Tectonic evolution of the WSW Rae craton of Laurentia: 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 relatively recent movements of the continents are well fairly known, 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 within 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 (Ga) years ago to form Earth's first supercontinent, Nuna. The Rae craton was once thought to be connected to its nearest neighbour, the Hearne craton, in a landmass known as Kenorland. However, the Rae is now recognized to have special characteristics, setting it apart from the Hearne, and indicating that it likely originated from an independent landmass, ~2.6 to 2.3 Ga Nunavutia. The Rae margin is well exposed in the western Athabasca region of Saskatchewan-Alberta-southern NWT where the Precambrian record of tectonic amalgamation of Nunavutia are overlapped by features marking break-up, followed by re-assembly of dispersed blocks to form ~2.0-1.8 Ga Nuna. We propose to investigate this region because it represents an excellent laboratory for study to monitor the Rae's geologic history. In doing so, we aim to characterize the driving forces of the 2.5 to 2.3 Ga Arrowsmith mountain-building episode, which is distinctive to the Rae, as well as to better establish how this margin transitioned toward the younger (1.99-1.93 Ga) Taltson mountain-building episode. This improved understanding will serve both to verify and better establish steps in Rae's travels from one ancient landmass (Nunavutia) to another (Nuna). 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 and fundamental changes in crustal architecture and tectonic style, including the probable onset of modern-style plate tectonics.