Rare Earth Element Distribution and Paleoenvironmental Implications of Harmanlı (Gölbaşı, Adıyaman) Coals, SE Anatolia

This study investigates in detail the lanthanide and yttrium (REY) geochemistry, mineralogical characterization, and paleoenvironmental conditions of the Harmanlı coal deposits (Gölbaşı, Adıyaman) located in the southwestern region of the East Anatolian Fault Zone (EAFZ). Analyses of coal samples using XRD, SEM-EDS, ICP-AES, and ICP-MS provide data on the mineralogical composition, distribution of major and trace elements, and REY enrichment mechanisms. The Harmanlı coal consists primarily of quartz, feldspar, and clay minerals (kaolinite, illite, and smectite), including small quantities of dolomite, gypsum, pyrite, and mica, and trace amounts of barite, Ti-oxide, Fe-oxide, phosphate minerals, and zircon. The range of REY concentrations is 20.6-78.2 ppm. Light REY (LREY) is more enriched than medium REY (MREY) and heavy REY (HREY). The strong correlation between REY and major oxides indicates that REY is concentrated in clay and Fe-Ti minerals. SEM-EDS analyses have confirmed that REY is associated with these minerals. Furthermore, several phosphate minerals have been discovered to display REY enrichments. Paleosalinity assessments suggest a depositional environment affected by freshwater, whereas redox indicators often point to reducing conditions. It is also understood that oxidizing conditions were effective in some areas during the coal deposition process. Paleoclimatic indicators show that the climate was generally humid and tropical, but arid phases also occurred in some areas. The geochemistry of detrital minerals and Al₂O₃/TiO₂ ratios indicate predominantly felsic sources for the detrital material, with a smaller amount of mafic/ophiolitic material present. Evaluation of the tectonic influences suggests that the sedimentary system developed under the control of the EAFZ.