Global Metallogeny of Tantalum Through Geological Time

Аннотация

The global distribution of tantalum deposits and their resources on the geological time scale is analyzed. The analysis is based on the data for 65 deposits of the world with a resource estimate from 2000 t of Ta₂O₅, which are classified into five types: pegmatitic, granitic, alkaligranitic, foidic, and carbonatitic. Placers and ore-bearing weathering crusts are taken into account with their bedrock sources. The variable features of the global metallogeny of tantalum are represented based on the comparison of the supercontinent cycle. It is established that the most significant resources in terms of quantity are confined in the deposits of the Rodinian cycle, among which the foidic type objects are fully dominant. Then, the descending order for the total resources is the Pangean and Columbian cycles, in which the main shares in the resources belong to the deposits of the alkaligranitic and foidic types. The Kenoran cycle, which lags behind them in its quantitative estimate, stands out in tantalum metallogeny by a monotype nature: only pegmatitic objects have created its resource potential. The current Amasian cycle is in the last place with respect to the total quantity of tantalum resources, which is explained to a great extent by its incompleteness. The resources of this cycle are distributed between the objects of the alkaligranitic, granitic, and pegmatitic types in comparable shares. It is noted that, due to their mineralogical features, the deposits of pegmatitic and granitic types make it possible to obtain the highest-quality concentrates and they are, therefore, of prime interest for tantalum extraction. The deposits of the pegmatitic types are known in all the cycles, while the deposits of the granitic type are known only in the Pangean and Amasian cycles. In total, they contain only one fifth of the estimated tantalum resources, and their major share accounts for the Kenoran and Pangean cycles.