Implications of the tectonic setting, magma-wallrock interaction and postemplacement evolution of carbonatites for their rare-metal (REE, Nb, Ta, Zr and U) potential

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Carbonatites and genetically related carbonate rocks are an economically important source of rare metals. In recent years, it has been increasingly recognized that carbonatites may have multiple origins and show fundamental differences specific to their tectonic setting and mantle sources. These relations between the tectonics and geochemistry of carbonatites (and, therefore, also their economic potential) have not been systematically studied to date. Neither the effects of magma-wallrock interactions on the transport and sequestration of rare elements, nor the impact of postemplacement textural and chemical changes on the geometry and composition of carbonatite-hosted ore bodies have been studied in adequate detail. The proposed research will address these existing gaps in an attempt to identify the principal factors that contribute to the development of economic concentrations of REE, Nb, Th and other rare metals in carbonatites. The novelty of the proposed research program is in that it will involve a systematic and integrated study of carbonatites containing documented rare-element mineralization from different tectonic settings. The program will build on the applicant's extensive experience with these geological systems and will involve acquisition of new material not studied previously, but representing important geologically distinct types of carbonatite. The program will include a large training component and will follow a multi-analytical approach to ensure that different styles of mineralization can be interpreted in the context of carbonatite evolution. This analycal work will involve geochemical characterization of samples, mineral identification, source-provenance studies, and petrogenetic modelling. The three major outcomes of this work will be: (1) an improved understanding of the sources and processes responsible for the formation of carbonatites; (2) refined exploration criteria for carbonatite-hosted ore deposits, and (3) training of highly qualified personnel. The results of the proposed research will be disseminated through publications in peer-reviewed international journals, web-based media, and presentations at conferences and mineral exploration conventions.