Neoarchean high-potassium granites of the Boothia mainland area, Rae domain, Churchill Province: U–Pb zircon and Sm–Nd whole rock isotopic constraintsThis article is one of a series of papers published in this Special Issue on the theme of Geochronology in honour of Tom Krogh.

Abstract

The Boothia mainland region of the north-central Rae domain is underlain by remnants of a Neoarchean volcano sedimentary sequence dismembered by two regionally extensive Neoarchean high-potassium granitoid suites with rare occurrences of a structurally interleaved, Paleoproterozoic sedimentary cover sequence. The granitoids and their gneissic equivalents are dominated by variably deformed and metamorphosed I-type, metaluminous, polyphase, commonly porphyritic to augen, biotite ± hornblende monzogranite, and subordinate granodiorite, with rare tonalite. New geochronological results, the first for this area, demonstrate that the widespread Neoarchean granitoid plutonism is dominantly 2.61-2.59 Ga, with a less prominent 2.66 Ga plutonic event. The age of zircon recrystallization suggests that ca. 2.60 Ga Archean metamorphism and fabric development (S1) affected the 2.66 Ga plutons prior to or contemporaneously with intrusion of the voluminous ca. 2.6 Ga suite. 3Nd(t) for the ca. 2.61-2.59 Ga suite range from 1.4 to -1.9, overlapping with the ca. 2.66 Ga suite that range from 1.4 to 1.5. The Nd isotopic data, coupled with the presence of inherited ca. 2.65, 2.70, and 2.85-2.90 Ga zircon, suggests recycling of older, Neoarchean to Mesoarchean crust in the formation of these suites. Metaplutonic rocks preserve Paleoproterozoic deformation (F4 and F5) and amphibolite-facies metamorphism, sporadically recorded in zircon rims that formed at 1.81 Ga. This event strongly reoriented the Neoarchean fabrics in metaplutonic rocks, generally without the development of a new coaxial Paleoproterozoic fabric, and we attribute this strain and metamorphism to the Hudsonian orogeny.Résumé : La région terrestre Boothia du domaine Rae centre-nord repose sur des vestiges d'une séquence volcano-sédimentaire datant du Néoarchéen; cette séquence est démembrée par deux suites granitoïdes d'échelle régionale, à teneur élevée en potassium et possédant de rares occurrences d'une séquence structurellement intercalée d'une couverture sédimentaire datant du Paléoprotérozoïque. Les granitoïdes et leurs équivalents gneissiques sont dominés par un monzogranite à déformation variable, métamorphisé, de type I, métalumineux, polyphasé, souvent porphyrique à oeillé et à biotite ± hornblende avec une granodiorite subordonnée et une rare tonalite. De nouveaux résultats géochronologiques, les premiers pour ce secteur, démontrent que le plutonisme granitoïde néoarchéen étendu date surtout de 2,61 à 2,59 Ga, avec un événement plutonique moins important vers 2,66 Ga. L'âge de la recristallisation du zircon suggère que, vers 2,60 Ga, le métamorphisme archéen et le développement de la fabrique (S1) aient affecté les plutons âgés de 2,66 Ga avant ou en même temps que l'intrusion de la volumineuse suite vers 2,6 Ga. Les valeurs 3Nd (t) pour la suite datant de~2,61 à 2,59 Ga varient de 1,4 à -1,9, chevauchant la suite datant~2,66 Ga, dont les valeurs 3Nd (t) varient de 1,4 à 1,5. Les données d'isotopes Nd, jumelées à la présence de zircons hérités dont les âges son...

Neoarchean Mantle-derived Magmatism within the Repulse Bay Block, Melville Peninsula, Nunavut: Implications for Archean Crustal Extraction and Cratonization

“…In this area, two pulses of magmatism are prominent at ca. 2.66 and 2.61-2.59 Ga, the second pulse being coeval with granulite-facies metamorphism and the intrusion of high-K granite (Hinchey et al 2011). Here we demonstrate, however, that Neoarchean magmatism in the adjacent RBb spans a continuous time period from 2.73 to 2.66 Ga, with granulite-facies metamorphism being coeval with the intrusion of, and localized to lithologies surrounding, the ca.…”

“…Intruded into the granite-greenstone belts and their high-grade equivalent gneiss complexes are ca. 2.73-2.67 Ga calc-alkaline, felsic to intermediate plutonic suites and gneiss (Bethune and Scammell 2003;van Breemen et al 2007;Rayner et al 2011;Hinchey et al 2011).…”

“…2.55 Ga (Davis et al 2006). Collision was followed by 2.62-2.58 Ga 'I-type' dominantly monzogranitic plutonism (Skulski et al 2003;Davis et al 2006;van Breemen et al 2007;Rayner et al 2011) that has been described in areas as 'high-K' (Hinchey et al 2011).…”

Origin and tectonometamorphic history of the Repulse Bay block, Melville Peninsula, Nunavut: exotic terrane or deeper level of the Rae craton?

“…There is also abundant evidence for contamination (zircon inheritance and Nd model ages) by a Mesoarchean to Paleoarchean crust in these basement rocks and in younger intrusions (e.g., Bethune and Scammell 2003;Hartlaub et al 2005;van Breemen et al 2007a;Hinchey et al 2011;Whalen et al 2011). Mesoarchean crust has also been documented in other terranes and blocks of the Churchill Province, including the Sugluk block (2.97-2.82 Ga; Wodicka and Scott 1997;Rayner et al 2008), and the southern Hearne craton (3.1 Ga; van Breemen et al 2007b).…”

“…Mesoarchean crust has also been documented in other terranes and blocks of the Churchill Province, including the Sugluk block (2.97-2.82 Ga; Wodicka and Scott 1997;Rayner et al 2008), and the southern Hearne craton (3.1 Ga; van Breemen et al 2007b). The Mesoarchean orthogneissic rocks and the Archean supracrustal belts of the Rae craton and Chesterfield block are generally intruded by 2.73-2.67 Ga tonalitic to granitic plutons and on the mainland by voluminous 2.62-2.58 Ga, dominantly monzogranitic plutons (e.g., Hanmer et al 1994;Williams et al 2000;Bethune and Scammell 2003;Skulski et al 2003;Davis et al 2006;van Breemen et al 2007a;Dumond et al 2010;Hinchey et al 2011;Rayner et al 2011;Wodicka et al 2011).…”