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.
Highlights
The coastal section of the gneiss complex in the region between Gyldenløve Fjord and Isertoq (640 to 65° 30'N; fig. 1) has been described by Bridgwater & Gormsen (1968, 1969), Bridgwater & Myers (1979) and Myers (1984, 1987) as comprising two structuraIly different areas
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 SouthEast Greenland
Was considered to belong to the Nagssugtoqidian mobile belt of East Greenland, and Nag. 1 and Nag. 2 events were distinguished. This was based on the assumption that the chronology established for the Nagssugtoqidian mobile belt of West Greenland could be directly correlated with events in South-East Greenland
Summary
The coastal section of the gneiss complex in the region between Gyldenløve Fjord and Isertoq (640 to 65° 30'N; fig. 1) has been described by Bridgwater & Gormsen (1968, 1969), Bridgwater & Myers (1979) and Myers (1984, 1987) as comprising two structuraIly different areas. Jens Munk ø and Gyldenløve Fjord (further referred to as 'the southern area') was considered by Bridgwater & Gormsen (1968, 1969) and Bridgwater & Myers (1979) as part of the Archaean craton of South-East Greenland, and unaffected by Proterozoic deformation. Our investigation confirms the main findings of Bridgwater & Gormsen (1968, 1969) and Bridgwater & Myers (1979), but it revealed important differences from the previous descriptions, interpretations and maps, with respect to the location of the southern boundary of the mobile belt and the Nagssugtoqidian interpretation modelof the deformational events inside the belt. They clearly pre-date most of the Proterozoic deformation of the mobile belt. The boundary between the two areas is forrned by a 25 km wide zone of gradual increase in deformation
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