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 3,400 km (2,100 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.
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Famous quotes containing the word belt:
“The shore is composed of a belt of smooth rounded white stones like paving-stones, excepting one or two short sand beaches, and is so steep that in many places a single leap will carry you into water over your head; and were it not for its remarkable transparency, that would be the last to be seen of its bottom till it rose on the opposite side. Some think it is bottomless.”
—Henry David Thoreau (1817–1862)