Two Archaean granulite-facies metamorphic events in the Nuuk-Maniitsoq region, southern West Greenland: correlation with the Saglek block, Labrador

Abstract

Two dilferent granulite-facies events have been identified using SHRIMP U-Pb zircon geochronology in the Nuuk-Maniitsoq tract of West Greenland, previously considered to comprise a continuous, contemporaneous granulite facies terrain. About 35 km north of Nuuk, a granulite-facies metasedment contains metamorphic zircon overgrowths recording a 207 Pb/ 206 Pb age of 2999 ± 4 Ma (2σ). Some l30 km further north, near Maniitsoq, an orthopyroxene-bearing granite contains metamorphic zircons recording an age of 2738 ±6 Ma. Previous correlations have liked the early Archaean rocks of the Saglek block of northern Labrador with those in the Nuuk region. However, this causes problems with correlation of crustal blocks on either side of the Labrador Sea. The proposal here, of correlating late Archaean metamorphic events at 2740 Ma, provides a better solution to the problem.