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Date submitted2018-03-02
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Date accepted2018-05-03
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Date published2018-08-26
PROBLEM OF THE INTERNATIONAL CHRONOSTRATIGRAPHIC CHART OF LOWER DEVONIAN AND STRATIGRAPHIC BOUNDARIES OF LOWER DEVONIAN STAGES IN SOUTHERN TIAN SHAN
- Authors:
- E. D. Mikhailova
- A. I. Kim
The boundaries of the International Chronostratigraphic Chart (ICC) are associated with the natural historical stages of the Earth's development, and their boundaries are usually determined by the palaeogeographical or palaeobiological event that is recognized in most regions of the world. Studies on the standardization of the Lower Devonian ICC stages duration have lasted more than 70 years. The first stages were Gedinnian, Siegenian and Emsian, but their duration was not accurately determined. The article shows the history of the establishment of the currently used Lochkovian, Pragian and Emsian stages. The key study method of the Lower Devonian stages deposits is biostratigraphic one, based on the use of archistratigraphic pelagic fossils, i.e. revealing of the zonal sequence over the conodonts, dacrioconarids and goniatites fossils and comparing them with the standard sequence adopted by the International Geological Congress (IGC). The article contains an analysis of the discussed problems related to the determination of the position of the global boundary stratotype section and point (GSSP) of the Lower Devonian stages. The use of the magnetostratigraphic method in comparison of the sections of the Emsian stage in Barrandian and Zarafshan range is also discussed. The Lower Devonian regional strata of the Zarafshan-Gissar and Turkestan-Altay mountain regions of the Southern Tian Shan are characterized. It is shown that the zonal sequences on conodonts and dacrioconarids presented in these regions almost completely coincide with the standard Lower Devonian sequences in the International Chronostratigraphic Chart. The characteristics of zones and volume of Bursykhirmanian, Sangitovarian, Khukarian, Kunjak, and Kitab horizons are given.
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Date submitted2017-11-16
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Date accepted2018-01-16
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Date published2018-04-25
Volume and surface distribution of radiation defect in natural diamonds
- Authors:
- E. A. Vasilev
- A. V. Kozlov
- V. A. Petrovskii
In the following article, we have studied the variations of natural irradiation of diamond crystals. The natural diamonds in some cases show homogeneous green colour, caused by irradiation of the entire crystals volume. Radiation damage effects, produced by the low-radiation doses, are detected by the luminescence of the GR1 system. The high-radiation doses cause bluish hue, turning into a greenish colour, while the maximum level of volume irradiation produces the black crystals. The crystals with homogeneous volumetric black colour distribution were also studied. The major source of radiation in such cases may represent a local stream containing water rich in 222 Rn and its decay products. There is a review of the geological environment in which diamonds could be irradiated due to the decay of the 222 Rn containing in water.
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Date submitted2017-11-09
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Date accepted2017-12-28
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Date published2018-04-25
Chemical weathering of lower paleozoic black shales of south Sweden
- Authors:
- D. O. Voronin
- E. G. Panova
Lower Paleozoic black shales are widespread in Sweden and form part of the Baltic paleobasin, which deposits are also known in Estonia and the Leningrad Oblast of Russia. These rocks are enriched in a carbon substance and characterized by the significant content of uranium, vanadium, molybdenum, copper, nickel, cobalt, zinc, and lead. Black shales contain high levels of Sr – 968; Ba – 337; U – 229; V – 509; Mo – 165; Zn – 411; Ni – 214; Cu – 112 (ppm) in secondary minerals composition formed on their surface. Retrograde diagenetic conditions facilitate the black shales chemical weathering. Elements of the first (U), second (Mo, Sr, Zn), and third (V) hazard classes are washed out of black shales and secondary minerals and can further enter biological cycles.
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Date submitted2017-09-02
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Date accepted2017-11-22
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Date published2018-02-25
Age and metamorphic conditions of the granulites from Capral-Jegessky synclinoria, Anabar shield
The paper presents the results of the isotope, geochemical and thermobarometric study of plagio-crystalline schist containing in the Upper Anabar series of the Anabar Shield. Granulite complexes of the paleoplatforms are the most important issue in addressing the fundamental problem of the Earth's crust origin and its composition. The early stages of crust formation which correspond to the deeply metamorphosed rocks of the platform basements, available for study within the shields, are of particular interest. The study of the age and metamorphic conditions of granulites by the case of the Upper Ananbar series allows specifying the stages the Anabar Shield's ancient crust formation. Isotope-geochemical (U-Pb geochronology for zircon and Sm-Nd for garnet-amphibole-WR) and thermoba-rometric (Theriak-Domino) studies of plagio-crystalline schist allowed to identify two Paleoproterozoic metamorphism stages within the territory of the Anabar Shield with an age of about 1997 and 1919 million years. The peak conditions of granulite metamorphism are determined as 775±35 С and 7.5±0.7 kbar, the parameters of the regressive stage are 700 C and 7 kbar. The sequence of the rocks metamorphic transformations can be assumed: high-thermal metamorphism of the granulite facies (T ≤ 810 C) and subsequent sub-isobaric (about 7 kbar) cooling to 700 C with a water activity increase and formation of Grt-Amp paragenesis corresponding to the transition from the granulite to amphibolite facies. Data on the REE and other trace elements distribution in zircon and rock-forming minerals obtained by the ion microprobe analysis contribute significantly to the isotope-geochemical data interpretation.
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Date submitted2017-09-17
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Date accepted2017-11-06
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Date published2018-02-25
Collaborative interpretation of the data obtained by resistivity and ground penetrating radar methods for assessing the permeability of sandy clay soils
- Authors:
- D. A. Lalomov
- V. V. Glazunov
A method for estimating the filtration factor of sandy clay soils is considered on the basis of a joint interpretation of the data of a set of methods of engineering electrical exploration, including electrical resistivity tomography and ground penetrating radar studies. The solution of this problem is based on the use of known empirical connections between the imaginary and real parts of the complex dielectric permittivity, specific electrical resistance, and Q factor. An example of the effective joint use of the ground penetrating radar and non-contact electrical resistivity tomography shows how to obtain qualitative and quantitative estimates of a changing filtration factor in a draining road layer. It is necessary to use precise engineering geological information in order to provide the required estimates. The proposed approach makes it possible to describe continuous profiles of a pavement and underlying layers by ground penetrating radar and electrical resistivity tomography, as well as to assess soil properties when conducting an electrical survey from the surface of asphalt concrete pavement. Recommendations for the implementation of the developed methods of complex engineering and geophysical research are given for solving issues of repair work design, supervision, and quality control of road construction.
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Date submitted2017-07-13
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Date accepted2017-09-17
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Date published2017-12-25
Complex study of neogenous deposit thickness of pannon basin on the basis of seismostratigraphic approaches with elements of seismofacial analysis
- Authors:
- T. V. Olneva
- E. A. Zhukovskaya
From 2011 to 2017, large-scale seismic surveys were carried out by PJSC Gazprom Neft within the Pannonian Basin (territory of Serbia). Currently, the coverage area of seismic surveys in the modification of MOGT 3D is approaching the stage of regional study and is about 5,600 km 2 . The obtained data signify a new stage in the geological study of the region and represent a rich material for further understanding of the geological structure of the research area. The full-scale introduction of seismic prospecting in the modification of the MOGT 3D has made it possible to use modern approaches to interpretation, such as seismostratigraphic and seismic facies analysis. On the one hand, the results obtained contribute to a more successful geological exploration. On the other hand, the adaptation of seismostratigraphic approaches, sequestration techniques and seismic facies analysis techniques to the regional features of the Pannonian basin makes it possible to develop the methods themselves, since the subject of research, in the opinion of many scientists, is in many senses a natural laboratory. The article describes the main seismostratigraphic complexes, the principles of their isolation, the features of interpretation approaches for seismic facies analysis in each of them, and the results of seismic facies analysis are combined with core studies. Within this region, more than 500 deposits with total reserves of over 1,400 million tons of conventional oil have been discovered. Despite the small size of the vast majority of deposits, they are profitable and further exploration is of great practical interest.
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Date submitted2017-07-11
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Date accepted2017-09-15
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Date published2017-12-25
Pedagogical experiment of the first rector of the Ural state mining institute P.P. Von Weymarn as an effort to reform the higher education institution in 1917-1920
- Authors:
- N. G. Valiev
- A. G. Shorin
Based on sources recently discovered and included in the database of scientific publications, the article analyzes the pedagogical activity of the scientist-chemist, the first rector and founder of the Ural Mining Institute in Ekaterinburg Petr Petrovich von Weymarn, whose name is now almost forgotten. The article shows that this activity can be evaluated as a pedagogical experiment on reformation of the higher education institution system, which could have been adopted in Russia if Bolsheviks lost the Civil War. Pedagogical activity of von Weymarn has a theoretical basis that he developed under the influence of Wilhelm Ostwald, the Nobel Prize winner in chemistry and the idealist philosopher, as well as the example of the Petrograd (Petersburg) Mining Institute, which for von Weymarn was not only an alma mater but an example of a reformist attitudes toward the scientific and pedagogical process in higher education. The article gives a detailed analysis of the currently available philosophical and pedagogical essays of P.P. von Weymarn, known as «Essays on the Energy of Culture», as well as the practical application of these theoretical works on the basis of the Ural Mining Institute in Ekaterinburg and in Vladivostok. With the advent of Soviet power, von Weymarn's pedagogical experiment was forcibly interrupted, and he became «persona non-grata» in the Soviet Union, but now his name is being restored. Unfortunately, he is known either as a chemist or as the founder and first rector of the current Ural State Mining University, but not as a teacher who offered his view of reforming the higher school system. This article fills this gap, revealing not only the work of von Weymarn, but also describing the difficult period of changing the old scientific school system, which could have taken a completely different development path.
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Date submitted2017-07-03
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Date accepted2017-09-15
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Date published2017-12-25
Engineering-geological aspects of negative consequences of contamination of dispersive soils by petroleum products
- Authors:
- R. E. Dashko
- I. Yu. Lange
The article presents the features of transformation and migration of petroleum products in the underground environment, which are determined by the physical and physicochemical properties of petroleum hydrocarbons (density, viscosity, solubility in water, etc.) and their enclosing soils (sorption capacity, humidity, etc.). The main processes of degradation of oil products in the soil stratum are considered. The influence of oil products on the change in oxidation-reduction and acid-alkaline conditions of the underground space, development of activity of various forms of microorganisms is shown. The change in the composition and properties of dispersive soils of various degrees of water saturation is experimentally studied. The analysis of the causes of the reservoir destruction used for storage of fuel oil is given. It was established that the development of microbial activity at its base led to the transition of sands to quicksands, and moraine loams to quasi-plastic varieties. Intensive gas formation of methane and its homologues, nitrogen, carbon dioxide, hydrogen in sands was recorded. Based on the analysis of the results of long-term monitoring of the effect of contamination of dispersive soils by oil products, their bearing capacity in the base of the structures has been reduced to 50% of the initial value. The role of microbial activity in the formation of an aggressive environment in relation to building materials is shown.
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Date submitted2017-04-30
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Date accepted2017-06-25
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Date published2017-10-25
On the connection of the hydrocarbons presence and epigenetic sulfides in the south of Yakutia
- Authors:
- M. S. Shkirya
- Yu. A. Davydenko
Currently the prospecting and exploration for hydrocarbons continues to be one of the most promising directions in geological exploration. The use of pulsed electrical exploration technique for prospecting of hydrocarbon reservoirs in combination with seismic prospecting makes it possible to significantly increase the probability of discovering the deposit, thereby lowering the likelihood of drilling an exploratory well that will not give an inflow. Also with the help of seismic exploration it is quite difficult to identify non-structural deposits. One of the reasons for the occurrence of anomalies caused by induced polarization (IP) is the epigenetic pyrite formed above the deposit as a result of the formation of a geochemical barrier at the boundary of the penetration of atmospheric oxygen. The presence of abnormally high values of induced polarization in the upper part of the section that differed from the background value within one of the deposits located at the southern part of Yakutia was manifested in the results of a one-dimensional inversion of the data from the electromagnetic sounding and induced polarization (EMS-IP) technology, performed within the polarizing horizontally layered model of the medium, in which the frequency dependence of the resistivity is described by the Cole-Cole formula. The idea of EMS-IP is to maximize the full use of information from transient processes induced by rectangular polarity pulses that are used in traditional DC methods. For the EMS-IP method, a high resolution and depth of study were obtained using the mean gradient setup. The investigated anomaly of the induced polarization is present at a depth of about 150 m and is confined to the pyritized interval of intensely fractured rocks of the Jurassic deposits, which is confirmed by a core sample data selected from the exploration hydrogeological wells. The one-dimensional mass inversion of the data showed sensitivity to the layer with an abnormally high value of the IP. The discrepancy in the model containing the pyrite layer is much higher than in the model not containing the pyrite layer.
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Date submitted2017-05-11
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Date accepted2017-07-12
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Date published2017-10-25
Geochemistry of spinels from xenoliths of mantle lherzolites (sverre Volcano, spitsbergen Archipelago)
The paper presents the results of a study (LA-ICP-MS method) of spinel from the collection of mantle xenoliths of lherzolites (seven xenoliths) selected in quaternary alkaline basalts of the Sverre volcano, the Spitsbergen archipelago. The study of two large (more than 15 cm in diameter) xenoliths made it possible to study changes in the composition of minerals in the central, intermediate, and marginal parts of the samples of chromium diopside spinel lherzolites. The sinusoidal character of the REE distribution in spinels, which indicates the manifestation of mantle metasomatism, is established. The results obtained for the first time on the trace-element composition for spinels from mantle xenoliths in alkaline basalts of the Spitsbergen archipelago are supplemented by data on the geochemistry of spinels of mantle origin published in the world literature.
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Date submitted2017-05-01
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Date accepted2017-07-06
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Date published2017-10-25
Prospects of hydrocarbon deposits exploration using the method of induced polarization during geomagnetic-variation profiling
- Authors:
- K. M. Ermokhin
Traditionally it is believed that the effect of induced polarization is an interfering factor for the measurement of electromagnetic fields and their interpretation during conducting works using magnetotelluric sounding and geomag-netic-variation profiling methods. A new method is proposed for isolating the effects of induced polarization during geomagnetic-variation profiling aimed at searching for hydrocarbon deposits on the basis of phase measurements during the conduct of geomagnetic-variation profiling. The phenomenon of induced polarization is proposed to be used as a special exploration mark for deep-lying hydrocarbon deposits. The traditional method of induced polarization uses artificial field sources, the powers of which are principally insufficient to reach depths of 3-5 km, which leads to the need to search for alternative - natural sources in the form of telluric and magnetotelluric fields. The proposed method makes it possible to detect and interpret the effects of induced polarization from deep-seated oil and gas reservoirs directly, without relying on indirect signs.
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Date submitted2017-03-25
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Date accepted2017-05-06
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Date published2017-08-27
Prospects of gas hydrate presence in the Chukchi sea
The purpose of this study is to forecast the scale and distribution character of gas hydrate stability zone in the Chukchi Sea under simulated natural conditions and basing on these results to estimate resource potential of gas hydrates within this area. Three types of stability zone have been identified. A forecast map of gas hydrate environment and potentially gas hydrate-bearing water areas in the Chukchi Sea has been plotted to a scale of 1:5 000 000. Mapping of gas hydrate stability zone allowed to give a justified forecast based on currently available data on geologic, fluid dynamic, cryogenic, geothermal and pressure-temperature conditions of gas hydrate formation in the Chukchi Sea. It is the first forecast of such kind that focuses on formation conditions for hydrates of various types and compositions in the Arctic seas offshore Russia. Potential amount of gas, stored beneath the Chukchi Sea in the form of hydrates, is estimated based on mapping of their stability zone and falls into the interval of 7·10 11 -11.8·10 13 m 3 .
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Date submitted2017-03-21
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Date accepted2017-04-30
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Date published2017-08-27
Petrophysical approach to electrical properties of loose soils
- Authors:
- V. A. Shevnin
- D. A. Kvon
- A. A. Ryzhov
The paper focuses on the relation between geoelectrical characteristics of the soil: resistivity, polarizability and normalized polarizability (ρ, η, M n ) – and its superficial conductivity (SC or σ") using methods of vertical electrical sounding with induced polarization (VES-IP), electric profiling with induced polarization (EP-IP) and frequency characteristic (FC-IP). The authors demonstrate that superficial conductivity can be determined not only from spectral IP data, but also from soil resistivity obtained through petrophysical measurements. In this case normalized polarizability (M n ) is equal to superficial conductivity (SC). Superficial conductivity, in its turn, is proportionate to clay content of the soil. Increasing clayiness reduces hydraulic conductivity. It has been demonstrated that interpretation of EP-IP results benefits from combined study of the plots of three abovementioned parameters (ρ, η, M n ). In the aeration zone, incomplete humidity has a significant effect on geoelectrical parameters of the soil. Petrophysical modelling helps to investigate the impact of humidity.
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Date submitted2017-01-08
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Date accepted2017-02-25
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Date published2017-06-25
Age of hydrothermal processes in the central iberian zone (Spain) according TO U-Pb dating of cassiterite and apatite
Results of isotope-geochemical studies by PbLS step-leaching method of cassiterite from greisens located in Logrosán granite massif (Central Iberian Zone, Spain) and apatite from hydrothermal quartz-apatite vein on its exocontact indicate that in both cases a hydrothermal event is recorded in the interval of 114-126 Ma, which has been accompanied by lead supply. Within the limits of estimation error, the same age around 120 Ma corresponds to crystallization of hydrothermal apatite, formation of sticks and micro-inclusions in cassiterite from greisens and is suggested for Au-As-Sb-Pb ore mineralization, which calls for further confirmation. Xenogenous zircon from quartz-apatite vein does not react to this relatively low-temperature hydrothermal event either with building up new generations (sticks, areas of recrystallization) or with rebalancing of U-Pb isotope system. The age of greisen formation has been confirmed to be around 305 Ma by PbLS method on final phases of cassiterite leaching. Earlier it was estimated with 40 Ar/ 39 Ar method on muscovite.
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Date submitted2017-01-07
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Date accepted2017-03-21
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Date published2017-06-25
Modeling of geochemical processes in the submarine discharge zone of hydrothermal solutions
- Authors:
- S. M. Sudarikov
The paper reviews the main methods and analyzes modeling results for geochemical processes in the submarine discharge zone of hydrothermal solutions of mid-ocean ridges. Initial data for modeling have been obtained during several marine expeditions, including Russian-French expedition SERPENTINE on the research vessel «Pourquoi Рas?» (2007). Results of field observations, laboratory experiments and theoretical developments are supported by the analysis of regression model of mixing between hydrothermal solutions and sea water. Verification of the model has been carried out and the quality of chemical analysis has been assessed; degree and character of participation of solution components in the hydrothermal process have been defined; the content of end members has been calculated basing on reverse forecasting of element concentration, depending on regression character; data for thermodynamic modeling have been prepared. Regression model of acid-base properties and chloridity of mineralizing thermal springs confirms adequacy of the model of double-diffusive convection for forming the composition of hydrothermal solutions. Differentiation of solutions according to concentrations of chloride-ion, depending on temperature and pH indicator within this model, is associated with phase conversions and mixing of fluids from two convection cells, one of which is a zone of brine circulation. In order to carry out computer thermodynamic modeling, hydro-geochemical and physicochemical models of hydrothermal discharge zone have been created. Verification of the model has been carried out basing on changes of Mn concentration in the hydrothermal plume. Prevailing forms of Mn migration in the plume are Mn 2+ , MnCl + , MnCl 2 . Two zones have been identified in the geochemical structure of the plume: 1) high-temperature zone (350-100 °С) with prevalence of chloride complexes – ascending plume; 2) low-temperature zone (100-2 °С), where predominant form of transfer is a free divalent ion – lateral plume. Sulfate complex in insignificant quantities (1.5 %) is detected in the lateral plume, whereas hydroxide complex is stable at temperatures 325-125 °С and can only be found in the ascending plume. Results of modeling almost fully correspond to field observations. Verification of thermodynamic model proves its adequacy and allows to make a transition to the next stage of research – examination of geochemical dissipation for key ore components of hydrothermal solutions – Fe, Cu, Zn etc.
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Date submitted2016-11-03
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Date accepted2016-12-27
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Date published2017-04-25
Evolution of mineral forms of rare element accumulation in ore-bearing granites and meta-somatites of Verkhneurmiysk ore cluster (Priamur region)
It has been attempted to expand existing understanding of accessory mineralization evolution of rare metal-granite series at post-magmatic stage of their development and formation of associated hydrothermal deposits. Composition and distribution of rare elements of Verkhneurmiysk ore cluster have been examined from the position of mineralogy: the study focused on accessory and ore minerals Sn, W, Nb, Ta, Bi, Y, rare earth elements in rare metal Li-F granites and associated metasomatites. It has been discovered that accessory magmatic and hydrothermal mineral complexes share the same geochemical features, are formed under the leading role of abovementioned elements and consistently follow each other over time. It has been traced how mineral forms of accumulation of Sn, W, Nb, Ta, Y and rare earth elements evolve in the processes of magmatic crystallization and post-magmatic metasomatism in the time series: rare metal granites → zwitters → tourmalinites → chloritites. Mineral rocks of each stage were noted to inherit mineralogical and geochemical distinctions from the rocks of the previous stage. A significant number of minerals, forming in the course of two-three stages, have been discovered, as well as omnipresent magmagene-hydrothermal minerals. For a number of accessory minerals of rare metal granites post-magmatic generations have been identified. Special diversity among accessories of rare metal granites and zwitters was observed in tungsten, tin and bismuth minerals. Composition of Verkhneurmiysk ore cluster mineralization is in many aspects similar to the one of metasomatic accessory minerals of rare metal granites. Tungsten-tin deposits of Verkhneurmiysk ore cluster are polyformational and combine mineralogical features of cassiterite-quartz and cassiterite-silicate formations. Evolution of mineral forms of the key rare elements (Sn, W, Bi, Nb, Ta, rare earth elements) points to a genetic link between tungsten-tin mineralization of zwitter-tourmalinite formation and rare metal Li-F granites of the region. The evidence of that is a specific genetic category of accessory materials, formed as a result of pseudomorphism of protominerals, – transformational minerals or metasomatic accessory minerals. The list of metasomatic accessories includes exactly those minerals which are considered indicators of ore generation capacity of Far Eastern leucogranites: cassiterite, wolframite, scheelite, a number of sulphides. Similar qualitative composition of magmatic and post-magmatic minerals demonstrates metallogenic specialization of parent granite magma. Predicted mineragenic significance of research in the field of mineral forms evolution of rare elements accumulation in ore-bearing granites and metasomatites is associated with possibilities to assess metallogenic specialization of parent granite magma. Understanding of accessory paragenesis evolution should serve as a base for exploration geo-technologies in the Far East metallogenic province.
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Date submitted2016-10-30
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Date accepted2017-01-02
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Date published2017-04-25
Result of combining data from impulse electrical prospecting and aeromagnetic prospecting for groundwater exploration in the south of Yakutia
In 2014 in the south of Yakutia in the course of groundwater exploration works a complex of geophysical methods was tested: aeromagnetic and electrical prospecting was carried out using near-field transient sounding and electromagnetic sounding with induced polarization. Prospective structures for hydrogeological drilling are zones of discontinuous tectonic faults. In order to identify them, data from aeromagnetic and electrical prospecting were used. Results of drilling confirmed the presence of watered areas; however, analysis of obtained information allowed to come to the conclusion that the amount of water in the faults has no direct connection to electrical conductivity.
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Date submitted2016-10-26
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Date accepted2016-12-29
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Date published2017-04-25
Inversion modeling of the natural state and production history of Mutnovsky geothermal field in 1986-2006
- Authors:
- A. V. Kiryukhin
- O. O. Usacheva
Numerical 3D model of Mutnovsky geothermal field (Dachny springs), which consist of 517 elements and partially takes into account double porosity, was developed in 1992-1993 using computer program TOUGH2. Calibration of the model was based on data from test yield of the wells and initial distribution of temperature and pressure in the reservoir. This model was used for techno-economic justification of power plant construction (Mutnovskaya GeoES, 2002). The model was recreated in the program PetraSim v.5.2, the calibration was carried out using additional data on production history before year 2006 and inversion iTOUGH2-EOS1 modeling. Comparison of reservoir parameters, estimated using inversion modeling, with previous parameter estimations (given in brackets) showed the following: upflow rate of heat-transfer agent in natural conditions 80.5 (54.1) kg/s, heat flux enthalpy 1430 (1390) kJ/kg, reservoir permeability 27∙10 –15 -616∙10 –15 (3∙10 –15 -90∙10 –15 ) m 2 . Inversion modeling was also used to estimate reinjection rates, inflow of meteoric water in the central part of geothermal field and compressibility of reservoir rocks.
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Date submitted2016-11-11
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Date accepted2017-01-21
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Date published2017-04-25
Conducting lithospheric heterogeneities as a criterion of predictive assessment for promising diamond areas (on the example of Siberian kimberlite province)
- Authors:
- E. V. Pospeeva
Results of magnetotelluric tests, carried out in Siberian kimberlite province, are examined from the viewpoint of structural control over location of kimberlite fields and bunches of kimberlite pipes. It is demonstrated that the key factors controlling occurrence of kimberlite magmatism are: deep systems of rift-driven fractures; areas of their intersection within high-ohmic blocks of Earth crust; conducting permeable areas, located at the intersections of deep faults. Various-rank objects of kimberlite magmatism are characterized by a certain combination of geoelectric heterogeneities, differing in resistance, lateral sizes and depth. The province is situated within the boundaries, limited by isolines 180-220 km of current asthenosphere; kimberlite areas – within the contours of high-resistance regional heterogeneities. Fields and bunches of kimberlite pipes are concentrated within boundaries of conducting subvertical zones. These factors can be used as criteria of predictive assessment for promising diamond areas of the ancient platforms.
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Date submitted2016-11-18
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Date accepted2016-12-28
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Date published2017-04-25
Frequency electromagnetic sounding with industrial power lines on Karelia-Kola geotraverse
The paper describes theory, method and first experimental results of research on the interaction between electromagnetic waves of extremely low and ultra low frequency (0.1-200 Hz), the Earth crust and ionosphere in the field of two mutually orthogonal industrial power lines, 109 and 120 km long, in the course of FENICS experiment (Fennoscandian Electrical conductivity from Natural and Induction Control Source soundings). The main focus was on the observation results along the line of Karelia-Kola geotraverse over a distance of 700 km from the source. High horizontal homogeneity of geoelectrical lithosphere section has been detected in the eastern part of the Baltic shield at depth range from 10-15 to 50-70 km. Parameters of «regular» lithosphere section have been specified to the depth of 60-70 km. As a result of inverse problem solution for the western part of Karelia and Central Finland, a zone of decreased transverse resistivity has been detected at the depth of 50-60 km, corresponding to the area, detected by seismic methods, where Moho boundary reaches the same depth.