Neoarchean arc magmatism and subsequent collisional orogenesis along the eastern Rae domain, western Churchill Province: Implications for the early growth of Laurentia

Abstract

The Athabasca granulite terrane, on the eastern margin of the Rae domain of the western Churchill Province, contains a well exposed record of Neoarchean magmatism, deformation, and metamorphism. Circa 2.63-2.60 Ga plutonic rocks range from 58.01 to 73.71 SiO 2 , and vary from ferroan to magnesian. They form shallow linear trends on modified alkali-lime index, plotting largely in the calcalkaline field. On tectonic discrimination diagrams, all samples plot in the volcanic arc field. Samples are LREE enriched, and contain relatively steep negative slopes, and flat, depleted, HREE profiles when normalized to chondrites. The entire Neoarchean plutonic complex, independent of lithology, contains strong enrichments in the LILEs and Pb, and depletions in HFSEs. Monazite U-Th-total Pb results from a migmatitic paragneiss suggest that partial melting occurred at ca. 2.57 Ga within the Chipman subdomain. Monazite results from the adjacent northwestern subdomain suggest that deformation occurred at ca. 2.57 Ga. IN-SIMS and ICP-MS zircon U-Pb geochronology corroborates these conclusions. Although the region is dominated by Paleoproterozoic localized shear zones, internal to each subdomain is evidence of a widespread tectonothermal event during the Neoarchean that involved arc plutonism, crustal thickening, lower crustal flow at pressures exceeding 1.0 GPa, and extensive partial melting of the lower continental crust. We interpret this sequence of magmatic, deformational, and anatectic processes to reflect the transition from a continental arc to a collisional tectonic setting. The recognized series of events presented herein is likely correlative to the 2.60-2.50 Ga MacQuoid Orogen, which has been recognized further to the northeast, and likely parallels the eastern margin of the Rae domain of the western Churchill Province. These data support an important component of modern style plate tectonics during continental magmatism and accretion in the Neoarchean. Paleoproterozoic orogenic belts (Fig. 1; Hoffman, 1988). The region offers a superb opportunity to investigate the growth and evolution of the North American continent, and to evaluate the degree with which modern tectonic processes were active during the growth and ultimate stabilization of the Archean lithosphere. Many of the stitching Paleoproterozoic orogenic belts (Hoffman, 1988), perhaps none quite as well characterized as the Trans-Hudson Orogen (

Insights into the metamorphic history and origin of flake graphite mineralization at the Graphite Creek graphite deposit, Seward Peninsula, Alaska, USA

“…6d). Similar traits employing similar methods are associated with lower crustal migmatites exposed in the Neoarchean Athabasca granulite terrain (Canada; Dumond et al 2015;Regan et al 2017) and the southern part of the Mesoproterozoic Grenville Province (USA; Williams et al 2019). In both regions, these systematic compositional attributes in monazite from migmatitic paragneisses are attributed to biotite-dehydration melting (Dumond et al 2015;Williams et al 2019), as follows:…”

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

“…Summary of geochronological data from crustal domains along the southeast Rae craton margin (data are from Ashton, 2009; Ashton, Card, et al, 2007; Ashton, Knox, et al, 2007, Ashton et al, 2009, 2014; Ashton, Knox, Card, et al, 2017; Ashton, Knox, Rayner, Creaser, & Bethune, 2017; Baldwin, Bowring, & Williams, 2003; Baldwin et al., 2004; Berman, Pehrsson, et al, 2013; Bethune et al., 2013; Bracciali, Parrish, Horstwood, Condon, & Najman, 2013; Davis et al., 2015; Dumond et al., 2008; Dumond et al., 2010; Dumond et al., 2015; Flowers, Bowring, et al, 2006; Flowers, Mahan, et al, 2006; Flowers et al., 2008; Hartlaub, Heaman, Ashton, & Chacko, 2004; Mahan, Goncalves, et al, 2006; Mahan, Williams, et al, 2006; Martel et al., 2008; Regis, Acosta‐Gongora, et al, 2017; Regis, Martel, et al, 2017; Regis & Kellett, 2018; Regan et al., 2014; Regan, Williams, Chiarenzelli, et al, 2017; Regan, Williams, Mahan, et al, 2017; Shiels et al., 2016; Thiessen et al., 2018, 2019; Williams & Jercinovic, 2002, 2012; Williams, Jercinovic, & Terry, 1999). D 1 –D 3 are deformational events discussed herein and superimposed on the data…”

“…Berman et al., 2007; Bethune et al., 2013; Martel et al., 2008; this work), interpretations from the Tantato domain are that 1.9 Ga metamorphism therein (D 2 ) relates to far‐field stress and mafic underplating in an intracontinental setting (e.g. Dumond et al., 2015; Dumond et al., 2017; Flowers, Bowring, et al, 2006; Flowers et al., 2008; Regan, Williams, Chiarenzelli, et al, 2017; Regan et al., 2014; Regan, Williams, Mahan, et al, 2017). Since high P–T conditions at 1.9 Ga are documented within the Tantato, Dodge‐Snowbird and Beaverlodge domains (Figure 13), we suggest these domains have a shared orogenic history at 1.9 Ga.…”

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

“…2.6–2.5 Ga Snow Island—Macquoid orogenies (e.g. Dumond et al., 2008, 2015; Flowers et al., 2006; Regan, Williams, Chiarenzelli, et al., 2017; Regan, Williams, Mahan, et al., 2017), or a younger ca. 1.9 Ga suture associated with collision between the Archean Rae and Hearne cratons during assembly of the supercontinent Nuna (e.g.…”