Superior Craton

The Superior Craton is a stable crustal block covering Quebec, Ontario, and southeast Manitoba in Canada, and northern Minnesota in the United States.

[1] A craton is a large part of the Earth's crust that has been stable and subjected to very little geological changes over a long time.

[1] Researchers have divided the Superior Craton into many different domains based on rock types and deformation styles.

[3] Forming the core of the Canadian Shield, the Archean Superior craton is encompassed by early Proterozoic orogens.

[4] The southern side meets the Keweenawan rift, while the southernmost tip of the craton in Minnesota reaches the Central Plain orogen.

The outer arc high is formed by the flexural upward motion of the oceanic crust edge before it enters the subduction zone.

The accretionary wedges are formed from the accumulation of marine sediment scraped off from the oceanic crust before it is subducted.

The hanging walls of the thrusts slide up along the fault plane and stacks above the footwall, forming a ramp anticline or fault-bend fold.

[8] The last part is the southern region like the Minnesota River Valley, which are metavolcanic or metasedimentary subprovinces with an east–west orientation.

- Mafic-intermediate volcanic rocks[4][16][17] - Minor greywacke[4][16][17] - Amphibolite-forming metamorphism caused by tectonic accretion[4] - Diamond-containing kimberlite pipes[19] - Volcaniclastic rocks (Oxford Lake assemblage)[20] - Underlain by tonalitic, granodioritic, granitic pluton with mafic intrusion[4] - Sealed the sediment after the collision of NSS and NCS[4] - Pervasive granitic to tonalitic pluton in the central region[4] - Rifting in the southern margin[4] - Massive sulphide deposits[23] - Amphibolite and low-pressure granulite[4][25] - Migmatite and diatexite[26] - Granite[28] - Native silver deposits[4][30] - Greenstone belts intruded by granitoid pluton in the East[4] - Continental margin setting in the East[36] - Metarsedimentary successions intruded by tonalite,[4] nepheline, syenite, carbonatite[37] and granite[38] - Sanukitoids[4] - Shebandowan-Schreiber belt (Fe, Au,[45] VMS,[46] Ni)[47] - Central: Plutonic rocks and minor volcanic rocks[50] - South: Younger greywackes, conglomerate and alkaline volcanic rocks[51] - Central: Massive sulphide deposits and vein gold deposits[50] - South: Gold deposits, Cu-Zn massive sulphide deposits, intrusive Ni deposits, and minor porphyry deposits[4][52] - South: volcanic rocks[53] - Gabbroic-sill-hosted Ni-Cu sulphide deposits[4] - massive leucogranite intrusion[59] - Granulite[61] - Intrusion of diatexite,[61] syenite, granodiorite and granite[4][62] - komatiites[4] - South: massive granodioritic complex[64][65] - II: pyroxene-bearing plutonic rocks[4] - IV: metasedimentary and pyroxene-bearing pluton[66] - V: pyroxene-bearing pluton with minor tonalite[4] - VI: magnetic pyroxene-bearing pluton[67] - VII: tonalitic complex[7][6] - Epigenetic: Cu, Ni, Ag, Au, rare earth elements (REE) and limited U deposits[4] Research of the Superior Craton in the past focused on how the western part formed.

Before 2720 Ma, there were many pieces of microcontinent fragments which E-W trending conduit-like ocean crusts (with unknown extent) separates them.

Over time, it united the North Caribou Superterrane and confined the Oxford-Stull domain, which contains rock assemblages related to the continental margin and oceanic crust.

[71] The docking of the Northern Superior Superterrane is evident by the >3.5 Ga detrital zircons found in synorogenic (meaning that it forms during an orogenic event) sedimentary rocks aged <2.711 Ga.[71] The docking also initiated the eruption of shoshonitic volcanic rocks during 2710 Ma and the regional shortening.

The regional shortening had undergone folding and foliation to form right-lateral, NW-trending shear zones.

[71] Arc-related magmatic activities sustained in other areas of the southern North Caribou Superterrane margin at <2710 Ma.

[71] Two types of models were proposed to illustrate the process accretion with distinctive subduction polarity: Sanborn-Barrie and Skulski (2006)[73] suggested that the accretion was achieved by the northeastward subduction of the Western Wabigoon Terrane underneath the Winnipeg River Terrane.

[1] The northward direction of the subduction is evident due to the ceased arc magmatism in Winnipeg River superterrane at about 2695 Ma.

This also trapped the clastic sediments fluxing into the belt, marking its transition from an accretionary wedge to a foreland basin.

[71] The northward direction of the subduction is proven by the peraluminous granitoid magmatism in the southern margin of the Abitibi terrane, as well as the isotopic signature of the ancient crust underneath it.

[76] However, the study of seismic reflection images by Percival et al.[71] reveals that Minnesota River Valley Terrane positions at the bottom of a thrust sequence, providing evidence that it is an oceanic slab.

The western to the northeastern part of the craton is bounded by the Trans-Hudson orogens . The eastern and the southeastern side is neighbouring the Grenville orogens . The southern side is generally meeting the Keweenawan rift , while the southernmost tip of the craton in Minnesota is reaching the Central Plain orogen.
Some of the terranes were formed from the structures of a volcanic arc, including the volcanic arc chain and the forearc setting.
Some terranes, such as the Pontiac Terrane, were previously a fold-thrust belt. A fold-thrust belt is a zone consisting of a series of thrusts (reverse faults) and fault-bend folds separated by main thrust faults.
This map shows the major domains of the Superior Craton. NSS: Northern Superior Superterrane; OSD Oxford-Stull Terrane; NCT: North Caribou Terrane; ERT: English River Domain; WRT: Winnipeg River Domain; WWT: Western Wabigoon Terrane; EWT: Eastern Wabigoon Terrane; MT: Marmion Terrane; QT: Quetico Terrane; WT: Wawa Terrane; MRVT: Minnesota River Valley Terrane; KU: Kapuskasing Uplift; AT: Abitibi Terrane; PT: Pontiac Terrane; OcS: Opatica Subprovince; AC: Ashuanipi Complex; OnS: Opinaca Subprovince; LG: La Grande Subprovince; BS: Bienville Subprovince; I: Inukjuak Domain; II Tikkerutuk Domain; IV: Lake Minto Domain; V: Goudalie Domain: VI Utsalik Domain; VII: Douglas Harbour Domain
Before 2720 Ma, there were many pieces of microcontinent fragments which E-W trending conduit-like ocean crusts (with unknown extent) separates them. [ 70 ]
Northern Superior Superterrane moves southward to dock onto the North Caribou Terrane. [ 70 ] [ 71 ]
During this period, the Winnipeg River Terrane at the south docked northward onto the North Caribou Terrane. [ 71 ] The two terranes then sutured to form the English River belt, which was no earlier than <2705 Ma. Also, it marks the accretion of the younger Western Wabigoon terrane to the southwestern margin of the Winnipeg River Terrane. [ 71 ]
The Wawa-Abitibi terrane moved northward to collide with the growing craton. [ 1 ]
Minnesotan River Valley Terrane moved northward to collide with the pre-mature craton. [ 71 ]