Geochemistry of carbonatites in Maoniuping REE deposit,Sichuan province,China

Carbonatites in the Maoniuping REE deposit, Sichuan Province, which are spatially and temporally associated with rare earth mineralization, were emplaced at the time of Himalayan. The rocks are carbonatite-syenite complexes, with the mineral assemblages of calcite-aegirine-acmite-arfvedsonite-mica-orthoclase. The rocks are characterized by the enrichment in incompatible elements, such as Sr, Ba and REE, with C and O isotopic compositions of the “primary igneous carbonatites”, relatively high initial ⁸⁷Sr/⁸⁶Sr ratios and low ?_nd values. All of these suggest that the rocks were derived from the metasomatic enriched mantle. It is demonstrated by geological and geochemical evidence that the mixing of the Himalayan subducting crustal materials with mantle source EM1 is probably the main factor responsible for the formation of carbonatites. The carbonatite-syenite complexes were generated from liquid immiscibility of CO₂-rich alkalic silicate magma, which was derived from partial melting of the metasomatic mantle.