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—Electrical resistivity tomography has been widely applied in prospecting and exploring gold deposits, but its potential for studying placers has not been sufficiently revealed. It is shown on the basis of numerical simulation and the example of field studies that linear anomalies with high electrical resistivity identified in floodplains correspond to gold-promising stream pool and riffle facies. It is concluded from working with alluvial placers in Kamchatka, Altai, and the Baikal Region that electrical resistivity tomography has a high resolution for solving geological problems, which means that it can be used as the main method for prospecting and exploring placers.

The efficiency of archaeological studies inside caves could be greatly enhanced by geophysical methods because of their potential for examining deposit structure and features. Application of those methods in caves entails a number of problems caused by limited space for measurements and the complexity of the surrounding medium s structure as compared to above-ground measurements. In 2017, Selungur Cave in the Fergana Valley, Kyrgyzstan, was examined using electrical resistivity tomography. Because of the above concerns, in the course of the work the question of the reliability of the results arose. To clarify the issue, a numerical experiment was performed to assess the effect of the three-dimensional cave geometry on the results of a two-dimensional inversion. It was found that variations of cave geometry parameters result in unexpected false anomalies, and considerable errors in bedrock location and resistivity can occur. In the case of downward diverging cave walls, an accurate resistivity section can be obtained by using the inversion based on a two-dimensional model. Therefore, electrical resistivity tomography in caves with similar geometry can yield reliable results concerning the shape of bedrock surface, the thickness of sedimentary layers, and size and position of inclusions such as fallen fragments of roof therein.

Ore mining and processing dumps are open and technogenic systems, which change intensively with time under the influence of environmental factors. Active transformations of such “technogenic deposits” are in close relationship with environmental factors. The purpose of this paper is to determine the nature and causes of the electrical resistivity (ER) changes in the mine tailings dump over time. The investigations were carried out by the method of electrotomography by determining the ER of the section to a depth of 1.5 m with an interval of one hour during the day with simultaneous recording of the substance temperature at a depth of 0.1 m. The maximum daily ER dynamics is observed over intensely transformed technogenic ores. ER is in a numerical relationship with the temperature of the solid matter by an exponential law with a certainty of 96%. A direct dependence of the ER daily changes amplitude on the cementation index m was revealed with the help of the Archie law. The primary material of the heap has a monodisperse composition and small values of m, so the amplitude of the ER dynamics is minimal. As a result of oxidative transformations, the solid matter of the dump becomes polydisperse, which is reflected in the cementation index and the amplitude of the ER daily oscillations increase.

The article presents the results of studies of freezing talik under lake with using of electrical resistivity tomography. The research was conducted on one of paleolake – khasyrey. The measurements performed in two perpendicular profiles by pole-dipole array with a maximum spacing of 435 m. According to results of two-dimensional inversion, an area of low electrical resistivity of rocks at a depth of 25-30 m associated with a freezing talik under lake was identified. It was determined that the depth of freezing within drained lake for the period from 1996 to 2018 is 17-22 m. The approximate rate of freezing is 1 m/year. Formation of talik have a resistance of 5-15 Ω·m. Frozen formations in the contours of young paleolake have apparent resistivity hundreds Ω·m. Within the boundaries of the more ancient khasyrey apparent resistivity of the frozen rocks up to several thousand Ω·m.

Climate warming and anthropogenic impact causes transformation of geocryological conditions in the river basins of the North-East of Russia. Changes in the thickness of the active layer, configuration of taliks, types of landscapes and other factors lead to transformation of water exchange processes between surface and groundwater runoff. This is manifested in the seasonal redistribution of the components of the water balance, accelerated melting of aufeis, change in the ratio of waters of different genesis in the structure of river runoff. As a result, natural and anthropogenic risks that affect the safe and efficient development of infrastructure and socio-economic processes are increasing. At the same time the system of observations developed in the Soviet period has been practically destroyed in the region. This paper offers a vision of organizing complex multidisciplinary research to assess and project the changes in the conditions of underground and surface water interaction in natural and disturbed river basins of the cryolithozone of the North-East of Russia, including for solving applied problems, based on permafrost, hydrology, hydrogeology, landscape science and geophysics with applications of remote sensing and field research integrated through mathematical modeling methods. To achieve the goal, the identification of natural and disturbed landscapes using remote sensing data, and key areas for detailed research will be selected. Geophysical and drilling works will be carried out within the sites to establish permafrost-hydrogeological conditions, monitoring stations will be equipped to determine hydrogeological, hydrometeorological and geocryological characteristics, including sampling for isotopic and hydrogeochemical studies. As the main key sites, it is proposed to use the area of ​​the Kolyma water-balance station and the site on Anmangynda aufeis, for which there are long-term observation series in the 20th century. Field data will become the basis for improving the mathematical model of runoff formation, considering the relationship between groundwater and river runoff in the conditions of permafrost. Mathematical modeling will make it possible to quantitatively analyze the water balance of rivers considering various factors and project water availability both for specific industrial facilities and for the region as a whole.

Rapid climate warming at northern high latitudes is driving geomorphic changes across the permafrost zone. In the Yamal and Gydan peninsulas in western Siberia, subterranean accumulation of methane beneath or within ice-rich permafrost can create mounds at the land surface. Once over-pressurized by methane, these mounds can explode and eject frozen ground, forming a gas emission crater (GEC). While GECs pose a hazard to human populations and infrastructure, only a small number have been identified in the Yamal and Gydan peninsulas, where the regional distribution and frequency of GECs and other types of land surface change are relatively unconstrained. To understand the distribution of landscape change within 327,000 km2 of the Yamal-Gydan region, we developed a semi-automated multivariate change detection algorithm using satellite-derived surface reflectance, elevation, and water extent in the Google Earth Engine cloud computing platform. We found that 5% of the landscape changed from 1984 to 2017. The algorithm detected all seven GECs reported in the scientific literature and three new GEC-like features, and further revealed that retrogressive thaw slumps were more abundant than GECs. Our methodology can be refined to detect and better understand diverse types of land surface change and potentially mitigate risks across the northern permafrost zone.

Summary The paper presents the capabilities of the electrical resistivity tomography for determining the thickness of loose sediments and the topography of an alluvial placer bedrock. Particular attention pays to identifying induced polarization anomalies associated with zones of gold-sulfide mineralization in bedrocks. These zones are the primary sources of placer gold in the region.

Summary Soil thawing occurred during the operation of the frozen embankment dam. This led to the formation of leaks through the dam body and at the foundation along the fault in bedrocks. The main goal of the research was to identify leak locations for planning wells of the groundwater cut-off. Electrical resistivity tomography was carried out over parallel survey lines, 3-D inversion was performed, and electrical resistivity maps at depths of 4, 10, and 20 m were made. Anomalies of low electrical resistivity showed the line of water filtration in the body of the dam body and foundation. The 3-D model provide insight into thawing from the upper pool and filtering along the fault.

Summary Alluvial gold deposits are associated with alluvium. We found that the channel facies of alluvium has an increased electrical resistivity as compared with the host rocks. This makes it possible to use the method of electrical resistivity tomography (ERT) for the prospecting for alluvial gold placers. The paper presents the results of geophysical studies by the method of ERT with measurement of induced polarization in the Baikal region. ERT was performed using a system of parallel profiles, 3-D inversion was performed, and resistivity and polarization maps were constructed. Perspective local dives in the bedrocks (pockets) are highlighted on the loose rocks thickness map. Linear anomalies of increased polarization associated with the alleged bedrock sources of gold have been discovered.

We assess the potentialities of ultrawideband (UWB) electromagnetic pulse sounding of low-resistivity geoenvironments using the ground-penetrating radar (GPR) system developed by us and compare the obtained results with 2D electrical resistivity tomography and standard GPR data. The research was performed in an area of Quaternary clay deposits with a resistivity of 20–50 Ohm⋅m. For an OKO-2 GPR antenna with a center frequency of 150 MHz, the sounding depth is 2–4 m, whereas UWB sounding provides penetration of the GPR pulse to a depth of 30–40 m. Deep UWB sounding of low-resistivity environments is possible under the following conditions: use of generators based on drift step recovery diodes (DSRDs), high matching of the UWB receiving and transmitting antennas to the environment, and an increase in the noise immunity of the recording system, in particular, due to a decrease in the intensity of air waves.

Sulphide-bearing mill wastes of the Ursk Ore Processing Plant situated in the Kemerovo region (Russia) were investigated in the 2013 – 2015. Multipurpose studies of the Ursk mining tailings allowed to determine the composition of the wastes pore waters, acid mine drainages and affected groundwater. Electrical resistivity tomography (ERT) was used to trace the geoelectric zoning of the wastes, expressed as a consistent change of the electrical resistivity from zone to zone. Layers with low resistivity indicate areas with pore spaces filled by highly mineralized solutions with high concentrations of Cu, Zn, Cd, As, and Sb up to 12 g/L in total.

Thawing of subsea permafrost can impact offshore infrastructure, affect coastal erosion, and release permafrost organic matter. Thawing is usually modeled as the result of heat transfer, although salt diffusion may play an important role in marine settings. To better quantify nearshore subsea permafrost thawing, we applied the CryoGRID2 heat diffusion model and coupled it to a salt diffusion model. We simulated coastline retreat and subsea permafrost evolution as it develops through successive stages of a thawing sequence at the Bykovsky Peninsula, Siberia. Sensitivity analyses for seawater salinity were performed to compare the results for the Bykovsky Peninsula with those of typical Arctic seawater. For the Bykovsky Peninsula, the modeled ice‐bearing permafrost table (IBPT) for ice‐rich sand and an erosion rate of 0.25 m/year was 16.7 m below the seabed 350 m offshore. The model outputs were compared to the IBPT depth estimated from coastline retreat and electrical resistivity surveys perpendicular to and crossing the shoreline of the Bykovsky Peninsula. The interpreted geoelectric data suggest that the IBPT dipped to 15–20 m below the seabed at 350 m offshore. Both results suggest that cold saline water forms beneath grounded ice and floating sea ice in shallow water, causing cryotic benthic temperatures. The freezing point depression produced by salt diffusion can delay or prevent ice formation in the sediment and enhance the IBPT degradation rate. Therefore, salt diffusion may facilitate the release of greenhouse gasses to the atmosphere and considerably affect the design of offshore and coastal infrastructure in subsea permafrost areas., Key Points The thawing of ice‐bearing subsea permafrost was modeled by coupling heat and salt diffusionThe boundary conditions reflect sea ice dynamics during the transition from terrestrial to marine permafrostThe modeled ice‐bearing permafrost depths were validated with geoelectric surveys

Summary Electrical resistivity tomography and cone penetration test were carried out on the slope of the M–7 Volga highway. The main goal of the research is to localize areas of increased landslide hazard. Electrical resistivity and the mechanical properties of soils depend on their moisture content, lithological composition and porosity. This made it possible to determine the correlation links between the electrical resistivity and the mechanical parameters of the soil, to predict the deformative and strength characteristics of the soil. Soils with abnormally low resistivity have low values of drag under the cone and friction of the side surface of the probe. They correspond to areas of potential landslide formation.

A new approach to interpretation of shallow electrical resistivity tomography (ERT) data discussed for the case of the Olkhon area (western Baikal region) stems from tectonophysical ideas of faulting phases and deformation levels in rocks. The deformation levels, identified statistically from ERT responses, constrain fault boundaries and subboundaries associated with the formation of main and subsidiary fault planes. Information of this kind creates a basis for solving various fundamental and applied problems of tectonics, mineral exploration, and engineering geology.

Combined geophysical and geochemical investigations of drainage streams from sulfide-containing waste dumps of the Novo-Urskoe deposit allow determining two directions of highly mineralized toxic solutions. Surface drainage stream flows over the natural slope of the valley. In addition, along the natural fault, vertical penetration of drainage solutions into groundwater occurs to a depth of 20 m. Based on geophysical-data interpretation, we assume that penetration of solutions into geologic environment leads to their dilution by groundwater, followed by a six-fold decrease in total mineralization.

Based on comprehensive geophysical and hydrogeochemical study of mud volcanism within Bulganak center (Kerch Peninsula), periodicity of ejections of Andrusov mud volcano are defined during its activity.

The effect the metal casing of a vertical borehole may exert on transient electromagnetic (TEM) responses has been studied in a field experiment. Eddy currents in the casing affect transients only slightly at early times, but the casing effect predominates at late times. Therefore, early-time TEM response measured near a borehole can provide information on shallow subsurface. The late-time TEM signals induced by the eddy currents in the casing show exponential behavior b⋅ exp(–t/τ). The time constant τ refers to the rate of eddy current decay in the casing; the amplitude b is M12⋅ M23⋅ L–1⋅ τ–1, where L is the casing self-inductance, and M12 and M23 are the mutual inductances between the transmitter loop and the borehole and between the borehole and the receiver, respectively. Both M12 and M23 are controllable, while M23 is especially important for survey applications: by reducing it, one can reduce the casing effect on the TEM data. © 2014, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.

Electromagnetic soundings with controlled and natural sources (TEM and MT, respectively) integrated with IP and geochemical surveys have been tested for petroleum exploration in West Siberia. The TEM method, with loop sizes smaller than the depth to the target, provide high resolution, sufficient penetration depth, and data locality. The MT method sounds deeper earth and can place constraints on the Paleozoic basement structure and its electrical properties. The petroleum implications of IP and geochemical data are associated with secondary alteration (mineralization) of rocks over oil traps.

The structure of the Earth’s crust at the junction of the Siberian craton and Sayan–Baikal Fold Belt was studied along the Bayandai Village–Cape Krestovskii profile (85 km long) by a set of geological and geophysical methods: structural survey, interpretation of long-distance photographs, emanation survey, electrical prospecting with self-potential (SP) and direct-current (DC) resistivity profiling, magnetotelluric sounding, magnetic survey, and hydrogeochemical sampling of water objects. Interpretation of the data refined the main features of the tectonic structure of western Cisbaikalia and revealed the disruption pattern and hierarchic zone–block structure of the Earth’s crust. The Obruchev fault system (≈50 km wide), which is the northwestern shoulder of the Baikal Rift, is the main interblock zone of the studied region. It consists of the Morskoi, Primorskii, and Prikhrebtovyi interblock zones, traced from depths of tens of kilometers and widening near the surface owing to superior structures. The studies gave an insight into the regularities in the occurrence of interblock zones and the criteria for their identification in different geologic-geophysical fields. An efficient complex of methods for mapping the Earth’s crust zone–block structure is proposed.

Results of measurements of fast decaying induced polarization (IP) on Quaternary clay samples in comparison of the geochemical data executed on a site in Western Siberia are discussed. The higher clay chargeability was observed in zones with abnormal contents of aromatic hydrocarbons. Conclusions are made, that higher concentration of hydrocarbons in Quaternary clay and their abnormal chargeability can be attribute to oil-and-gas deposits at depth. It is supposed to use near-surface IP measurements for contouring the epigenetically changed rocks above deposits of hydrocarbons.

The paper discusses the results of investigation into fast-decaying induced polariza-tion of frozen rocks forming the near-surface geology of the Mirny kimberlite field in Yakutiya, Russia. Time domain galvanic IP response was measured in the range from 0.1 to 12.8 ms in combined sounding and profiling mode with the pole-dipole array. The measurements were carried out along surveying lines going over and in the vicin-ity of a known kimberlite pipe embedded in carbonate rock. Measured data were transformed into apparent resistivity, chargeability, and the rate of decay of the IP response. As indicate the survey results, frozen carbonate rocks exhibit high resistiv-ity, chargeability and rate of the IP decay. Such combination of parameters is typical of frozen ion-conductive rocks containing no electron-conductive minerals. As for the known kimberlite pipe, in comparison with the host rock it is marked by low resistiv-ity, chargeability and rate of the IP decay. The IP survey resulted in discovering two anomalous objects the parameters of which differ from those typical of carbonate rocks. The combinations of these parameters suggest that one of the above objects might be an unknown kimberlite body whereas the other presents an area with en-hanced concentration of sulfide minerals