Structural evolution of the Archean rocks in Ivisârtoq and the neighboring inner Godthåbsfjord region, southern West Greenland

Reconnaissance and some detailed mapping of Archean rocks in the inner Godthåbsfjord region has revealed a remarkable set of interference fold structures. These folds have amplitude and wavelength values on the order of 30 km. They are delineated by Malene metavolcanic, meta-sedimentary, and ultramafic bodies (3,100 m.y. old) and two generations of gneisses. In the Ivisârtoq area at the center of the region, evidence is preserved of early interleaving by thrusting of the Malene rocks with the ancient Amîtsoq gneiss (3,700 m.y. old). These two juxtaposed complexes then underwent two slightly oblique phases of major folding during which the younger Nûk gneiss (2,900 m.y.) was injected.