Geochemical and Nd isotopic constraints from plutonic rocks on the magmatic and crustal evolution of Southampton Island, Nunavut

Abstract

Precambrian rocks exposed on Southampton Island, Nunavut, are dominated by plutonic units, consisting mainly of tonalite-granodiorite-monzogranite and minor mafic units. Based on geochemistry, 80 plutonic samples analyzed can be subdivided into 1) a mafic group, 2) a syenite to quartz monzonite group, and 3) a voluminous tonalite to syenogranite group. Compositional gaps and field relationships argue against either a consanguineous or a co-genetic relationship between mafic and felsic compositions. Most samples are metaluminous, magnesian, calcic to calc-alkalic, and exhibit large variations in trace-element concentrations. Thirty regionally distributed Nd isotopic samples yielded TDM ages ranging from 2.79 to 3.65 Ga, indicating a Meso- to Paleoarchean crustal substrate. Strongly negative eNd (1.9 Ga) values (-4.91 to -19.81) argue against significant material input from depleted mantle sources (e.g. MORB) during Paleoproterozoic granitoid petrogenesis. Regional Nd isotopic data sets plus U-Pb crystallization data sets from these Precambrian rocks support correlation with the diamond-hosting Repulse Bay block of the Rae Province.

The Hudson Bay Lithospheric Experiment (HuBLE): insights into Precambrian plate tectonics and the development of mantle keels

“…Zircon inheritance and Nd model ages of up to 3.6 Ga confirm the ancient nature of the northern Rae domain (e.g. Whalen 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).…”

“…To the south and southwest, the RBb continues to at least the Wager shear zone (Henderson and Roddick 1990), and perhaps (based on the regional Nd isotopic and U-Pb crystallization datasets of Southampton Island) slightly beyond (e.g., Skulski et al 2006;Whalen et al 2011;Rayner et al 2013). The LIBZ mimics the nature of aeromagnetic map patterns produced by the ≤1808 Ma Wager shear zone (e.g., dextral shear), which is interpreted to be a strike-slip fault related to terminal collision during the TransHudson orogeny (Fig.…”

Neoarchean continental crust formation and Paleoproterozoic deformation of the central Rae craton, Committee Bay belt, Nunavut

“…2.95-2.75 Ga tonalite-granodiorite exposed southwest (i.e., White Hills -Woodburn: Davis and Zaleski 1998) and northeast (i.e., Melville Peninsula: Frisch 1982;Baffin Island: Jackson et al 1990;Bethune and Scammell 2003) of the Committee Bay area likely constitutes thinned basement to the supracrustal belts. In contrast, there is considerable isotopic evidence (U-Pb and Sm-Nd) of Mesoarchean ancestry along the Rae craton's present-day margins (van Schmus et al 1986;Crocker et al 1993;Henderson and Thériault 1994;Thériault et al 1994;Young et al 2007;Peterson et al 2010;Whalen et al 2011;Rayner et al 2013). The plutonic basement rocks and supracrustal belts are cut by widespread and voluminous ca.…”

“…Peripheral >3 Ga "proto-Rae" crust reflecting earlier protracted break-up events. U-Pb crystallization ages >3 Ga denoted by filled triangles, >3 Ga Sm-Nd model ages denoted by white squares (data from Hartlaub et al 2005;Young et al 2007;Connelly et al 2006;Peterson et al 2010;Whalen et al 2011;Rayner et al 2013). (b) Circa 2.5-2.35 Ga setting of the western Rae craton illustrating how potential easterly subduction below Queen Maud block (>3 Ga proto-Rae margin) led to ca.…”