Posušje bauxites in Bosnia and Herzegovina: A source of critical raw materials and a paleoclimatic marker

The present study provides geochemical and geochronological data about Posušje bauxites in Bosnia and Herzegovina with the aim to characterize them as Critical Raw Materials (CRMs) sources and to put constraints on the time and genesis of the deposit. Boehmite is the bauxites’ main Al-bearing mineral, while gibbsite is a minor constituent. Hematite is the dominant Fe-phase, whereas goethite is rare. The chemical analyses indicate that the Al2O3 content ranges from 49.6 to 63.0 wt %, Fe2O3 varies from 16.5 to 33.7 wt % and the SiO2 content is usually <0.5 wt %. TiO2 content ranges between 2.6 and 3.2 wt %. Typical trace elements are V (353–787 ppm), Cr (498–1055 ppm), Zr (382–558 ppm), Sc (42–72 ppm), and Ga (40–47 ppm). The sum of REEs is 357–1112 ppm. The U-Pb zircon dating indicates an age of Posušje bauxite formation at 56.6±0.5 Ma. This age closely aligns with the global climatic event that occurred approximately 56 Ma ago, called Paleocene–Eocene Thermal Maximum (PETM).