Magmatism, sedimentation and the uranium mineral system in the Paleoproterozoic core of Canada

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The Precambrian Shield makes up a significant portion of the crust in Canada, and many of the Archean (>2.5 billion years old) components were joined together about 1.8 billion years ago during a cataclysmic collision, called the Trans-Hudson orogeny, that is preserved in a linear belt that extends from Saskatchewan to Baffin Island. The collision, which was related to the motion of lithospheric plates, formed a mountain range that was probably of the same scale as the present-day Himalayas. In the lead up to the collision, there were complex interactions between different crustal elements which generated magmas, sediments, and structures. The aim of part of this research, which involves mapping and sampling in the field by a number of graduate and undergraduate students, and the application of modern analytical techniques for the analysis of trace elements and isotopes is to unravel the interaction between different crustal blocks just prior to the major collision 1.8 billion years ago, with a focus on the well-exposed rocks in northern Saskatchewan and Manitoba. It will be necessary to define the composition of different parts of the crust and mantle in order to understand how they interacted. In addition the Precambrian rocks in central Canada host world-class hydrothermal deposits of copper, zinc, gold, uranium, and rare earth elements, and their formation is intimately related to the evolution of the mountain belt.****The research will focus on the youngest igneous rocks (about 1.85 to 1.82 billion years old) that formed during this mountain-building event, partly because this represents the most complex part of this event, and will provide a chemical and isotopic “fingerprint” of the parts of the crust and mantle that might have been involved in the formation of these rocks. In addition, the sedimentary rocks that formed in basins as continental collisions were occurring preserve zircons as detrital minerals, and they record the age and character of the source regions for these sediments. The mountain belt was then eroded, and sediments were deposited in the uranium-rich Athabasca Basin, under which is a zone of alteration that may represent an ancient weathered profile. This will be examined to determine its origin, and whether this might be an important source of metals, including uranium, for the younger mineral deposits. Direct outcomes of all this work will be student theses and journal papers, and well-trained new geoscientists to work in academia, government or the Canadian minerals industry.***