Tectono-stratigraphic evolution of the Posušje area, External Dinarides, Bosnia and Herzegovina: controls on bauxite formation and exploration potential

Bauxites, a key source of multiple critical raw materials, including aluminum, rare earth elements (REEs), titanium, and gallium, have gained renewed interest due to Europe's ambition of becoming the first carbon-neutral economy by 2050. The External Dinarides, part of the Alpine orogenic system, provide an ideal setting for examining the interplay between lithospheric deformation and surface processes in fold-thrust belts, with a particular focus on the formation and preservation of karst bauxite deposits. Multiple emersions with associated bauxite deposits and occurrences have been reported from the Adriatic microplate throughout its tectonio-stratigraphic evolution from rifting to passive margin and tectonic inversion, including Triassic, Jurassic, Lower and Upper Cretaceous, and Paleocene-Eocene age deposits.

This study investigates the tectono-stratigraphic evolution of a portion of the External Dinarides and its controls on the generation and preservation of Late Cretaceous-Paleogene karst bauxites in the Posušje area, Bosnia and Herzegovina.

A 3D geological model was developed using detailed geological maps, borehole data, and remote sensing, integrating structural interpretations and cross-section analyses to determine deformation style, and tectonic control over basin evolution and paleogeography.

The study reveals a complex structural history characterized by both thin- and thick-skinned tectonics, with multiple detachment levels and the inversion of inherited normal faults. Late Cretaceous-Paleogene bauxite deposits are closely associated with the Late Cretaceous to Early Paleocene forebulge uplift and subsequent erosion, where karst-related depressions served as primary traps for bauxite accumulation and preservation. Paleocene to Oligocene syn-orogenic deposits are reviewed in the context of the Dinaric Foredeep Basin's evolution and its progressive migration towards the foreland. Finally, the 3D-modeled top Cretaceous unconformity highlights extensive underexplored areas where bauxite deposits might exist at mineable depths, offering improved targeting efficiency for future exploration campaigns.

Through the integration of tectono-stratigraphic data within a validated structural model, this work provides new insights into the evolution of the External Dinarides and valuable information on the formation and preservation of Late Cretaceous-Paleogene karst bauxites. These findings contribute to enhancing exploration strategies for critical mineral resources in this portion of the fold-thrust belt and other regions with similar geological settings.