Superior Craton - Southern Superior Province

Southern Superior Province

The Southern Superior province is of Late Archean origin: 2.75-2.65 Ga. There were two primary volcanic associations: the tholeiitic basalt-komatiite and the tholeiitic to calc-alkaline bimodal basalt-rhyolite. The tholeiitic basalt-komatiite association is "characterized by near-flat REE patterns and complex Th-U-Nb-LREE systematics; rare transitional to alkaline basalts and Al-depleted komatiites have fractional crystallization REE patterns and OIB-like trace element signatures. This is interpreted as representing an oceanic plateau derived from a heterogeneous mantle plume. The latter bimodal association has fractionated REE patterns and negative Nb, Ta, P, and Ti anomalies typical of arc magmas. Turbidites plot on mixing hyperbolae between mafic and felsic end members. This association is interpreted as an arc-trench system. Tonalite plutons derived from partial melting of subducted oceanic slabs intrude the subduction-accretion complex as the magmatic arc axis migrated towards the trench....The variability of the mantle mineral ratios in these oceanic plateau basalts is interpreted in terms of recycling variable quantities of oceanic crust processed through a subduction zone (high Nb/U, Nb/Th), and complementary arc crust (low Nb/U, Nb/Th) into the source of the plumes. Collectively, these events are interpreted as a part of a late Archean supercontinent cycle, involving accretion of oceanic plateaus, island arcs, continental fragments, closure of ocean basins, rifting of magmatic arcs, and plume arc interactions." (Polat et al., 2001).

The Southern province consists of the following early Paleoproterozoic thick cover sequence: from west to east there is the Animikie Group, Marquette Range Supergroup, Huronian Supergroup-Whitewater Group and Mistassini-Otish Mountains Group. Glacial diamictites characterize the Southern province sequence All of the successions are characterized by deep-water marine deposits, Fe-formation and mafic volcanic rocks above the quartzarenites. Above the deep-water deposits is a ca. 1.95-1.85 Ga upward-coarsening succession thought to have been formed during collisional orogeny during the formation of Laurentia. (Rainbird, 2004).

The 1.85 Ga Sudbury Intrusive Complex is situated on the southern edge of the Superior Province and represents one of the most richly mineralized bodies of the Canadian Shield. Current thinking regards the gabbro-noritic intrusion to have been generated in response to meteorite impact. (Percival, 2006).