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排序方式: 共有182条查询结果,搜索用时 15 毫秒
11.
Lyudmila V. Malakhova Viktor N. Egorov Tatiana V. Malakhova Sergey B. Gulin Yury G. Artemov 《Geo-Marine Letters》2010,30(3-4):391-398
Concentrations of dissolved methane in seawater and bottom sediments, as well as of methane emanating from gas seeps were measured at 18 stations including several small bays in the Sevastopol coastal area (Black Sea) during 2007–2008. Methane concentrations in surface waters ranged from 10 to 2,970 nmol l?1, and correlated well with values recorded for sediments. Methane concentrations in the water column were influenced by water depth, as well as by air and water temperatures. In the spring and summer of 2008, in situ CH4 saturation relative to air was in the range of 970–71,900%. Maximum saturation was in summer. CH4 fluxes to the atmosphere from the Sevastopol coastal area were estimated to vary from 190 to 1,550 μmol m?2 day?1. Gas bubbles escaping from the seepages contained about 57 vol% methane. Radiocarbon dating of the methane revealed an age not exceeding 150 years, implying a biogenic origin. 相似文献
12.
13.
Main stages in tectonic evolution of the Eastern Arctic region 总被引:1,自引:0,他引:1
14.
N. I. Filatova 《Doklady Earth Sciences》2007,413(2):362-366
15.
Evolution of Cretaceous active continental margins and their correlation with other global events 总被引:1,自引:0,他引:1
N. I. Filatova 《Island Arc》1998,7(1-2):253-270
16.
17.
Adri��n Rodr��guez Tatiana A. Michtchenko Octavio Miloni 《Celestial Mechanics and Dynamical Astronomy》2011,111(1-2):161-178
We investigate the secular dynamics of two-planet coplanar systems evolving under mutual gravitational interactions and dissipative forces. We consider two mechanisms responsible for the planetary migration: star-planet (or planet-satellite) tidal interactions and interactions of a planet with a gaseous disc. We show that each migration mechanism is characterized by a specific law of orbital angular momentum exchange. Calculating stationary solutions of the conservative secular problem and taking into account the orbital angular momentum leakage, we trace the evolutionary routes followed by the planet pairs during the migration process. This procedure allows us to recover the dynamical history of two-planet systems and constrain parameters of the involved physical processes. 相似文献
18.
The Arctida Craton and Neoproterozoic-Mesozoic orogenic belts of the Circum-Polar region 总被引:1,自引:0,他引:1
An attempt is made to characterize an assembly of Arctic tectonic units formed before the opening of the Arctic Ocean. This
assembly comprises the epi-Grenville Arctida Craton (a fragment of Rodinia) and the marginal parts of the Precambrian Laurentia,
Baltica, and Siberian cratons. The cratons are amalgamated by orogenic belts (trails of formerly closed oceans). These are
the Late Neoproterozoic belts (Baikalides), Middle Paleozoic belts (Caledonides), Permo-Triassic belts (Hercynides), and Early
Cretaceous belts (Late Kimmerides). Arctida encompasses an area from the Svalbard Archipelago in the west to North Alaska
in the east. The Svalbard, Barents, Kara, and other cratons are often considered independent Precambrian minicratons, but
actually they are constituents of Arctida subsequently broken down into several blocks. The Neoproterozoic orogenic belt extends
as a discontinuous tract from the Barents-Ural-Novaya Zemlya region via the Taimyr Peninsula and shelf of the East Siberian
Sea to North Alaska as an arcuate framework of Arctida, which separates it from the Baltica and Siberian cratons. The Caledonian
orogenic belt consisting of the Scandian and Ellesmerian segments frames Arctida on the opposite side, separating it from
the Laurentian Craton. The opposite position of the Baikalian and Caledonian orogenic belts in the Arctida framework makes
it possible to judge about the time when the boundaries of this craton formed as a result of its detachment from Rodinia.
The Hercynian orogenic belt in the Arctic Region comprises the Novozemel’sky (Novaya Zemlya) and Taimyr segments, which initially
were an ending of the Ural Hercynides subsequenly separated by a strike-slip fault. The Mid-Cretaceous (Late Kimmerian) orogenic
belt as an offset of Pacific is divergent. It was formed under the effect of the opened Canada Basin and accretion and collision
at the Pacific margins. The undertaken typification of pre-Late Mesozoic tectonic units, for the time being debatable in some
aspects, allows reconstruction of the oceanic basins that predated the formation of the Arctic Ocean. 相似文献
19.
Natalia V. Lubnina Satu Mertanen Ulf Söderlund Svetlana Bogdanova Tatiana I. Vasilieva Dmitry Frank-Kamenetsky 《Precambrian Research》2010
Palaeomagnetic and geochronological studies on mafic rocks in the Lake Ladoga region in South Russian Karelia provide a new, reliably dated Mesoproterozoic key paleopole for the East European Craton (Baltica). U–Pb dating on baddeleyite gives a crystallisation age of 1452 ± 12 Ma for one of the studied dolerite dykes. A mean palaeomagnetic pole for the Mesoproterozoic dolerite dykes, Valaam sill and Salmi basalts yields a paleopole at 15.2°N, 177.1°E, A95 = 5.5°. Positive baked contact test for the dolerite dykes and positive reversal test for the Salmi basalts and for the dykes confirm the primary nature of the magnetisation. Comparison of this Baltica palaeopole with coeval paleomagnetic data for Laurentia and Siberia provides a revised palaeoposition of these cratons. The results verify that the East European Craton, Laurentia and Siberia were part of the supercontinent Columbia from the Late Palaeoproterozoic to the Middle Neoproterozoic. 相似文献
20.
Tatiana Pertuz Alireza Malehmir Jordan Bos Bojan Brodic Yinshuai Ding Richard de Kunder Paul Marsden 《Geophysical Prospecting》2022,70(1):79-94
A prototype electromagnetic vibrator, referred to here as E-Vib, was upgraded and developed for broadband hardrock and mineral exploration seismic surveys. We selected the iron oxide mine in Blötberget, central Sweden, for a test site in 2019 for the newly developed E-Vib because of the availability of earlier seismic datasets (from 2015 to 2016) for verification of its performance for hardrock imaging purposes. The two-dimensional data acquisition consisted of a fixed geometry with 550 receiver locations spaced at every 5 m, employing both cabled and wireless seismic recorders, along an approximately 2.7 km long profile. The E-Vib operated at every second receiver station (i.e. 10 m spacing) with a linear sweep of 2–180 Hz and with a peak force of 7 kN. The processing workflow took advantage of the broadband signal generated by the E-Vib in this challenging hardrock environment with varying ground conditions. The processed seismic section shows a set of reflections associated with the known iron oxide mineralization and a major crosscutting reflection interpreted to be from a fault system likely to be crosscutting the mineralization. The broadband source data acquisition and subsequent processing helped to improve signal quality and resolution in comparison with the earlier workflows and data where a drophammer seismic source was used as the seismic source. These results suggest new possibilities for the E-Vib source for improved targeting in hardrock geological settings. 相似文献