Carbonatites in plate-collision zones: implications for mantle processes, carbon cycling and rare-earth metallogeny

碳酸盐岩在其组成、物理性质和工业潜力方面是低体积幔源岩浆活动的显著表现。这些岩石及其风化产物长期以来一直是稀土元素（REE）和铌等技术上“关键”金属的主要来源。尽管在这方面发表了大量的文献，但在地壳再循环和岩浆-地壳相互作用在碳酸盐岩成岩中的作用、流体渗透、变形和交代作用下碳酸盐岩中稀有金属富集和扩散过程的性质、特定地球化学特征（如元素或同位素比值）对勘探矢量的适用性等关键问题上尚未达成共识。近年来，由于在（古）造山带发现的碳酸盐岩越来越多，认识到一些最重要的稀土矿床与板块碰撞过程有关，以及新的同位素证据，有必要对原有的碳酸盐岩演化模式进行修订。拟议的研究计划旨在获取新的数据，以弥补现有的知识空白，并为发展板块碰撞带碳酸盐岩岩浆作用的成岩成矿模式提供基础。拟议工作的新颖之处在于其综合和包容的方法，其重点是目前几乎没有同位素数据的岩石和矿床。该项目建立在我25年的碳酸盐岩研究经验和与马尼托巴地质调查局的持续合作基础上。下一个“发现格兰特”周期的主要预期成果是提高对板块碰撞带碳酸盐岩的地幔源的认识，对这些环境中碳酸盐岩岩浆活动的地球动力学和构造控制，以及对稀有金属矿床发展的源特异性、岩浆作用和置地后作用的相对贡献。这些领域的进展将为改进目前的矿物勘探做法提供基础。拟议方案的其他好处将是出版一些潜在勘探目标的新地质数据，并培训具有矿物勘探和研究所需的理论知识和实际技能的高素质人员。马尼托巴大学在提供这类培训方面具有独特的工具性能力。我以前在碳酸盐岩方面的工作得到了学术界、工业界和政府部门的认可和支持。拟议的研究结果将通过出版物、在会议和采矿公约上的发言、知识使用者讲习班和其他外联形式加以传播。

Carbonatites are a remarkable manifestation of low-volume, mantle-derived magmatism in terms of their composition, physical properties and industrial potential. These rocks and their weathering products have long served as the principal source of such technologically “critical” metals as rare-earth elements (REE) and niobium. Despite the large volume of literature published on this subject, no consensus has been reached yet on such key issues as the role of crust recycling and magma-crust interaction in carbonatite petrogenesis, the nature of processes responsible for the concentration and dispersal of rare metals in carbonatites subjected to fluid infiltration, deformation and metasomatism, and the applicability of specific geochemical characteristics (e.g., element or isotope ratios) to exploration vectoring. In recent years, revision of the previously existing models of carbonatite evolution has been necessitated due to: an increasing number of carbonatite discoveries in (paleo)orogenic belts, the realization that some of the most important REE deposits are associated with plate-collision processes, and new isotopic evidence. The proposed research program is aimed at acquiring new data to address the existing knowledge gaps and to provide a basis for the development of a petrogenetic-metallogenic model for carbonatitic magmatism in plate-collision zones. The novelty of the proposed work is in its integrated and inclusive approach, and its focus on rocks and mineral deposits for which little isotope data are presently available. The program builds on my 25 years of research experience with carbonatites and ongoing collaboration with the Manitoba Geological Survey. The principal expected outcomes of the next Discovery Grant cycle are an improved understanding of the mantle source(s) of carbonatites in plate-collision zones, of geodynamic and structural controls on carbonatitic magmatism in these settings, and of the relative contribution of source-specific, magmatic and postemplacement processes to the development of rare-metal deposits. Progress in these areas will provide a basis for refining the current mineral exploration practices. Other benefits of the proposed program will be in the publication of new geological data for a number of potential exploration targets, and in the training of highly-qualified personnel equipped with theoretical knowledge and practical skills required for mineral exploration and research. The University of Manitoba has unique instrumental capabilities for providing this type of training. My previous work on carbonatites has been recognized in, and supported by, academic, industrial and government sectors. The results of the proposed research will be disseminated through publications, presentations at conferences and mining conventions, workshops for knowledge users and other forms of outreach.