Geodynamic control on bauxite deposit distribution in fold and thrust belts and their associated foreland basins: the External Dinarides (Croatia and Bosnia-Herzegovina)

The interaction of the lithosphere with surface processes in fold-and-thrust belts often leads to the formation of mineral ore deposits, including economically significant resources like bauxites. These interactions are driven by complex geological dynamics, including crustal deformation, sedimentation, and erosion, which create favourable conditions for ore deposition. Bauxite, an essential ore for aluminium production, has become increasingly critical due to global demand and is now included in the European Union's fifth list of critical raw materials. The Dinarides, a branch of the Alpine Belt in south-eastern Europe, are notable for their multiple bauxite levels, making them an important case study for understanding bauxite ore deposits. The External Dinarides are traditionally divided into two tectonic units: the High Karst Unit and the Dalmatian Unit. Historically, these external Dinarides have been interpreted as a thin-skinned fold-and-thrust belt, characterized by significant horizontal shortening and detachment along sedimentary layers.

This study proposes a new model for the evolution of the Dinarides, mapping the spatial and temporal distribution of bauxites providing valuable insights into the processes that control their formation, with the ultimate aim to provide broader implications for exploration strategies in similar geological settings.

The new model is based on regional balanced and restored cross-section through the External Dinarides of Bosnia and Herzegovina and Croatia that integrates offshore 2D seismic data, borehole data, fieldwork and remote sensing to determine style of deformation, and paleogeographic evolution of this portion of the belt.

The balanced and restored cross-section revises the traditional view, proposing a mixed thin-skinned/thick-skinned tectonic model that emphasizes the role of deep-seated structures and salt tectonics in shaping the region, with much less shortening than previous models. Salt tectonics, involving the deformation of evaporite layers, plays a critical role both in the passive margin stage and its subsequent inversion, localising the deformation and controlling the structural style. In this revised tectono-stratigraphic framework, potential scenarios for bauxite generation, accumulation and preservation are outlined. The combination of surface processes and tectonic activity creates zones where bauxite deposits are likely to be concentrated, both at local (thrust ramp anticlines, diapir roof uplift or extensional footwall uplift) and regional (see level fluctuation, forebulge migration) scales. Understanding these scenarios not only enhances the exploration potential in the Dinarides but also offers valuable analogues for bauxite exploration in other fold-and-thrust belts worldwide.