Purpose. The studies are aimed at the investigation of geological structure and mineragenetic zonation, description of ore clusters, genetic types of ore deposits and geodynamic conditions of their formation, prediction and prospects of future commercial exploration of the Selenga ore district of the Buryat Republic. Methods. The study employs complex structural-geological and mineragenetic researches including thematic, explorative-surveying and geological-prospecting works carried out earlier. The analysis of the material composition of magmatic rocks and strategic raw material ores is performed by means of modern petrological-geochemical and isotope-geochronological methods using the composition of rare and rare-earth elements, microprobe minerals identification as well as isotope (U-Pb, Sm-Nd, Rb-Sr, Sr-Sr, Ar-Ar, O, C etc.) and lithological-biostratigraphic data. Results. It is found that Upper Paleozoic and Early Mesozoic tectono-magmatic structures are widely developed within the ore district. They are associated with the development of the transregional Upper Paleozoic Selenga-Vitim volcano-plutonic belt of riftogenic type as well as with the formation of the West Transbaikalian Mesozoic zone of riftogeneous (intraplate) magmatism. The main commercially important strategic mineral raw material resources of the Selenga ore district which are located in the ore clusters (the Kunaley, Kizhinga, Cheremshanka-Oshurkovo, Tashir et al.) and beyond their bounds are associated with the Late Paleozoic-Mesozoic magmatic activity. It is found that molybdenum and beryllium are the main ore minerals within the district which determine the mineragenetic features of the investigated ore district. Conclusions. The new material characteristics of the Upper Paleozoic and Mesozoic intraplate magmatic complexes, the associated deposits of strategic mineral raw material (Mo, Be, Ti, quartz, fluorite and apatite raw material) and other promising ore objects of copper, gold, uranium and rare-earth-barium-strontium mineralization are obtained. The geodynamic conditions of their formation and the main age boundaries of the ore-forming processes are revealed. The mining prospects of the Selenga ore district and the involvement of this ore potential in the program of the region's economic modernization are estimated.

The Purpose of the paper is to analyze the zoning nature of mineralization and metasomatites in the known porphyry copper deposits of the Goshgarchai ore magmatic system (OMS) associated with the Murovdag group of intrusives.

The Methods used in the study include complex structural and geological, metallogenic, geological-petrological, ore metasomatic and petrochemical parameters of metasomatites as well as the studies that take into account science-based geological prospecting works carried out earlier. There is some regularity between the petrochemical parameters of metasomatites and the contents of copper and molybdenum.

Results. It has been found that the thickness of methasomatically altered rocks varies from several meters to tens and hundreds of meters (in the intersections of multi-oriented faults) within the Goshgarchai OMS. Their length ranges from 500-1000 m to 2000-3000 m. Three gradually changing each other elliptical metasomatic zones are distinguished around the ore generating intrusives of the Goshgarchai OMS. They border the intrusive massif of porphyry composition. The inner zone including the endocontact and apical parts of the porphyry intrusive is represented by strongly silicified rocks, which are almost completely transformed into secondary quartzirtes. The middle zone is determined as quartz-sericite-chlorite facies of secondary quartzirtes. The third external zone of the metasomatic column is represented by the propylite facies of secondary quartzirtes.

Conclusions. Having studied ore zoning within the borders of the Goshgarchai deposit we have obtained the following series of vertical zonality of elements (bottom-up): Mo→Cu→Со→Ni→Cr→Ag→Pb→Zn. Hydrothermal metasomatic variations of enclosing rocks in the zones of different types of metasomatites generated under deposit formation have been studied and compared on the basis of petrochemical data.

The Purpose of the study is to carry out the correlation of profiles of the Precambrian deposits of the Siberian and China platforms, to compare tectonic scales by the age of the Precambrian final folding, to distinguish geological and structural backgrounds of the oil-and-gas content of Siberian and North China platform Rifeide (siniede). The Methods used in the study include the comparison of the coeval structural and material complexes formed in similar geodynamic conditions, correlation of classical basic profiles of the Precambrian of the Siberian platform, its southern frame and the North China platform. Results. The scales of structural and material complexes of the Precambrian of Siberia and China are composed. The correlation is performed which is based on the regional scales of structural and material complexes, that is material expression of regional geological systems of Siberia and China, and age-wise tectonic scales, which are also accepted in Russia and China. It is noted that drastic change in the orientation of the Riphean structures with the Pre-Riphean structures on the Asian continent coincides with the Liu Liang movement, which corresponds to the Vyborg movement on the territory of Europe, to early Riphean movement in Siberia, to the Hudson movement in the American continent: 1800-1600 million years. This planetary stage of continental destructions is also the time of disintegration of the Sino-Siberian pracontinent into the Siberian and North China cratons. The detailed analysis of the Pre-Riphean evolution of Sino-Siberian pracontinent and the geological history of the Riphean structures has allowed to distinguish the geological-structural backgrounds of the oil-and-gas content of the Siberian and North China platform Rifeides (sineides). Conclusions. The correlation of the Precambrian of the Siberian and North China platforms shows the analogy of the structural-material complexes composition. The comparison of tectonic scales by the age of final folding allows to draw a conclusion on the industrial oil-and-gas content of the Riphean and Sinian formations on the Siberian and China platforms.

The purpose of the paper is to determine the crystallization order of rocks based on the study of the mineralogical and petrographic composition of the Khentei Range Cenozoic basaltoids. Methods. A microprobe X-ray spectral analysis by means of the JXA-8200 tool (JEOL Ltd., Japan) has been used in the study. Results. The research results in the determination of chemical compositions of rock-forming minerals and the sequence of minerals formation. Conclusions. Melt movement to the surface was accompanied with the capturing of mantle xenoliths. Olivine and pyroxene of the first generation were formed first, then, olivine and pyroxene of the second generation were formed, as well as oxide bearing minerals. Plagioclase, potassium feldspar, nepheline and leucite were crystallized last from the interstices. The presence of residual glass has also been noticed in the interstices.

The Purpose of the work is to study the reflection patterns of the interblock tension zones structure in relief at various scale levels of the Earth's crust tectonic divisibility in the Baikal rift. Methods. The study involves the analogue modeling on elastic-plastic material (clay paste) with the following construction of digital models of the control sample surface relief. The resulting digital terrain models are analyzed by constructing the distributions of vertical motion gradient. The similar method is used to study the readily available digital terrain models of the natural analogue of the experimental models of the Baikal rift. The data obtained in the analysis of the two types of digital models are compared. Results. Distributions of the gradient of vertical motions for the experiment and the relief gradient of the north-west and south-east flanks of the Baikal rift have been obtained and analyzed. Sections reflecting the extension zones of different ranks and their internal structure have been distinguished in the gradient field. A procedure has been proposed to identify the interblock zones of different hierarchical levels based on the relief gradient of Earth’s fault zones. Conclusions. The fault zones and their structure formed under extension are reflected in gradient distribution by the increased parameter values. The maximum values of the parameter are characteristic of the main fault of the zone, smaller values are referred to second-order cracks. Strike-slip cracks formed under extension are not demonstrated by special gradient values but they can be traced by the displacement of local maxima associated with other cracks. In most cases, found regularities are valid for experimental and natural extension zones.

The goal of the paper is to analyze the changes in mineral crystal lattice under acid activation. Methods. Clay from the Slyudyanka deposit is the material under investigation. The methods used in the study include x-ray phase analysis using Bruker D8 Advance diffractometer. The diffractogram is recorded using the EVA program installed on a PC in combination with the diffractometer. The quantitative composition is calculated using the Topas 3.0 program. The study also uses the methods of scanning microscopy of the oriented sample, titrimetric analysis methods (the methods of neutralization and complexometry 0; conductivity measurement (determination of solution electrical conductivity); potentiometric measurements (determination of electrokinetic potential at electrophoresis); sedimentation analysis in gravitational and centrifugal fields. Modern databases and Excel are used for thermodynamic calculations. Results. Crystallochemical analysis of mineral structure and thermodynamic assessment of process spontaneous flow conditions allowed to explain the nature of the potential curve after acid activation of the clay from the Slyudyanka deposit. The extreme nature of this dependence is associated with the changes in the field of force on the surface of particles as a result of the flow of the complex of physico-chemical interactions, the most important of which are interactions of backbone ions with the components of environment. In its turn, the changes in the interaction energy of clay particle weight calculated by the results of colloid-chemical studies allow to analyze the processes occurring in the crystal lattice of clay under acid activation. Experimental data confirm the similarity of some patterns of acid activation of clay minerals associated to the fact that the process is accompanied by the washout of ions from the crystal lattice skeleton and formation of structure defects. The defects of crystal lattice causing the disturbance of its regularity, the transition of surface silica in amorphous state provide the change in both system dispersion and porosity of clay samples. Conclusions. It is more preferable to use the acid activation for the production of mineral sorbents with developed porosity when minerals with an expanding structural cell are used as a source material.

The Purpose of the paper is to evaluate the possibilities of regression and variance analyses in the quantitative interpretation of gravity anomalies when solving gravity inversion problem in complex geological conditions. Methods. The paper considers the possibilities to use a factor analysis and singular matrix decomposition under the gravity field inversion of the Ulaanbaatar depression (Mongolia), which is characterized with a complex geological structure. Results. We have obtained the quantitative characteristics of the loose sediment thickness in the structure under investigation and the data on morphological features of the immersed part of the crystalline basement. The Ulaanbaator depression has a complicated block structure. The transverse uplift of the foundation divides it into two basins: Western and Central. In the Western part, which is the area of tectonic disturbances, the identified basin is oval in shape with the dimensions of 3×6 km and the thickness of the deposition lens of 100-120 meters. The maximum thickness of Cenozoic deposits in the Central basin is 130-160m. Obtained quantitative assessments are confirmed by the results of mathematical modeling under gravity field inversion of the studied basin with the help of analytical methods. Conclusions. The thickness of loose deposits has been estimated and the surface morphology of the Ulaanbaator depression basement has been described by means of regression and variance analyses under gravity field interpretation in complex geological conditions. The results of gravity field inversion by means of the considered mathematical tools coincide with the calculation results of the analytical methods when solving a one-dimensional inverse problem for a contact surface (for a flat layer), which confirms the efficiency of the proposed interpretation method of gravity anomalies.

The Purpose of the paper is development of an efficient technology for complex polymetallic ore processing based on the improved gold gravity separation in the head of the production train. Methods. The following analytical and experimental methods are used: chemical and fire assay analyses of the feed and concentrate, size fraction analysis, bench scale and pilot plant gravity tests, statistical analysis of experimental data and mathematical modeling. Results. The study results show that the direct gravity concentration provides relatively good recovery of valuable components. The recovery of gold to the primary gravity concentrate varies from 27.57 to 36.48 %, silver from 14.79 to 22 % and lead from 14.66 to 27.94 %. The highest recovery of gold was achieved under ore dressing using a modernized jigging box. The conducted studies show that there is a possibility in principle to increase the recovery of valuable component to the gravitation concentrate. In this case the recovery of gold to the gravity concentrate may be increased by 3 %, silver by 7.5 %, lead by 3.8 %. The expected economic effect from the introduction of the proposed technical solution will estimate RUB129,562,579.

The purpose of the article is to focus on the breakdown pressure of the well bore when drilling offshore for oil and gas. It is much lower than the one when drilling on shore and can vary significantly. Domestic articles on this topic are little to choose. One of the reasons of this situation is that drilling on the already explored offshore deposits is not performed now as the oil prices are low, and drilling from the floating drilling rigs is too expensive. Moreover, severe ice conditions and imperfection of drilling equipment for offshore drilling hinder the development of drilling works in the Northern and Eastern seas. We should also note the lack of experience of Russian drillers in the development of offshore oil and gas fields. Methods. The study uses a refined analytical calculation of the breakdown pressure of the well bore and its gradient. Results. To determine the breakdown pressure it is proposed to allow for the shelf depth and rotary table elevation above the average level of the shelf surface. The depth of the shelf is often not taken into account allegedly because of its small depths. But the described factor is not the only one that causes a short-term increase in the hydrostatic pressure. It could also be caused by daily tides, swabbing under RIH/POOH operations and etc. All together they can cause the loss of circulation. Besides, the article presents the average overburden and formation pressure gradients in tabular variants instead of graphical ones in order to facilitate the calculations. Conclusions. Analytical determination of the fracture pressure when drilling offshore wells (water holes) is an important task as it gives the real values of the fracture pressure. This can help to prevent the loss of circulation.

The purpose of the paper is to conduct a study evaluating the efficiency of the developed humic mineral complex against arsenic and heavy metals under the remediation of agricultural and residential soils subjected to prolonged anthropogenic impact. Methods. The studies have been conducted in order to determine the optimal concentration of the humic preparation, to estimate the effect of the detoxicating preparations under the investigation on the reduction of soil toxicity. Results. Using infrared spectra it has been proved that there are significant changes in the structure of the humic mineral complex as compared with the standard of humic acid. Conclusions. It is shown that the calculated coefficients of the synergistic effect of the combined action of humic acids and lime of the developed humic mineral complex are two or three times higher than those under the individual effect of humic acid and lime when conducting the detoxification of arsenic contaminated soils.