Major, trace, and rare earth elements geochemistry and enrichment in the Neogene organic-rich sediments from the Aleksinac deposit (Serbia): Part A

The composition of inorganic matter and the enrichment of trace and rare earth elements (TEs and REEs) in the Neogene organic matter-rich sediments in the Upper layer of the Aleksinac deposit (Dubrava block, Serbia) were analysed. Correlation analysis clearly showed that TEs and REEs are associated with SiO2, Al2O3, K2O, and TiO2, clastic minerals, clay, and feldspar, as well as zeolite minerals natrolite and analcime, indicating that the TEs and REEs were brought into the basin mainly by clastic material. Their distribution indicates certain changes in the depositional environment during the formation of these sediments. According to enrichment factors (calculated in relation to World Oil Shales, Upper Continental Crust, and Post-Archaean Australian Shale) and the degree of enrichment (relative to argillaceous rocks), the Aleksinac oil shale shows significant enrichment in Mo, a lesser degree in Sr, and possible enrichment in Cu. Therefore, there are no concerns regarding toxic trace elements in the Aleksinac oil shale.