Program > Browse abstracts by speaker > Topalović Ena

Understanding rare earth element (REE) distribution in rocks is crucial because of their role in sustainable energy. Bauxite deposits are significant REE sources, with their distribution governed by mineral composition and weathering processes.We used quantitative X-ray diffraction (XRD) to determine mineralogic composition and inductively coupled plasma mass spectrometry (ICP-MS) with correlation analysis to identify REE-hosting phases in the Gljev deposit, Croatia, occurring at a transgressive contact between Upper Cretaceous and Eocene limestone [1]. The main mineral phases are boehmite (18–51%), gibbsite (17%), and goethite (15–20%). Böhmite, the dominant Al-mineral, indicates diagenesis between 35–50°C [2]. The minor presence of nordstrandite suggests the formation under alkaline conditions [2], although La/Y ratios (<1) point to acidic conditions. Anatase (2%) is the dominant titanium phase, with minor rutile suggesting early diagenesis [2], but a detrital origin of anatase cannot be excluded. Goethite, indicative of oxidizing conditions, contrasts with anatase, which forms under reducing conditions [2], possibly reflecting redox fluctuations during deposit formation. The dominance of goethite over hematite (≤4%) indicate groundwater level variations during diagenesis [3]. Kaolin minerals (≤17%) suggest early or incomplete phase of bauxitization. All samples contain minor florencite, a REE-hosting phosphate.Correlation analysis reveals strong positive relationship among La, Y and P₂O₅ (0.99), suggesting REE incorporation into phosphates (e.g., florencite). The correlation of La and Y with SiO₂ (0.98) suggests adsorption at kaolin minerals. Heavy REE (Ho, Er, Tm, Yb, Lu) exhibit similar correlations (0.96), while Ce and Eu correlate with TiO₂, suggesting adsorption at Ti-oxides. Their negative correlations with Al₂O₃ and Fe₂O₃ suggest minimal association with Al- and Fe-oxides.The REE in the Gljev deposit are primarily associated with phosphate phases, secondarily with clay minerals and Ti-oxides. Our findings contribute to the understanding of paleoenvironmental conditions influencing bauxite formation and related REE enrichment in karst-type bauxites.