Southeastern Transbaikal Region Research Articles

Soils of Lakeside Depressions of Pulsing Chloride Lakes of Internal Runoff in Central Asia: Morphology, Physical-Chemical and Geochemical Features

Data on saline soils of drainless lakeside depressions, which are formed in areas of extra continental climate with a cyclic 25–30-year change in the level of lakes within the arid and humid climatic phases, were obtained first. Different types of soils are shown to be formed on the landscapes adjacent to highly mineralized chloride lakes of southeastern Trans-Baikal Region: on superaqueous–subaqueous positions– gleyic solonchaks (Gleyic Solonchak (Loamic, Chloridic)); on superaqueous – humus–gley saline soils (Calcaric Mollic Gleysol (Arenic, Endosalic, Sodic)); on eluvial-superaqueous – light-humus saline soils (Fluvic Kastanozem (Epiarenic, Amphiloamic, Sodic)). Salinity degree of the soils under the study is different. Salinity chemistry is sodium taking into account cations. Anion content in solonchaks and upper horizon of humus-gley soil is mostly chloride. Soda-chloride and chloride-soda anion composition prevail in other soils. Gleyic solonchaks have strongly alkaline pH values, high content of carbonates, and a sharp dominance of Na+ among exchangeable cations. Many chemical elements are concentrated in the solonchakous horizon (Sr, S, Li, Mg, Ca); a high content of As is a regional feature. The humus-gley saline soil has the same properties as the light-humus saline soil in terms of physico-chemical parameters, and in terms of elemental composition and texture as solonchaks. This is due to it functions periodically in a semihydromorphic or hydromorphic regimes when changing the arid and humid phases. The high level of groundwater contributes to the enrichment of soils with the elements typomorphic for lake waters. The paleohydromorphic stage of development has been established to be recorded in lower layers of light-humus saline soil in the form of a high content of easily soluble salts and carbonates. The geochemical specialization of soil-forming rocks is associated with the significant accumulation of As, as well as concentration of Li, Ba, and Pb. It was also revealed that low Ca/Sr ratio is their geochemical feature. The use of cluster analysis of indicators of soils under the study revealed that both dynamic and stable soil parameters are reflected in humus-gley soil and it is recommended for monitoring of the dynamics of endorheic lakeside ecosystems in Central Asia with cyclic climatic phases.

Trace Element Composition of Beryl From the Sherlovaya Gora Deposit, Southeastern Transbaikal Region, Russia

Trace Element Composition of Beryl From the Sherlovaya Gora Deposit, Southeastern Transbaikal Region, Russia

The Hydrochemistry and Hydrobiology of Technogenic Reservoirs at Mining Territories of the Southeastern Transbaikal Region

The Hydrochemistry and Hydrobiology of Technogenic Reservoirs at Mining Territories of the Southeastern Transbaikal Region

Main formation conditions of soda-type groundwater: A case study from south-eastern Transbaikal region (Russia)

Chemical and isotopic groundwater composition analyses in the south-eastern Transbaikal case study region allowed three geochemical types of waters and fifteen subtypes to be identified: bisiallite (Ca–HCO3), soda (Na–HCO3) and salt (Na–HCO3–Cl–SO4). All three types differed significantly with respect to TDS content, pH, composition of chemical elements and heavy water isotopes. The transition from the first to the subsequent types was accompanied by CO32−, HCO3−, SO42−, Cl− and Na+ accumulation, whereas a weaker dependence was exhibited for Mg2+ and K+, and no relationship with Ca2+ was found. Water was found to be gradually enriched in heavy isotopes and some trace elements (e.g. F, Mo, Br, B and Li). Findings showed that the groundwater–rock system is one of an equilibrium-disequilibrium. From the extent of the deeper horizons to the surface water, groundwater in the study region continuously dissolves minerals that are in disequilibrium with the groundwater and simultaneously forms new minerals. Moreover, over time, not only does the composition of the solution change, but the type of secondary minerals and the ratio between chemical elements also changes because some elements precipitate out of solution, while others continue to accumulate. The stage of soda-type groundwater formation was found to be at an intermediate level between the formation of fresh bisiallite (Ca–HCO3) water of different cationic composition and salt (Na–HCO3–Cl–SO4) water with mixed anionic composition.

Influence of Environmental Factors on the Structure of Plankton Communities in Saline Lakes at Different Water-Fill Phases

The work is based on the results of long-term studies on phytoplankton and zooplankton in sodasaline lakes of the Uldz Gol-Torey basin (southeastern Trans-Baikal region). The unstable level regime of steppe lakes, due to climate fluctuations, leads to changes in the morphometric and hydrochemical regime of the lakes, and, as a consequence, to transformation of the plankton community. The goal of this work is to identify and analyze environmental factors that determine the structure of planktonic biocenoses in mineral lakes at different water-fill phases. According to statistical analysis of auxiliary models based on the redundancy analysis (RDA), the significance factors were mineralization and pH in the transgressive water-fill phase and pH in the regressive phase. Schematic drawings of interrelationships within the plankton community are constructed on the basis of the correlation matrix. There were nine interrelated components in the plankton natural associations in the high-water period and only five components at a low-water level. Chlo-rophyta was found to be a basic constructive element of the plankton community regardless of the water level. Euglenophyta, Bacillariophyta, and Cladocera were the second most significant elements in the structural organization during the full-water period and Charophyta, Dinophyta, Rotifera, and Copepoda were during the water-short period.

Geodynamic simulation of ore-bearing geological structural units by the example of the Strel’tsovka uranium ore field

Information on designing a 3D integrated model of the deflected mode (DM) of rock massif near the Strel’tsovka uranium ore field (SUOF) in the southeastern Transbaikal region is presented in the paper. This information is based on the contemporary stresses estimated by geostructural and tectonophysical techniques and by studying the seismotectonic deformation of the Earth’s surface using the data on earthquake source mechanisms and GPS geodesy focused on the recognition of active faults. A combination of the results of geostructural, geophysical, geotectonic, and petrophysical research, as well as original maps of faulting and the arrangement of seismic dislocations and seismotectonic regimes (stress tensors), allowed us to design models of the structure, properties, and rheological links of the medium and to determine the boundary conditions for numerical tectonophysical simulation using the method of terminal elements. The computed 2D and 3D models of the state of the rock massif have been integrated into 3D GIS created on the basis of the ArcGIS 10 platform with an ArcGIS 3D-Analyst module. The simulation results have been corroborated by in situ observations on a regional scale (the Klichka seismodislocation, active from the middle Pliocene to date) and on a local scale (heterogeneously strained rock massif at the Antei uranium deposit). The development of a regional geodynamic model of geological structural units makes it possible to carry out procedures to ensure the safety of mining operations under complex geomechanical conditions that can expose the operating mines and mines under construction, by the Argun Mining and Chemical Production Association (PAO PPGKhO) on a common methodical and geoinformational platform, to the hazards of explosions, as well as to use the simulation results aimed at finding new orebodies to assess the flanks and deep levels of the ore field.

Peltula daurica (Peltulaceae), a new lichen species from Dauria (Transbaikal Territory)

A description of a new lichen species Peltula daurica from the vicinity of the village of Aksha (South-Eastern Transbaikal Region), collected in the Onon River valley, near the river bank on steep basalt rocks along the road surrounded by steppe, is provided. The new species differs from all the known Peltula species by the presence of a prothallus and peltate squamules (with «pseudoumbilicus») developing from areoles. The species takes a separate position both among the peltate species and among the crustose species. Its affinity is unknown and may to a certain degree be established by using molecular analysis, for which additional materials are required.

The identification and use of petrophysical anomalies to forecast the mineralization at the Antey uranium deposit (Southwestern Trans-Baikal Region)

The determination of petrophysical parameters in conjunction with the geological, structural, mineralogical, and petrographic study of rocks is necessary to assess the localization conditions of uranium–molybdenum ore, the processing prospects, and the extent of mineralization at the Antey vein–stockwork deposit, which is the Russia’s largest, confined to the granitoid basement of the Streltsovo Caldera in the Southeastern Trans-Baikal Region.

Structure and formation properties of the haloalkaliphilic community of Lake Khilganta

The structural features of a cyanobacterial mat from Lake Khilganta (Southeastern Transbaikal Region) developing at different values of salinity and pH were determined based on our long-term investigation of the natural community, as well as results obtained during experimentation with its laboratory analogue. At water mineralization of 40–50 g/l, Microcoleus chthonoplastes and Phormidium molle play a key role in the formation of the cyanobacterial mat. As water mineralization increases, the diversity of cyanobacteria in the natural mat increases as well, reaches its maximum at 80 g/l NaCl, and decreases at 100 g/l. In the laboratory community, Nodularia sp. prevailed. It was able to form matlike structures within a broad pH range and at a salinity of up to 50 g/l NaCl. As the water mineralization level increased up to 100 g/l or higher, a replacement of the dominant complexes occurred both in the laboratory and natural communities: cyanobacterial species were substituted with green algae.

Fault tectonics, neotectonic stresses, and hidden uranium mineralization in the area adjacent to the Strel’tsovka Caldera

The scheme of recent fault tectonics and neotectonic stresses of the area adjacent to the Strel’tsovka Caldera in the southeastern Transbaikal region has been compiled for the first time on the basis of structural and geomorphic study. The faults were ranked by criteria of slip direction stability along separate segments and their expression in topography. Neotectonic stresses of corresponding ranks were ascertained as well. The heterogeneity of neotectonic stress field is related to the mosaic development of compression, extension, and the three-axial stress state. Comparison of morphogenetic features of recent and older faults shows the different character of the deformation mechanism and orientation of tectonic displacements. It has been established that the Strel’tsovka Caldera and its northwestern segment, in particular, developed as an echeloned system of pull-apart grabens, but the caldera itself is situated in a recent rise, whereas the northwestern segment is located in a neotectonic depression corresponding to the Dry Urulyungui Basin filled with volcanic and sedimentary rocks. Such a structure markedly expands the outlook for discovery of hidden uranium mineralization in the studied area. The elaborated scheme of neotectonic faults and stresses reflects the postore geodynamic setting and completes the reconstruction of geodynamic conditions pertaining to the periods of preore preparation and ore-forming tectonomagmatic reactivation.

Natural and technogenic changes in the mode of rock deformation in the uranium deposit in granites

The Antey deposit in the southeastern Transbaikal region is one of the main objects of uranium ore mining. It is localized in the Late Paleozoic granite basement of the Strel’tsovo Caldera formed during the Late Mesozoic tectono-magmatic activation of geological structures in the region. Vein ore bodies of the deposit are controlled by steep near-meridional faults being developed in zones of intense hydrothermal-metasomatic alterations, cataclasis, brecciation, and elevated rock fracturing. The upper parts of the ore bodies are located at a depth of 400 m and their lower parts are traceable up to depths of 1300 m below the surface. The mining activity involves progressively deeper levels of the section, which determines the necessity for the complex assessment of the deposit potential. The mode of rock deformation at the four lower horizons of mines occurring at depths of 500 to 700 m is discussed. It is shown that variations in the mode of deformation are determined by a combination of natural and technogenic factors, which should be taken into consideration in predicting the geomechanic behavior of the rocks for safe mining works.

The Antei uranium deposit: A natural analogue of an SNF repository and an underground geodynamic laboratory in granite

The estimation of the long-term stability of crystalline rock massifs with respect to natural and technogenic loads in the course of long-term storage of spent nuclear fuel (SNF) is a special area of surveys at underground research laboratories (URLs). In parallel with these surveys, data on uranium deposits—natural analogues of repositories of SNF consisting of 95% UO2—are used for obtaining insight into the dynamics of radionuclide migration and validating barrier properties of host rocks. Examples of URLs located in granitic massifs of Sweden (Aspo), Canada (Whiteshell), Switzerland (Grimsel), Japan (Mizunami), and Finland (ONKALO), as well as the El Berrocal (Spain), Palmottu (Finland), Sanerliu (China), and Kamaishi (Japan) deposits, are considered in the paper. The objects listed above are distinct in tectonic settings, geology, control of ore mineralization, redox conditions of uranium migration, and character and intensity of filtration and transportation, which predetermine the direction and specific features of research conducted therein. A variant in which a URL and a natural analogue are combined in one object is especially promising for validation of safe long-term isolation of SNF. The Antei vein-stockwork uranium deposit in the southeastern Transbaikal region, localized in Paleozoic granite at a depth of 400–1000 m and opened by mine workings at six levels, is such an object. Its geological features, stress-strain state, and infrastructure of mine workings offer an opportunity to study the entire spectrum of processes proceeding in near-and far-field of an SNF repository. The structural geology, mineralogy and petrography, and petrophysical and tectonophysical features of the deposit at its three lower levels are considered. The sequence of metasomatic alteration of rocks and the dynamics of formation of ore-bearing faults that crosscut prototectonic elements, as well as relationships of physicomechanical properties of rocks as a function of the intensity of their metasomatic alteration and the distance from master fault planes, have been established. A 3D geological model of the deposit in combination with estimated parameters of the present-day stress field and physicomechanical properties of particular rock blocks serves as the basis for prediction of the geomechanical behavior of the massif. The practical implications of the results obtained for assessment of the long-term safety of SNF repositories in granites are discussed.

The effect of the pH level on the communities of anoxygenic phototrophic bacteria of soda lakes of the southeastern Transbaikal Region

The effect of pH on the structure of the communities of anoxygenic-phototrophic-bacteria (APB) was studied under laboratory conditions. Samples of natural APB communities were inoculated into media that differed in pH values, which were 7, 9.5, or 10.5. The structure of the APB communities in the obtained enrichment cultures depended on the pH values and on the mineralization levels of the media, which were the same as in the lakes from which samples were taken. The same dependence of the community structure on salinity was observed as in the case of the natural communities that had been described previously. APB were most diverse in the enrichment cultures grown at pH 9.5. The shift of the pH to either neutral or extremely alkaline values affected the species diversity within the APB community, resulting in marked predominance of the most adapted forms. It was shown that the status of Ectothiorhodospira within the community could serve as an indicator of both salinity and pH in soda lakes with a water mineralization of higher than 5 g/l. The statuses of various APB groups in the community as dependent on pH and salinity are discussed, as well as possible changes in these statuses due to changes in the water level and other environmental parameters in the studied lakes.

The structure of phototrophic communities of soda lakes of the southeastern Transbaikal Region

The structure of benthic phototrophic communities of 24 soda lakes of the southeastern Transbaikal Region was studied. The physicochemical properties of the lakes were determined. The results of the cell count of anoxygenic phototrophic bacteria (APB) belonging to various groups are presented. The influence of salinity on the structure of APB communities was investigated. The APB reaction to environmental conditions was determined. Massive development of phototrophic microorganisms in the form of mats and films was observed in the majority of the investigated lakes. The APB communities were characterized by a wide diversity of species and evenness of species composition. Purple sulfur bacteria of the families Ectothiorhodospiraceae and Chromatiaceae were predominant. Purple nonsulfur bacteria of the family Rhodobacteraceae, green filamentous bacteria Oscillochloris sp., and heliobacteria were also detected. According to preliminary data, no less than 15 species of APB occur in the studied lakes. Among them, three novel genera and four species have already been described. Identification of other isolates is still in progress. The lakes make an almost continuous series of fresh, brackish, and saline water bodies, varying in their degree of mineralization. It was demonstrated that the structure of APB communities was unaffected by salinity ranging from 5 to 40 g/l. At salt concentrations of lower than 5 g/l, the level of water mineralization became a limiting factor. Experiments with the isolated cultures showed that the APB were obligately dependent on the presence of carbonate ions in the medium. They were haloalkalitolerant or haloalkaliphilic. Thus, they are well adapted to the conditions of soda lakes with a high mineralization. It was demonstrated that soda lakes of the southeastern Transbaikal Region represent a special type of habitat which harbors a peculiar autochthonous microflora and differs from both highly mineralized soda lakes and shallow saline water bodies of the sea origin.

The Phototrophic Community Found in Lake Khilganta (an Alkaline Saline Lake Located in the Southeastern Transbaikal Region)

The structure of the phototrophic community found in Lake Khilganta (the Agin-Buryat Autonomous Area), a shallow saline soda lake (depth, 35-45 cm; water mineralization, 45 g/l; alkalinity, 30 mg-equiv/l; pH 9.5) has been studied. The bottom of the lake is covered with a 10- to 15-mm microbial mat, whose basis is formed by the filamentous cyanobacterium Microcoleus chthonoplastes. The mat exhibits pronounced layering and contains a significant amount of minerals. Six zones, which have characteristic colors and consistencies and are composed of intermittent layers, have been identified along the vertical profile. Live phototrophic bacteria have been found in the three upper zones. The bulk of the cyanobacteria is concentrated in the upper zone. In the lower zones, the development of purple bacteria has been observed. The diurnal dynamics of the vertical distribution of phototrophic microorganisms, which results from variations in the physicochemical environmental parameters, is described. Ectothiorhodospira sp. are dominant among the anoxyphotobacteria present. Their number, determined according to the inoculation method, is 10(6)-10(7) cells/ml. The purple bacteria of the genera Allochromatium, Thiocapsa, and Rhodovulum are also present. Experiments with isolated pure cultures have shown that the anoxygenic photosynthetic bacteria of Lake Khilganta are halotolerant and alkalitolerant or alkaliphilic. In liquid enrichment cultures, at pH 9.5, the ratio of anoxyphotobacteria species is close to that observed in the lake. When the pH is increased to 10.4, it is Ectothiorhodospira, which is the most adapted to life under increased mineralization and alkalinity, that predominantly develops. Photosynthetic activity has been observed in the three upper mat zones and constitutes, on average, 1.5 g C/(m2 h); the share of anoxygenic photosynthesis accounts for 75-95% of the total productivity. The main role in sulfide oxidation belongs to the phototrophic anoxyphotobacteria and cyanobacteria. In terms of the physicochemical conditions and structure of the phototrophic community, Lake Khilganta is similar to shallow saline water bodies of marine origin. The main differences consist in the increased alkalinity and in the consequent prevalence of alkaliphilic and alkalitolerant microorganisms and in the absence of representatives of the neutrophilic group of green sulfur bacteria.

Taxonomic Characterization of New Alkaliphilic and Alkalitolerant Methanotrophs from Soda Lakes of the Southeastern Transbaikal Region and description of Methylomicrobium buryatense sp.nov.

Five strains of obligate methanotrophic bacteria (4G, 5G, 6G, 7G and 5B) isolated from bottom sediments of Southeastern Transbaikal soda lakes (pH 9.5-10.5) are taxonomically described. These bacteria are aerobic, Gram-negative monotrichous rods having tightly packed cup-shaped structures on the outer cell wall surface (S-layers) and Type I intracytoplasmic membranes. All the isolates possess particulate methane monooxygenase (pMMO) and one strain (5G) also contains soluble methane monooxygenase (sMMO). They assimilate methane and methanol via the ribulose monophosphate pathway (RuMP). The isolates are alkalitolerant or facultatively alkaliphilic, able to grow at pH 10.5-11.0 and optimally at pH 8.5-9.5. These organisms are obligately dependent on the presence of sodium ions in the growth medium and tolerate up to 0.9-1.4 M NaCl or 1 M NaHCO3. Although being mesophilic, all the isolates are resistant to heating (80 degrees C, 20 min), freezing and drying. Their cellular fatty acids profiles primarily consist of C(16:1). The major phospholipids are phosphatidylethanolamine and phosphatidylglycerol. The main quinone is Q-8. The DNA G+C content ranges from 49.2-51.5 mol %. Comparative 16S rDNA sequencing showed that the newly isolated methanotrophs are related to membres of the Methylomicrobium genus. However, they differ from the known members of this genus by DNA-DNA relatedness. Based on pheno- and genotypic characteristics, we propose a new species of the genus Methylomicrobium Methylomicrobium buryatense sp. nov.