排序方式: 共有71条查询结果,搜索用时 234 毫秒
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N. G. Patyk-Kara E. N. Levchenko A. I. Stekhin V. V. Barsegyan A. A. Bochneva I. A. Chizhova E. A. Andrianova V. T. Dubinchuk 《Geology of Ore Deposits》2008,50(3):218-239
The study of mineral assemblages at the Central deposit allowed us to substantially refine the evolutionary model of the deposit and reveal the two main factors that control the variability of its mineralic space: (1) heterogeneity of the ore layer, consisting of a sublittoral bottom placer (the lower part) and a subaerial dune complex partly reworked in the course of a new transgression (the upper part), and (2) postore epigenetic alteration of the ore constituent of sands, which affected the quality of ore concentrates. The results obtained will be used in geological and technological mapping and development of the production program. 相似文献
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N. M. Sushchevskaya O. V. Levchenko E. P. Dubinin B. V. Belyatsky 《Geochemistry International》2016,54(3):237-256
The study of magmatism and tectonic structure of the East Indian or Ninetyeast Ridge (NER) reveals the geochemical similarity of mantle sources for the NER and Kerguelen Plateau melts. Magmas related to the Kerguelen plume were derived from an enriched mantle source, whereas the NER tholeiitic basalts originated from a source contaminated by a depleted material. While, depleted basalt varieties were not found within the NER basalts. It was shown that magmatic rocks forming the NER were generated by high degrees (30%) of partial melting within the ancient Wharton spreading ridge due to the activity of the Kerguelen plume, which was located at this time in the vicinity of the ridge. The most significant impact of the plume on the NER structures was recorded at 70–50 Ma ago. 相似文献
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D. G. Levchenko 《Oceanology》2009,49(2):257-264
Several anomalous phenomena related to the measurement of storm microseisms in northwestern Europe and on Greenland have been considered. It has been indicated that these phenomena can be explained by analyzing the microseism propagation in oceanic waveguides in the regions of abyssal plains and transformation on continental slopes of different steepness. A model of the oceanic waveguide with an inclined elastic bottom has been presented. An analysis of the family of dispersion dependences for such a model makes it possible to find an explanation for the specific features of microseism field transformation at the ocean-continent boundary into Rayleigh waves propagating on the land. 相似文献
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Polyakov A. S. Roslyakov A. G. Lobkovskii L. I. Levchenko O. V. Putans V. A. Ambrosimov A. K. Merklin L. R. Anan’ev R. A. Dmitrevskii N. N. Libina N. V. 《Doklady Earth Sciences》2010,431(1):376-379
By means of mathematical modeling, the parameters of flows forming sedimentary waves on the western slope of the Derbent basin
were estimated. The height of these flows depends on the slope steepness and varies from 25 to 170 m to reach its maximum
values at gentler slope areas. However, the flow rate is independent of the slope steepness and depends only on the concentration
of sediment matter supplied by the flow. At the upper part of the slope (the flow starting), the rate amounts to 0.4–1.4 m/s,
being almost halved at the depths where the sedimentary waves are damped. The present rates of near-bottom currents show pronounced
seasonal differences, and their values are close to flow rates obtained by numerical modeling. 相似文献
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Oceanology - The volcanic structure of the Seymour Sewell seamount appears to have formed over a relatively long time in at least two stages. Its main massif was formed as a result of volcanic... 相似文献
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John Dodson Xiaoqiang Li Ming Ji Keliang Zhao Xinying Zhou Vladimir Levchenko 《Quaternary Research》2009,(3):309-314
Understanding of the origin and development of bronze technology in eastern Asia remains unresolved. Here we report on the distribution of copper and associated cations in sediments from Huoshiliang in northwestern Gansu, China, strontium and lead isotope analyses of ore and slag samples, and some artifact fragments at archaeological sites at Ganggangwa and Huoshiliang in the Black River valley.We conclude that bronze production began perhaps as early as 2135 BC and that the Baishantang modern mine site at Dingxin was a possible source of copper ore. There was at least one other, but currently unidentified, source of ore. The Bronze Age people were also farmers and planted cereals such as wheat, and they may have abandoned the region when wood was exhausted and desertification took over. 相似文献
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N. V. Simagin I. O. Murdmaa E. A. Seitkalieva D. G. Borisov E. V. Dorokhova E. M. Emel’yanov O. V. Levchenko 《Lithology and Mineral Resources》2017,52(6):427-434
Facts confirming the hypothesis of contourite sediment infill of the Equatorial Mid-Ocean Canyon (EMOC) are presented. We examined two cores recovered in Cruises 37 and 43 of the R/V Akademik Ioffe (2012, 2013). The cores recovered upper Quaternary miopelagic clays on the EMOC floor (AI-3149) and the adjacent abyssal plain (AI-2620). The study of these cores unraveled significant differences in their composition. In contrast to the lithologically homogeneous Core AI-2620, Core AI-3149 includes interlayers enriched in the biogenic CaCO3, terrigenous silt, and authigenic ferromanganese micronodules. These peculiarities are attributed to activity of the Antarctic Bottom Water (AABW) contour currents along the EMOC. 相似文献