排序方式： 共有8条查询结果，搜索用时 46 毫秒
1
1.
2.
E.P. Solotchina E.V. Sklyarov P.A. Solotchin E.G. Vologina V.N. Stolpovskaya O.A. Sklyarova N.N. Ukhova 《Russian Geology and Geophysics》2012,53(12):1351-1365
We present results of mineralogical and crystallochemical studies of the Holocene carbonate sediments of a small saline lake localized in the Borgoi dry-steppe region, western Transbaikalia. Mg-calcites with a varying Mg content are predominant in the assemblage of endogenic carbonate minerals from bottom sediments. Mathematical modeling of the XRD spectra of carbonates permitted us to identify excess-Ca dolomites, which are an indicator of a shallow (playa) lake. The studies showed that the lacustrine Mg-calcites do not form a continuous series from low- to high-Mg varieties. We discuss the cause of this phenomenon and also consider the existing viewpoints of the structure of low-temperature Mg-calcites and excess-Ca dolomites and their formation conditions in lacustrine sediments. Juxtaposing the carbonate record with the data of lithological analysis, determined stable isotopes (δ18O and δ13C), and distribution of some geochemical indicators of climatic changes, we reconstructed the intricate evolution of Lake Verkhnee Beloe, which was controlled by the regional climate since the postglacial period till the present day. 相似文献
3.
T. G. Ryashchenko N. N. Ukhova S. I. Shtel’makh N. I. Belyanina P. S. Belyanin 《Russian Journal of Pacific Geology》2011,5(3):238-249
This paper addresses the hypotheses of the formation of the brown loams widely spread in the zone with hummocky relief within
the intermontane Razdol’noe-Khanka Depression. These hypotheses were proposed in the 1970s–1980s. The accumulation of information
on the loess formation in southern East Siberia, as well as obtaining new analytical data on the microtextural, mineralogy,
and major and trace-element composition of the brown loams, and the comparative analysis of these deposits provided for the
formulation of a more substantiated view concerning the place of the brown loams in the group of loess-type rocks. 相似文献
4.
5.
D.P. Gladkochub T.V. Donskaya A.V. Ivanov R. Ernst A.M. Mazukabzov S.A. Pisarevsky N.A. Ukhova 《Russian Geology and Geophysics》2010,51(9):952-964
The Phanerozoic history of mafic magmatism in the southern Siberian craton included three major events. The earliest event (～500 Ma) recorded in dolerite dikes occurred during accretion and collision at the early stage of the Central Asian orogen. Injection of mafic melts into the upper crust was possible in zones of diffuse extension within the southern Siberian craton which acted as an indenter. The Late Paleozoic event (～275 Ma) produced dikes that intruded in a setting of subduction-related extension at the back of the active continental margin of Siberia during closure of the Mongolia–Okhotsk ocean, as well as slightly older volcanics (290 Ma) in the Transbaikalian segment of the Central Asian orogen. Early Mesozoic magmatism in the southern Siberian craton resulted in numerous 240–250 Ma mafic intrusions in the Angara–Taseeva basin. The intrusions (Siberian traps) appeared as the subducting slab of the Mongolia–Okhotsk ocean interacted with a lower mantle plume. The post-Late Paleozoic ages of flood basalts (290–275 Ma) correspond to progressive northwestward (in present coordinates) motion of the slab beneath the southern craton margin which likely ceased after the slab had reached the zone of the Siberian superplume. Since its consolidation after the Early Mesozoic activity, the crust in the area has no longer experienced extension favorable for intrusion of basaltic magma. 相似文献
6.
E.V. Sklyarov E.P. Solotchina E.G. Vologina N.V. Ignatova O.P. Izokh N.V. Kulagina O.A. Sklyarova P.A. Solotchin V.N. Stolpovskaya N.N. Ukhova V.S. Fedorovskii O.M. Khlystov 《Russian Geology and Geophysics》2010,51(3):237-258
We present results of a complex study of evaporite sediments from one of the small saline lakes with carbonate sedimentation in the Ol’khon area and substantiate their high significance for paleoclimatic reconstructions. The mineral composition of the bottom sediments was studied by XRD analysis, IR spectroscopy, scanning electron microscopy, elemental analysis (SR-XFA), etc. By decomposition of the complex XRD profiles of carbonate minerals into individual peaks by Pearson VII function, we identified carbonate phases in each sample and determined their proportions. A high-resolution carbonate record has been obtained for the first time for the lacustrine sediments. It bears the information about the stratigraphic distribution of Mg-calcites (a continuous series of structurally disordered low- to high-Mg calcites, up to Ca-dolomites), in which the amount and proportions of phases with different Mg contents are controlled by Mg/Ca, salinity, and total alkalinity of the lake water changing depending on the climatic cycles and lake level fluctuations. Comparison of the carbonate record for the Holocene section dated by the radiocarbon (14C) method with results of lithological, diatom, and palynological analyses, data on stable isotopes (δ18O and δ13C), and the distribution of some geochemical indicators of climatic changes permitted the reconstruction of the intricate evolution of the Lake Tsagan-Tyrm basin, which was controlled by the regional climate from the Atlantic period to the present time. The directed change in various characteristics of essentially carbonate sediments evidences that the Ol’khon regional climate has become more arid in recent 6.5 kyr. Moreover, drastic frequent changes of climate and, correspondingly, the Lake Tsagan-Tyrm water level in different periods of its existence have been revealed. The widespread saline and brackish lakes in southern East Siberia, Mongolia, and North China and the highly informative (in terms of paleoclimate and paleolimnology) carbonate sediments might help to recognize the general tendencies of paleoclimate changes and local fluctuations in Central Asia. 相似文献
7.
Solotchina E. P. Sklyarov E. V. Vologina E. G. Solotchin P. A. Stolpovskaya V. N. Sklyarova O. A. Izokh O. P. Ukhova N. N. 《Doklady Earth Sciences》2011,436(2):295-300
A new high-resolution Holocene climate record of the Western Baikal region from the evaporite sediments of one of the small
saline lakes with the carbonate type of sedimentation are obtained on the basis of detailed mineralogical and crystallochemical
studies of chemogenic carbonates. All carbonate phases occurring in the sediment are identified by decomposition of complex
XRD-profiles of carbonates into individual peaks using the Pearson VII function, and the quantitative relationships between
them are determined. Mg-calcites provide the major paleoclimatic information. The carbonate record contains data on the stratigraphic
distribution of Mg-calcites, in which the number and ratio between the phases of different magnesium contents are determined
by the past values of the Mg/Ca ratio, salinity, and total alkalinity of lake water that vary according to climatic cycles
and fluctuations of the lake level. The high potential of the approach proposed for paleoclimatic reconstructions is demonstrated. 相似文献
8.
1