Late Neoarchean terrane and Paleoproterozoic HT–UHT metamorphism on southern Devon Island, Canadian Arctic

Abstract

The northernmost exposures of the Laurentian shield in Canada outcrop on Devon and Ellesmere islands, near the tectonic domains of the ≥2.6 Ga Rae Province and ca. 2.0–1.9 Ga Thelon–Inglefield orogenic arc. We report (Th)–U–Pb zircon and monazite ages along with phase equilibrium modelling pressure–temperature estimates for southern Devon Island, the only area on Devon or Ellesmere islands with previously known Archean rocks. Our results demonstrate that southern Devon Island is a late Neoarchean (ca. 2.55–2.47 Ga) terrane composed of lower to middle crustal, granulite facies rocks with evidence of anatexis and pervasive solid-state ductile deformation. Protoliths of clinopyroxene–garnet quartzofeldspathic gneiss, orthopyroxene quartzofeldspathic gneiss, two-pyroxene metabasite and biotite granite gneiss were emplaced between ca. 2.55–2.51 Ga, and a clastic sedimentary protolith for rutile–garnet metasedimentary rocks was deposited at ca. ≥2.47 Ga. Earlier, poorly constrained metamorphic events are recorded at ca. 2.54, 2.47 and 2.30 Ga, possibly associated with pulses of the Arrowsmith orogen (ca. 2.5–2.3 Ga). Most recently, this terrane was reworked by high temperature (HT) to ultrahigh temperature (UHT) metamorphism at ca. 1.91 Ga during with the Thelon–Inglefield orogen; obtaining peak P–T conditions of ca. 9 kbar and >850 °C. The discovery of a sapphirine–quartz metapelite assemblage is a first for the Canadian Arctic and is diagnostic evidence of UHT conditions within the Thelon-Inglefield orogenic zone.