Mineralogy, chemistry, and distribution of selected trace elements in coal and shale from the Ibar Basin (South Serbia)

Abstract

Coal samples from the Jarando, Tadenje, and Progorelica mines and organic-rich shale samples from the Piskanja boron deposit, all located in the Tertiary Ibar Basin, were studied using several methods such as transmitted light microscopy, X-ray powder diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), Fourier-transform infrared spectroscopy (FTIR), as well as inductively coupled plasma-mass spectrometry (ICP-MS) and X-ray fluorescence (XRF) spectrometry for evaluating their mineralogical and geochemical compositions. The Ibar Basin hosts high-volatile bituminous coal de-posits and boron mineralisations. The mineralogical and geochemical data indicated that the main minerals in coals are quartz, pyrite, with a variable amount of clay (kaolinite, montmorillonite, illite), calcite and sulphates, while borates occur in low amounts. Framboidal pyrite is the main form of sulphur in coals. Clay and carbonate are often associated with macerals in mineral-bituminous groundmass, implying high ash yield and limited possibilities of coal cleaning treatment. Very high content of As, Co, Cu, Cr, and Ni was detected in high temperature coal ash (HTCA), especially in the Tadenje deposit. Contents of Mo, Sb, Pb, V, and Zn are slightly higher than the relevant Clarke values for bituminous coal ash. The shale samples from the Piskanja deposit mostly consist of a mixture of quartz, dolomite, and clay minerals (illite and chlorite) with variable amount of plagioclase, K-feld-spar, and mica. Lead, Zn, and Cu sulphides, gypsum, celestine, barite, rutile, and apatite were detected in low amounts.