Tošići-Dujići bauxite deposit, situated in Dalmatian inlands, Croatia, contains minor remaining bauxite reserves. The deposit lies on Lower Eocene foraminiferal limestone and is covered by Upper Eocene Promina sediments. Bauxite samples were analyzed for textural, mineralogical, and geochemical features in order to determine absolute REE abundances and their relation to mineralogy, as well as to devise the origin of REE enrichment and to trace weathering and bauxitization paths of the parent material. The samples show total REE abundances up to 3500 mg/kg with significant HREE enrichment in some cases. All samples are gibbsitic with hematite and anatase as major phases. Kaolinite occurs in most of the samples, and goethite, böhmite, and nordstrandite are minor phases. Monazite-(Ce) and xenotime-(Y) were identified as detrital REE minerals as well as authigenic florencite-(Ce). In the REE most abundant sample, REE are most likely bound to Fe- and Ti-oxide phases as suggested by correlation analysis. Chemical weathering proxies show intensive weathering. Geochemical and textural data imply that the REE enrichment is influenced by intensive weathering (CIA 97.87–99.26) of detrital material, and also by possible deposition/redeposition of residual material potentially derived and mobilized from various sedimentary rocks of the area.

We explored the potential incorporation of Sentinel-2A imagery for rock unit determination in the Croatian karst region dominated by carbonate rocks. The various lithological units are potential sources of both stone aggregates and dimension stone, and their spatial distribution is of high importance for mineral resource management. The presented approach included the preprocessing and processing of existing analog data (geological maps), Sentinel-2A satellite images and the United States Geological Survey spectral indices, all in combination with ground truth data. Geological mapping and digital processing of legacy maps using the K-means and random forest algorithm reduced the spatial error of the geometry of geological boundaries from 100 m and 300 m to below 100 m. The possibility of discriminating individual lithological units based on spectral analysis and discriminant function analysis was also examined, providing a tool for evaluating the geological potential for mineral resources. Despite the challenges posed by the lithological homogeneity of karst terrain, the results of this study show that the use of spectral signature data derived from Sentinel-2A satellite images can be successfully implemented in such terrains for the enhancement of existing geological maps and mineral resources exploration.

Karst bauxites are valuable terrestrial records of paleoclimate and tectonic evolution formed under tropical to subtropical conditions during the subaerial exposure of carbonate platforms. This study explores Croatian bauxite deposits within the Adriatic–Dinaric Carbonate Platform (ADCP), with a focus on the distribution and enrichment of rare earth elements (REE) across eight bauxite horizons from the Triassic to Neogene periods. The research applies statistical analyses of geochemical data, as well as developed models, to assess the factors influencing REE distribution and fractionation. The study found that variations in parent material, along with changes in paleogeographical and paleotectonic settings, significantly affected the REE content. The median REE concentrations in the analyzed bauxite horizons range from approximately 250 to 570 mg/kg. Notable REE enrichment was observed in the Late Paleogene, particularly in the Middle and Upper Eocene horizons. The analysis highlights the importance of physicochemical conditions, such as Eh and pH, during the weathering processes that lead to bauxite formation. The results suggest that the presence of REE-bearing minerals, rather than clay minerals, could possibly contribute to elevated concentrations of heavy REE (HREE). These findings indicate that Croatian bauxites, enriched in REE and associated trace elements, are significant not only as geological markers of past climatic and tectonic events but also as potential sources of critical raw materials. This study underscores the potential for the economic exploitation of these deposits in the context of modern technological demands.

The evolution of map development has been shaped by advancing techniques and technologies. Nevertheless, field and remote mapping with cabinet data analysis remains essential in this process. Geological maps are thematic maps that delineate diverse geological features. These maps undergo updates reflecting changes in the mapped area, technological advancements, and the availability of new data. Herein, a geological assessment example focused on enhancing mapped data using digitally processed historical (legacy) aerial images is presented for a case study in the Dinarides karst area in Croatia. The study area of Bribirske Mostine is covered by the Basic Geological Map of Yugoslavia (BGMY) at a 100,000 scale, which was developed during the 1960s. As the BGMY was developed 60+ years ago, one of its segments is further analyzed and discussed, namely, faults. Moreover, applying modern-day technologies and reinterpretation, its data, scale, presentation, and possible areas of improvement are presented. Georeferenced digital historical geological data (legacy), comprising BGMY, archive field maps, and aerial images from 1959 used in BGMY development, are reviewed. Original faults were digitalized and reinterpreted within the geographic information system with the following conclusions: (i) more accurate data (spatial positioning) on faults can be gained by digitally processing aerial photographs taken 60+ years ago with detailed review and analysis; (ii) simultaneously, new data were acquired (additional fault lines were interpreted); (iii) the map scale can be up-scaled to 1:25,000 for the investigated area of Bribirske Mostine; and (iv) a newly developed map for the Bribirske Mostine study area is presented.

Reliable and up-to-date information on mineral resources is an essential foundation for strategic decision-making and long-term mining project planning. In Croatia, solid mineral resources have traditionally been classified using the national ABC1 system, which is not aligned with internationally recognised reporting frameworks. This study applies the United Nations Framework Classification for Resources (UNFC) to a representative group of Croatian exploitation fields. In the national regulatory context, this term refers to a formally defined project category used by the mining authority to describe the legal and operational status of the mining project. The analysed group includes active and non-active exploitation fields, historic exploitation fields, and examples characterised by temporary administrative irregularities, defined as situations in which mining activities continue under acquired rights, rather than under an active concession. Two complementary approaches were used: the ORAMA (2019) PROJECT (2019) decision-flow methodology and the direct application of the UNFC Guidance Europe (UNECE, 2022). Independent assessments on the non-active exploitation fields conducted by two experts, resulted in fully aligned UNFC classifications despite differences in analytical emphasis. This outcome demonstrates the reproducibility and robustness of the UNFC framework. An additional example illustrates the dynamic nature of the UNFC by showing how temporary changes in project status can influence the project maturity and assigned category. The results confirm that the UNFC provides a transparent, adaptable and harmonised framework suitable for integrating Croatian mineral resource data into national and European reporting systems. Rather than replacing the national system, this study demonstrates a practical and transparent pathway for UNFC implementation and interoperability with wider relevance beyond the Croatian context.

Karst bauxites represent important archives of paleoenvironmental conditions and potential sources of REE and other critical raw materials (CRMs). This study presents a multiproxy investigation of the Upper Eocene Mamutovac-1a bauxite deposit (Croatian Dinarides), integrating petrography, X-ray diffraction (XRD), magnetic susceptibility, whole-rock geochemistry, and aqua regia extractions along a 25.1 m drill core. The deposit shows clear vertical variability defined by four facies-based zones, accompanied by systematic mineralogical and geochemical changes. The bauxite is dominated by böhmite, gibbsite, hematite, and anatase, with subordinate goethite and clay minerals. ΣREE concentrations range from 276 to 670 mg/kg and increase toward the deeper zones, with consistent LREE enrichment relative to HREE, negative Eu anomalies, and variable Ce anomalies. Correlations suggest that REE are likely associated with phosphate phases, with a possible secondary contribution from clay minerals. The integrated dataset indicates a polygenetic, multi-stage evolution involving both in situ bauxitization and episodic reworking and redeposition, controlled by variable redox conditions and fluid–rock interaction. Geochemical signatures suggest a mixed provenance with contributions from intermediate to ultramafic sources. The elevated concentrations and enhanced extractability of selected elements (La, Sc, Ga, V) indicate that the deposit may represent a potential secondary source of CRMs.