Bauxitic Horizons and Geogenic Radon Potential in the Dajti Massif (Tirana, Albania)

Abstract

The Kruja–Dajti carbonate belt in central Albania hosts lateritic–karstic bauxite bodies
concentrated along angular unconformities and paleokarst surfaces. In the Dajti area, these bauxitic
horizons are characterized by lens- to pocket-shaped ore bodies, locally reaching decametric thicknesses,
and a major-oxide chemistry dominated by Al2O3 (typically ~40–50%) with significant Fe2O3 and clay
fractions. National radiometric syntheses and in situ gamma-spectrometric measurements indicate that
Albanian bauxites can exhibit elevated equivalent uranium (eU-238 up to ~628 Bq kg-1, mean ~338 Bq
kg-1) and substantial Th-232, implying non-trivial radon (Rn-222) source potential. This study integrates
(i) the geological description of the Dajti bauxite-bearing horizon, (ii) occurrence-level reserve and
geochemical data (Profile 109), (iii) georeferenced bauxite occurrence points (KML), and (iv) the national
gamma-radiometric framework, to evaluate the geogenic potential for radon emissions. We propose a
mechanic model in which radon risk is controlled by coupled 'source' (U/Ra enrichment and radium
retention in clay–Fe-oxide matrices) and 'pathway' factors (fault/fracture corridors, karst pathways, and
brecciated cover units enhancing advective transport). The resulting screening-level assessment highlights
bauxite–carbonate contacts and structurally damaged zones as priority targets for soil-gas radon transects
and long-term indoor monitoring in the Dajti–Tirana corridor.