排序方式: 共有54条查询结果,搜索用时 15 毫秒
31.
E. F. Letnikova S. I. Shkolnik F. A. Letnikov E. A. Karakovskii Yu. A. Kostitsyn I. A. Vishnevskaya L. Z. Reznitskii A. V. Ivanov A. I. Prochenkin 《Doklady Earth Sciences》2017,474(2):668-673
The U–Pb age of zircons from Ediacaran sandstones of the cover of the Tuva–Mongolian microcontinent and the rocks of its Early Precambrian basement (Gargan block) was analyzed by the LA–ICP–MS method. The major stages of tectonomagmatic activity of this block include the Neoarchean, Paleoproterozoic (no younger than 2 Ga), and Neoproterozoic. Comparison of the age of zircons from Ediacaran terrigenous rocks of the Tuva–Mongolian microcontinent and sandstones of the reference sections of the Ediacaran shelf of the Siberian platform undeniably indicates their independent accumulation. 相似文献
32.
Doklady Earth Sciences - Tantalum metallogeny throughout the geological history is analyzed. The respective deposits are presented by five types (pegmatitic, granitic, alkaligranitic, foidic, and... 相似文献
33.
Geology of Ore Deposits - The global distribution of tantalum deposits and their resources on the geological time scale is analyzed. The analysis is based on the data for 65 deposits of the world... 相似文献
34.
Doklady Earth Sciences - This paper reports on lithium metallogeny in geological time. The geochronological analysis was conducted on the basis of data on 71 lithium deposits distributed globally.... 相似文献
35.
S. V. Yasinskii I. A. Vishnevskaya S. I. Shaporenko T. S. Bibikova 《Water Resources》2018,45(4):490-502
A retrospective review of the current scientific publications on the problems of water protection zones at water bodies is given. The content of regulations on water protection zone in the RF Water Code 2006 now in force is interpreted. The legislations regarding the establishment of water protection zones and riparian buffer strips at water bodies in Russia and other countries are compared and analyzed. The technologies and specifics of the development of geoinformation system “Water Protection Zone and Riparian Buffer Strip of a Water Body” are demonstrated as applied to determining the boundary of the water protection zone and riparian buffer strip for the Uglich Reservoir. Assessment of the anthropogenic load onto a drainage basin within the water protection zone of the Uglich Reservoir and a method for geoecological zoning of its territory are considered as an example. 相似文献
36.
The carbonate sediments from the Vendian–Cambrian shelf of the Tuva-Mongolian microcontinent were dated by Sr and C isotope chemostratigraphy. Analysis of the Sr-isotopic characteristics (0.70725–0.70873) and δ13C variations (+ 10.5 to –3.5‰), as well as their comparison with the data on the key sections of Siberia, Africa, Central Asia, Australia, South America, and Spitsbergen, showed that the carbonate sedimentary cover of the Tuva-Mongolian microcontinent accumulated at 600–520 Ma and the carbonate sediments of the Muren Formation and the basal beds of the Bokson Group near the Ukha-Gol River are the oldest. Their sedimentation followed the Marinoan global glaciation. 相似文献
37.
E.F. Letnikova A.B. Kuznetsov I.A. Vishnevskaya S.V. Veshcheva A.I. Proshenkin H. Geng 《Russian Geology and Geophysics》2013,54(10):1177-1194
Geochemical and isotopic (Sm–Nd and Sr) studies of deposits of the Baikal and Oselok Groups in the southern Siberian Craton and LA-ICP-MS U–Pb dating of detrital zircons show that they accumulated in passive continental-margin settings in the Vendian. The time limits of sedimentation were assessed on the basis of Sr chemostratigraphy of carbonate deposits of the Baikal Group and LA-ICP-MS U–Pb dating of detrital zircons in first-cycle terrigenous deposits of the Oselok Group. The main provenances for rocks of these groups were constant. These were rocks of the cover and basement of the Siberian Craton. Tuffite horizons in upper portions of the groups are the only sign of Late Vendian activation of this block, which is reflected in changes of geochemical indices of terrigenous rocks and their younger Sm–Nd model ages. 相似文献
38.
G. N. Aleksandrova V. N. Beniamovskii V. S. Vishnevskaya A. S. Zastrozhnov 《Stratigraphy and Geological Correlation》2012,20(5):426-465
This work discusses the complex characteristic of the Upper Cretaceous (Turonian-Lower Maastrichtian) section recovered by two boreholes in the southern part of the Volgograd region (right side of the Volga River) in the Gremyach??e potash deposit. Lithological and paleontological data (benthic foraminifers, radiolarians, and dinocysts) suggest several lithological-facies and biotic reorganizations. The analysis of the distribution of these microfossils through the section allowed the ages of the Zakharovo Group, Mozhzhevelovyi Ovrag, Mezino-Lapshinovka, Pudovkino, Zarya, Nalitovo, and Bereslavka Formations to be specified. Benthic foraminifers characterize zones of the Upper Cretaceous high-resolution scale available for the East European Platform and local (facies) units, while radiolarians and dinocysts reveal stratigraphic units in a bed rank. Using complex paleontological characteristics (benthic foraminifers, radiolarians, dinocysts), the defined biostratigraphic units are correlated between each other and with their counterparts in neighboring and remote regions of different paleobiogeographic regions and provinces. The Upper Cretaceous biostratigraphic scale is supplemented by the first defined dinocyst and radiolarian biostratigraphic units of the East European Platform. The new data provides evidence in favor of a three-substage division of the Campanian Stage instead the two-substage system presently accepted in Russia. It is shown that the traditional position of the lower boundary of the Maastrichtian Stage in the East European Platform is close to that of this boundary in the Standard Stratigraphic Scale. Some aspects of environmental and biotic evolution in the Volgograd region through the Late Cretaceous Epoch are considered. 相似文献
39.
I. A. Vishnevskaya B. B. Kochnev E. F. Letnikova A. B. Kuznetsov A. I. Proshenkin 《Doklady Earth Sciences》2012,443(2):431-435
This paper presents the first Sr isotopic data for the Late Precambrian carbonate rocks of the southern Yenisei Ridge. Their
geochemical study allowed estimation of the degree of secondary alterations and gave the possibility to reveal rocks with
a less disturbed Rb-Sr isotopic system. The Sr isotopic data indicated Neoproterozoic sedimentation of the rocks about 1070–750
Ma ago. Sr and C isotopic data showed that carbonate rocks of the Sukhoi Pit, Tungusik, and Shirokino groups are Late Riphean
and could be comparable with sedimentary sequences of three Precambrian key sections of the Northern Eurasia: the subsequent
Derevnino, Burovaya, and Shorikha formations from the Turukhansk Uplift, the Lakhanda Group from the Uchur-Maya region, and
the Karatav Group from the South Urals. All studied carbonate rocks are older than 750 Ma and, according to the International
Stratigraphic Chart, accumulated prior to global glaciations in the Cryogenian. This is evident from sedimentological study
indicating the absence of tillite horizons in the studied sections. δ13C values in the sections vary from +0.4 up to +5.3‰, which testifies to the absence of periods of great cold. 相似文献
40.
The problem of correlating the isolated outcrops of allochthonous Middle Mesozoic deposits developed in northeastern Asia
and western North America includes several aspects: (1) the stratigraphic subdivision of the sequences using the radiolarian
assemblages and taking into account the complex nappe-thrust structure of the region; (2) the analysis of their facies composition
with reconstructing the geodynamic depositional settings; (3) the search for features in common (with respect to the previous
two aspects) in all these localities. The first widely applied radiolarian analysis revealed that the Middle Mesozoic marine
rocks from separate nappes and slices of tectono-stratigraphic sections in East Asia enclose 20 different-age (Norian to Hauterivian)
radiolarian assemblages. The correlation of these assemblages revealed the wide lateral distribution of their host Middle
Mesozoic marine sequences in the regions under consideration. The significance of the presented materials is determined by
the following facts: (1) using the radiolarian analysis, the Middle Mesozoic marine sequences of northeastern Asia are first
subdivided into stage and substage units with defining their analogs in western North America; (2) despite the discrete distribution
of Mesozoic allochthons, it is shown that the defined stratigraphic units are widespread in northeastern Asia; (3) it is established
that these allochthons consist of rocks formed in different geodynamic depositional settings: ocean floor, island arc, fore-arc,
and marginal-sea domains. This spectrum of heterogeneous rocks is traceable practically through the entire northeastern Asia
region. 相似文献