The Superior Craton is a stable crustal block covering Quebec, Ontario, and southeast Manitoba in Canada, and northern Minnesota in the United States. It is the biggest craton among those formed during the Archean period. 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.Bleeker, W., & Davis, B. W. (2004, May). What is a craton? How many are there? How do they relate? And how did they form?. In AGU Spring Meeting Abstracts. The size of Superior Craton is about 1,572,000 km2. The craton underwent a series of events from 4.3 to 2.57 Ga. These events included the growth, drifting and deformation of both oceanic and continental crusts.

Researchers have divided the Superior Craton into many different domains based on rock types and deformation styles. These domains (grouped into western and eastern superior provinces), include the North Superior Superterrane and Wawa Terrane, among others (shown in the table below).

Studies on the formation of the Superior Craton varied in progress between the western and the eastern part. For the western part, five major orogenies were involved. They include the Northern Superior Orogeny (2720 Ma), the Uchian Orogeny (2720–2700 Ma), the Central Superior Orogeny (2700 Ma), the Shebandowanian Orogeny (2690 Ma), and the Minnesotan Orogeny (2680 Ma). For the eastern part, two models are suggested. The first model by Percival and Skulski (2000) focuses on the collision between the terranes. The second model by Bédard (2003) and Bédard et al. (2003) focuses on the effect of an active anorogenic magmatic activity.

Location

The Superior Craton covers central Canada; it occupies the northern and central part of Quebec, extending across the central and the southern part of Ontario, and also covers most of Manitoba and eastern North and South Dakota, with its tip reaching central South Dakota. Sims, P.K., Peterman, Z.E., Hildenbrand, T., and Mahan, S., 1991, Precambrian basement map of the Trans-Hudson orogen and adjacent terranes, northern Great Plains, U.S.A.: U.S. Geological Survey IMAP 2214, 1 map, https://doi.org/10.3133/i2214.

Tectonic setting The Archean Superior Craton extends over 1,572,000 km2 of the North American continent. Forming the core of the Canadian Shield, the Archean Superior craton is encompassed by early Proterozoic orogens. The western to the northeastern part of the craton is bound by the Trans-Hudson orogens. To the eastern and the southeastern side are the neighbouring Grenville orogens. The southern side meets the Keweenawan rift, while the southernmost tip of the craton in Minnesota reaches the Central Plain orogen.

Regarding the faults, there are three major trends of subparallel faults slicing the craton into linear subprovinces. In the northwestern part, faulting occurs in a west–northwest direction. The northeastern part has northwest-trending faults. The faults in the remaining southern part possess an east–west direction.

Growth history of the terranes The craton-forming terranes are created from very diverse settings, such as oceanic arc, ancient forearc, oceanic tectonic melange, uplift within the craton, fold-thrust belt and extra. Common among them is that these features were mostly formed in a compression setting.

Oceanic arc setting Some terranes, such as the Western Wabigoon Terrane, are formed from the setting of an oceanic arc. An oceanic arc is a chain of volcanoes which formed above and parallel to the subduction zones. Due to tectonic activities in the Earth, the relevant continental and oceanic crusts collided before 2.70 Ga. The denser oceanic crust subducted underneath the continental crust and melted into the mantle, which generated more magma. The huge amount of magma then rose up, penetrated through the crust above and erupted. The continuous eruption of volcanic material cooled down and accumulated around the centers of eruption, forming a chain of volcanoes in the shape of an arc.Grove, T. L., Till, C. B., Lev, E., Chatterjee, N., & Médard, E. (2009). Kinematic variables and water transport control the formation and location of arc volcanoes. Nature, 459(7247), 694.

Ancient forearc basin setting Some terranes, such as the Quetico Terrane, were forearcs in the past. A forearc is the region between the volcanic arc and the subduction zone. It includes several components, including the subduction trench, the outer arc high of the oceanic crust, the accretionary wedges, and the sedimentary basin. 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 sedimentary basin is formed from the accumulation of erosive material from the volcanoes, which lying flatly between the volcanoes and the topographic high of the accretionary wedge.

Uplift setting Some terranes, such as the Kapuskasing Uplift, were formed from the uplifting of the crustal block. For example, during 1.85 Ga, the American Midcontinent and the Superior Craton collided. The collision between the two cratons triggered an Archean reverse fault, the Ivanhoe Lake fault. The upward movement of the hanging wall causes the uplift of a crustal block, known as the Kapuskasing Uplift.Zhang, B. (1999). A study of crustal uplift along the Kapuskasing Zone using 2. 45 Ga Matachewan dykes. University of Toronto.

Fold-thrust belt 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. The fold-thrust belt is formed in a compression setting like crust collision. when the crust is compressed, thrusts dipping towards where the compression comes formed. 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.Poblet, J., & Lisle, R. J. (2011). Kinematic evolution and structural styles of fold-and-thrust belts. Geological Society, London, Special Publications, 349(1), 1-24.

General composition

The Superior Province can be divided into three parts. The first part is the northwestern region characterized by high-grade gneiss, such as Minto and Pikwitonei. The second part is the northeastern region, which is characterized by pervasive metamorphic rocks of granulite-facies. The last part is the southern region like the Minnesota River Valley, which are metavolcanic or metasedimentary subprovinces with an east–west orientation.

The general geological characteristics of the terranes are listed below.

List of subprovinces and their dominating rocks SubprovinceAgeDominating rockPossible tectonic eventMineral depositWestern Superior ProvinceNorthern Superior Superterrane (NSS) - Granitic and gneissic rocksSkulski, T., Percival, J. A., Whalen, J. B., Stern, R. A., Harrap, R. M., & Helmstaedt, H. H. (1999). Archean crustal evolution in the northern Superior Province. Tectonic and magmatic processes in crustal growth: A Pan-Lithoprobe perspective. Edited by, RM Harrap and HH Helmstaedt. Lithoprobe Secretariat, The University of British Columbia, Vancouver, BC, Lithoprobe Report, 75, 128-129.

- Mafic-intermediate volcanic rocks

- Minor greywacke - Granitoid magmatism

- Amphibolite-forming metamorphism caused by tectonic accretion - Lode gold depositsStone, D. (2005). Geology of the Northern Superior Area, Ontario. Ministry of Northern Development & Mines, Ontario Geological Survey.

- Diamond-containing kimberlite pipesOxford-Skull Domain (OSD) - Basalt (Hayers River Assemblage)Corkery, M. T., Cameron, H. D. M., Lin, S., Skulski, T., Whalen, J. B., & Stern, R. A. (2000). Geological investigations in the Knee Lake belt (parts of NTS 53L). Report of activities, 129-136.

- Volcaniclastic rocks (Oxford Lake assemblage)

- Underlain by tonalitic, granodioritic, granitic pluton with mafic intrusion - Oceanic setting

- Sealed the sediment after the collision of NSS and NCS - Lode gold deposits (like Monument Bay gold deposit)North Caribou Superterrane (NCS) - Plutonic base overlain by arc sequences

- Pervasive granitic to tonalitic pluton in the central region - Dominating plutonism

- Rifting in the southern margin - Gold deposits (like Red Lake Gold Camp)

- Massive sulphide depositsEnglish River Domain (ERT) - Sedimentary rocks like wackes

- Amphibolite and low-pressure granulite

- Migmatite and diatexite - Related to the suture of the NCS and WRT/Winnipeg River Terrane (WRT)- Gneiss and foliated tonalite

- Granite - Tonalitic plutonism followed by granitic plutonism - Iron deposits

- Native silver depositsWabigoon Terrane (WwT/EwT) - Mafic volcanic rocks and tonalitic pluton in the West - Greenstone belts intruded by granitoid pluton in the East - Oceanic arc setting in the West - Continental margin setting in the East/Quetico Terrane (QT) - Mainly greywacke, migmatite, granite - Metarsedimentary successions intruded by tonalite, nepheline, syenite, carbonatite and granite - Ancient forearc/Wawa Terrane (WT) - Calc-alkalic to alkalic rocks - Sanukitoids - Oceanic tectonic mélange - Michipicoten-Mishubishu belt (Fe, Au, Cu and minor Ni) - Shebandowan-Schreiber belt (Fe, Au, VMS, Ni)Kapuskasing Uplift (KU) - Tonalite, paragneiss and anorthosite - Intracratonic Uplift/Eastern Superior ProvinceAbitibi Terrane (AT) - North: Layered-intrusion-related volcanic rocks - Central: Plutonic rocks and minor volcanic rocks - South: Younger greywackes, conglomerate and alkaline volcanic rocks/ - North: Massive sulphide deposits, Cu-Zn vein deposits, lode gold deposits - Central: Massive sulphide deposits and vein gold deposits - South: Gold deposits, Cu-Zn massive sulphide deposits, intrusive Ni deposits, and minor porphyry depositsPontiac Terrane (PT) - North: schists and paragneiss - South: volcanic rocks - Fold-thrust belt - Quartz-vein-hosted gold deposits - Gabbroic-sill-hosted Ni-Cu sulphide depositsOpatica Subprovince (OcS) - Tonalite, granodiorite, granite and pegmatite - West-verging shearing followed by south-vergent movement - Volcanogenic massive sulphide (VMS) deposits, Cu-Au vein deposits, Intrusion-hosted Ni-Cu deposits and iron formationOpinaca Subprovince (OnS) - metagreywacke - massive leucogranite intrusion/ - Rare metals in peraluminous granites and pegmatitesAshuanipi Complex (AC) - Tonalite and diorite - Granulite - Intrusion of diatexite, syenite, granodiorite and granite//La Grande Subprovince (LG) - Gneissic basement - komatiites/ - Porphyry and igneous mineralizationBienville Subprovince (BS) - North: granitic and granodioritic intrusions - South: massive granodioritic complex//Northeastern Superior Province(NESP) - I: tonalite and tonalitic gneiss - II: pyroxene-bearing plutonic rocks - IV: metasedimentary and pyroxene-bearing pluton - V: pyroxene-bearing pluton with minor tonalite - VI: magnetic pyroxene-bearing pluton - VII: tonalitic complex/ - Syngenetic: Algoma-type iron formation, volcanogenic massive sulphide, Ni-Cu deposits, Fe-Ti-V deposits (hosted by mafic intrusions), and U-Th-Mo bearing porphyry deposits - Epigenetic: Cu, Ni, Ag, Au, rare earth elements (REE) and limited U deposits

Development Research of the Superior Craton in the past focused on how the western part formed. This leaves uncertainties in the linkage between the west and the east.

Western Superior Craton