Basites of Vilyui-Markhinsky dike belt (Vilyui paleorift) and their relations with Nakyn field kimberlites

The Vilyui-Markhinsky dike belt (VMDB), which was formed as a result of Devonian rifting on the eastern margin of the Siberian Platform, is the marginal part (area of scattered rifting) of the Vilyui paleorift structure. The Nakyn field is located in the central part of the belt, but is controlled by an independent system of NNE-trending tectonic faults. The belt dyke intrudes the Nyurbinskaya kimberlite pipe. On their contact, specific breccias were formed resulting from the interaction between degassing products of basic magma with kimberlites. The typical zonality of the dyke endocontact indicates a later dyke introduction. Dolerite dikes thermally metamorphosed breccias in which high-temperature neoplasms of andradite, Al-lizardite, and clinochrysotile were generated. VMDB basites represent a single association, in which two series of rocks are distinguished: moderate-titanium (TiO2 ~ 2.5 wt. %) with normal alkalinity and low P2O5 content, and high-titanium (TiO2 ~ 4.4 wt. %), occasionally with moderate alkalinity. The differences in the dike composition are insignificant and are the result of natural variations in the composition of individual bodies. 40Ar/39Ar dating of the VMDB basites, the method characterized by the best results convergence, shows that they formed in a narrow timeframe corresponding to the Upper Frasnian – Famenian stage of the Upper Devonian (368.5 to 376.3 Ma). The location of the Nakyn field basites and kimberlites is controlled by faults of various types, orientation and age. Kimberlites formed first, and VMDB intrusions followed.

On the Issues of Spatial Modeling of Non-Standard Profiles by the Example of Electromagnetic Emission Measurement Data

This paper examines the possibility of the spatial modelling of the Earth’s natural pulsed-electromagnetic-field measured values, which form a closed profile without the data inside. This geophysical method allows us to map active tectonic movement which breaches the integrity of pipes. During the experiment, 4.5 km of profiles were measured in the Admiralteysky district of St. Petersburg, Russia. Regular electromotive force (EMF) values and anomalous EMF values were obtained, ranging from 0 to 900 µV and above 900 µV, respectively. The anomalous values are associated with tectonic faults in the bedrock. The data obtained are characterized by complex spatial anisotropy associated with the development of two groups of tectonic faults of different orientations. The authors have considered the problems of the spatial modeling of the data obtained. The main problems, the solutions to which should allow the obtaining of adequate models, have been identified. Based on the analysis of the measurement results, geological features of the studied areas, as well as variography, the following possible solutions were proposed: changing the measurement technique; dividing the data array according to the main directions of anisotropy; the need to introduce additional correction coefficients. The problem revealed in this article requires further research on the basis of the obtained results, which will reduce the cost and timing of such studies, and, as a result, give an opportunity to take into account active tectonic disturbances during the construction and scheduled maintenance of underground utilities, which is especially important within the framework of the concept of sustainable development.

A hydrogeochemical approach to the characterization of low-enthalpy geothermal systems: the Scordia – Lentini graben (Sicily, Italy)

We describe the geochemical characteristics of groundwater samples collected in 23 water wells located on the northern margin of the Hyblean plateau (East Sicily). This area, mostly made of highly permeable carbonate rocks, is rich in low temperature (T < 50° C) hydrothermal groundwaters, distributed in an active sismogenetic zone, with several ENE-WSW-directed tectonic structures that drove magma to the surface during Upper Pliocene and Pleistocene. The chemical features suggest complex mixing between rainwater, CO2-rich groundwater, steam-heated groundwater and geothermal brines, as highlighted by Principal Component Analysis (PCA). Some parameters, however, indicate widespread pollution of the aquifers from human activities. Stable isotopes analysis confirms the meteoric origin of groundwater and supports the origin of dissolved CO2 mostly from mantle degassing through deep tectonic faults. Geothermometric estimates, mostly based on quartz and Saturation Indexes geothermometers, suggest minimum reservoir temperature between 100 and 120° C.

Volcanic and fault-fractured ore-controlling structures and minerals of the Azerbaijan part of the Lesser Caucasus

This article is focused on volcanic and fault-fissure ore-controlling structures of the Lesser Caucasus. The territory of the Lesser Caucasus is dissected by many deep tectonicfaults, along which volatile compound sofpostmagmatic products and water vapor migrate from great depths. The presence of numerous tectonic deep faults, which provide hydrodynamic connection of waters of fracturse, and fracture-veins, determines the complex mineralization of the chemical and gas composition of mineral-thermal waters throughout the studied area. The study of volcano-intrusive and fault-fracture ore-controlling structures, volcanogenic formations, petrochemical composition of rocks and associated mineral deposits and mineral-thermal waters of the Azerbaijan part of the Lesser Caucasus is relevant from a scientific and practical points of view. A detailed study of the modern structure of the Lesser Caucasus shows that transverse rupture faults and deep flexures cut through the folded system. Deposits of various minerals, including mineral and thermal waters, are confined to these ruptured faults. The study revealed that the formation and discharge of numerous outcrops of carbonic mineral and thermal waters occurs mainly in fissure systems, in deep tectonic faults. In the Lok-Karabakh zone, most of the sources of the formation of gold-bearing placers belong to the deposits and manifestations of the gold- quartz-low-sulphide formation. Gosha, Kedabek, Karadag, Chovdar, Dagkesemen, Gyzylbulag and less significant deposits and ore occurrences are located in this zone. The Dashkesan ore region is distinguished by the reserves of iron, alunite and cobalt. The Zaylik alunite deposits are world famous in terms of large reserves. Analysis of geological materials confirms that the origin and distribution of deep tectonic faults plays a major role in the formation of geological, including volcanoplutonic, metamorphic processes and associated ore formation. Currently, there are dozens of variously evaluated and explored gold deposits on the territory of the Republic. The bulk of the primary deposits are located in the Lesser Caucasus part of the Republic.

Peculiarities of Interaction of Underground and Surface Water in Zones of Disjunctive Tectonic Faults (on the Example of Eastern Donbass)

Eastern Donbass, where coal has been mined for over a century, has become a natural-technogenic system (NTS), affecting all components of the natural environment. Among the elements most affected by it are groundwater and surface water exposed to mine waters. The state of the NTS is due to the interaction of technogenic and natural factors such as the geological structure of the territory. For many years, the environmental assessment has taken into account the organized discharge of mine water. At the same time, this region is characterized by widespread development of disjunctive tectonic faults. The hypothesis seems logical that not only the treatment facilities of closed coal mining enterprises, but the faults and associated fracture zones are channels for the drainage of mine water and deep highly mineralized solutions to the surface, where they are unloaded into the river network. Studies carried out in one of the promising areas, where drainage of groundwater takes place through fractured rocks developed along the fault displacement fault, showed their significant impact on the composition of the surface waters of the river Small Nesvetay. Taking into account the very complex tectonics of the Eastern Donbass, it would be logical to assume a similar influence of other numerous disjunctive structures. Their study will contribute to a comprehensive assessment of the region&#x27;s environment and the adoption of management decisions, and the development of effective measures for water purification and stabilization of the ecological and social situation in the region.

Probabilistic estimation of reliability values for frame buildings based on the results of certification taking into account tectonic faults

With budget funding for two years in 2017-2018, the total certification of the housing stock of multi-apartment buildings was carried out for the first time. A total of 8,171 buildings were entered into the database, of which 1,847 are multi-storey frame buildings of various storeys and design solutions. It is established that 1628 frame buildings are earthquake-resistant, 59-buildings with the first flexible floor are non-earthquake-resistant and 160-are located in the zone of tectonic faults on the territory of the city. The hypothesis is accepted that buildings located in the zone of tectonic faults will be destroyed. Under these conditions, quantitative estimates of the failure probability and reliability values for frame buildings of various types were obtained for the first time. The frequency of earthquakes is taken into account according to the current "Map of seismic zoning of the Republic of Kazakhstan". The results of the reliability and failure estimates are used for practical recommendations to reduce the risk and expected losses in possible earthquakes. Total reinforcement of frame buildings with the first flexible floors (59 buildings) is proposed. However, the conditional probability of failure for a group of residential frame buildings will remain nonzero. The method of amplification should be determined based on the results of experimental studies.

Changing friction at the base of an Alpine glacier

Repeating earthquakes are a global phenomenon of tectonic faults. Multiple ruptures on the same fault asperities lead to nearly identical waveforms characteristic for these seismic events. We identify their microseismic counterparts beneath an Alpine glacier, where basal sliding accounts for a significant amount of ice flow. In contrast to tectonic faults, Alpine glacier beds are subject to large variations in sliding velocity and effective normal stresses. This leads to inter- and sub-seasonal variations in released seismic moment from stick–slip asperities, which we explain with the rate-and-state friction formalism. During summer, numerically modelled effective normal stresses at asperities are three times higher than in winter, which increases the local shear resistance by the same factor. Stronger summer asperities therefore tend to form in bed regions well connected to the efficient subglacial drainage system. Moreover, asperities organise themselves into a state of subcriticality, transferring stresses between each other. We argue that this seismic stick–slip behavior has potentially far-reaching consequences for glacier sliding and in particular for catastrophic failure of unstable ice masses.

USE OF A SATELLITE GEODESIC NETWORK IN THE QUASIGEOID MODEL

The article deals with the possibility of using seismic exploration in solving problems of ore geology in complex mining and geological conditions of Kazakhstan. The substantiation and characterization of geological and geophysical conditions for conducting experimental 3D seismic surveys at the deposits of the Zhilandinsky group of copper sandstones located in the Karaganda region of Central Kazakhstan are presented. The tasks are defined and the technique of conducting high-resolution 3D seismic exploration is developed, accompanied by modern processing and interpretation complexes for obtaining high-quality seismic materials for solving geological problems: studying the structural and tectonic structure of ore areas, identifying and refining ore-controlling structures, detecting and deep mapping of tectonic faults, volumetric mapping of intrusive massifs. The directions and technology of the process of modeling ore horizons and tracing them in space based on the results of a comprehensive interpretation of three-dimensional seismic exploration and geological and geophysical data, which will significantly increase the reliability coefficient of forecasting ore deposits, are indicated.