Geochemistry of carbonatite in the Muluo REE deposit, Sichuan

Abstract：The Muluo REE deposits is genetically closely related to carbonatite-alkaline complexes. Carbonatite is mainly composed of calcite (>90%) with a CaO/(CaO+MgO+FeO+Fe2O3+MnO) ratio of 95.7-99.6%, so it is calcite carbonatite. The carbonatite is characterized by relative enrichment in the LILE Ba, Sr and LREE, relative depletion in the HFSE Nb, Ta, Ti, Zr and P, higher ratios of Zr/Hf and La/Nb and lower ratios of Sm/Nd and Rb/Sr, implying that the rock was derived from the enriched mantle (EMI). Geochemical study shows that the Muluo carbonatite is the product of reactivation of the mantle remnants of the Emeishan mantle plume caused by the Himalayan orogenic movement；however, the carbonatitic molten magma was contaminated with crustal material during its ascent. The molten magma of carbonatite-alkaline rocks brought substantial REE to extensional sites resulting from orogeny in the Himalayan orogenic phase and formed REE deposits.