Mineralogy of various types of Th-U-REE mineralisation in the iron oxide – apatite deposits of the Bafq district, Central Iran.

This article focuses on the characterization and genesis of thorium-uranium-rare earth element (Th-U-REE) mineralisation associated with Kiruna-type iron oxide-apatite (IOA) deposits in the Bafq mining district, Central Iran. The Bafq district, part of the Early Cambrian volcano-sedimentary sequence, hosts over 2 billion tonnes of iron ore and diverse mineralisation types including REE-P, Th-REE, Th-only, U-REE, and REE-U-Th mineralisation, with apatite identified as the main host of light rare earth elements (LREE). The study highlights two dominant mineralisation stages: an Early Cambrian felsic calc-alkaline magmatic event forming the IOA deposits and sodic-calcic alteration, followed by a later stage involving post-magmatic alkaline fluids enriched in Th, U, and REEs that produced secondary mineralisation in brecciated zones. Transport of Th and REEs is primarily attributed to carbonate complexes, while U and REEs in certain deposits are likely mobilized by uranyl sulfate complexes under high-temperature conditions.