ON A GEOCHEMICAL MODEL OF THE FORMATION OF EARLY OLIGOCENE MANGANESE ORES IN THE EASTERN PARATETHYS - THE NIKOPOL AND OTHER DEPOSITS OF THESOUTHERN UKRAINIAN BASIN

Data on lithology, mineralogy, and geochemistry of main components, tr ace elements, and REE in ores and host rocks of the Nikopol' and other early Oligocene deposits in the southern Ukrainian maganese-bearing b asin are discussed. These and other manganese deposits of the Eastern Paratethys are related to a single chronostratigraphic level-the base of the Rupelian (Stampian) Stage of the European early Oligocene. The formation of manganese deposits was associated with the early Oligocen e ingression of relatively dense salty oceanic waters, which resulted in squeezing out waters from stagnant basins (in particular, the paleo -Black Sea) enriched in Mn and other metals and their migration to the shelf shallow-water parts with a normal aeration regime. In these env ironments, manganite and Mn-carbonate ores were formed during near-bot tom sedimentation and diagenesis. In the post-Oligocene time, these or es were transformed in the hypergenesis zone into Mn oxyhydroxides (ma nganite II, pyrolusite, todorokite, and cryptomelane).