A genetic model and geochemical exploration tools for magnetite-apatite REE deposits

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The heavy rare earth elements (HREE) and Nd are of strategic importance because of their application in new technologies designed to address the issue of global warming, and are critical raw materials for future economic development. Because there are no major producers of these metals outside China, Focus Graphite Inc. has a significant opportunity to exploit the potential resources of the Kwyjibo magnetite-apatite REE deposits (Québec). The proposed research builds on research undertaken through the NSERC Engage program and aims to formulate a comprehensive model for the genesis of the deposits and develop tools that could be used in their ongoing exploration. In contrast to most base and precious metal ore systems, for which robust genetic models have been developed, we have a poor understanding of how the REE are concentrated to economic levels, and almost no understanding of how this occurs in magnetite-apatite rocks. Indeed, even the genesis of magnetite-apatite rocks is a matter of debate, with opinion being divided over whether they are magmatic or hydrothermal in origin. Moreover, many of them have sub-economic concentrations of the REE. The Kwyjibo deposits are exceptional in having high concentrations of the REE, particularly the HREE. This may be because they experienced subsequent hydrothermal alteration that remobilised the REE and could have introduced additional REE resources. We plan to study the magnetite-apatite rocks and their hydrothermally altered equivalents using the results of a combination of major and trace element analyses of the bulk rocks, minerals and, if present, melt and fluid inclusions. These data will be complemented by results of analyses of the stable and radiogenic isotope chemistry of mineral separates and bulk rocks. In addition, we will conduct microthermometric analyses of fluid inclusions and thermodynamic modelling. The sum of these activities will allow us to determine the genesis of the magnetite-apatite rocks, the source of the REE, and how hydrothermal fluids mobilised the REE. Through an analysis of the mineral chemistry, the project should also yield tools for the exploration and discovery of similar deposits both locally and elsewhere in Canada.