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The behavior of silver (Ag) in the oxidation zone of the Kyzyk-Chadr gold-sulfide-quartz deposit (Tuva Republic, Russia) has been studied. The main focus was on the mechanisms of Ag differentiation under supergene conditions, including the formation of its secondary minerals and its incorporation as an isomorphic impurity into other phases. It was found that Ag in the oxidation zone forms chalcogenides (acanthite, petrovskaite, uytenbogaardtite, jalpaite) and halides (iodargyrite, bromargyrite, mayersite), which are associated with malachite, chrysocolla, brochantite, quartz, and iron hydroxides. Electron probe microanalysis (EPMA) revealed that Ag concentrates in secondary copper sulfides (covellite, chalcocite, yarrowite, etc.), with levels as high as 0.7 wt.%. Optimization of EPMA parameters to improve resolution lowered the detection limit, enabling the determination of low Ag contents in chalcopyrite (up to 0.05 wt.%) and bornite (up to 0.09 wt.%). The sources of Ag are primary Ag tellurides and selenides, as well as primary and secondary Cu sulfides that break down during oxidation. Thermodynamic modeling simulated the behavior of Fe, Cu, and Ag during progressive oxidation of the primary assemblages (bornite, chalcopyrite, acanthite). The Eh-pH conditions controlling mineral migration and reprecipitation were calculated, and the element concentrations necessary for the formation of secondary phases were estimated.

The authors substantiate the method for the qualitative assessment of stresses and permeability parameters characterizing mass transfer in gas-saturated fractured porous coal mass, namely: mass transfer coefficient β, and permeability coefficients of fractured zone and matrix, k₁ and k₂, respectively. The method consists in formulation and solving of a mixed-type inverse problem within the framework of a dual porosity/dual permeability model to estimate the values of β, k₁ and k₂ by the measurement data of the pressure P(t) in a shut-in vertical well. The solvability of the inverse problem is demonstrated on the basis of the analysis of the introduced objective function, and an original algorithm is developed to find a minimum value of the function using additional information on the behavior of P(t). It is found that in the course of time, the function P(t) reaches a stationary value which is independent of the model parameters and is equal to the pressure of gas in an intact seam, which makes it possible to calculate the horizontal stresses outside the influence zone of the well. The proposed method can be used to provide parameters for geomechanical modeling in justification of technologies of pre-mine drainage and methane recovery.

Different coals preserve characteristic acoustic features of failure in self-sustained burning irrespective of the ignition cause. Phenomena which promote coal disintegration in heating are described. The failure mechanism of live coal in a seam is set, and appropriateness of the rating of the typical acoustic features revealed in coal burning on a lab scale is proved on this basis.

The article sets forth the studies on the longwall top coal caving technology with the powered roof support under development using the discrete element method in RockyDEM. The computer-assisted modeling with regard to geological and geotechnical conditions determines the LTCC technology parameters. They ensure the most efficient performance of the technology in terms of the integrated combination of caved coal mass, coal dilution, coal loss behind the support and frequency of poor roof caving events.

The problems connected with the adjustment of drill-and-blast patterns for the volume change in a charge cavity in case of deformation of borehole walls in case of drilling in open pit coal mining in the permafrost zone in Russia’s Far East are justified. The examples show that in drilling on benches 10 and 15 m high, 2-17% of boreholes require redrilling because of partial disintegration of rocks beyond the hole perimeter and due to caving of rocks inside the holes. In case of redrilling, the drill-and-blast patterns undergo decrease in the borehole spacing, which leads to the increase in the range of hazards in terms of the damage factors (flyrock and seismic impact). Borehole wall caving changes the charge cavity volume, which affects the quality of liquid emulsion explosive charges in mechanical pumping. A set of devices is proposed for the charge decoupling to ensure stability of the explosive charge cavity under conditions of large block blasting at mineral deposits situated in the zones of discontinuous permafrost.

The authors assess prospects for recycling of carbonate-fluorite ore processing waste in the Voznesensky ore district in the Primorski Krai. The main factors that can influence processing of slime are determined. The flotation-based recoverability of fluorite from low-grade (11.56-13.12% CaF₂) and fine-dispersion secondary material containing up to 88% of particles less than 10 µm is demonstrated. A rational process flow sheet to produce concentrates with CaF₂ content more than 93% mass at fluorite recovery to 52% is substantiated and proposed. Processibility of samples having different degrees of dispersion is compared. The use of electrochemically pretreated water in the process increases recovery of fluorite in concentrate by 3.6-4.7%. The variants of joint processing of charge material from different areas of the manmade deposit are discussed.

The article exhibits possibility of efficient treatment of coal siftings 0-13 mm in size as a case-study of the combined dry and wet separation of coking low-caking, low-metamorphozed coal. On the basis of estimation of processing behavior of the initial material, as well as the sieve, fraction and mineral analyses of different size grades of coal, several process flow sheets are developed. These process flow sheets include dry pneumatic separation of coal size grades of 1-13 mm, wet spiral separation of coal slime 0.2-3.0 mm in size, as well as flotation and oil agglomeration to separate coal and rock particles in fine coal slime. The proposed process flow sheets allow producing concentrates with the ash content from 15.3 to 9.9% at the mineral-free matter recovery to 90% and the calorific value over 7000 kcal/kg.

The articles describes the studies into the physical properties and composition of loparite ore processing waste from the dormant tailings ponds Karnasurt-1 and Umbozero in the Murmansk Region. The test samples were obtained by drilling to a depth to 4 m. The implemented studies included geological and geotechnical investigations, as well as the sieve, chemical, X-ray phase and radionuclide analyses. The properties and composition of the test tailings exhibited essential nonuniformity. The mineral composition is dominated by nepheline, and K- and Na-feldspar. The radioactivity of the waste is mostly due to radium and thorium. The obtained information of the peculiarities of change in the properties and composition of loparite ore mill tailings depending on their depth of burial are important for the development of the environmental measures and for the design of process flow sheets for manmade materials.

An engineering geological block model is conceptualized as a framework for the integrated digital model of a deposit. The scope of the article encompasses the methods of import and transformation of data from different sources, implementation of multi-level generalization, selection of scalable control systems for data bases and hybrid storage systems, as well as integration with MGIS, ERP and other information systems via standardized interfaces. It is shown that an engineering geological block model ensures highly accurate modeling, supports analytical and forecasting activities, becomes a single source of actual information on a deposit, and shapes a core of a digital twin of a mine. The engineering geological block model is the key element of digital information, which ensures data consistency, enhanced efficiency and risk reduction at all mining phases.

The analysis of 10 years-long seismic monitoring data at the Sheregesh deposit revealed the spatiotemporal patterns in the blasting-induced seismicity. Response of rock mass to blasting features a high spatial nonuniformity conditioned by geological medium anisotropy and tectonic faulting. The use of the k-means algorithm enables segmenting rock mass into process zones and allows identifying stress concentration areas. The cluster-specific time patterns in seismic response are confirmed, and the median time of delay in activation of post-blasting shocks varies in different zones. It is proved that the correlation dependence between the blasting energy and the post-blasting shock parameters is statistically insignificant, which highlights prevalence of the local geomechanics influence over the external effect. It is found that each blast induces 9.4 aftershocks on the average, at a high standard deviation, which proves variability of rock mass response. The research findings are of current interest in mining practices at rockburst-hazardous deposits in the conditions of complex geology and high tectonics.