The Circum-Superior Belt is a widespread Paleoproterozoic large igneous province in the Canadian Shield of Northern, Western and Eastern Canada.

[1][2][3][4] It extends more than 3,400 km (2,100 mi) from northeastern Manitoba through northwestern Ontario, southern Nunavut to northern Quebec and into western Labrador.

[3][5] A number of magmatic features are present in the Circum-Superior Belt, including dikes, sills and volcanics that comprise geologic formations.

[3][4] 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.

The Circum-Superior Belt was formed 1,884 to 1,870 million years ago[3][4] when the Superior craton was surrounded by mountain building processes, including the Trans-Hudson, New Quebec and Penokean orogenies.

[6] Massive orogenic belts with a change in horizontal direction are represented by the double promontory structure of the Superior craton that seem to have come from the beginning of a rifting event.

[6] 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.

[6] Because most of the Circum-Superior Belt was formed by widespread mafic-ultramafic magmatism 1,884 to 1,870 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.

[6] 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.

[6] Numerous tectonic settings have been suggested for triggering magmatism in the Fox River Belt, including a marginal basin rifting event.

[6] 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.

[6] 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.

[6] 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.

[8] In the Cape Smith Belt of northern Quebec, the Raglan Mine lies in copper-nickel deposits of the ultramafic Katiniq Suite sills.

[6] 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.