Intrusion sequence of carbonatite dykes and REE accumulation mechanism in Bayan Obo district
白云鄂博地区碳酸岩脉侵位序列与稀土元素富集机制

Three types of carbonatite dykes including dolomite, calcite and coexisted dolomite-calcite are distinguished by mineralogical composition in Bayan Obo rare earth element (REE) deposit district. Incision contact shows that intrusion of calcite carbonatite dykes were later than dolomite type, which indicated that carbonatite magma in Bayan Obo district had special evolution trend from dolomite through coexisted to calcite type. Moreover the content of light rare earth element (LREE) in carbonatite dykes gradually increasing with the proportion of calcite minerals from dolomite through coexisted to calcite type. Geochemical data also shows that long term crystallizational differentiation was the inner mechanism of REE (especially LREE) accumulation in the residual magma.