Resources of niobium(Nb)and rare earth elements(REEs)are dominantly sourced from deposits associated with carbonatites and alkaline rocks.To strength the study of Nb and REEs mineralization in the carbonatite-alkaline rock system is of great significance to guide the exploration of Nb and REEs resources in China.In this paper,the mineralization and genetic mechanism of Nb-REEs deposits related to carbonatite-alkaline rocks are reviewed and summarized.The initial enrichment of Nb and REEs in the carbonatite-alkaline rock system is generally associated with the partial melting of the enriched mantle.The enrichment of rare and alkali metals and volatiles in the mantle source is the key to the Nb and REEs mineralization in the system.The high degree fractional crystallization of early-stage mgamatic minerals such as olivine and clinopyroxene resulted in the further enrichment of Nb and REEs in the residual alkaline magma,and then the crystallization of Nb and REEs minerals.The cumulate genesis and metasomatism models are two mechanisms both proposed for the formation of niobium minerals in carbonatites.Most carbonatite-alkaline rock associated Nb-REEs deposits had undergone the hydrothermal alteration.The hydrothermal niobium minerals were formed through the in-situ alteration of magmatic niobium minerals,whereas the REEs minerals were formed through the dissolution of REEs-bearing magmatic ore and gangue minerals,migration of the REEs and precipitation of new REEs minerals in the hydrothermal process.The surface weathering process,including physical enrichment,chemical enrichment,and/or biological enrichment processes,can further enhance Nb and REEs grades of ores in carbonatite type Nb-REEs deposits.The weathering of a few alkaline rock associated Nb-REEs deposits resulted in the enhancement of Nb and REEs grades of ores through the physical enrichment,whereas the weathering most alkaline rock associated Nb-REEs deposits resulted in the decomposition of hydrothermal REEs minerals and the formation of some secondary REEs minerals that are not easily and economically utilized.
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