A Comprehensive Study of the Spatial Variations in the Distribution of Rare Earth Elements (REE) and Their Potential in the Coals of the Shubarkol Deposit, Kazakhstan

Due to the gradual depletion of traditional metallic mineral resources, the search for new potential sources is an important issue. One such source is coal deposits. The extraction of metals from coal is a way to produce clean energy. This study presents the results of detailed research on geochemical features and mineralogy to understand the processes of microelement enrichment in the coal-bearing deposit of Shubarkol, in Central Kazakhstan. Modern analytical techniques were used to obtain information about the conditions and processes of trace element accumulation in coal, as well as the modes of occurrence of these elements. Geochemical data were analyzed using multidimensional statistical methods, including correlation, clustering, and factor analysis, which allowed us to draw several scientific conclusions. Numerous factors indicate that the enrichment of trace elements in sediments is controlled by clastic terrigenous material and low-temperature hydrothermal solutions circulating in the coal basin. The main sources of removal of trace elements from coal are ancient igneous rock complexes located within deposits that were directly involved in coal enrichment through secondary geological processes. According to estimates, the degree of enrichment of Jurassic coals at Shubarkol was close to the average value for world coals (0.5 < CC < 2), and coal seams were enriched with lithophilic and chalcophilic elements such as Ba, U, Yb, Co, La, Nb, Hf, Sc, V, Sr, Cu, and Zn. A correlation analysis of coal deposits revealed a significant correlation between main oxides and rare earth elements (REEs). The strongest correlation was between Zr, Hf, Th/Ta, and REEs. The positive correlations between Zr and Al2O3, Nb and Al2O3 indicate that these elements (Zr, Hf, Nb, Ta, and REY) are probably related to Al. The results obtained make it possible to consider coal as a potential mineral resource for the production of rare metals and serve as a guide for the industrial processing of the most important elements found in coal.