Geochemistry and mineralogy of rare earth elements in high-phosphorus ooidal ironstones: A case study of the Kamysh-Burun deposit (Azov–Black Sea iron Province)

•The Early Pliocene ooidal ores of the Azov–Black Sea region store high-REE contents.•The Fe3+-(oxy)hydroxides are main carriers of MREE and HREE.•LREE are mainly hosted by early-diagenetic hydrous phosphates.•The REEs stored in ooidal ironstones have a diagenetic source.