Algoman orogeny
Blocks were added to the Superior province along a 1,200 km (750 mi) boundary that stretches from present-day eastern South Dakota into the Lake Huron area.
These three subprovinces lie linearly in southwestern- to northeastern-oriented belts about 140 km (90 mi) wide on the southern portion of the Superior Province.
[8]: 158 The collision between terranes folded the Earth's crust, and produced enough heat and pressure to metamorphose then-existing rock.
[6] This was followed by intrusions of granite plutons[10] and batholithic domes within the gneisses[11] about 2,700 million years ago;[12] two examples are the Sacred Heart granite of southwestern Minnesota and the Watersmeet Domes metagabbros (metamorphosed gabbros) that straddle the border of Wisconsin and Michigan's Upper Peninsula.
[5]: 32 The action of metamorphism on the border between granite and gneiss bodies produces a succession of metamorphosed volcanic and sedimentary rocks called greenstone belts.
[5]: 31 Most Archean volcanic rocks are concentrated within greenstone belts;[14]: 45 the green color comes from minerals, such as chlorite, epidote and actinolite that formed during metamorphism.
[5]: 31 Large-scale faults typically occur along the margins of the greenstone belts where they are in contact with enclosed granitic rocks.
[5]: 26 Most greenstone belts, with all of their components, have been folded into troughlike synclines; the original basaltic rock, which was on the bottom, occurs on the outer margins of the trough.
[5]: 32 The Superior province forms the core of both the North American continent and the Canadian shield, and has a thickness of at least 250 km (160 mi).
Later terranes docked on the periphery of continental masses with geosynclines developing between the fused nuclei and oceanic crust.
[5]: 25 Its western part contains a regional pattern of east–west-trending 100 to 200 km (60 to 120 mi) wide granitic greenstone and metasedimentary belts (subprovinces).
It begins in north-central Minnesota and continues northeasterly into central Ontario; it is partially interrupted by the Southern province.
[19] The three subprovinces are separated by steeply dipping shear zones caused by continued compression that occurred during the Algoman orogeny.
[20] This Rainy Lake – Seine River fault zone is a major northeast–southwest trending strike-slip fault zone; it trends N80°E to cut through the northwest part of Voyageurs National Park in Minnesota and extends westward to near International Falls, Minnesota and Fort Frances, Ontario.
[9]: 1 Radiometric dating from the Rainy Lake area in Ontario show an age of about 2,700 million years old, which favors a moving tectonic plate model for the formation of the boundary.
[21] Most of the flattened large crystals in the fault indicate a simple compression rather than a wrenching, shearing or rotational event as the two subprovinces docked.
[22] This provides evidence that the Quetico and Wawa subprovinces were joined by the collision of two continental plates,[22] about 2,690 million years ago.
[24] These metamorphosed rocks are volcanically derived greenstone belts, and are surrounded and cut by granitic plutons and batholiths.
The granitic intrusions within the high-grade metasediments were produced by subduction of the ocean crust and partial melting of metasedimentary rocks.
Immediately south of Voyageurs National Park and extending to the Vermilion fault is a broad transition zone that contains migmatite.
[15]: 47 The Wawa subprovince is a formerly active volcanic island chain,[6] consisting of metamorphosed greenstone belts which are surrounded by and cut by granitic plutons and batholiths.
With continued updoming of the isotherms, the third phase produced minor folding but caused major metamorphic recrystallization, resulting in the emplacement of granite at the core of the thermal dome.
[25] Geochronology of several Archean rock units establishes a sequence of events, approximately 75 million years in duration, leading to the formation of a new crustal segment.
Rocks comprising the Slave province represent a high grade of metamorphism, intrusion and basement remobilization typical of Archean terranes.
[16]: 102 Greenland separated from North America less than 100 million years ago and its Precambrian terranes align with Canada's on the opposite side of Baffin Bay.
[16]: 102 The southern tip of Greenland is part of the Nain Province, this means it was connected to North America at the end of the Kenoran orogen.
