Department of geochemistry of sedimentary series of oil- and gas-bearing provinces

The head of the department  - PhD in Geology Anatoliy R. Galamay

• The department was created in 1969 under the name «Department of Salt Structures of Oil and Gas-bearing Regions». Corresponding Member of the National Academy of Sciences of Ukraine Vasyl I. Kityk was appointed the first head of the department. Doctor of Geological and Mineralogical Sciences, Professor Oleg Y. Petrychenko was headed the department from 1984 to 2007. The duties of the head of the unit from 2007 to 2015 were performed by the PhD in Geological and Mineralogical Sciences Igor V. Dudok, and since 2015 was the PhD in Geology Sergiy V. Vovnyuk. Since 2019, the department has been headed by the PhD in Geology Anatoliy R. Galamay. The basis of the department’s activities is natural research of deposits of evaporite formations in order to study the composition and structure of the Earth, the evolution of its geospheres. They include geological, mineralogical, geochemical, paleoclimatic, hydrological, oceanological, palynological studies and are aimed at a comprehensive study of the problems of halogenation: the physicasl and chemical parameters of the sedimentation environment and recrystallization of salts, questions the evolution of the seawater composition as a component of the general historical development of the Earth. Using a complex of methods: thermobarogeochemical (ultramicrochemical, thermometric, barometric), mineralogical-petrographic, isotopic, electron-microscopic, chemical, X-ray spectral, X-ray diffractometric and other methods, criteria for searching for minerals associated with evaporites (primarily oil, gas, trace elements, valuable forms of complex sulfate potassium-magnesium salts for the production of fertilizers). the development of criteria for searching for minerals (primarily oil, gas, trace elements, valuable forms of complex sulfate potassium-magnesium salts for the production of fertilizers), associated with evaporites in general and with salt structures in particular. The department actively develops the world-famous scientific thermobarogeochemical school of evaporites study formed in previous years and obtains fundamental and applied achievements of world level in the field of geochemistry and thermobarometry of mineral-forming solutions. The chemical composition of brines of fluid inclusions in salts is determined by a unique ultramicrochemical (UMСА) method, developed in the late 60s of the 20th century at the IGGKM of the National Academy of Sciences of Ukraine by Doctor of Geological and Mineralogical Sciences, Professor Oleg Y. Petrychenko. This method allows the determination of basic (K, SO₄, Cl, Ca, Mg) ions in a microvolume (up to 0.00006 mm³) of brine. When creating the method, the idea of ​​quantitative determination of components in brines by the volume of precipitate obtained as a result of the reaction of brine with the appropriate reagent was used. The reactions are carried out in manufactured capillaries, which are glass tubes with a diameter of 200–250 μm with a conical end with a diameter of 4–9 μm. The time for determining one component in brine (from brine extraction to sediment measurement) is less than 20 minutes. In terms of ease of use, the ability to analyze microvolumes of brines, and good convergence of measurement results, the UMСA method is currently the most advanced among other methods (LA-ICP-MS, Cryo-SEM-EDS, ESEM-EDS, Extraction-IC) for determining the chemical composition of inclusion brines. Since the creation of the UMСA method and up to the present time, its methodology has been constantly improved. In recent years, the department has modernized the method, which has allowed reducing the error of a single determination by more than two times. Thermobarometric studies are carried out in the department by the thermometric method using the thermal chamber of Doctor of Geological Sciences, Prof. Volodymyr A. Kalyuzhny, the design features of which were slightly changed for the study of salt minerals in the department by Doctor of Geological Sciences, Prof. Oleg Y. Petrychenko and Doctor of Geological Sciences, Prof. Volodymyr M. Kovalevich. In recent years, the department's staff has developed a new design of the thermal chamber and the entire measuring setup to improve the accuracy and reproducibility of measurements. These improvements have allowed us to achieve high system stability and good reproducibility of measurement results.

The department has two certified laboratories:

• a) X-ray diffractometric analysis;
• b) analytical methods of analysis.

Laboratory certifications were carried out in 2023:

• a) certificate No. RL 034/23 (laboratory of X-ray diffractometric analysis);
• b) certificate No. RL 015/19 (laboratory of analytical methods of analysis).

The accumulation of significant factual material obtained by the department employees has made it possible to identify global age-related fluctuations in the chemical composition of sea water (from SO₄-rich to Ca-rich type) over the last 545 million years. The limits of fluctuations in the chemical composition of sea water from year to year are being clarified based on the results of research into previously unstudied salt-bearing basins. Among the achievements of the department's scientists in recent years, the following should be mentioned:

• a) for the first time, the paleoclimate of the Carpathian region (Ukraine, Poland, Romania, Slovakia) was reconstructed at the Mi3b stage and the Messinian of Southern Turkey, which resolves some controversial issues of the tectonic features of the structure of ancient continental margins in general and sedimentation in the Badenian and Messinian salt basins in particular;
• b) for the first time, based on the results of the study of halite from the Ordos Basin (China), the chemical composition of Ordovician seawater was reconstructed and the limits of fluctuations of calcium and sulfate ions, which determine the type of seawater, were clarified;
• c) the source of salts from the Tuz Gölü Basin (Turkey) was established, the genesis of which caused sharp controversies among the scientific community. The concentration of sedimentary brines of the Basin and the content of ions indicate the lack of prospects for detecting potash layers in the salt section, but its high prospects for detecting glauberite layers;
• d) for the first time, the physical and chemical features of halite crystallization in four basins of East China were established, which indicate the existence of marine Paleogene transgressions in the region with continental halogenation, which has been the subject of scientific discussions in the petroleum geology of China for over 70 years. A direct correlation was established between the data of the study of microorganisms in halite and ultramicrochemical studies;
• e) for the first time, the features of the physical and chemical conditions of polyhalite formation in individual salt-bearing basins were established, which complement the theoretical component of polyhalite mineralization in fundamental and applied studies of polyhalite and are geochemical criteria for the prediction of polyhalite deposits;
• f) it was established that the distribution of high-magnesium clay minerals in marine evaporites during the Phanerozoic correlates with age-related changes in the chemical composition of sea water. Magnesian minerals are confined to the stages of its SO₄-rich type, which is one of the confirmations of the interconnection of geological processes of Earth's evolution;
• g) it was established that the associations of clay minerals of the Early Eocene rock salt of Pakistan allow us to clarify the time of the transition of the chemical type of sea water from Ca-rich type to SO₄-rich type. The change in the type of sea water of this stage of the Phanerozoic occurred not in the Early Eocene, as previously believed, but in the Paleocene.

To solve the actual scientific and practical tasks of finding minerals related to salt-bearing formations, scientific and technical cooperation is currently being carried out with scientific research organizations, geological institutions of Ukraine and foreign countries: Ukraine (State Institution State Scientific Research and Design Institute of Basic Chemistry (NIOCHIM), Kharkiv; Poland (Akademia Gόrniczo-Hutnicza, Krakόw), Turkey (Department of Geological Engineering, Engineering and Natural Sciences Faculty, Konya Technical University, Konya, Türkiye); China (University of Mining and Technology, Xuzhou, Jiangsu Province, China). The department has 10 employees, among them 5 candidates of sciences and 3 leading engineers.