Nuvvuagittuq greenstone belt

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An outcrop of metamorphosed volcano-sedimentary rocks at Porpoise Cove.

The Nuvvuagittuq greenstone belt, originally named the Porpoise Cove greenstone belt, is a greenstone belt on the eastern shore of Hudson Bay in northern Quebec, Canada.

With an age of about 4.4 billion years,[1] it is the only portion of the Earth's crust known to have survived after its formation during the Hadean Eon.[2]

The Nuvvuagittuq greenstone belt is mainly composed of cummingtonite-plagioclase-biotite-garnet mafic amphibolites called the Ujaraaluk unit (formerly called the "Faux-amphibolite" due to its unusual color).

Geographical extent[edit]

There are few detailed maps of the region, but this belt is only known to occupy a small part of Hudson's Bay

Formation[edit]

Rocks from the Ujaraaluk unit have a neodymium-142 isotopic signature that can only be acquired in the Hadean, prior to 4 billion years ago. This isotopic tool has been used to date these rocks at up to 4.4 billion years old.

The mafic rocks from the Nuvvuagittuq belt are interpreted to be volcanic rocks that were hydrothermally altered and includes a banded iron formation between a lower basalt and an upper unit which includes basalt and andesite.[3]

In 2014, a detailed geochemical analysis, revealing layered gradients of ytterbium and niobium,[4] suggested that this formation consists of pillow lavas from a tectonic subduction zone, similar to the modern Mariana trench.[5]

See also[edit]

References[edit]

Coordinates: 58°18′N 077°45′W / 58.300°N 77.750°W / 58.300; -77.750