NEW PERSPECTIVES ON TECTONIC ASSEMBLY OF THE WESTERN RAE CRATON: EVIDENCE FROM THE ATHABASCA REGION OF SASKATCHEWAN, CANADA

The full history of the tectonically complex Rae craton is by no means fully resolved but evidence is accumulating that it was independent of the Hearne craton before later incorporation within Laurentia/Nuna. The concept of an independent Rae reframes perspectives on how the supercontinent concept applies to the Precambrian and the pivotal role Rae craton may have played. Because it holds key evidence of Rae’s earlier involvement in Nunavutia (Arrowsmith orogenesis) as well its subsequent involvement in Nuna (Thelon-Taltson orogenesis), the western Rae is of fundamental importance. The Thelon orogen of the western Rae was once ascribed to collision and indentation of the Slave craton and Buffalo Head terrane with Rae. Evidence is mounting, however, for a distinct late Neoarchean to Early Paleoproterozoic orogenic belt inboard of the Thelon tectonic zone, the ‘Arrowsmith orogen’. Robust Arrowsmith effects have now been recognized well into the Rae interior. The western Rae thus may represent a long-lived accretionary margin, but important questions remain. Among these are: when did the process of accretion begin, at 2.3 Ga, or earlier and what colliding blocks were involved? Furthermore, when did accretion end and what was involved in the transition to Thelon-Taltson orogenesis? The Athabasca region holds important clues to these questions. In this region, an internal block dominated by Neoarchean (2.6 Ga) crust (Nolan domain) is bounded across a high-strain zone to the west and south by Paleo- to Mesoarchean (3.4-3.0 Ga) crust intermixed with Early Paleoproterozoic (2.5-2.3 Ga) crust, including a distinctive suite of syn- to post-collisional Arrowsmith-age granites. Intrusive relationships suggest that this hybrid crust, effectively the extension of the Taltson basement complex, was generated by 2.5-2.3 Ga accretion of a Paleo- to Mesoarchean terrane. During subsequent Taltson orogenesis, 1.99-1.93 Ga I- and S-type granites were emplaced within this hybrid crust and the internal suture zone was intensively reworked, with competent granites of the Nolan domain acting as a buttress. Further study is required to trace this fundamental boundary eastward toward the Snowbird tectonic zone and more fully understand its significance.