Nuvvuagittuq greenstone belt

Nuvvuagittuq Greenstone Belt Stratigraphic range: Eoarchean-Hadean (disputed)
A map showing geological formations in the Nuvvuagittuq Greenstone Belt
Type	Geological formation
Area	Approx. 20 km2 (7.7 sq mi)
Location
Coordinates	58°17'18"N 77°36'42"W
Region	Northern Quebec
Country	Canada

The Nuvvuagittuq Greenstone Belt (NOO-voo-AG-it-tuck) (NGB) is a sequence of metamorphosed mafic to ultramafic volcanic and associated sedimentary rocks (a greenstone belt) located on the eastern shore of Hudson Bay, 40 km southeast of Inukjuak, Quebec. These rocks have undergone extensive metamorphism, and represent some of the oldest rocks on Earth. Using uranium-lead dating on zircons, these rocks have been dated to be no younger than 3.7 billion years. More recently, measurements were made using samarium-neodymium dating that suggest a formation age of 4.3 billion years ago. These measurements, however, remain controversial.

Formerly called the Porpoise Cove Greenstone Belt, the Nuvvuagittuq Greenstone Belt was first mapped in 1965 by the Quebec Ministry of Natural Resources. The area remained more or less unexamined until the 2000s when preliminary reports of U-Pb zircon dating in the area of the belt found zircons with ages up to 3750 Ma. Since then, the Nuvvuagittuq Greenstone Belt has become the focus of intense study. There is still considerable disagreement between scientists regarding the history and age of this structure. The Nuvvuagittuq Greenstone Belt is part of a mafic unit called the Ujaraaluk unit, both of which are in the Inukjuak subprovince of the Minto Block.

As mentioned above the Nuvvuagittuq was measured to have a minimum age of 3750 Ma. This measurement was made using uranium-lead dating on zircons found within granitic intrusions that cut portions of the belt, and are therefore younger than the features it cuts. This measurement is widely accepted, however it alone does not provide a maximum age.

In 2012 samarium-neodymium dating and neodymium isotope fractionation was used to establish an age of 4321 Ma for the Nuvvuagittuq Greenstone Belt. This was done by dating intruding gabbros and measuring neodymium isotope fractionation in less-deformed members of the Ujaraaluk unit. The age of 4321 Ma would make the Nuvvuagittuq Greenstone Belt the oldest known rocks on Earth.