Tectonic evolution of the WSW Rae craton, Athabasca region, Canada: Laboratory for study of Precambrian crustal processes

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Continents are complex tectonic aggregations that have evolved over hundreds of millions of years. The continents of the earth have coalesced and dispersed several times in earth's history forming ‘supercontinental’ landmasses. Whereas the movements of the continents are fairly well known in recent history, knowledge of their positions and roles in ancient landmasses becomes increasingly fragmentary going back in geological time. This proposal deals with a distinctive Archean (greater than 2.5 billion year) crustal block, the Rae craton, located centrally in the Precambrian shield of North America, known as Laurentia. Within Laurentia, the Rae craton is surrounded by five other distinctive Archean blocks that were assembled ~2 billion years ago to form Earth’s first supercontinent, ‘Nuna’. Rae craton was once thought to be connected to its nearest neighbour, the Hearne craton, in an even older Archean landmass known as ‘Kenorland’. However, we now recognize that the Rae has special characteristics, distinctive from the Hearne, suggesting that it originated from an independent landmass, ‘Nunavutia’. The Rae therefore appears to have been part of one ancient landmass (2.5 to 2.3 billion year 'Nunavutia') and, following break-up, became incorporated in another (2.0 to 1.8 billion year old 'Nuna'). The proposed research will investigate the tectonic history of Rae craton to better understand its journey from its place of origin within Nunavutia to its later involvement in Nuna about 2 billion years ago. Work will focus along the west-southwest Rae margin in the Athabasca region, an excellent laboratory for study of tectonic events that affected the Rae through time. A major aim is to characterize tectonic activity associated with a 2.5 to 2.3 billion-year-old mountain-building episode, the Arrowsmith orogeny, which sets Rae apart from other Archean blocks. This improved understanding will serve both to verify and better establish steps in Rae’s travels from one ancient landmass to the other. On a broader scale, this will help determine whether, and if so how, the supercontinental concept can be applied to the Precambrian. It will also shed light on an important period in early earth development, the early Paleoproterozoic (2.5 to 2.0 billion years ago), when significant changes occurred in the earth system such as the emergence of the continents (above sea level), oxygenation of the atmosphere, the first significant glaciations, as well as fundamental changes in crustal architecture and tectonic style, including the probable onset of modern-style plate tectonics.