Detrital Zircon Geochronology and Provenance of the Paleoproterozoic Huron (∼2.4–2.2 Ga) and Animikie (∼2.2–1.8 Ga) Basins, Southern Superior Province

Abstract

The Archean nucleus of Laurentia, the Superior province, formed between 2.7 and 2.6 Ga. There is little record of sediment deposition on the craton for 100 m.yr. until deposition of the Huronian clastic sedimentary rocks (4–12 km thick) began along the south-central margin of the Superior province between 2.5 and 2.2 Ga. Huronian detrital zircon ages ( zircon SHRIMP 207Pb/206Pb ages from six samples) are dominantly 2.6–2.7 Ga, with a small population aged 3.0–3.5 Ga in the middle of the Huron section. The mainly younger, and western, Animikie basin (6–12 km thick; 2.21–0.8 Ga) contains a wide range of nearshore and deep-water clastic rocks, including banded iron formations and the 1.85 Ga Sudbury “impactite” deposits with overlying turbidites. Animikie detrital zircon ages ( laser ablation ICP-MS 207Pb/206Pb zircon ages from 10 samples) contain a complex spectrum, with ages ranging from 1.8 to 3.8 Ga: the basal Chocolay (Denham, East Branch Arkose) samples contain zircons ranging in age from 2.1 to 3.7 Ga, with a dominant population at ∼2.6 Ga; the basal Animikie (Menominee) quartzites contain zircons with ages between 2.1 and 3.8 Ga, with peaks variably at 2.1, 2.3, 2.6, and 3.0 Ga; the upper Animikie (Baraga) turbidites contain zircons with ages between 1.8 and 3.6 Ga, with a dominant peak at 1.85 Ga. The Huron and Animikie basins were intensely deformed by Penokean orogenic (1.85 Ga) accretion from the south. Deposition into the Huron basin was from the north and west for 200 m.yr.; then the depocenter shifted to the west at ∼2.2 Ga, with the Animikie basin receiving clastic debris from all directions, including from terranes (e.g., Marshfield and the Wisconsin Magmatic Terrane) approaching from the south. Combined Huron and Animikie detrital zircon results record a migrating east-to-west depocenter, perhaps in conjunction with the dynamics of the central Marathon large igneous province mantle plume and dike swarm (∼2.07 Ga), over a period of 500 m.yr.