Biogeochemical Redox Processes Controlling the Element Cycling: Insights from Karst-Type Bauxite, Greece

The occurrence of very-high-grade bauxite ores karst-type deposits resulting from Fe-leaching is particular importance, because they are widespread in the Mediterranean metallogenetic province and result natural beneficiation ore quality. present study focuses on mineral transformations variations major trace elements, including platinum-group elements (PGE) chemistry along a profile Parnassos-Ghiona deposit, Greece underlying fault. most salient feature multicolor (grey–whitish, yellowish, deep red, grey to brown-red color, top bottom) their association with fossilized present-day microorganisms, which, by reducing and/or oxidizing activity, catalyze redox reactions provide nucleation sites for precipitation secondary minerals. Texture relationships between chemistry, suggesting sequence formation, indicate multistage evolution. recorded compositional show that Al enrichment accompanied increase TOC, As, Pd U, chondrite-normalized REE patterns exhibit similar trend positive Ce anomalies. A lower (Pt + Pd) content higher Pd/Pt ratio, ranging 1.0 5.5 compared those Fe-Ni laterite ratio 0.1 0.68, reflect solubility mobility Pt, differences origin genesis. correlation As elevated (up 960 mg/kg) samples (average 10 mg/kg As) confirms mobilization redeposition.