Original article Neotectonic formation and localization conditions of groundwater reserves in over-deepened sections of the Kitoy River valley

The purpose of the study is to identify the main neotectonic formation features of over-deepened valleys where fresh groundwater is localized. The object and the subject of the study is the Kitoy deposit of drinking groundwater located in the U-shape valley of the Kitoy river, which is composed of constratal alluvium, as well as hydrogeological and hydrogeochemical conditions of the deposit. The study of the over-deepened alluvial dislocation is carried out based on the analysis of the works performed at the Kitoy fresh groundwater deposit for the period from 1956 to 2020. The deposit is located at the southern margin of the Siberian platform within the Irkutsk-Cheremkhovo plain. The article studies the origin of the dislocation formed by the intersection of waves of pitching and subsidence of the Baikal and Sayan directions accompanied by the groundwater localization. The described over-deepened valley is 9-39 m thick. It is represented by boulder-gravelpebble material with sandy aggregate. The average filtration coefficient for the deposit is 122 m/day, the average water permeability coefficient is 3400 m2 /day, whereas beyond its limits the indicators decrease. The qualitative composition of groundwater meets the standards, but some areas feature increased mineralization, high content of iron and manganese due to the inflow of groundwater from the underlying Jurassic aquifers. The authors made a generalization on the variations of the effective thickness of the aquifer and analyzed the favorable conditions for the formation of fresh groundwater within the depression structure for the purpose of water supply for drinking and household uses.

Analytical Resources of Digital Procedures in Monitoring and Controlling the Processes in Drilling the Wells

Drilling is traditionally considered as one of the most challenging and expensive areas in oil and gas industry, and its efficiency, against the background with the of unstable forecast in current situation with growing oil prices, both defines the efficiency of capital investments at well construction stage and the cost of production as a whole. Changing drilling conditions, such as well depths, their complicated architectures due to reservoir depletion and their complex localization conditions, pose the task of attracting advanced technologies aimed at modifying the labor process, reduction in costs and increase in production efficiency ("GazpromNeft", 2015). However, not all such procedures are mass-produced due to high price that you need to pay for them, as well as possible limitations of obtaining these technologies. There is a need to implement the tasks in short term with the available resources without involving any expensive equipment and additional personnel (Litvinenko et al., 2017). This opportunity is opened by effective data management in the progress of well construction as well as in information and analytical supporting tools that allow you to receive, process and control this data in a short time and to take the appropriate management decisions based on it (Ivanov, 2017). Of course, one of the foundations in the controlling over the industrial processes is the reference book of time standards to perform basic operations in drilling and casing the wells (Unified Time Regulations in Process, 1987), which is mainly aimed at preventing unjustified costs during the process of well construction (excess time), planning the duration of operations, conducting procedures to select the applicants for work.

Molybdenum mineralization of Serhiivka Au-Mo deposit (Middle Dnipro, Ukrainian Shield)

The article is devoted to molybdenum mineralization of the Eastern flank of Au-Mo Serhiivka deposit, located in the Middle Dnipro megablock of the Ukrainian Shield (USh). The generalized description of mineralization is performed on such important questions: discovery and exploration history, structure and composition of the host rocks, metamorphic and metasomatic alteration of rocks, structural position and localization conditions of molybdenum mineralization, ore composition, description of major ore minerals, morphology of mineralization and the most widespread views about its genesis. Molybdenum ores were discovered and named East-Serhiivka occurrence for the first time in 1974, before the discovery of gold mineralization, which occurred in 1985. Serhiivka deposit consists of two Mesoarchaean volcanic-plutonic associations (VPA) of different composition: the early mafic and the late felsic. The Eastern flank of the deposit, where the molybdenum mineralization is concentrated, is a structural knot similar to the lying letter “T”. It is formed by complex joint of the sub-latitudinal Serhiivka and sub-meridional Solone subvolcanic bodies and the East-Serhiivka massif of plagiogranitoids of the late VPA, which intrude basic rocks of early VPA. Molybdenum mineralization is localized in linearly elongated zones with a chaotic network of thin quartz, carbonate-quartz veinlets and poor (2–5 %) sulfide impregnation, including molybdenite. About 20 vein-impregnated ore zones have been recovered with up to 100–150 m thickness and 0,01 to 0,3 %, sometimes more than 1 % average molybdenum grade. The ores are subdivided into two major mineral types: 1) quartz-molybdenite; 2) quartz-sulfide-gold-molybdenite. The main components of ores molybdenite and native gold are associated with pyrite, chalcopyrite, magnetite, occasionally – pyrrhotite, arsenopyrite, scheelite, bismuth telluride, silver and others. Typical non-metallic minerals are quartz, carbonate, feldspar, chlorite, amphibole, biotite, sericite. It is supposed hydrothermal-metamorphogenic genesis of molybdenum (and gold) ores. Molybdenite and gold are rarely detected in the same intersections, which indicates separate genesis of these minerals. According to the accepted classification molybdenum mineralization is systemized as linear stockwork. Molybdenum ores of Serhiivka deposit are mostly considered as independent, separate from gold mineralization, potentially workable mine. It is the most prospective one in the Middle Dnipro region, USh and Ukraine in general. We suggest a comprehensive approach to studying, resource and reserves evaluation of Serhiivka deposit, taking into account the potential of both molybdenum and gold mineralization, as well as concentrations of rhenium and osmium in molybdenite. Geological exploration on the base of this approach will increase investment prospects of Serhiivka gold-molybdenum deposit.

Analysis of the spatial patterns in localization of gold mineralization relative to the system of deep faults in the Chortomlyk greenstone structure of the Ukrainian shield

The results of analysisof the patterns of the spatial relationship between hydrothermal gold ore formations and the zones of metasomatites and systems of deep faults within the Chortomlyk greenstone structure of the Middle Pridniprovie megablock in the Ukrainian Shield are given. As a result of studying the localization conditions of gold mineralization, it was established that the gold-bearing mineralization is confined to tectonically fractured zones and is localized among metasomatically altered rocks. The hydrothermal series of metasomatites in the Chortomlyk greenstone structure is represented by greisens, propylites, amphibole-carbonate metasomatites and listvenite-berezites. The mineralization of Au and Mo is associated with metasomatites of the greisen type. The study of spatial relationship between the fields of metasomatites and the gold mineralization and zones of deep faults revealed that the closest relationship is expressed with systems of faults with azimuths of 0° and 270°, 17° and 287°, 77° and 347°. The results of the studies allowed us to develop a newprospecting criterion, which, in turn allows us to state that the gold mineralization within the Chortomlyk greenstone structure is spatially confined to metasomatites related to the schistosity, fracture, millonitization, and cataclase zones with high content of sulphide mineralization. These zones are localized in nodes of intersecting faults of the first order of the system 77° and 347° with discontinuous violations of high orders of azimuths of 0° and 270°, 17°and 287°. The results of the research can be used to develop a set of predictive criteria and the allocation of promising sites of hydrothermal mineralization of gold within the Chortomlyk greenstone structure of the Middle Pridniprovie megablock in the Ukrainian shield.