, specifically to address the effect of C solubility in Fe-metal on siderophile element partitioning. The results were used to examine whether there is categorical evidence that a significant portion of metal-silicate equilibration occurred under very high pressures during core-mantle fractionation on Earth. Although the depletion of V from the mantle due to core formation is significantly greater than that of Nb, our results indicate that both elements have similar siderophile tendencies under reducing conditions at low pressures. With increasing pressure, however, Nb becomes less siderophile than V, implying that average metal-silicate equilibration pressures of at least 10-40 GPa are required to explain the Nb/V ratio of the mantle. Similarly the moderately-siderophile, volatile element ratios Ga/Mn and In/Zn are chondritic in the mantle but both volatility and core-mantle equilibration at low pressure would render these ratios strongly sub-chondritic. Our results indicate that pressures of metal-silicate partitioning exceeding 30-60 GPa would be required to render these element ratios chondritic in the mantle. These observations strongly indicate that metal-silicate equilibration must have occurred at high pressures, and therefore support core-formation models that involve deep magma oceans. Moreover, our results allow us to exclude models that envisage primarily low-pressure (<1 GPa) equilibration in relatively small planetary bodies. We also argue that the core cannot contain significant U as this would require metal-silicate equilibration at oxygen fugacities low enough for significant amounts of Ta to have also been extracted from the mantle. Likewise, as In is more siderophile than Pb but similarly volatile and also quite chalcophile it would have been difficult for Pb to enter the core without reversing the relative depletions of these elements in the mantle unless metal-silicate equilibration occurred at high pressures >20 GPa. 相似文献