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重点解剖了一条距白云鄂博ＲＥＥＮｂＦｅ 矿床东矿， ＮＥ 方向３ ｋｍ 并切割白云鄂博群Ｈ１ 及Ｈ２岩性段的细粒方解石碳酸岩岩墙的岩石地球化学特征。结果表明， 碳酸岩的稀土元素含量变化大， 最高可达２０ ％ （ 质量分数）， 已构成稀土富矿石。碳酸岩的轻稀土元素高度富集， 轻、重稀土元素之间发生了极度分馏， 但无铕异常显示。形成这种岩石地球化学特征的可能机制为： 碳酸岩浆直接来源于岩石圈富集地幔的低程度部分熔融作用（ Ｆ＜１ ％ ） ， 残留地幔矿物组合以富含柘榴石为特征； 碳酸岩浆在地壳深部岩浆房中的分离结晶作用。碳酸岩的稀土元素和微量元素分布型式均与白云鄂博ＲＥＥＮｂＦｅ矿床的赋矿细粒白云石大理岩十分相似。然而， 碳酸岩的主要元素以钙质为特征， 不同于赋矿细粒白云石大理岩， 造成这种差异的原因在于碳酸岩岩墙没有遭受大规模的白云岩化作用， 而赋矿细粒白云石大理岩则可能是碳酸岩经白云岩化作用的产物。
The geochemical characteristics of a fine calcite carbonatite dyke wall that is located east of the REENbFe deposit in the Bayan Obo region and is located 3 km in the NE direction and cut into lithologic sections H1 and H2 of the Bayan Obo Group were mainly studied. The results show that the REE content of carbonate rocks varies greatly, up to 20% (mass fraction), which constitutes rare earth rich ore. The light rare earth elements of carbonate rocks are highly enriched, and the extreme fractionation occurs between light and heavy rare earth elements, but there is no anomalous display of europium. The possible mechanism of forming this geochemical characteristics of the rocks is that carbonate magma is directly derived from the low degree partial melting (F <1%) of the lithosphere-enriched mantle and the remnant mantle mineral assemblage is characterized by the enrichment of garnet. Separation and crystallization in the deep magma chamber of the crust. The REE and trace element distribution patterns of carbonate rocks are very similar to the ore-bearing fine dolomite marble of the REENbFe deposit in the Bayan Obo area. However, the main element of carbonate rocks is characterized by calcareous, which is different from the ore-bearing fine-grained dolomite marble. The reason for this discrepancy is that the carbonate rock wall is not subjected to large-scale dolomitization, Dolomite marble may be the result of dolomitization of carbonate rocks.