North Baikal Research Articles

MORBIDITY RATE OF MALIGNANT NEOPLASMAS AND ANALYSIS OF THE ECOLOGICAL STATE OF THE TERRITORY OF THE REPUBLIC OF BURYATIA

The authors analyzed the incidence rate of malignant neoplasms in the population of the Republic of Buryatia without division into separate locations by regions over a long period, beginning from 1995 to 2015 in comparison with that in the Russian Federation, using a comparative-geographical method. According to statistical data, the growth of general oncopathology has been revealed every year, in connection with which the aim of the work was to search for its causes in the analysis of environmental factors in the region. There was established a high morbidity rate in the population during analyzed four periods: over 1995-2000; 2001-2005; 2006-2010; 2011-2015 in the same regions of the republic, as Bountov, Tarbagataysky, Kabansky, Pribaikalsky, Zaigraevsky, North Baikal, Barguzin and Ulan-Ude. The authors explain this pattern by the abnormal natural conditions of the region, the development of the mining industry, in particular the development of powerful reserves of uranium and polymetallic ores. And the city of Ulan-Ude, where the entire industrial hub and fuel and energy complex is concentrated, is one of the ten most polluted cities in Russia due to the location in a closed basin of a mountainous country. In the first three analysis periods until 2011 there was a low incidence in the high-altitude region of Okinsk, and in Tunkinsky until 2006, in Muisky until 2001, however, in their territories in the last five years, sharp gain was seen respectively from 147%, 205% in relation to 231% initial period. This is probably due to the fact that the development of natural raw materials, begun in the 1960s by the Soviet authorities, is still a handicraft way, leaving a pathological “trace” on the health of the population, manifested in tens of years. The gradual gain of oncopathology is observed in Dzhidinsk, Kizhinginsky, Mukhorshibirsky, Selenginsky, Khorin, Kyakhta districts. However, there are territories of the regions of the republic, like Eravnensky and Ivolginsky, where the incidence is insignificant.

ДИКИЕ РОДИЧИ КУЛЬТУРНЫХ РАСТЕНИЙ НА ТЕРРИТОРИИ СЕВЕРО-ЗАПАДНОГО ПРИБАЙКАЛЬЯ (ПО МАТЕРИАЛАМ ЭКСПЕДИЦИИ 2014 ГОДА)

The explorations carried out by a collecting team over the territory of the northwestern Baikal region made it possible to study the diversity of crop wild relatives (CWR) in 37 natural habitats in Bayandayevsky, Kachugsky, Zhigalovsky, Kazachensky-Lensky, Olkhonsky and Ekhirit-Bulagatsky districts of Irkutsk Province and the North Baikal district of the Republic of Buryatia. As a result, the areas richest in CWR species diversity were identified. Herbarium specimens and 102 seed and layering samples of 56 species from 23 genera representing wild relatives of fodder, legume, fruit, cereal and fiber crops were collected, including endemics listed in the Red Data Books of the Russian Federation, Irkutsk Province and the Republic of Buryatia.

Soil desiccation as indicator of desertification of forest–steppe ecosystems in the Barguzin depression

This article presents study data on the status of plant and soil cover in the Barguzin Depression related to soil desiccation as the result of a 3-year drought, which caused the death of natural pine forests and shelterbelts composed of pine and balsam poplar. The main factors of tree death, as well as the soil conditions that favor survival under long-term air drought, have been revealed. A negative trend in the development of forest steppes under climate aridization in the North Baikal region was determined.

Современное состояние и использование лечебно-оздоровительных ресурсов (на примере Северо-Байкальского и Курумканского районов Республики Бурятия)

Современное состояние и использование лечебно-оздоровительных ресурсов (на примере Северо-Байкальского и Курумканского районов Республики Бурятия)

The influence of deep convection on aeration of the bottom zone in Baikal

We investigated the influence of deep forced temperature convection on aeration of the bottom water layer in the pelagic zone of Baikal. Temperature T (± 0.002°C) and oxygen O2 concentration (± 0.01 mg/L) were measured by using the SBE-25 probe with the SBE-43 oxygen sensor in May-July 2006−2007 and 2009−2013. Oxygen input into the bottom layer with cold intrusions was determined for 79 cases. The study revealed a quantitative correlation between the heat deficit and the rise in oxygen content in the bottom layer during cold intrusions. This correlation was used to reconstruct the values of intrusion aeration of the bottom layer during 1993−2005. It is ascertained that the intrusion-caused 2006−2013-average oxygen input into Baikal’s bottom layer is virtually close to the annual oxygen demand for oxidation processes in the water column and bottom sediments. In the southern and middle parts of Baikal, intrusion-caused input of oxygen corresponds to a higher rate of its demand (4.5−4.6x10-4 mg/L per day). A slight increase in oxygen concentration was detected in the bottom layer of the South and Middle Baikal and a slight decrease in the bottom layer of North Baikal during 1993−2013.

Neoproterozoic ophiolite and related high-grade rocks of the Baikal–Muya belt, Siberia: Geochronology and geodynamic implications

We report zircon for from ophiolitic and high-grade rocks of the Neoproterozoic Baikal–Muya belt of Siberia that occupies an arc-shaped area on the southeastern margin of the Siberian craton. It consists of arc-related plutonic, metavolcanic and metasedimentary rocks as well as fragmented ophiolites and high-grade metamorphic assemblages. Magmatic zircons from two plagiogranite dyke samples of the Mamakan ophiolite complex in the Sredne–Mamakan massif of the eastern Baikal–Muya belt yielded similar and concordant SHRIMP mean 206Pb/238U ages of 640.0±4.1 and 650±6Ma, respectively, that reflect the time of dyke emplacement and from which we suggest an age of ca. 645Ma as the most likely time of ophiolite formation.Enderbitic gneisses of the North Baikal area, in the western part of the Baikal–Muya belt, contain complex zircon populations that reflect variable recrystallization, Pb-loss and metamorphic overgrowth during granulite-facies metamorphism. LA-ICP-MS dating of these zircons yielded inconclusive results that led us to undertake a detailed study of cathodoluminescence images combined with U–Pb SHRIMP dating. Well-preserved magmatic domains in zircons from enderbite sample 2821 yielded concordant results with a mean 206Pb/238U age of 640±5Ma, slightly higher but broadly comparable with the data obtained by LA-ICP-MS. The zircon populations of two more enderbitic gneiss samples are more complex, and their LA-ICP-MS data constitute broad swaths along concordia between ca. 840 and 600Ma, reflecting two end-member isotopic components, namely an igneous crystallization event at ca. 800Ma and a Pb-loss and recrystallization event at ca. 600Ma. SHRIMP analyses of magmatic zircon domains of these samples yielded concordant data with identical mean 206Pb/238U ages of 826±7.5Ma and 826±8Ma, respectively, whereas low-U metamorphic rims crystallized at 640±7Ma. Newly crystallized ball-round metamorphic zircons in one sample produced a mean 206Pb/238U age of 640±6Ma. We suggest that the protoliths of the enderbitic gneisses crystallized at 826±7.5Ma and experienced granulite-metamorphism at 640±6Ma. The LA-ICP-MS analyses are fully compatible with this interpretation.Our geochronological data and previously published ages for Neoproterozoic igneous rocks of the Baikal–Muya belt define two age groups at 830–780 and 650–640Ma. We interpret that the older group reflects the evolution of a large arc system in the Baikal–Muya belt and the eastern Sayan–northwestern Mongolia region, whereas the younger group documents collision between the above arc system and the southern margin of the Siberian craton.

Natural pollutants of Northern Lake Baikal

Hot and cold springs in the northwestern shore of Lake Baikal are investigated as natural pollutants of the lake, which can interfere with its chemistry. The study includes chemical analyses of lake water samples from different depths in the North Baikal basin, as well as waters of hot and cold onshore springs, and Baikal tributaries collected in 2007 through 2013. Thermal waters in the shore of Lake Baikal have much higher SO4, Cl, F, Na, and SiO2 concentrations than those in the lake water, as well as ten to hundred times greater enrichments in Li, Rb, Cs, Ga, As and W. Mineral water in cold springs is generally similar to the Baikal water with respect to total dissolved solids (TDS) and major- and trace-element chemistry. However, the Milky cold spring discovered in the lower reaches of the B. Cheremshan River within a few km from the lake stands out in its unusual Ca–Mg–SO4 composition, low pH (3.57) and high TDS (535 mg/l), and trace-element enrichments in Al, Mn, Ni, Co, Zn, Y, and REE. The concentrations of these elements are still higher, up to one or two orders of magnitude, in suspended solids abundant in the spring water. This water composition is typical rather of mine drainage in sulfide mineralization provinces and prompts the existence of a sulfide orebody in the area. Mn, Co, Ni, Zn, and Cd occur in the dissolved form, and their concentrations in stream water near the B. Cheremshan inlet into Baikal are only slightly lower than immediately downstream of the spring; REE and Y are ten times lower because of precipitation from the river water. However, all metals the spring water leaches from the surrounding rocks eventually end up in Lake Baikal. Although the spring has much greater enrichments relative to the Baikal water in a number of elements, it hardly can cause any significant change to the lake composition. Only local chemical anomalies of Mn, Al, Co, Ni, Zn, Cd, REE and Y can be expected in the bottom sediments where the lake uptakes the B. Cheremshan stream.

Геоботаническое картографирование растительного покрова котловин Северо-Восточного Прибайкалья

This paper presents the results of study of the vegetation cover in the North Baikal and the Upper Angara basins. The vegetation mapping was carried out in a scale 1 : 200 000 using the field and archive data as well as GIS-technologies. The structure of the map legend was based on the principles of multi-stage vegetation classification developed by V.B. Sochava. The vegetation map shows the basic structural-coenotic diversity of the vegetation cover of the study area. Due to the high disturbance of forest vegetation special attention was paid to structural-dynamic analysis to identify potential plant communities. The rows of transformation were estimated as well. The map provides a possibility to make a prognosis for further vegetation successions under the natural and anthropogenic influences.

In alliance with a nocturnal landscape: memory and water law in the north Baikal, Siberia

ABSTRACTThis paper examines the ethnography of nocturnal fishery and relationships with water, relevant for Evenkis occupying the northern coastal area of Lake Baikal, Siberia. The material arises from Evenkis of Kumora village who live near Lake Irkana and from archival sources. Although the nocturnal fishery is declared illegal in official legislation, local residents invoke memories to mark that practice as traditional and important for the local community since it is not merely a subsistence activity but also an emotional experience and long-term relationships with the landscape. This paper argues that local social memory devoted to this practice serves as a kind of fishing tool and a tool for supporting local ideas of how fishing should be governed. The collision between memory and water law is not discussed in terms of antagonism between local groups and authorities but as ignorance between memory-gifted people and the landscape, and memory-disabled official approaches to nocturnal fishing and its histories. Finally, memory-gifted human landscape relationships termed as ‘alliance’ are approached as a powerful conglomerate that ‘consumes’ authorised visions of fishing patterns in their own way.

GPS-measurements of recent crustal deformation in the junction zone of the rift segments in the central Baikal rift system

Based on multiyear measurements of present-day motions in the central area of the Baikal rift system, new data on the kinematics of horizontal motions, relative horizontal deformation rates, and rotation velocities in the area of junction of the South Baikal, North Baikal, and Barguzin rift basins have been obtained. This area is an intricate structure with two transfer zones: Ol’khon–Svyatoi Nos and Ust’-Barguzin.It is shown that crustal blocks are moving southeastward, normally to the structures of transfer zones and at an acute angle to the Baikal Rift strike, which corresponds to the right-lateral strike-slip extensional faulting along the major structure. The average horizontal velocities increase from 3.0 mm yr–1 in the northern South Baikal basin to 6.5 mm yr–1 in the Barguzin basin. The elongation axes prevailing in the study region are mainly of NW–SE direction. The areas of intense deformations are confined to structures with high seismic activity in the South Baikal and, partly, Barguzin basins. This confirms the existence of a present-day zone of the Earth’s crust destruction in the Baikal rift system, which is the most likely source of strong earthquakes in the future. Two zones with rotations in opposite directions are recognized in the rotation velocity field. Clockwise rotation is typical of structures of N–NE strike (Maloe More basin, southern North Baikal basin, Barguzin Ridge rise). Counterclockwise rotation is determined for NE-striking structures (northern South Baikal basin, southern Barguzin basin). In general, the obtained data show an intricate pattern of present-day horizontal dislocations and deformations in the area of junction of NE- and N–NE-striking rift structures. This suggests left- and right-lateral strike-slip faults, respectively, within them.

SPATIAL AND TEMPORAL DYNAMICS OF THE BAIKAL COASTAL LINE CAUSED BY CONTROL OF THE LAKE LEVEL REGIM

The paper presents the results of a study on changes in the coastal line of the Yarki islands (North Baikal) using remote sensing data of the Earth. Vector shape files were generated from the automated classification of the multi-temporal Landsat data. The analysis suggests a systematic decrease in the Yarki’s sandbar area

Vegetation and Climate Changes in the Bolshoe Inyaptukskoe Lake Basin (North Baikal Plateau) in the Middle and Late Holocene

This article presents new interdisciplinary observations relating to environmental changes in the Bolshoe Inyaptukskoe Lake Basin, North Baikal Plateau. A column taken from a loam/turf deposit at 1320 m above sea level is shown to reflect changes in vegetation and climate over the last 8–9 thousand years through its palynology, radiocarbon chronology, and the count of charcoal particles. The chronology of the reconstructed changes in the vegetation around the Ozernyi-5 trench agrees well with existing regional and global climatic trends. However, the local processes also show their own peculiarities. The discrepancies are associated with the elevation and the altitude of the site.

Upwellings in Lake Baikal

Based on shipboard and satellite observations, the characteristics of upwelling in Lake Baikal in the period of direct temperature stratification have been determined for the first time. Coastal upwellings appear annually under the effect of run-down and alongshore winds and are traced along the coast to a distance of up to 60–100 km and up to 250 km in North Baikal. Analogous to the way it occurs in seas, water rises from the depths of 100–200 m (350 m as a maximum) at the velocity of 0.1 × 10−2−6.5 × 10−2 cm/s. Divergence in the field of intrabasin cyclonic macrovortices produces upwelling in the Baikal pelagic zone and downwelling in the vicinity of shores; this lasts from 7 to 88 days and covers the depth interval of 80–300 m in August and up to 400–800 m in early-mid November. The area of upwellings occupies up to 20–60% of the separate basins of the lake. Vertical circulation of water in the field of pelagic upwellings leads to intensification of coastal currents and to formation of the thermobar with a heat inert zone in the central part of the lake in November, and this thermobar is not observed in other lakes, at that.

Renewal of deep waters of Lake Baikal revisited

The patterns of renewal of bottom waters in Lake Baikal under the influence of deep convection and intrusion of cold waters have been considered based on the data of temperature surveys of Lake Baikal conducted in 1993–2009. The volumes of the cold bottom layer with the maximums of 200–470 km3 in individual years and the values of its total cooling (−20–60 × 109 MJ) have been determined for South, Middle, and North Baikal. The renewal process is asynchronous and proceeds with different activity in these parts of the lake, which indicates that the mechanisms that cause deep convection in the context of the great latitudinal length and differences in the climate and hydrological processes manifest themselves regionally. The volume of intrusions has been determined. Its average value for the period was higher in South Baikal (20 km3) than in Middle Baikal (9.8 km3) and North Baikal (8.6 km3). The volume of the intrusions in these parts of the lake was 30–70 km3 in some years.

Paleoproterozoic basaltoids in the North Baikal volcanoplutonic belt of the Siberian craton: age and petrogenesis

The oldest igneous rocks in the Paleoproterozoic (~1.88–1.85 Ga) North Baikal postcollisional volcanoplutonic belt of the Siberian craton are the basaltoids of the Malaya Kosa Formation (Akitkan Group). The youngest are the composite (dolerite–rhyolite) and doleritic dikes cutting the granitoids of the Irel’ complex and the felsic volcanic rocks of the Khibelen Formation (Akitkan Group). The position of Malaya Kosa basaltoids in the Akitkan Group section and published geochronological data on the felsic volcanic rocks overlying Malaya Kosa rocks suggest that their age is ~1878 Ma. The rhyolites from the center of a composite dike were dated by the U–Pb zircon method at 1844 ± 11 Ma, and the dolerites in the dikes are assumed to be coeval with them. Malaya Kosa basaltoids correspond to high-Mg tholeiites and calc-alkaline andesites, whereas the dolerites in the dikes correspond to high-Fe tholeiites. Geochemically, these basaltoids and dolerites are both similar and different. As compared with the dolerites, the basaltoids are poorer in TiO 2 (an average of 0.89 vs. 1.94 wt.%), Fe 2O 3 ∗ (9.54 vs. 14.71 wt.%), and P 2O 5 (0.25 vs. 0.41 wt.%). However, these rocks are both poor in Nb but rich in Th and LREE, ε Nd(T) being negative. According to petrographic and geochemical data, they derived from compositionally different sources. It is assumed that the basaltoids originated from subduction-enriched lithospheric mantle, whereas the dolerites originated from refractory lithospheric mantle metasomatized by subduction fluids. The isotopic and geochemical features of mafic rocks in the North Baikal belt are well explained by their formation during crustal extension which followed subduction and collision in the region. The early stages of postcollisional extension evidenced the melting of subduction-enriched lithospheric mantle with the formation of parent melts for Malaya Kosa basaltoids. At the final stages of the formation of the North Baikal belt, during the maximum crustal extension, Fe-enriched melts rose to the surface and generated the dolerites of the dikes.

Age and tectonic setting of charnockites of the Tatarnik Complex (Northwestern part of the Baikal region)

Charnockite intrusions of the Tatarnik Complex located in the Davan shear zone are the youngest man� ifestations of granitoid magmatism in the northwest� ern part of the Baikal region [1]. The shear zone has a submeridional zone of dislocations separating the Chuya salient composed of Early Precambrian high� grade metamorphic rocks and granitoids and the North Baikal volcano–plutonic belt comprised of Early Proterozoic (1.88–1.85 Ga) volanogenic–sedi� mentary rocks of the Akitkan Group and granitoids of the Irel Complex. Earlier Paleoproterozoic metamor� phic rocks of the Sarma Group are located to the south of this belt. It is necessary to mention that the latest events of Early Proterozoic magmatism within the considered region, such as volcanic rocks of the North Baikal belt, granitoids of the Chuya–Kodar, Kodar, Sayan, and Tarak Complexes, as well as rapakivi of the Primorsk and charnockite of the Shumikhin Com� plexes, are related to the formation of the postcolli� sional Southern Siberian magmatic belt (1.88– 1.84 Ga) extending for a distance of >2500 km along the southwestern boundary of the Siberian Platform from the Yenisei Ridge to the Aldan Shield [2]. Charnockite of the Tatarnik Complex usually forms relatively small intrusive bodies located in the Davan zone and cuts blastomilonites of this zone, as well as rocks of the Sarma and Akitkan Groups (Fig. 1). As a rule, they have a massive texture. Only sometimes is trachytic texture observed in endocontact zones. The chemical composition of charnockite relates to quartz

Height of faceted spurs, a proxy for determining long‐term throw rates on normal faults: Evidence from the North Baikal Rift System, Siberia

We present new results on the long‐term throw rates of active normal faults in the North Baikal Rift (NBR), eastern Siberia, based on a statistical analysis of triangular faceted scarps. Fault‐bounded ridges in the NBR display typical morphologies with several contiguous facets separated by fault‐perpendicular catchments. Over a range of 20 fault segments analyzed, triangular facet heights vary from ∼200 to >900 m. As fault scarps have been developing under similar long‐term climatic conditions, we infer that the scatter in mean facet height arises from long‐term differences in fault throw rate. We compare the morphology of NBR facets with results obtained in a previously published numerical model of facet growth. Using facet height as an input, model results provide estimates of the long‐term fault throw rate. NBR throw rates vary between 0.2 and 1.2 mm yr−1. The throw rates are then compared with the cumulated throw, which has been constrained by geophysical and stratigraphic data in the basins. This provides an estimate of the age of fault and basin initiation. We show that the modern stage of basin development started circa 3 Myr ago, except for the North Baikal basin (∼8 Ma). Our results also suggest that a proportion of the observed throw is inherited from an earlier tectonic stage.

Deposition and remobilization of uranium in the North Baikal region: Evidence from the U-Pb isotopic systems of uranium ores

Based on the study of local volumes of minerals, including their microsampling and subsequent analysis of Pb/Pb and U/Pb isotope ratios with the classic methods of isotopic dilution and thermoionization mass spectrometry (TIMS), U-Pb and Pb-Pb isotopic datings of minerals were carried out in uranium ores from deposits in the Akitkan and Nechera-Nichatka ore districts (North Baikal region). Reliable evidence in favor of the Middle Devonian (384 ± 8 Ma) remobilization of Paleoproterozoic primary uranium concentrations and the redeposition of uranium as pitchblende 2 has been obtained for the first time for ores of the Akitkan district. The Paleoproterozoic (1832 ± 13 Ma) age of uraninite mineralization and the timing of the latest (377 ± 5 Ma) transformation of uranium ores at the Chepok deposit (Nechera-Nichatka district) are substantiated.

Petrogenesis and age of the felsic volcanic rocks from the North Baikal volcanoplutonic belt, Siberian craton

Detailed geochemical, isotopic, and geochronological studies were carried out on felsic volcanic rocks from the southern part of the North Baikal volcanoplutonic belt. U-Pb zircon dating showed that the rocks previously ascribed to a single stratigraphic unit (Khibelen Formation of the Akitkan Group or the Khibelen Complex) have significant age differences. The Khibelen Formation was found out to include both the oldest dated rocks (1877.7 ± 3.8 Ma) of the North Baikal belt and the younger volcanic rocks (1849 ± 11 Ma). Two other dated volcanic rocks have intermediate ages (1875 ± 14 and 1870.7 ± 4.2 Ma). It was established that the volcanic rocks from various areas in the southern part of the North Baikal belt not only have different ages but also differ in geochemical and isotopic signatures. In particular, the felsic volcanic rocks from various sites show the following variations in trace-element composition: from 220–280 to 650–717 ppm Zr, from 8–12 to 54–64 ppm Nb, and from 924–986 to 1576–2398 Ba. The ɛNd obtained for felsic volcanic rocks and comagmatic granitoids from various areas in the southern part of the North Baikal belt vary, respectively, from −1.7 to −2.8 and from −8.0 to −9.2. Based on geochemical and isotopic signatures, the felsic volcanic rocks in various areas of the southern part of the North Baikal volcanoplutonic belt were formed via the melting of a Mesoarchean crustal source of tonalite composition with contribution of variable amounts of juvenile mantle material at different magma generation conditions. Isotopic data indicate that the contribution of juvenile mantle material to their sources varied from ∼33–40 to 77–86%. The maximal calculated temperatures of the parent melts for felsic volcanic rocks were 908–951°C, and the lowest temperatures were 800–833°C. The geochemical signatures of dacites with an age of 1877.7 ± 3.8 Ma such as high Th (46–51 ppm) and La (148–178 ppm) contents indicate that these rocks, along with Mesoarchean granitoid and juvenile mantle material, contain an upper crustal component with high Th and LREE contents. Extremely low Y and Yb contents in these dacites implies their formation at pressures of ∼ 12–15 kbar in equilibrium with garnet-bearing residue. These rocks were presumably formed in the collisional-thickened crust at the earliest stages of its collapse, possibly during syncollisional collapse, with additional hear input to the lower crust. Other felsic rocks are geochemical analogues of A-type granites and were formed during the subsequent stages of collapse (post-collisional collapse).

Results of paleomagnetic study of Early Proterozoic rocks in the Baikal Range of the Siberian craton

This paper presents paleomagnetic results obtained from the study of Early Proterozoic rocks in the Baikal Range of the Siberian craton, namely, the 1850–1880-Ma volcanicalstic rocks of the Akitkanskian series of the North Baikal volcanic-plutonic belt) and 1674-Ma basic dikes of the Chaya complex within the massif. The data of this work are used to reconstruct the development of the Siberian craton structure in the Early Precambrian. The projections of the inferred paleomagnetic directions onto a sphere form S (southern) and W (western) groups of vectors of characteristic magnetization components. The S group consists of three clusters representing primary magnetization components belonging to different time levels of the end of the Early Proterozoic. The W group is represented by directions associated with a metachronous magnetization probably acquired during the Riphean. Four paleomagnetic poles are obtained. Two of them that can be regarded as key poles correspond to time levels of 1875 and 1670 Ma (the Early Proterozoic). The two other poles can be used for a detailed reconstruction of the Proterozoic segment of the Siberian apparent polar wander path. The data presented in the paper indicate that the formation of the southern Siberian craton structure was accomplished at the end of the Early Proterozoic, which resulted in a synchronous motion of different blocks composing the southern flank of the craton (in particular, the Sharyzhalgai and Baikal Ranges).