Circum-Superior Belt
Encyclopedia
The Circum-Superior Belt is a widespread Paleoproterozoic
large igneous province
in the Canadian Shield
of Northern
, Western
and Eastern Canada
. It extends more than 3400 km (2,112.7 mi) from northeastern Manitoba
through northwestern Ontario
, southern Nunavut
to northern Quebec
. Igneous rocks of the Circum-Superior Belt are mafic
-ultramafic in composition, deposited in the Labrador Trough
near Ungava Bay
, the Cape Smith Belt
near the southern shore of Hudson Strait
and along the eastern shore of Hudson Bay
in its northern portion; the Thompson
and Fox River
belts in the northwest and the Marquette Range Supergroup in its southern portion.
A number of magmatic features are present in the Circum-Superior Belt, including dikes
, sills
and volcanics that comprise geologic formations. This geologic belt is considered to be a large igneous province because its magmatic rocks were emplaced over an extremely short geological time span. Even though the Circum-Superior Belt was emplaced during an extremely short geological time span, the associated magmas were probably derived from a number of separate sources.
Most of the Circum-Superior Belt lies along the margin of the Superior craton
, which is the most extensive fragment of Archean
crust
on Earth. However, a number of igneous rocks within the Superior craton remain undated, indicating the existence of magmatic rocks with the same age as those of the Circum-Superior Belt is probable. It contains two large copper
-nickel
mining districts; the nickel-bearing Thompson Belt at the northwestern portion of the Superior craton and the Cape Smith Belt at the northern portion of the Circum-Superior Belt.
, New Quebec and Penokean
orogenies. The major Trans-Hudson orogeny had its appearance when the Superior craton collided with the Rae
-Hearne craton 1,900 to 1,800 million years ago. Massive orogenic belts with a change in horizontal direction are represented by the double promontory structure of the Superior craton that seem to have came from the beginning of a rift
ing event. The New Quebec orogen, also known as the Labrador Trough, lies at the northeastern portion of the Superior craton and is related to ocean closure and collision with the southeastern portion of the Rae craton. At 1,900 and 1,800 million years ago, an ocean closure and collision with the Wisconian arc terrane resulted in the creation of the Penokean orogeny at the southern Superior craton margin. The last collision occurred on the southeastern portion of the Superior craton to produce the Grenville orogeny
1,100 million years ago.
Because most of the Circum-Superior Belt was formed by widespread mafic-ultramafic magmatism 1,884 to 1,864 million years ago along the Superior craton margin during these orogenies, a number of different suggestions have been made to explain the questionable origins of this large igneous province. It is also not clear if the Circum-Superior Belt has a single origin or it has several origins. Suggestions include back-arc rifting, foredeep flexure, mantle plume
s and the breakup of a microcontinent. The geochemical indication of the Circum-Superior Belt is also poorly known; either it contains major regional differences or it is the same throughout the magmatic zone. With the discovery of the Pickle Crow dike swarm throughout the western Superior craton, the likelihood of other 1,880 million year old dike groups throughout the Superior craton remains. This is partly because several dike zones in the Superior craton remain undated. The relationship of the Circum-Superior Belt with similar age magmatism throughout the nearby Trans-Hudson belt and elsewhere on Earth is also unknown. This includes the 1,860 million year old magmatism of the East Kimberly event in Australia
and 1,860 million year old magmatism of the Mashonaland event in Africa
. The other questionable suggestion related to the Circum-Superior Belt is the existence of a suggested 1,900 million year old global superplume event.
through Quebec and Labrador, includes two volcano-sedimentary series, the first ranging from 2,170 to 2,140 million years old and second ranging from 1,883 to 1,870 million years old. This magmatism is considered to have formed as a result of back-arc volcanism. The youngest magmatic series (1883-1870 Ma) contains 1,880 million-year-old carbonatite
s and lamprophyre
s. 1,883 to 1,874 million-year-old mafic and a few ultramafic magmas comprise the Willbob and Hellancourt formations and Montagnais sills. The youngest magmatism of the youngest magmatic series is 1,870 million-year-old felsic
and carbonatitic
volcanics. These igneous rocks of the Labrador Trough cover an area of 30000 square kilometre.
To the northwest at the northern tip of Quebec near Hudson Strait
, the Cape Smith Belt includes the 2,040 to 1,970 million-year-old Povungnituk volcano-sedimentary group and the 1,880 million-year-old Chukotat Group. The 5.6 km (3.5 mi) thick Chukotat Group is made of picritic and tholeiitic basalts. These basaltic lavas are intruded by narrow mafic and ultramafic sills. At least three different types of lava compositions exist in the Chukotat Group, including olivine phyric, pyroxene-phyric and plagioclase phyric. The upper unit of the Chukotat Group is 1,870 million years old whereas the lower unit is associated with the Katiniq Suite sills, which cut through the underlying Povungnituk Group. In 1989, the Katinq Suite sills were thought to be 1,918 million years old, but more recent dating and a reinterpretation of the original age in 2004 suggests that the Katinq Suite sills are closer to 1,880 million years old. Therefore, the age range for the Chutotat Group is 1,880 to 1,870 million years. Volcanism of the Chukotat Group might have originated from rifting of a microcontinent that now forms the southwestern portion of Baffin Island
.
On the Belcher Islands
of southern Nunavut, two volcanic groups are known as the Flaherty and Eskimo volcanics. The underlying Eskimo volcanics are related with the Richmond Gulf, Persillon, Pachi and Nastapoka Group volcanics. The 1,998 million-year-old Minto dikes are also interpretend to be related with the Eskimo volcanics. The overlying Flaherty volcanics remain undated apart from a lead-lead dating of . However, the Flaherty volcanics are suggested to have relationships with the Stton Inlier and Haig sills. Geochemical indications suggest that the overlying Flaherty volcanics might also have relationships with the Povungnituk volcano-sedimentary group in the Cape Smith Belt, indicating the Flaherty volcanics might be 2,040 to 1,960 million years old. Sills on the Belcher and Snowy islands in Hudson Bay are dated to 1,870 million years old, indicating the 1,880 million-year-old magmatism also exists in this section of the Circum–Superior large igneous province.
The Fox River Belt in northern Manitoba is composed of sediments, volcanics and sills. Fox River Belt sills and Molsen dikes are 1,883 million years old, but the Molsen dikes at the northwestern Superior craton margin intrude an older, 2,090 to 2,070 millon-year-old dike swarm. The Ospwagan Group is younger than and the 1,864 million-year-old Winnipegosis komatiite belt
lies to the southwest. Numerous tectonic settings have been suggested for triggering magmatism in the Fox River Belt, including a marginal basin rifting event.
At the southern portion of the Circum-Superior Belt, a group of fragmental sediments composed of iron formation was formed during a period of magmatic activity in the Marquette Range Supergroup. Included in the Marquette Range Supergroup is the Hemlock Formation, a bimodal volcanic group
that is estimated to have an age of . Another volcanic series in the Marquette Range Supergroup, known as the Gunflint Formation, has an age of . Further geologic units that are related to the Gunflint Formation include the Badwater volcanics and the Kienan sills. A number of origins have suggested for the Marquette Range Supergroup magmatism. This includes subsidence being driven ahead related to thrusting of the Penokean orogeny or a possible back-arc basin
, and lateral flow through the Pickle Crow dikes transported magma from the Fox River Belt area through the Superior craton for placement in the Marquette Range Supergroup. This suggested long-range origin has been suggested for magmatism of the 2,215 million-year-old Nipissing sills
as well, which the Ungava dike swarm could have transported magma to the Nipissing sills area.
Before 2003, all magmatism of the Circum-Superior Belt was thought to only occur along the outer margin of the Superior craton. However, the Pickle Crow dike was discovered in 2003 in the interior of the Superior craton and it has since been recognized as a magmatic event related to the Circum-Superior Belt. The dike is dated to 1,880 million years old and associated dikes are traced for at least 400 km (248.5 mi). These dikes likely extend over 700 km (435 mi) across the western portion of the Superior craton from near the Fox River Belt in the north to near Lake Superior
in the south. This magmatic crossing creates a relationship with the 1,880 million-year-old magmatism in the northwestern portion of the Circum-Superior Belt and magmatism in the Marguette Range Supergroup on the southern portion of the Circum-Superior Belt. In addition, the north-northwest trend of the Pickle Crow dikes and the absolute north-northeastern trend of the Molson dike swarm combine to an area north of the northwestern portion of the Circum-Superior Belt. This might determine the zone of a mantle plume that was the source for the 1,880 million-year-old magmatism in the Circum-Superior Belt.
mines. At least 70 million pounds of nickel has been mined since 2005. At the city of Thompson
, nickel of the Thompson Belt is smelted and refined in facilities. This smelting and refining process contributes to about one-third of the total nickel output in Canada.
In the Cape Smith Belt of northern Quebec, the Raglan Mine lies in copper-nickel deposits of the ultramafic Katiniq Suite sills. The Katiniq Suite sills are also within an area that is presently explored for nickel, copper and platinum group element deposits. Copper, nickel and platinum group elements are associated with mafic-ultramafic rocks in the Labrador Trough that were formed during a period of magmatism 1,883 to 1,870 million years ago.
Paleoproterozoic
The Paleoproterozoic is the first of the three sub-divisions of the Proterozoic occurring between . This is when the continents first stabilized...
large igneous province
Large igneous province
A Large Igneous Province is an extremely large accumulation of igneous rocks—intrusive, extrusive, or both—in the earth's crust...
in the Canadian Shield
Canadian Shield
The Canadian Shield, also called the Laurentian Plateau, or Bouclier Canadien , is a vast geological shield covered by a thin layer of soil that forms the nucleus of the North American or Laurentia craton. It is an area mostly composed of igneous rock which relates to its long volcanic history...
of Northern
Northern Canada
Northern Canada, colloquially the North, is the vast northernmost region of Canada variously defined by geography and politics. Politically, the term refers to the three territories of Canada: Yukon, Northwest Territories, and Nunavut...
, Western
Western Canada
Western Canada, also referred to as the Western provinces and commonly as the West, is a region of Canada that includes the four provinces west of the province of Ontario.- Provinces :...
and Eastern Canada
Eastern Canada
Eastern Canada is generally considered to be the region of Canada east of Manitoba, consisting of the following provinces:* New Brunswick* Newfoundland and Labrador* Nova Scotia* Ontario* Prince Edward Island* Quebec...
. It extends more than 3400 km (2,112.7 mi) from northeastern Manitoba
Manitoba
Manitoba is a Canadian prairie province with an area of . The province has over 110,000 lakes and has a largely continental climate because of its flat topography. Agriculture, mostly concentrated in the fertile southern and western parts of the province, is vital to the province's economy; other...
through northwestern Ontario
Ontario
Ontario is a province of Canada, located in east-central Canada. It is Canada's most populous province and second largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa....
, southern Nunavut
Nunavut
Nunavut is the largest and newest federal territory of Canada; it was separated officially from the Northwest Territories on April 1, 1999, via the Nunavut Act and the Nunavut Land Claims Agreement Act, though the actual boundaries had been established in 1993...
to northern Quebec
Quebec
Quebec or is a province in east-central Canada. It is the only Canadian province with a predominantly French-speaking population and the only one whose sole official language is French at the provincial level....
. Igneous rocks of the Circum-Superior Belt are mafic
Mafic
Mafic is an adjective describing a silicate mineral or rock that is rich in magnesium and iron; the term is a portmanteau of the words "magnesium" and "ferric". Most mafic minerals are dark in color and the relative density is greater than 3. Common rock-forming mafic minerals include olivine,...
-ultramafic in composition, deposited in the Labrador Trough
Labrador Trough
The Labrador Trough or the New Quebec Orogen is a long and wide geologic belt in Canada, extending south-southeast from Ungava Bay through Quebec and Labrador....
near Ungava Bay
Ungava Bay
Ungava Bay is a large bay in northeastern Canada separating Nunavik from Baffin Island. The bay is shaped like a rounded square with a side length of about and has an area of approximately...
, the Cape Smith Belt
Cape Smith Belt
The Cape Smith Belt is an early Proterozoic thrust belt in northern Quebec, Canada....
near the southern shore of Hudson Strait
Hudson Strait
Hudson Strait links the Atlantic Ocean to Hudson Bay in Canada. It lies between Baffin Island and the northern coast of Quebec, its eastern entrance marked by Cape Chidley and Resolution Island. It is long...
and along the eastern shore of Hudson Bay
Hudson Bay
Hudson Bay , sometimes called Hudson's Bay, is a large body of saltwater in northeastern Canada. It drains a very large area, about , that includes parts of Ontario, Quebec, Saskatchewan, Alberta, most of Manitoba, southeastern Nunavut, as well as parts of North Dakota, South Dakota, Minnesota,...
in its northern portion; the Thompson
Thompson Belt
The Thompson Belt, also referred to as the Thompson Nickel Belt, is an Archean and early Proterozoic geologic feature in Manitoba, Canada. It contains gneiss related to deformation of the Trans-Hudson orogeny....
and Fox River
Fox River Belt
The Fox River Belt is a long and to wide Paleoproterozoic geologic feature located in northern Manitoba, Canada. It consists of sedimentary and mafic/ultramafic igneous rocks....
belts in the northwest and the Marquette Range Supergroup in its southern portion.
A number of magmatic features are present in the Circum-Superior Belt, including dikes
Dike (geology)
A dike or dyke in geology is a type of sheet intrusion referring to any geologic body that cuts discordantly across* planar wall rock structures, such as bedding or foliation...
, sills
Sill (geology)
In geology, a sill is a tabular sheet intrusion that has intruded between older layers of sedimentary rock, beds of volcanic lava or tuff, or even along the direction of foliation in metamorphic rock. The term sill is synonymous with concordant intrusive sheet...
and volcanics that comprise geologic formations. This geologic belt is considered to be a large igneous province because its magmatic rocks were emplaced over an extremely short geological time span. Even though the Circum-Superior Belt was emplaced during an extremely short geological time span, the associated magmas were probably derived from a number of separate sources.
Most of the Circum-Superior Belt lies along the margin of the Superior craton
Superior craton
The Superior craton forms the core of the Canadian Shield at the heart of the North American continent. It extends from Quebec in the east to eastern Manitoba in the west...
, which is the most extensive fragment of Archean
Archean
The Archean , also spelled Archeozoic or Archæozoic) is a geologic eon before the Paleoproterozoic Era of the Proterozoic Eon, before 2.5 Ga ago. Instead of being based on stratigraphy, this date is defined chronometrically...
crust
Crust (geology)
In geology, the crust is the outermost solid shell of a rocky planet or natural satellite, which is chemically distinct from the underlying mantle...
on Earth. However, a number of igneous rocks within the Superior craton remain undated, indicating the existence of magmatic rocks with the same age as those of the Circum-Superior Belt is probable. It contains two large copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
-nickel
Nickel
Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...
mining districts; the nickel-bearing Thompson Belt at the northwestern portion of the Superior craton and the Cape Smith Belt at the northern portion of the Circum-Superior Belt.
Formation
The Circum-Superior Belt was formed 1,884 to 1,864 million years ago when the Superior craton was surrounded by mountain building processes, including the Trans-HudsonTrans-Hudson orogeny
The Trans-Hudson orogeny, Trans-Hudsonian orogeny, Trans-Hudson orogen , or Trans-Hudson Orogen Transect , , was the major mountain building event that formed the Precambrian Canadian Shield, the North American craton , and the...
, New Quebec and Penokean
Penokean orogeny
The Penokean orogeny was a mountain-building episode that occurred in the early Proterozoic about 1.85 to 1.84 billion years ago, in the area of North America that would eventually become Minnesota, Wisconsin, Michigan and Ontario...
orogenies. The major Trans-Hudson orogeny had its appearance when the Superior craton collided with the Rae
Rae craton
right|thumb|250px|North America cratons and basement rock.The Rae craton is an Archean craton located in northern Canada north of the Superior craton.-Ungava Peninsula:...
-Hearne craton 1,900 to 1,800 million years ago. Massive orogenic belts with a change in horizontal direction are represented by the double promontory structure of the Superior craton that seem to have came from the beginning of a rift
Rift
In geology, a rift or chasm is a place where the Earth's crust and lithosphere are being pulled apart and is an example of extensional tectonics....
ing event. The New Quebec orogen, also known as the Labrador Trough, lies at the northeastern portion of the Superior craton and is related to ocean closure and collision with the southeastern portion of the Rae craton. At 1,900 and 1,800 million years ago, an ocean closure and collision with the Wisconian arc terrane resulted in the creation of the Penokean orogeny at the southern Superior craton margin. The last collision occurred on the southeastern portion of the Superior craton to produce the Grenville orogeny
Grenville orogeny
The Grenville Orogeny was a long-lived Mesoproterozoic mountain-building event associated with the assembly of the supercontinent Rodinia. Its record is a prominent orogenic belt which spans a significant portion of the North American continent, from Labrador to Mexico, as well as to Scotland...
1,100 million years ago.
Because most of the Circum-Superior Belt was formed by widespread mafic-ultramafic magmatism 1,884 to 1,864 million years ago along the Superior craton margin during these orogenies, a number of different suggestions have been made to explain the questionable origins of this large igneous province. It is also not clear if the Circum-Superior Belt has a single origin or it has several origins. Suggestions include back-arc rifting, foredeep flexure, mantle plume
Mantle plume
A mantle plume is a hypothetical thermal diapir of abnormally hot rock that nucleates at the core-mantle boundary and rises through the Earth's mantle. Such plumes were invoked in 1971 to explain volcanic regions that were not thought to be explicable by the then-new theory of plate tectonics. Some...
s and the breakup of a microcontinent. The geochemical indication of the Circum-Superior Belt is also poorly known; either it contains major regional differences or it is the same throughout the magmatic zone. With the discovery of the Pickle Crow dike swarm throughout the western Superior craton, the likelihood of other 1,880 million year old dike groups throughout the Superior craton remains. This is partly because several dike zones in the Superior craton remain undated. The relationship of the Circum-Superior Belt with similar age magmatism throughout the nearby Trans-Hudson belt and elsewhere on Earth is also unknown. This includes the 1,860 million year old magmatism of the East Kimberly event in Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
and 1,860 million year old magmatism of the Mashonaland event in Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
. The other questionable suggestion related to the Circum-Superior Belt is the existence of a suggested 1,900 million year old global superplume event.
Geologic features
The 1600 km (994.2 mi) long Labrador Trough, extending from Ungava BayUngava Bay
Ungava Bay is a large bay in northeastern Canada separating Nunavik from Baffin Island. The bay is shaped like a rounded square with a side length of about and has an area of approximately...
through Quebec and Labrador, includes two volcano-sedimentary series, the first ranging from 2,170 to 2,140 million years old and second ranging from 1,883 to 1,870 million years old. This magmatism is considered to have formed as a result of back-arc volcanism. The youngest magmatic series (1883-1870 Ma) contains 1,880 million-year-old carbonatite
Carbonatite
Carbonatites are intrusive or extrusive igneous rocks defined by mineralogic composition consisting of greater than 50 percent carbonate minerals. Carbonatites may be confused with marble, and may require geochemical verification....
s and lamprophyre
Lamprophyre
Lamprophyres are uncommon, small volume ultrapotassic igneous rocks primarily occurring as dikes, lopoliths, laccoliths, stocks and small intrusions...
s. 1,883 to 1,874 million-year-old mafic and a few ultramafic magmas comprise the Willbob and Hellancourt formations and Montagnais sills. The youngest magmatism of the youngest magmatic series is 1,870 million-year-old felsic
Felsic
The word "felsic" is a term used in geology to refer to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium....
and carbonatitic
Carbonatite
Carbonatites are intrusive or extrusive igneous rocks defined by mineralogic composition consisting of greater than 50 percent carbonate minerals. Carbonatites may be confused with marble, and may require geochemical verification....
volcanics. These igneous rocks of the Labrador Trough cover an area of 30000 square kilometre.
To the northwest at the northern tip of Quebec near Hudson Strait
Hudson Strait
Hudson Strait links the Atlantic Ocean to Hudson Bay in Canada. It lies between Baffin Island and the northern coast of Quebec, its eastern entrance marked by Cape Chidley and Resolution Island. It is long...
, the Cape Smith Belt includes the 2,040 to 1,970 million-year-old Povungnituk volcano-sedimentary group and the 1,880 million-year-old Chukotat Group. The 5.6 km (3.5 mi) thick Chukotat Group is made of picritic and tholeiitic basalts. These basaltic lavas are intruded by narrow mafic and ultramafic sills. At least three different types of lava compositions exist in the Chukotat Group, including olivine phyric, pyroxene-phyric and plagioclase phyric. The upper unit of the Chukotat Group is 1,870 million years old whereas the lower unit is associated with the Katiniq Suite sills, which cut through the underlying Povungnituk Group. In 1989, the Katinq Suite sills were thought to be 1,918 million years old, but more recent dating and a reinterpretation of the original age in 2004 suggests that the Katinq Suite sills are closer to 1,880 million years old. Therefore, the age range for the Chutotat Group is 1,880 to 1,870 million years. Volcanism of the Chukotat Group might have originated from rifting of a microcontinent that now forms the southwestern portion of Baffin Island
Baffin Island
Baffin Island in the Canadian territory of Nunavut is the largest island in the Canadian Arctic Archipelago, the largest island in Canada and the fifth largest island in the world. Its area is and its population is about 11,000...
.
On the Belcher Islands
Belcher Islands
The Belcher Islands are an archipelago in Qikiqtaaluk Region, Nunavut, Canada. Located in Hudson Bay, the Belcher Islands are spread out over almost . The hamlet of Sanikiluaq is on the north coast of Flaherty Island and is the southernmost in Nunavut. Along with Flaherty Island, the other large...
of southern Nunavut, two volcanic groups are known as the Flaherty and Eskimo volcanics. The underlying Eskimo volcanics are related with the Richmond Gulf, Persillon, Pachi and Nastapoka Group volcanics. The 1,998 million-year-old Minto dikes are also interpretend to be related with the Eskimo volcanics. The overlying Flaherty volcanics remain undated apart from a lead-lead dating of . However, the Flaherty volcanics are suggested to have relationships with the Stton Inlier and Haig sills. Geochemical indications suggest that the overlying Flaherty volcanics might also have relationships with the Povungnituk volcano-sedimentary group in the Cape Smith Belt, indicating the Flaherty volcanics might be 2,040 to 1,960 million years old. Sills on the Belcher and Snowy islands in Hudson Bay are dated to 1,870 million years old, indicating the 1,880 million-year-old magmatism also exists in this section of the Circum–Superior large igneous province.
The Fox River Belt in northern Manitoba is composed of sediments, volcanics and sills. Fox River Belt sills and Molsen dikes are 1,883 million years old, but the Molsen dikes at the northwestern Superior craton margin intrude an older, 2,090 to 2,070 millon-year-old dike swarm. The Ospwagan Group is younger than and the 1,864 million-year-old Winnipegosis komatiite belt
Winnipegosis komatiite belt
The Winnipegosis komatiite belt, also called the Winnipegosis komatiites, is a volcanic belt composed of komatiite in central Manitoba, Canada. It is part of a large igneous province surrounding much of the Superior craton called the Circum-Superior Belt....
lies to the southwest. Numerous tectonic settings have been suggested for triggering magmatism in the Fox River Belt, including a marginal basin rifting event.
At the southern portion of the Circum-Superior Belt, a group of fragmental sediments composed of iron formation was formed during a period of magmatic activity in the Marquette Range Supergroup. Included in the Marquette Range Supergroup is the Hemlock Formation, a bimodal volcanic group
Bimodal volcanism
Bimodal volcanism refers to the eruption of both mafic and felsic lavas from a single volcanic centre with little or no lavas of intermediate composition...
that is estimated to have an age of . Another volcanic series in the Marquette Range Supergroup, known as the Gunflint Formation, has an age of . Further geologic units that are related to the Gunflint Formation include the Badwater volcanics and the Kienan sills. A number of origins have suggested for the Marquette Range Supergroup magmatism. This includes subsidence being driven ahead related to thrusting of the Penokean orogeny or a possible back-arc basin
Back-arc basin
Back-arc basins are geologic features, submarine basins associated with island arcs and subduction zones.They are found at some convergent plate boundaries, presently concentrated in the Western Pacific ocean. Most of them result from tensional forces caused by oceanic trench rollback and the...
, and lateral flow through the Pickle Crow dikes transported magma from the Fox River Belt area through the Superior craton for placement in the Marquette Range Supergroup. This suggested long-range origin has been suggested for magmatism of the 2,215 million-year-old Nipissing sills
Nipissing sills
The Nipissing sills, also called the Nipissing diabase, is a large 2217– to 2210–million year old group of sills in the Superior craton of the Canadian Shield in Ontario, Canada, which intrude the Huronian Supergroup...
as well, which the Ungava dike swarm could have transported magma to the Nipissing sills area.
Before 2003, all magmatism of the Circum-Superior Belt was thought to only occur along the outer margin of the Superior craton. However, the Pickle Crow dike was discovered in 2003 in the interior of the Superior craton and it has since been recognized as a magmatic event related to the Circum-Superior Belt. The dike is dated to 1,880 million years old and associated dikes are traced for at least 400 km (248.5 mi). These dikes likely extend over 700 km (435 mi) across the western portion of the Superior craton from near the Fox River Belt in the north to near Lake Superior
Lake Superior
Lake Superior is the largest of the five traditionally-demarcated Great Lakes of North America. It is bounded to the north by the Canadian province of Ontario and the U.S. state of Minnesota, and to the south by the U.S. states of Wisconsin and Michigan. It is the largest freshwater lake in the...
in the south. This magmatic crossing creates a relationship with the 1,880 million-year-old magmatism in the northwestern portion of the Circum-Superior Belt and magmatism in the Marguette Range Supergroup on the southern portion of the Circum-Superior Belt. In addition, the north-northwest trend of the Pickle Crow dikes and the absolute north-northeastern trend of the Molson dike swarm combine to an area north of the northwestern portion of the Circum-Superior Belt. This might determine the zone of a mantle plume that was the source for the 1,880 million-year-old magmatism in the Circum-Superior Belt.
Mineralization
The Circum-Superior Belt is the host for widespread mineral deposits, including copper, nickel and platinum group elements. However, the origins of this widespread mineralization is unknown. The Thompson Belt in Manitoba is one of the most comprehensive nickel producing zones on Earth. It has the potential to contain platinum group elements, but the age of the mafic-ultramafic volcanic rocks comprising the nickel deposits are not well known. Since its foundation during the 1950s, numerous mining operations throughout the Thompson Belt have produced over four billion pounds of nickel. At least two nickel deposits are in progress by Vale Inco at the Thompson and BirchtreeBirchtree Mine
Birchtree Mine is an underground nickel mine, owned and operated by Vale Inco in the city of Thompson, Manitoba, Canada. It lies in the nickel containing Thompson Belt, a geologic feature associated with the Circum-Superior Belt large igneous province throughout the Superior...
mines. At least 70 million pounds of nickel has been mined since 2005. At the city of Thompson
Thompson, Manitoba
Thompson is a city in northern Manitoba. As the "Hub of the North" it serves as the regional trade and service centre of northern Manitoba. Thompson is located north of the Canada – United States border, north of the provincial capital of Winnipeg, and is northeast of Flin Flon...
, nickel of the Thompson Belt is smelted and refined in facilities. This smelting and refining process contributes to about one-third of the total nickel output in Canada.
In the Cape Smith Belt of northern Quebec, the Raglan Mine lies in copper-nickel deposits of the ultramafic Katiniq Suite sills. The Katiniq Suite sills are also within an area that is presently explored for nickel, copper and platinum group element deposits. Copper, nickel and platinum group elements are associated with mafic-ultramafic rocks in the Labrador Trough that were formed during a period of magmatism 1,883 to 1,870 million years ago.
See also
- Volcanism of Canada
- Volcanism of Northern CanadaVolcanism of Northern CanadaVolcanism of Northern Canada has led to the formation of hundreds of volcanic areas and extensive lava formations across Northern Canada, indicating volcanism played a major role in shaping its surface...
- Volcanism of Eastern CanadaVolcanism of Eastern CanadaVolcanism of Eastern Canada has led to the formation of hundreds of volcanic areas and extensive lava formations, indicating volcanism played a major role in shaping its surface. The region's different volcano and lava types originate from different tectonic settings and types of volcanic...
- Volcanism of Western CanadaVolcanism of Western CanadaVolcanism of Western Canada produces lava flows, lava plateaus, lava domes, cinder cones, stratovolcanoes, shield volcanoes, submarine volcanoes, calderas, diatremes and maars, along with examples of more less common volcanic forms such as tuyas and subglacial mounds.-Volcanic belts:*Anahim...