重点解剖了一条距白云鄂博REE-Nb-Fe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REE-Nb-Fe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.
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