Plant communities with Ulmus japonica (Rehd.) Sarg. in Eastern Transbaikalia

The article presents the data of long-term studies of communities with U. japonica in Eastern Transbaikalia, in particular, the results of anatomical studies, floristic, ecological and biological, biomorphological and arealogical analysis of the flora of elms.

Synanthropic rodent fauna of Eastern Transbaikalia in the early 21st century

The article provides information on the synanthropic rodent fauna of Eastern Transbaikalia. In 2017–2020 the city of Chita, the town of Baley and small settlements of Zabaykalsky krai were surveyed. True synanthropes: the house mouse and the brown rat are most abundant in residential landscapes. Natural populations of the house mouse are typical for coastal biotopes of the steppe zone, and the brown rat is typical for forest-steppe zone of Zabaykalsky krai. In Chita (administrative centre of Zabaykalsky krai) the share of the brown rat in rodent communities has considerably increased in recent decades. There is an extension of the brown rat’s habitat in the area of Baikal-Amur Mainline. Optional synanthropes: striped field mouse, striped dwarf hamster, Maximowicz’s vole, and narrow-headed vole are less important in residential landscapes of the region. In the beginning of the 21st century the field mouse is extending its habitat to the disjunct zone to the west of Transbaikalia: it is now common in the residential area of the town of Baley. Penetration of another optional synanthropic species recorded in the neighbouring Siberian regions – the East European vole – has not been detected.

Technogenesis and Ecological State of Natural Waters in Eastern Transbaikalia

The research on the state of water ecosystems is significant in terms of future biological impacts of natural and anthropogenic effects. The key branches of natural resources management in Eastern Transbaikalia (agriculture, hydraulic power industry) are based on using water resources. The findings show that technogenesis affects surface waters of the region. Alluvial gold mining represents a significant part of mining industry. Gold mining in river channels results in run-of-stream diversion and interferes with the ecosystem of watercourses. A newly formed structure of a water ecosystem is not favourable for self-purification capacity of rivers. This leads to pollutants accumulation in water objects and deteriorates ecological state of watercourses. Natural components in the technoecosystem of hydropower objects in Eastern Transbaikalia are Lake Kenon and the Kharanor Reservoir. Although the catchment area is polluted by TPP-1, the ecosystem of the lake is still capable of self-purification due to biodiversity of hydrobionts. Under the dry climate in recent years, the Kharanor Reservoir ecosystem turned as rather unstable due to constant refilling from the Onon River. However, generally, pigment indices show physiological activity of primary producers of organic matter.

Rare Alkali Metals in the Waters of Lithium-containing Deposits in Eastern Transbaikalia

The results of hydrogeochemical studies on the content of rare alkaline elements in man-made waters of mining facilities at Zavitinskoye, Orlovskoye, and Etykinskoye rare metal deposits of Eastern Transbaikalia are presented. Concentrations of these elements are determined both by the content in the ores and rocks of deposits and by their water-migration properties. It was found that the acidic sub-basement waters of the Orlovskoye and the quarry waters of the Zavitinskoye deposits contain abnormally high concentrations of lithium, up to 3.74 and 3.88 mg / L, respectively. The high content of lithium (Li) in the waters of these deposits was determined relative to the average values for the waters of the hypergenesis zone, as well as the standards of maximum permissible concentrations (MPC) of chemicals for water bodies used for fisheries, drinking water, and other activities.

Features of the metal distribution in the technogenic and natural waters of the Novoshirokinsky deposit (Eastern Transbaikalia)

To identify the degree of impact of technogenic activity on the main water bodies located in the immediate vicinity of mining production, an analysis of the composition and pH of the water, the chemical components of which are normalized by the Order of the Ministry of Agriculture of the Russian Federation (dated 13.12.2016, No. 552 with amendments), was carried out starting on 10.03.2020.

Changing parameters of waters chemical composition in the Lake Arakhley water column (Eastern Transbaikalia)

The need to preserve the quality of water resources under conditions of anthropogenic impact is one of the most urgent problems of our time. The purpose of this work was to study the features of the distribution of the parameters of the chemical composition of the waters of Lake Arakhley in a vertical section. The investigated waters are characterised by a constancy of mineralisation and chemical composition, both within the water area and in the vertical section. The waters are ultra-fresh (salinity less than 200 mg / L), neutral and slightly alkaline (average pH 7.9), HCO3 Mg-Ca chemical composition. The carbon dioxide content in the water column has a significant impact on the concentration of hydrogen ions, as evidenced by the inverse relationship between pH and CO2 content. The observed increase in the nitrogen form and CO2 contents in the bottom part of the lake is most likely related to the life processes of organisms and vegetation. The recorded excess concentrations of Mn, Cu, Ni, and Al over maximum permissible concentrations indicate the need for additional studies to identify their sources.

The impact of the placer gold mining in Eastern Transbaikalia (Russia) on the environment components of river valleys in the Amur River basin

Based on the results of the analysis of satellite images and field observations, data on the length of the gold-bearing placers disturbed by the development along a number of main tributaries of the Shilka and Argun rivers are presented, the formed technogenic relief forms are indicated. Depending on the method of development, two types of technogenic landscapes have been identified - the excavation-dump with hydromonitor mining and belt trench-dump when washing with drags. The main directions of research on the assessment of placer gold mining in the natural complexes of river valleys are proposed.

The features of the biotopic distribution of Orthoptera insects in the Adon-Chelon terrain (Daursky Nature Reserve, Southern Transbaikalia)

The features of the species composition and abundance of orthoptera insects (Insecta, Orthoptera) in different stations of the Adon-Chelon locality (Daursky Biosphere Reserve, south-eastern Transbaikalia) were studied. The differences in these parameters were revealed for Orthoptera communities inhabiting different stations. The differences in the Orthoptera fauna were noted in comparison with previous studies, which may be associated with cyclical climatic changes characteristic of Southern Transbaikalia.

Mineral waters and sediments of the ferruginous spring Ulan-Bulak Urulyunguevsky (South-Eastern Transbaikalia, Russia)

The data on the chemical composition and content of balneological components (Fe, H2SiO3, CO2, S2-) for three water samples from the Ulan-Bulak acidic ferruginous spring are presented. For the first time, carbonic water was released in the composition of the spring waters, the origin of which is explained by the ingress of hydrocarbonate water into an acidic medium, followed by dissociation according to the HCO3 - + H+ → H2CO3 → H2O + CO2 scheme. An acidic environment is formed as a result of oxidation of sulfide mineralization, presumably gold-bearing. From secondary minerals at the spring, modern sulfate minerals (gypsum, jarosite), hydromica (illite) were found, ocher sediments are widely developed. Given the uncertain nature of the formation of the spring waters, it is considered worthy of special studies, including an inspection of the presence of sulfide mineralization.

Rock-Forming (Biotite and Plagioclase) and Accessory (Zircon) Minerals Geochemistry as an Indicator of the Metal Fertility of Magmas by the Example of Au-Cu-Fe-Skarn Deposits in Eastern Transbaikalia

Many gold and gold-bearing complex deposits related to the Late Jurassic and Early Cretaceous magmatism are known in Eastern Transbaikalia. The largest deposits are the Lugokan, the Kultuma and the Bystrinsky. These deposits are in a paragenetic relationship with the Late Jurassic magmatic rocks of the Shakhtama complex. According to the available data, the total resources of gold in these three deposits are estimated to be approximately 443 tons: the Lugokan, Au~53 tons, Cu~302 thousand tons; the Kultuma, Au~121 tons, Cu~587 thousand tons, Fe~33 mln t; the Bystrinsky, Au~269 tons, Cu~2070 thousand tons, Fe~67 mln t. One of the main aims of this work was to reveal the criteria of fertility for the classical porphyry type, based on the specific geochemical features of rock-forming and accessory minerals. A comparison of the obtained results with other data on the large porphyry and skarn deposits of the world showed that the magmatic rocks of the Bystrinsky massif, specifically porphyry species dated 159.6–158.6 Ma, are potentially ore-bearing for the porphyry type mineralization. The magmatic rocks that widely occur at the Lugokan and Kultuma deposits are most close to the Fe-skarn deposits. The best indicators of the magma fertility for the porphyry rocks are Ce/Ce*, Eu/Eu*, Yb/Dy, (Ce/Nd)/Y in zircons. Thus, magmatic rocks characterized by Ce/Ce* > 100, Eu/Eu* > 0.4, Yb/Dy > 5.0 and (Ce/Nd)/Y > 0.01 may be classified as high fertile for the classical porphyry mineralization in Eastern Transbaikalia. The plagioclase and biotite chemistry data also showed that the magmatic rocks that occurred at the Bystrinsky deposit are the most fertile for the porphyry type mineralization. The magmatic rocks classified as ore-bearing porphyry type have Al* > 1 in plagioclase, high values of IV(F) and IV(F/Cl) and low ratios of X(F)/X(OH) in biotites. The assessment of the metal fertility of magmatic rocks is most effective in combination with data on both the composition of rock-forming and accessory minerals. The obtained data may be used to develop the methods of prediction and search for gold, copper and iron mineralization.