Mafic Layered Intrusions Through Time

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Mafic layered intrusions crystallize from basaltic magma to form large bodies of igneous rocks that exhibit prominent layering, preserving stunning rock records of the processes by which magma evolves within the Earth's crust. These intrusions contain world-class deposits of chromium (Cr), platinum group elements (PGE), and vanadium (V), metals that are vital to industry and society in general. Despite their scientific and practical importance, precise age constraints are lacking and many aspects of their origin and formation are still poorly known. The proposed research aims to fill these critical knowledge gaps and will take advantage of recent analytical developments and state-of-the-art instrumentation to constrain the age, duration, and cooling of mafic layered intrusions. This will be achieved by detailed fieldwork and geochemical analysis of rocks and minerals from some of the world's largest and most influential layered intrusions that collectively represent a significant span of Earth history (over 2.5 billion years): (1) the Stillwater Complex, the exposed fragment of a large layered intrusion in the Beartooth Range of the Wyoming Archean Province, including the PGE-rich J-M Reef, (2) the Bushveld Complex, the world's largest layered intrusion, located in the northern Kaapvaal craton of South Africa, and host to some of the richest Cr-PGE-V ore deposits on Earth, (3) the Great Dyke, a 550 km-long layered intrusion in the Zimbabwe craton of southern Africa, containing the world's second largest reserve of PGE, (4) the Kiglapait Intrusion, a bowl-shaped intrusion exposed in the Nain Plutonic Suite of coastal Labrador, and (5) the Skaergaard Intrusion of eastern Greenland, one of the most remarkable layered igneous bodies on Earth that is related to thick sequences of continental flood basalts and opening of the North Atlantic Ocean. The proposed research will yield new scientific insights on timescales of magmatic processes and cooling for these striking rocks, challenging presently known basic concepts of magma crystallization and evolution. The results of this work will have direct implications for the origin of magmatic ore deposits and can be applied to the investigation of less well-studied intrusions in Canada and worldwide.