This article considers the disjunctive deformation of the upper crust in the Tien Shan and Altai-Sayan regions of the Central Asian folding belt. An analysis of the diagrams of fault directions constructed on the basis of information on more than 3000 faults revealed orthogonal fault system assemblages in these regions. Among them, a significant number of faults were functioning during two or more epochs of orogenic deformations. The direction of displacements was determined by the deformation field existing in that epoch, irrespective of the fault kinematics in the previous deformation epochs. The Tien Shan is a Paleozoic folded belt that experienced cover-folded deformations and orogenesis in the Paleozoic, as well as neotectonic orogenesis in the Late Cenozoic. The Paleozoic Tien Shan consists of the Caledonian and Variscan provinces, which underwent a different number of deformation epochs. Two deformation epochs — Late Paleozoic and Late Cenozoic — covered the entire Variscan province of the Tien Shan. Late Paleozoic deformations were associated with a collision of the Tarim and Kazakhstan paleocontinents. The Turkestan Ocean having separated these blocks was closed in the Late Carboniferous. The orogenesis having occurred during Permian was a late stage of that deformation epoch. Four or more orogenic epochs were characteristic of the Caledonian Northern Tien Shan. In the middle Ordovician, the Terskey Ocean, which had separated the Kokchetau-Issyk-Kul and Syrdarya microcontinents in the early Paleozoic, was closed. The collision of these blocks was accompanied by orogenic deformations and the formation of the Late Ordovician molasses. The distribution of the Late Devonian molasses in the region indicates orogenic processes having occurred at that time. Subsequently, the Caledonide territory, along with the entire Tien Shan, was covered by orogenesis in the Permian and Late Cenozoic. During the Late Cenozoic deformation, no fault systems appeared in the Variscan and Caledonian provinces of the Tien Shan; rather, a movement along the Paleozoic faults of a corresponding direction took place. Orogenic dislocations occurred in the different parts of the Altai-Sayan region in Cambrian, Ordovician, Silurian, Devonian, Late Paleozoic and Late Cenozoic. In this region, the Late Paleozoic assemblages of fault systems activated in the most recent epoch were identified, and the fault system assemblage in the Late Cenozoic was revealed.

Background. For a long time, deep deflections present in the Arctic basin seafloor have been a site for accumulating a thick sedimentary cover and a subsidence epicentre. Issues associated with the geological structure and tectonics of these formations have been addressed in numerous publications devoted to the East Arctic shelf.

Aim. To discuss the question of the geological and tectonic structure of Mesozoic-Cenozoic East Arctic water areas by analysing the existing geological and geophysical data on the Arctic shelf. Information on the structural evolution of the sedimentary basin is important from a practical point of view, since these areas contain a large number of extractable resources, in particular, hydrocarbon deposits.

Materials and methods. The present work reviews the results of exploration works using modern  technologies of basin analysis and numerical basin modelling. A structural-tectonic model of the East Arctic sedimentary basin was developed using the structural representations of the 1:5,000,000 scale performed by VSEGEI specialists in 2014. The developed model includes four main sedimentary complexes: pre-Aptian, Apt-Upper Cretaceous, Paleogene and Neogene-Quaternary. The modelling strategy was determined by the geological structure and evolution features of the sedimentary basin under study, as well as by the quality of available geological, geophysical and geochemical information. The East Arctic water areas were combined into a single model, since their sedimentary basins are part of the same continental margin and their boundaries do not always coincide with the conventional boundaries.

Results. On the basis of the conducted analysis of initial data, we developed a structural-tectonic model of the East Siberian and Chukchi Seas, as well as their surrounding areas. This model describes the  distribution of the main structural elements, their spatial relationships, as well as their regional hierarchical nomenclature. The developed model includes four main sedimentary complexes: pre-Aptian, Apt-Upper Cretaceous, Paleogene, and Neogene-Quaternary. The structural model covering the aquatic areas of the Laptev Sea, East Siberian and Chukchi Seas includes five main surfaces: the basement of the sedimentary cover; the Pre-Aptian unconformity; the Cenozoic base; the unconformity in the lower part of the Oligocene and the basement of the Quaternary sediments; as well as the modern bottom  topography.

Conclusion. Using the technology of basin modelling, a structural-tectonic model of the basement and sedimentary cover of East Arctic water areas was created, which can be used for planning exploration works.

From ten to fifteen percent of the global supply of copper, zinc and lead, as well as a significant amount of silver, gold, cadmium, selenium, tin, bismuth and barium are mined from massive sulphide deposits. Massive sulphide deposits of copper and zinc containing minor lead, gold and silver are located in the region of Central Cuba. These deposits are localised in sedimentary-volcanogenic rocks of the Lower Cretaceous Los Pasos Formation, which are considered the oldest manifestations of magmatism in the island arc of the Caribbean Sea. These deposits include massive sulphide ores and are referred to as volcanogenic massive sulphides (VMS), common among the volcanic deposits of the Greater Antilles. The San Fernando deposit is the most important industrial site featuring stratiform deposits of massive, breccia and disseminated sulphide ores and chalcopyrite-pyrite stockworks localised in the covers and tuffs of rhyolites and dacites. Lenticular ore bodies lie on three levels with an en-echelon overlapping. This article set out to indicate the vertical and lateral mineralogical-geochemical zonality of the San Fernando deposit using 1075 ICP MS analyses of ordinary geochemical samples, a core documentation of 65 exploratory wells and ore microscopy of 146 polished sections. Data for the study was obtained during 2009—2012 exploration work. The main ore bodies of the deposit are lenticular. The relative abundance of chalcopyrite, sphalerite, galena, pyrite, and pyrrhotite was estimated across ore-bearing levels using ore polished sections, which was compared with Cu, Zn, Pb, Cd, Au, and Ag concentrations. An analysis of the data was carried using the QGIS geographic information system. The distribution of copper and zinc-copper ores at the upper level, as well as pyrite ores at the lower level of the deposit, was established. The established geochemical regularities were generally confirmed by the prevalence of the main ore minerals — chalcopyrite and sphalerite. The relatively independent distribution of gold and silver in the Cu and Zn concentration contours indicates possible superimposed processes of noble metal
concentration. According to the conducted mineralogical and chemical analysis, the highest  concentrations of useful components were determined at two depth levels of 60—85 and 125—160 m within the limits of the most productive north-eastern and south-western flanks of the deposit.

This article discusses issues involved with changes in the strength properties of rock mass during serial explosions of borehole explosive charges while performing mining operations in quarries. During the analysis of the research methods for changing the strength properties of rock mass, the zones of decrease in rock mass strength beyond the quarry contour, which are formed as a result of multicyclic explosive loads, were not taken into account while determining the parameters of borehole charges in a row.
In a quasistatic simulation of a single explosion leading to rock destruction, the nature of the propagation of radial cracks in the rock resulting from the pressure of the shock wave, detonation products, and stress concentration in the vicinity of the crack tips was revealed. Moreover, the growth of cracks in granite due the explosion occurs within 15 ms, and in limestone within 20—25 ms, depending on the physicomechanical properties of rocks, their degree of fracturing, and the use of a special type of tamping. The operating principle of the locking tamping is based on the reflection of shock waves from the internal funnel-shaped profile, as a result of which a partial detonation of the detonation products occurs. Tamping retention in the borehole is maintained due to its expansion by detonation products.
From the analysed studies conducted in laboratory conditions, the strength of ore limestone and magnetite samples after a single explosive loading was found to decrease by 38.6 and 40.8% of the initial static compressive strength, respectively, and after repeated exposure, on average, 5-10%. The dimensions of the zone of reduced strength in the surrounding massif was found to be dependent on the height of the  quarry ledge and the energy characteristics of applied explosives.

This paper investigates the aggregation forms, sizes and composition of native gold present in the ore deposits and placers of the Amur province. The province corresponds to the zone of the Late Mesozoic collision of geoblocks of the South-Eastern framing of the Siberian craton, Amur composite massif and Mongol-Okhotsk folded system. The collision was accompanied by an intrusive and volcanic activity, as well as by the formation of gold mineralisation superimposed on block matrices. Further erosion processes led to the formation of numerous placers. Eight metallogenic zones with 80 ore-placer nodes have been identified in the province, which contain about 1,500 placers and 45 gold deposits. It has been established that the placers in the Cis-Amur region contain gold of mostly small- and medium-size classes. Coarse gold appears less frequently, with the discovered nuggets weighing from first grams to several kilograms. The form of the gold deposits in the placers is diverse — from predominantly flat, pancake-like, lumpy and wire-shaped to crystalline, including dendritic. The crystals and intergrowths of gold with quartz are occasionally observed. Gold is frequently covered with a film of iron hydroxides. In terms of composition, the placer gold in the Cis-Amur region belongs to that of moderately high-grade (800—899‰) and high-grade (900—1000‰). Low-grade gold (799—700‰) and electrum are less common. The coarsest gold and nuggets are found in placers in the central part of the Amur province. It is shown that the gold-quartz formation is the main placer formation. The frontal, middle and basal parts of the ore column are distinguished in the deposits of this formation. An increase in the gold grade and size of its aggregates in the frontal part of the ore column has been established. Most of the nuggets found in placers are assumed to be located in the upper part of ore deposits. This is evidenced by a large number of nuggets in terrace placers as compared to the channel ones. In the Unya-Bomsky ore-placer cluster rich in coarse gold and nuggets, native gold in placers and ores has a high grade and a significant concentration of trace mercury, reaching the level of first percent.

This work analyses the development of reefs, which represent thick morphologically expressed carbonate massifs created by the activity of frame-forming organisms. Major stages in the development of reefs include the periods of Early Cambrian, Ordovician, Silurian-Devonian, Late Viséan-Serpukhovian and Permian, the upper boundaries of which are generally determined by mass extinction events.
The main reef builders during the Early Cambrian were archaeocyatha and epiphytaceans, while Ordovician reefs were created by sponges, stromatoporoids, tabulata and bryozoans. Stromatoporoid, tabulata, rugose and, to a lesser extent, bryozoans were the reef builders during the longest Silurian-Devonian period. Bryozoans and corals served as the frame-forming organisms for Upper Viséan-Serpukhovian reefs. However, during the Permian, reefs were built primarily by sponges and, to a lesser extent, by bryozoans and corals.
It is shown that there is no strict correspondence between the termination of reef formation and the beginning of extinction events. During extinction periods, potential reef builders did exist, although beyond the reef biocoenosis structure. Similarly, the beginning of reef formation occurs somewhat later than the appearance of the corresponding frame-forming organisms. Apparently, it takes time for organisms to develop such a biocoenosis that could trigger the formation of reef ecosystems. Reef ecosystems are stable under relatively constant external conditions, changes in which cause first the degradation of the biocoenosis and then the extinction of its constituent organisms. Therefore, the process of reef formation is terminated before the actual extinction of organisms.

Background. The majority of the world’s deserts were formed within the valleys and coasts of ancient alluvial rivers and lakes. The material carried across many hundreds and thousands of kilometres by the wind was mixing with sediments of various genetic types. In addition, due to the similar physical nature of the wind and water transport of sediments, the recognition of the aeolian environment can be problematic.

Aim. Using innovative research approaches, to provide a qualitative structural description of sands; to identify and characterize factors contributing to the formation and preservation of a ferruginous film on grains; to establish the genesis of the transferred sediments, as well as the relationship with the parent rocks.

Materials and methods. Samples for analysis were collected from aeolian deposits in three deserts: Rub al Khali (United Arab Emirates), Nubian desert (Egypt) and Grand Erg Oriental (Algeria). Particle size analysis was used to characterize samples in terms of three parameters (length, width, thickness). X-ray diffraction analysis was carried out using an ARL X’tra diffractometer (Switzerland). The collected samples were also studied using a binocular microscope in reflected light and a scanning electron microscope.

Results. The mineral composition of the sands under study was examined. The graphs (histograms) of the size distribution of quartz grains (being the most common sand mineral in terms of size and frequency of occurrence) were plotted. The shape and nature of the grain surface were analysed.

Conclusion. The frosting on aeolian sand grains can result not only from micro-cracking as the most common sign of wind transfer, but also from the presence of a calcite film on grains. Factors contributing to the formation and preservation of a ferruginous film (desert varnish) were identified. The conditions for the formation of aeolian sands, as well as the genesis of such sand sediments, were established.

Background. Clarification of the structure of sedimentary formations located on the Siberian Platform by means of lithological and petrographic core studies has a theoretical and practical significance for the creation of geological models for oil and gas prospecting and exploration works.

Aim. To characterize and compare the composition of the upper Vendian of the central and southern parts of the Prilensk-Nepsky structural-facies zone.

Materials and methods. Core samples for analysis were obtained from boreholes in the Preobrazhenskaya, Verkhnechenskaya, Danilovskaya, Yaraktinskaya and other areas. The article is based on the results of a layered lithological description of the cores from 15 wells with a total core output of 560 m in the interval of the Nepsky and Tirsky formations; the petrographic analysis of 540 thin sections; the determination of grain size distribution of rocks by laser light scattering in 220 samples; and X-ray diffraction analysis of 540 samples.

Results. The Nepsky formation is represented by the following lithotypes: conglomerates, gravelites,  sandstones, aleurolites and argillites. The section of the southern part of the structural-facies zone, compared to its central part, is characterised by increased claying. This is associated with the location of this zone in transitional coastal-marine environments, where large river systems were discharged carrying sandy-clay material into the basin. The source of the terrigenous rocks was felsic igneous rocks. The section of the Tirsky formation of the central part is represented (from bottom to top) by a transition from argillites and aleurolites to dolomites. In the section of the southern part, basal sandstones lie at the base, alternating upstream with clay-carbonate rocks.

Conclusion. The material composition of the studied sediments reflects the specifics of sedimentation during the Nepsky and Tirsky time periods. For the first time, the Tirsky formation of the southern part  of the structural-facies zone was divided into four lithological members. The formation of basal sandy rocks at the bottom of the sub-formations is associated with the stages of tectonic activity and positive tectonic movements that initiated relatively rapid weathering and transportation of terrigenous material from adjacent heights to the sedimentation basin.

The upper section part of the Republic of Tatarstan comprises complexes of poly-facial Middle and Upper Permian, Mesozoic, and Pliocene-Quaternary sediments. Surface and groundwater here is characterised by wide variations in composition and mineralisation due to natural and technogenic factors. The most important natural factor is the interaction of atmospheric precipitation and its derivatives with the soils and rocks of the section. To assess the scale of this interaction, water extracts from the main soil varieties based on distilled and melt snow water were analysed. The composition of aqueous extracts was compared with that of the least mineralised (up to 250 mg/l) spring water. The compounds delivered to the upper part of the section by soils include organic matter, nitrogen compounds in nitrite and ammonium forms and, to a lesser extent, iron and manganese. It is shown that the composition of groundwater outside zones of technogenic impact is largely determined by the interaction of atmospheric precipitation with the soil cover. This is explained by the fact that water extracts from soil samples have a mineralisation of over 100 mg/l, while the minimum mineralisation of spring water is 150—200 mg/l. Soils within forests and meadows are characterised by the maximum mineralising role. The soils of river valleys and cultivated fields contribute to water mineralisation to a lesser extent. The maximum amount of mineral and organic complexes that are readily soluble in water was found in blacksoils and grey forest soils, while their minimum was determined in grey-coloured sod-podzolic soils.