碳酸岩–碱性岩岩浆–热液演化与稀土成矿作用

稀土元素被称为“工业维生素”，是世界强国觊觎的战略性矿产资源，对稀土矿床的成因及分布规律的研究具有十分重要的意义。与火成碳酸岩–碱性岩有关的矿床是世界上最重要的稀土成矿类型，该类矿床往往也赋存大量铌、钪、钍等稀有金属元素。为深入揭示碳酸岩–碱性岩岩浆活动与稀土成矿的成因联系，本项目拟选取华北克拉通内典型的稀土矿床（内蒙白云鄂博、鲁西微山）与不成矿的岩体（鲁西莱芜–淄博碳酸岩、山西紫金山碳酸岩–碱性岩杂岩）开展对比研究。通过同位素示踪、矿物微区原位成分分析、熔/流包裹体原位成分测试、水/岩作用实验模拟等手段厘定成矿与非成矿岩体的源区性质和岩浆演化过程的异同点，阐述地幔交代过程对稀土成矿潜力的控制，约束岩浆–热液演化过程中稀土和铌等稀有金属元素的地球化学行为，试图回答为什么有的岩体成矿，而有的岩体不成矿这一关键问题。研究成果对丰富稀土成矿理论、指导矿产深部勘查和高效利用具有重要意义。

The rare-earth elements (REE) have unique and diverse properties that make them as “industrial vitamin” and thus, many countries consider them as strategically important resources. The increasing demand for REE has driven studies on REE ore genesis and exploration. Most REE deposits in the world are genetically related to carbonatitic-alkaline magmatism. Such a type of deposit may also contain appreciate amounts of rare metals, such as Nb, Th and Sc. In order to better understand the genetic relationship between REE mineralization and carbonatitic-alkaline magmatism, the proposed study will select two carbonatite-alkaline intrusion-related REE deposits (e.g., Bayan Obo in Inner Mongolia, Weishan in the western Shandong province) and two non-mineralized intrusions (e.g., carbonatite in the western Shandong province and carbonatite-alkaline complex in the Shanxi province) in North China Craton to conduct a comparative study. A comprehensive dataset will be obtained for the above-mentioned objectives, including bulk-rock elemental and isotopic data, in-situ mineral elemental and isotopic data, melt/fluid inclusion compositional data. We also plan to conduct a set of laboratory fluid/rock interaction experiments. The results will be used to characterize magma sources and evolutions processes of both mineralized and non-mineralized carbonatitic-alkaline intrusions, and also used to define the properties and evolution processes of REE ore-forming fluids. On this basis, we will evaluate the controls of mantle metasomatism and fluid-melt evolution on REE ore formation, and to better understand why some carbonatitic-alkaline intrusions could produce REE mineralization while some could not. Such a proposed study will largely increase our knowledge on REE ore genesis, and also have a great potential to provide guidance for explorations and efficient utilization of REE and certain rare metals.