Lower Proterozoic arc–microcontinent collisional tectonics in the western Churchill Province

Abstract

Arguments favouring evolution of the ‘Hudsonian’ orogen of the Churchill Province through plate tectonic processes^1–3 are generally supported by recent work in Saskatchewan and Manitoba^4–11. Palaeomagnetic data do not preclude operation of the Wilson cycle in this region during the Lower Proterozoic^12–15. At present, however, subduction-related sutures in the Churchill Province are unconvincingly documented. Even the Thompson Belt (‘Nelson Front’), forming part of the postulated suture between the Superior Province craton and the western Churchill mobile belt (Fig. 1), is markedly oblique to major volcanoplutonic and other lithostructural belts of the western Churchill and is thus unlikely to be a simple collisional junction. Orogens formed at consuming plate margins are likely to incorporate pre-terminal, arc-related sutures, variably obscured by later events¹⁶. Previous proposals for location of such intraorogenic sutures within the western Churchill belt, predicated largely on geophysical evidence¹⁷, are unsupported by recent geological investigations⁵. However, on the basis of recent fieldwork, I now outline a strong geological case for intraorogenic collisional suturing and microplate interaction in south-east parts of the Churchill Province in Saskatchewan.