Uranium mineralization in the Arya Jonoub iron oxide –apatite ore deposit

The Arya Jonoub iron oxide–apatite (IOA) deposit, located in the southern part of the Kashmar–Kerman tectono-magmatic belt, Central Iran, is hosted by Lower Cambrian volcano–sedimentary sequences intruded by diorite, gabbro, and diabase dikes. This study integrates detailed field mapping, petrography, ore microscopy, X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and whole-rock geochemical analyses (ICP-OES 1 and ICP-MS 2 ) to elucidate the mineralization processes. The principal Fe ore consists of magnetite–apatite mineralization, locally accompanied by titanomagnetite, ilmenite, and minor sulfides. Extensive alteration assemblages—including albitization, chloritization, silicification, and hematitization—are spatially and genetically associated with magnetite–apatite ore formation. Uranium mineralization occurs predominantly as uraninite and coffinite, closely associated with magnetite, pyrite, chalcopyrite, carbonates, chlorite, and REE-bearing phases such as monazite, allanite, and britholite. Geochemical data indicate uranium concentrations ranging from 369 to 3567 ppm, with strong positive correlations with Th and Y, and chondrite-normalized REE patterns characterized by LREE enrichment and pronounced negative Eu anomalies. These features support a multistage magmatic–hydrothermal evolution, in which primary Fe–P mineralization was subsequently overprinted by oxidizing, carbonate-rich fluids responsible for U and REE enrichment. Redox interactions between Fe 2+ and U 6+ played a critical role: oxidation of Fe 2+ to Fe 3+ (magnetite alteration to hematite) promoted the reduction of soluble uranyl species to insoluble U 4+ , resulting in uraninite precipitation. Collectively, these results provide new insights into uranium metallogeny in IOA systems and establish an exploration framework for U-bearing iron oxide–apatite deposits in Central Iran.