The distinct metamorphic stages and structural styles of the 1.94–1.86 Ga Snowbird Orogen, Northwest Territories, Canada

Abstract

Palaeoproterozoic orogenesis within the Archean southeastern Rae craton is related to the initial amalgamation of Laurentia. Characterizing the accompanying tectonic processes during this time has been complicated due to polymetamorphism, which results in the obscuring of the age record of the terranes involved.

The Precambrian paleogeography of Laurentia

“…2.0 to 1.9 Ga (Hoffman, 1989); the Snowbird orogen associated with ca. 1.90 Ga collision between the Rae and Hearne provinces and associated terranes (Berman et al, 2007;Thiessen et al, 2020); the Nagssugtoqidian orogen due to the ca. 1.86 to 1.84 Ga collision between the Rae and North Atlantic provinces (St-Onge et al, 2009); and the Torngat orogen resulting from the ca.…”

Circa 1.9 Ga Rae‐Hearne collision from Lu–Hf garnet chronology in eclogites

“…The prevalence of both 2.6-2.5 Ga and 1.92-1.86 Ga moderate to high pressure metamorphism and deformation in parts of the STZ (e.g. Baldwin et al, 2004;Berman et al, 2007;Dumond et al, 2015;Graziani et al, 2022;Martel et al, 2008;Regan, Williams, Chiarenzelli, et al, 2017;Sanborn-Barrie et al, 2019;Thiessen et al, 2020) and 3. The ambiguity in interpreting some previous accessory phase geochronology results in the poly-metamorphic and -deformed rocks of the STZ as they are difficult to link to specific P-T conditions given that they are not principal phases participating in major metamorphic reactions.…”

“…Ascertaining which of these hypotheses is accurate is complicated by: Four tectono‐metamorphic events that variably affected the south‐east Rae‐north‐west Hearne cratons (2.66–2.58 Ga Kenoran, 2.56–2.50 Ga Macquoid, 1.94–1.90 Ga Snowbird and 1.84–1.80 Ga Trans‐Hudson orogenies) (Pehrsson et al., 2013); The prevalence of both 2.6–2.5 Ga and 1.92–1.86 Ga moderate to high pressure metamorphism and deformation in parts of the STZ (e.g. Baldwin et al., 2004; Berman et al., 2007; Dumond et al., 2015; Graziani et al., 2022; Martel et al., 2008; Regan, Williams, Chiarenzelli, et al., 2017; Sanborn‐Barrie et al., 2019; Thiessen et al., 2020) and The ambiguity in interpreting some previous accessory phase geochronology results in the poly‐metamorphic and ‐deformed rocks of the STZ as they are difficult to link to specific P – T conditions given that they are not principal phases participating in major metamorphic reactions. …”