Jurassic uranium-bearing phosphorites of the Ionian Zone, Albania

Luca Piepoli¹, Giovanna Della Porta¹, Giovanni Grieco¹, Ana Fociro², Altin Karriqi², Mensi Prela² & Agim Sinojmeri^2
1Department of Earth Sciences, University of Milan, Via Mangiagalli 34, 20133 Milan, Italy.
²Department of Earth Sciences, Polytechnic University of Tirana, Via Elbasanit, Tirana, Albania.

This study presents a comprehensive petrographic, mineralogical, and geochemical investigation of Lower Jurassic uranium-bearing phosphorite deposits from the Bogaz and Fushëbardha localities within the Ionian Zone, Southern Albania. The phosphorites occur within carbonate successions and were analysed using thin section petrography, X-ray Diffraction (XRD), Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS), Electron Micro-Probe Analyses (EMPA) and Geiger-Müller radiation measurements. At Bogaz, phosphorites occur as interparticle cement within breccias composed of angular carbonate clasts. Brecciated carbonate facies consist of packstone with peloids, Pliensbachian (Lower Jurassic) benthic foraminifera (Siphovalvulina) and green dasycladacean algae (Palaeodasycladus mediterraneus), and wackestone with fenestrae indicative of shallow-marine, peritidal depositional environments. XRD and EMPA analyses confirm fluorapatite, francolite (carbonate fluorapatite), and calcite as dominant phases, with uranium incorporated within the apatite lattice. Carbonate fluorapatite crystals form rosette structures, tens of microns in diameter. These features suggest a tectonically influenced formation of hydraulic breccias and diagenetic fluid circulation driving a secondary diagenetic infiltration-type phosphogenesis. At Fushëbardha, the phosphorites form mainly nodular or lenticular structures within a carbonate matrix, with interbedded packstone and grainstone containing Bositra-type thin-shelled, pelagic bivalves. The stratiform phosphorites at Fushëbardha are interpreted as primary deposits linked to the Early Jurassic Toarcian Oceanic Anoxic Event (OAE), reflecting phosphogenesis in low-energy, oxygen-depleted marine environments associated with microbial organic remains as observed at SEM. Fluorapatite occurs as microcrystalline prisms with hexagonal base and radial rosettes; uranium is spatially restricted to phosphate nodules. The dual occurrence of diagenetic (Bogaz) and sedimentary stratiform (Fushëbardha) phosphorites reflects two distinct phosphogenic pathways in the Ionian Zone. These findings emphasize the role of global climate and ocean anoxia, tectonic regime, diagenesis, microbial mediation and redox-sensitive geochemical environments in the genesis of Mediterranean phosphorites. Albanian phosphate mining sites should be further evaluated for radioactivity hazard as part of any mining feasibility study in the future.

Albania, Lower Jurassic, phosphorite, carbonate fluorapatite, uranium.