Genesis and geochemical features of rare metal mineralization in the brown coal of Transcarpathia

Abstract

Background. On January 17, 2025, Law of Ukraine No 4154-IX "On Amendments to Certain Legislative Acts of Ukraine Regarding Updating the State Program for the Development of Mineral and Raw Materials Base of Ukraine for the Period Until 2030 and Regulation of Certain issues Regarding Minerals and Components of Strategic and Critical importance", amending the Code of Ukraine on Subsoil and the National Program for the Development of the Mineral and Raw materials Base of Ukraine for the Period Until 2030 was passed. Current research is aimed at the complex study of coal deposits development with extraction of associated minerals and components. In addition, the possibility of obtaining rare earth and other valuable components from brown coal and stockpiles is being considered. Transcarpathia, as one of the regions of Ukraine, known for its deposits of brown coal, which contain rare metals and rare earth elements, attracts attention of scientists.

Methods. The research on the genesis of rare metal mineralization, analysis of the influence of volcanic and hydrothermal processes on the formation of brown coal and rare metal mineralization is focused on:

• analytical methods: use of modern analytical methods, such as inductively coupled plasma mass spectrometry (ICP-MS), to determine the concentration of rare metals;
• modeling processes: development of models to describe the behavior of rare metals during carbonization and the influence of various factors on their distribution;
• economic assessment: assessment of the potential of the extraction of rare metals from brown coal as an additional reservoir of valuable elements.

It should be noted that rare metal mineralization in brown coal is an important object of investigation due to its economic significance and unique geochemical characteristics. During the period of field work, the Transcarpathian Geological Survey Party of the Institute of Mineral Resources selected and analyzed >3000 samples of brown coal and carbonaceous sedimentary materials and volcanic rocks. What is important is the number of samples collected from core material (Began, Berezinka, Rokosovo, Novoselytsya, Kriva), as well as from Girnichy extractions (Ilnytsia - mine No. 33, Gorbki – mine No. 29-bis). Based on the results of various analyses, it was established that some rare and rare earth metals are associated with organic parts of coal, some are concentrated in the ash part and thereby enrich terrigenous material with microelements, which gradually become present in brown coal.

Results. The clear and simple differences in the storage of microelements, as established by analyses, are determined by the specificity of volcanic and hydrothermal activity in various regions of Transcarpathia, and by the peculiarities of paleogeographic formation of coal deposits. The study of the forms of accumulation of microelements in brown coal is of great importance not only for the development of certain genesis, but also allows us to assess the prospects of brown coal for its industrial value. Recently, a number of methods of mathematical statistics, including coefficients of rank correlation, have been able to identify a number of elements, the accumulation of which is generated synchronously, which opens up new prospects for a complex history of Transparpathian brown coal. The combination of microelements in brown coal and clarke in the earth's crust clearly indicates the role of organic matter in concentrating rare metals and rare earth elements.

Conclusions. The results show that the brown coal seams of Transcarpathia are rich in rare and rare earth metals such as germanium, indium, gallium, strontium, scandium, nitrium, terbium, lanthanum under the influence of several factors:

1. Hydrothermal processes: Transcarpathia has an active geotectonic history, which resulted from the circulation of hydrothermal vents through sedimentary rocks, which led to the enrichment by rare metals.
2. Post-sedimentary changes: Organic brown coal deposits can become clayey and accumulate metals during diagenesis and catagenesis.
3. Local rocks: The presence of volcanic rocks in the region is an additional source of rare metals.

Investigations into the geochemistry of brown coal also indicate the ongoing influence of local tectonic structures. The understanding of the genesis and geochemical features of rare metal mineralization in the brown coal of Transcarpathia is the key for the effective development of these resources. Further study will involve the development of new methods of extraction and processing, as well as the deeper understanding of geological processes that lead to the formation of such unique deposits. A comprehensive approach, including geochemical, mineralogical, ecological, and economic analyses, will allow not only understanding the mechanisms of mineralization, but also assessing the prospects for using these resources in the future.