Late Neoarchean to middle Paleoproterozoic geology of Devon and Ellesmere islands, Canadian Arctic
The northernmost exposure of the Laurentian shield in Canada outcrops on Devon and Ellesmere islands within the Canadian Arctic Archipelago. Due to the remote location, the basement rocks of these islands have received little attention. From this study, zircon crystallization ages demonstrate that D...
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| Format: | Text |
| Language: | English |
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Scholarship@Western
2023
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| Online Access: | https://ir.lib.uwo.ca/etd/9219 https://ir.lib.uwo.ca/context/etd/article/11891/viewcontent/auto_convert.pdf |
| Summary: | The northernmost exposure of the Laurentian shield in Canada outcrops on Devon and Ellesmere islands within the Canadian Arctic Archipelago. Due to the remote location, the basement rocks of these islands have received little attention. From this study, zircon crystallization ages demonstrate that Devon Island is underlain by a late Neoarchean terrane comprising orthogneisses emplaced at ca. 2.55–2.51 Ga and an interleaved metasedimentary sequence deposited at ca. ≥2.47 Ga. On northern Devon Island, younger metasedimentary sequence(s) were deposited at ca. 2.2–1.9 Ga and intruded by ca. 2.01–1.95 Ga granitoids. Devon and Ellesmere islands experienced widespread metamorphic activity associated with the Thelon orogeny between ca. 1.95–1.87 Ga, peaking at ca. 1.91 Ga. Minimum peak temperatures of metamorphism are estimated at ca. >800 ℃ throughout Devon and Ellesmere islands and the first documented sapphirine + quartz assemblage in the Devon and Ellesmere islands area is diagnostic evidence of ultrahigh temperature conditions (>900 ℃). The abundance of spinel + quartz (ca. ≥940 ℃) metasedimentary rocks on Ellesmere Island likely provides further evidence of widespread ultrahigh temperature conditions. Peak pressures of ca. 1.9 Ga metamorphism are estimated at ca. 9 kbar on southern Devon Island and ca. 6–7.5 kbar for northern Devon and Ellesmere islands. Earlier, poorly constrained metamorphic events are recorded at ca. 2.54, 2.47 and 2.30 Ga, possibly associated with pulses of the Arrowsmith orogeny. The late Neoarchean Devon terrane potentially extends to the southwest on Boothia Peninsula and to the northeast in the Prudhoe Land area of northwestern Greenland. The juvenile middle Paleoproterozoic rocks of northern Devon and Ellesmere islands represent a northern extension of the Thelon tectonic zone, which we term the Ellesmere tectonic zone. |
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