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Anton terrane revisited: Late Archean exhumation of a moderate-pressure granulite terrane in the western Slave Province

¹ Continental Geoscience Division, Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A 0E8, Canada
² Department of Earth and Atmospheric Science, University of Alberta, Edmonton, Alberta T6G 2E3, Canada
³ Department of Geology, University of Regina, Regina, Saskatchewan S4S 0A2, Canada

The Anton terrane of the western Slave Province has been interpreted as a remnant of a meso-Archean (3500–2800 Ma) microcontinent. The largest coherent entity of the terrane is a previously unrecognized 50 by 250 km granulite complex, herein termed the Snare domain. The granulite facies mineral assemblages give the domain a characteristic magnetic signature that is distinct from areas of exposed meso-Archean basement in the Slave Province. The domain consists of interlayered 3100–2624 Ma orthogneisses and paragneisses and 2600–2585 Ma granitoid rocks; its structure was largely established during 2610–2590 Ma orogeny throughout the province that culminated in ca. 2590 Ma granulite facies metamorphism. Pressure-temperature (P-T) determinations yield peak conditions of 775–875 °C at 6–7 kbar. Shortly thereafter, 2–4 kbar of decompression occurred before the domain cooled below 450 °C. Decompression and retrogression textures are widespread but are most pervasive adjacent to late extensional detachment faults. U-Pb zircon age data suggest that the Snare domain was partially exhumed from mid-crustal levels ca. 2585–2580 Ma. We attribute exhumation to tectonic denudation of an overthickened crustal welt in the western Slave Province. Localization of the crustal welt in this part of the Slave Province may be related to the presence there of meso-Archean crust.

Key Words: Slave Province • extensional collapse • granulites • neo-Archean