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The Fe- and Al-rich metapelite of the Teiskaya Group in the trans-Angara part of the Yenisei Range are characterized by variable P-T parameters of their metamorphism. Geochemical data on these rocks were used to reproduce the nature and composition of their protolith. The metapelites were determined to be redeposited and metamorphosed Precambrian weathering crusts of the kaolinite type, which were produced by the erosion of Archean rocks of predominantly acid (granitoid) composition in shallow-water continental-margin basins in a humid climate. These results are consistent with the results of the lithological-facies analysis and geodynamic reconstruction of the Precambrian geological evolution of complexes in the Yenisei range. Differences were revealed between the REE patterns in metapelites in various metamorphic zones caused by both the compositional heterogeneity of the protoliths and the prograde (in terms of pressure) mineral reactions of collision metamorphism with the predominant effects of various processes during different evolutionary stages. 相似文献
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Chronicle
Aleksandr Georgievich Rozanov (on his 70th birthday) 相似文献4.
Doklady Earth Sciences - A continuous peat bog section from a barely accessible mid-mountain area in the northwestern Baikal region has been obtained for the first time. The materials were studied... 相似文献
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O. I. Bazhenova A. A. Cherkashina D. V. Kobylkin S. A. Makarov K. E. Vershinin 《Geography and Natural Resources》2017,38(2):154-164
A conjugate analysis of the processes of morphogenesis and sedimentation within small fluvial basins of Dauria revealed a rhythmic character of change of the Holocene processes which are combined into cycles of a different hierarchical level. It is shown that each cycle begins with an extreme phase of intense fluvial drift and delivery of matter from the system. The fluvial horizons comprise the lower part of deposits of the Holocene macrocycle in the Vesnyanka pad’ (a valley without a permanent watercourse). A disastrous fluvial drift was recorded repeatedly for the period 7–8.5 cal. ka and at the transition time from the Atlantic to Subboreal time. A normal zonal phase of integration of matter within the basins is exhibited by buried humus horizons of soils which give clear evidence of 1800-year cycles. A regional development in Dauria is recorded for the soils with the age of about 8, 6.4 and 4.6 as well as 1.2–1.4 cal. ka. The upper part of the deposits of each cycle is characterized by aeolian horizons of extreme arid phases. The profiles of proluvial trails are indicative of 130-year cycles. Based on results from studying buried soils, data of pollen analysis and radiocarbon dating of the deposits, we determined an enhancement in climate aridization for the last 10 ka and, in general, a decreased of the sedimentation and morphogenesis rate. 相似文献
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The results of first application of automated bottom station for studying chemical exchange across the water-bed interface
(IO RAS lander) were obtained for the case of sediments in the northwestern Black Sea near Gelendzhik (Golubaya Bay). The
lander is equipped with bottom chambers, sensors of environmental characteristics, and samplers, allowing fluxes of chemical
elements through the water-bed interface to be determined directly. Bottom sediments were represented by organogenous silts
containing hydrogen sulfide. The high activity of diagenetic processes resulted in a higher consumption of O2 by sediments (the flux from the bottom water was 130 mM/(m2/day), high fluxes of biogenic elements (P, Si,) and metals (Mn, Fe). At the same time, fluxes across the water-bed interface
were evaluated based on the difference between concentrations of these elements in the near-bed and silt water (Fick’s law).
The obtained data demonstrate the priority of direct measurements of fluxes (lander) over the calculation method. The first
application of the lander suggests the need for methodological improvements both of engineering character and in chemical-analytical
support. 相似文献
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The design and application of a lander (an apparatus developed at the Institute of Oceanology of the Russian Academy of Sciences (IO RAN) to study the chemical processes in the near-bottom layer) are described. The methodological foundations and design peculiarities of the lander were developed in the course of chamber experiments carried out at shallow depths with the assistance of divers. The transition to greater depths required development of a multifunctional automatic device capable of independently performing long-term surveys in the near-bottom layer, including those of the chemical exchange at the water-bottom interface. 相似文献
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Svetlana V. Pakhomova Per O.J. Hall Mikhail Yu. Kononets Alexander G. Rozanov Anders Tengberg Andrei V. Vershinin 《Marine Chemistry》2007
Fluxes of dissolved forms of iron and manganese across the sediment–water interface were studied in situ in the Gulf of Finland and the Vistula Lagoon (Baltic Sea), and in the Golubaya Bay (Black Sea) from 2001 to 2005. Fluxes were measured using chamber incubations, and sediment cores were collected and sliced to assess the porewater and solid phase metal distribution at different depths. Measured and calculated benthic fluxes of manganese and iron were directed out of sediment for all sites and were found to vary between 70–4450 and 5–1000 µmole m− 2 day− 1 for manganese and iron, respectively. The behavior of the studied metals at various redox conditions in the near-bottom water and in the sediment was the main focus in this study. Our results show the importance of bottom water redox conditions for iron fluxes. We measured no fluxes at oxic conditions, intermediate fluxes at anoxic conditions (up to 200 μmole m− 2 day− 1) and high fluxes at suboxic conditions (up to 1000 μmole m− 2 day− 1). Total dissolved iron fluxes were generally dominated by iron(II). Contribution of iron(III) to the total iron flux did not exceed 20%. Obtained fluxes of manganese at all studied regions showed a linear correlation (r2 = 0.97) to its concentration in the porewater of the top sediment layer (0–5 mm) and did not depend on dissolved oxygen concentrations of bottom water. Organically complexed iron and manganese were in most cases not involved in the benthic exchange processes. 相似文献
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A. P. Fedotov M. A. Phedorin I. V. Enushchenko K. E. Vershinin S. M. Krapivina E. G. Vologina S. K. Petrovskii M. S. Melgunov O. A. Sklyarova 《Environmental Earth Sciences》2013,68(6):1733-1744
Reconstruction of temporal and spatial climate development on a seasonal basis during the last few centuries may help us better understand modern-day interplay between natural and anthropogenic climate variability. The objective of this paper is to reconstruct hydrology and landscape changes of East Siberia during the termination of the Little Ice Age and the subsequent Recent Warming. We analysed sediment samples from the saltwater Sulfatnoe Lake, Bolshoye Alginskoe and freshwater Shuchie Lake using high-resolution X-ray fluorescence spectroscopy at 1-mm scan resolution, Fourier-transform infrared techniques and pollen analyses. The depth–age models of the cores were constructed by 210Pb activity using the constant rate of supply model. The lake sediment cover of these lakes began to form from ca. 1870. Three significant periods (1870–1895, 1895–1925 and from 1925 to the present) were defined in hydrology and chemical regime of these lakes for the past 140 years. Lake levels were extremely low and high saturated with salts during the final period of the Little Ice Age. Lake levels began to slowly rise from 1870 to 1895 and vegetation was poor at that period. Intensive desalination of the lakes occurred in 1895–1925, and environment conditions were temperate and favourable for the majority of the taxa of the regional vegetation. Regional precipitation significantly increased and water saturation of the catchments was high from 1925 to the present. The chemical precipitation of carbonate stopped completely in Lake Shichie and reduced considerably in Lake Sulfatnoe and B. Alginskoe. Strong increasing trend of weathering of the lake catchments began in 1970 and still continues. 相似文献