Scandium-bearing coals of the Shaim oil and gas region of the West Siberian basin

Relevance. The need to identify new sources of industrial production of strategic metals that are critical for modern technologies. Aim. To study the geological and geochemical conditions that led to the formation of anomalous scandium concentrations in the coals of the western part of the West Siberian Basin. Methods. A range of modern analytical methods, including ICP-MS, INAA and scanning electron microscopy; statistical methods; geological and geochemical analysis of the migration and concentration of elements. Results and conclusions. In the western part of the West Siberian Basin, within the Shaim oil- and gas-bearing region, the authors have discovered the coals containing anomalous amounts of scandium, with no analogues in world practice. The maximum Sc content in coal is 83.6 ppm and in coal ash is 0.4%. In the future, this is a new industrial and genetic type of scandium deposits. Alongside Sc, coal ashes are also anomalously enriched in a group of siderophilic and lithophilic metals, including Zr, Ge, Nb, Y, and yttrium lanthanides. The forms of scandium occurrence in coal and the character of its distribution in coal seams point to a hydrogenic mechanism of anomaly formation. Studies shown that uniquely scandium-bearing coals are formed in areas with specific basement rock compositions, characterized by a significant proportion of basite-hyperbasite rocks. Weathering of these rocks leads to the formation of coal-bearing rocks enriched in scandium. During diagenesis and early catagenesis, soda water were formed in coal-bearing strata, favouring the transfer of scandium from terrigenous sediments and buried weathering crusts into solution, as well as its redistribution into coal seams, resulting in uniquely high scandium concentrations in coal. Based on the size of the studied area, the thickness of scandium-bearing strata, and the average metal content within them, the inferred resources of scandium can be estimated at 200 thousand tons.