Redox-Sensitive (V-U-Mo) Element Enrichments in Lower Miocene Coals from Alatepe area of Mugla Basin (SW Anatolia, Turkiye)

Critical elements, a vital component both for energy and technology, are receiving more attention globally. These elements could be anomalously concentrated in the coals, host rocks, and associated byproducts. In this context, the Alatepe coal occurrences in Mugla Basin (SW Anatolia, Turkiye), one of the most productive coal basins, can attract attention to the economic possibilities of V-U-Mo enrichments. The Alatepe outcrop coal samples were collected for analysis. The V, U, and Mo contents of studied coals are up to 175 μg/g, 69 μg/g, and 26 μg/g respectively. These samples are characterized by relatively low Al and Fe contents (avg. of 2.5 and 1.0 wt.%, respectively) and high S contents  (avg. of 5.6 wt.%). The ash content of studied coals is up to 15 wt.% and petrographically characterized by a high huminite content. Based on the XRD analysis, the mineral composition of the studied samples is mainly of clay minerals, quartz, pyrite, gypsum, and mica suggesting that peatlands with a high detrital input, dominated by the quartz and clay mineral setting, may have been influenced by the sea in the Alatepe area. It can be stated that this situation increased coal ranking affecting the V content of studied coal samples and this higher maturation is probably attributed to more intensive post-depositional activities in these regions compared to the other coal fields in the Mugla Basin. Therefore, Alatepe coals can be classified as sub-bituminous C coal rank, while the main coal rank of the Mugla Basin is lignite. In addition, all of the redox indicators (such as V/Ni, V/(V+Ni), V/Cr, Ni/Co, Mo/Mn, and U/Th) suggest that reducing conditions provide a preservation condition for V-U-Mo. In these conditions, the form of V⁵⁺ reduced to its more reduced form, V³⁺, which then binds to organic material and surfaces like clays, leading to its accumulation. The U can be readily incorporated into organic and inorganic material as a form of insoluble U(IV). Moreover, Mo can form MoS₄²⁻, which readily precipitates and accumulates in sediments.

Keywords: V-U-Mo Enrichments, Critical Elements, Miocene Coals, Alatepe area, Mugla Basin (SW Anatolia of Turkiye)