The southern boundary zone of the Proterozoic mobile belt, South-East Greenland: geology of the area between Gyldenløve Fjord and Isertoq

Abstract

The Gyldenløve Fjord – Isertoq region consists mainly of grey amphibolite facies gneisses with rare units of supracrustal rocks. The region is cut by a dense swarm of E–W trending basic dykes which are presumed to be of Proterozoic age. The dykes clearly predate the Proterozoic deformation of the northern and central parts of the region, which represents the southern part of the Proterozoic mobile belt of South-East Greenland. The gneisses south of the mobile belt in the southern part of the region are presumed to be Archaean and are cut by undeformed dykes. The gneisses and dykes within the mobile belt, in contrast, have been strongly sheared and folded but contain occasional tectonic augen of nebulitic gneiss with variably preserved Archaean structures. The southern boundary of the mobile belt bordering the unmodified Archaean gneisses consists of an approximately 25 km wide zone of gradually declining deformation and is in many respects comparable to the northern boundary of the mobile belt, described elsewhere in this volume.