Rare Earth Element Deposits in Mongolia

In Mongolia, rare earth element (REE) mineralization of economic significance is related either to the Mesozoic carbonatites or Paleozoic peralkaline granitoid rocks. Carbonatites occur as part alkaline silicate-carbonatite complexes, which are composed mainly nepheline syenites and equivalent volcanic The complexes were emplaced in Gobi-Tien Shan rift zone southern Mongolia where usually form dikes, plugs intruded into brecciated mineralized carbonatites, REE fluorocarbonates (bastnäsite, synchysite, parisite) apatite. Apatite also present carbonatite-hosted apatite-magnetite (mostly altered hematite) bodies. Alkaline silicate rocks show common geochemical features such enrichment light but relative depletion Ti, Zr, Nb, Ta Hf similar Sr Nd isotopic characteristics suggesting involvement heterogeneous lithospheric mantle formation both associated Hydrothermal fluids magmatic origin played an important role genesis deposits. with felsic (peralkaline granites, pegmatites) occurs Mongolian Altai northwestern Mongolia. largely hosted accessory minerals (mainly elpidite, monazite, xenotime, fluorocarbonates), can reach percentage levels zones. These results protracted fractional crystallization magma that led REE, especially late stages evolution. primary was overprinted (remobilized enriched) by hydrothermal fluids. granitic contains significant concentrations Th U. There promising occurrences types at present, three them have already established potential. They Mushgai Khudag Khotgor Devonian Khalzan Buregtei granites