The stages of the formation of titanium-zirconium placers in the geological history of the Earth were systematized on the basis of analysis of the global distribution of reserves. It has been established that, despite the continuity of the accumulation since the Late Archean, the vast majority of industrial deposits have been formed since the Middle Devonian. Five main stages of concentration were identified. Each stage is characterized by a specific combination of tectonic, paleogeographic and climatic factors: (1) Pre-Middle Devonian (accumulation of non-industrial concentrations); (2) Middle Devonian–Early Carboniferous (significant influence of endogenous factors and magmatism); (3) Late Triassic–Middle Jurassic (connection with the epoch of crust formation, the appearance of eluvial placers); (4) Cretaceous (formation of short- and long-distance transported placers after relief planation and transgressions); (5) Cenozoic (maximum scale of the placer formation due to the development of crust weathering, contrasting relief and dynamics of coastlines). A conclusion is drawn about the cyclically-directed nature of the evolution of placer formation: direction of the process is expressed in a progressive increase in reserves, especially in the Cenozoic, and cyclicality is in a periodic combination of factors favorable for concentration. The results provide the basis for long-term forecasting and assessment of the minerogenic potential of placer provinces.
A. D. Savko (Mon,) studied this question.