Age of rocks, structures, and metamorphism in the Nagssugtoqidian mobile belt, West Greenland—field and Pb-isotope evidence

• Published in: Canadian Journal of Earth Sciences
• Main Authors: Kalsbeek, Feiko, Taylor, Paul N., Henriksen, Niels
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1984
• Subjects: Greenland
• Online Access: http://dx.doi.org/10.1139/e84-117; http://www.nrcresearchpress.com/doi/pdf/10.1139/e84-117

Two kinds of structural domains can be distinguished in the Nagssugtoqidian mobile belt: "Nagssugtoqidian" shear belts, which wrap around large areas in which "pre-Nagssugtoqidian" fold structures are preserved. It has been generally held that nearly all rocks in the Nagssugtoqidian mobile belt and the pre-Nagssugtoqidian fold structures are of Archaean age. We describe field and lead-isotope evidence suggesting that (1) some of the gneisses in the Nagssugtoqidian mobile belt are indeed Archaean, but that gneisses derived from Proterozoic intrusive rocks also occur; (2) most of the supracrustal rocks in the area are probably of Proterozoic rather than Archaean age; (3) the main phase of metamorphism took place at 1880 ± 50 Ma; and (4) most of the structures recognised in the Nagssugtoqidian mobile belt, including the pre-Nagssugtoqidian fold structures, developed during a Proterozoic orogeny that can be broadly correlated with the Hudsonian orogeny in the Canadian Shield.