Abstract
Previous workers in the Ketilidian orogen of South-East Greenland reported extensive outcrops of acid vo1canic rocks and related gneisses which they described as the Ikermit supracrustal suite. The suite was regarded as a favourable host for sulphide mineralisation. New fjeld and petrographic data show that the 'acid volcanic rocks' from the type locality on Ikermit island are entirely Archaean orthogneisses with abundant, but local, mylonites. These gneisses and mylonites occur within the wide border zone between the Ketilidian orogen and the Archaean foreland to the north. The name 'Ikermit supracrustal suite' should be abandoned.
Highlights
Previous workers in the Ketilidian orogen of South-East Greenland reported extensive outcrops of acid vo1canic rocks and related gneisses which they described as the Ikermit supracrustal suite
Recent interest in the Ketilidian of South-East Greenland was attracted by a statement by Andrews et al (1971, p. 37) who emphasised that: "... the considerable thickness of gneisses derived from acid vo1canic successions are favourable hosts for sulphides and that geologically the area mapped is more likely to yield ore minerals than most of the gneissose terrains so far described from Greenland"
The orogen has been divided into four broad east-west zones: (a) a Border Zone in the north consisting of the Archaean foreland which, in the west, is overlain imconformably by Ketilidian sedimentary and mafic vo1canic rocks; the underlying Archaean gneisses are cut by Early Proterozoic dolerite dykes which are increasingly metamorphosed and deformed towards the south; these dykes are correlated with the 'MD' dykes in the Archaean block further north (Bridgwater et al, 1976); dolerite dykes which are presumed to be part of the MD swarm are found cutting the Archaean orthogneisses in the coastal outcrop of the foreland in South-East Greenland; the dolerite dykes are cut by appinite dykes which occur in the foreland gneisses up to c. 80 km north of the bound
Summary
The Ketilidian orogen has been described in some detail by Allaart (1976) and more recently reviewed by Kalsbeek et al (1990). The orogen has been divided into four broad east-west zones:. (a) a Border Zone in the north consisting of the Archaean foreland which, in the west, is overlain imconformably by Ketilidian sedimentary and mafic vo1canic rocks; the underlying Archaean gneisses are cut by Early Proterozoic dolerite dykes which are increasingly metamorphosed and deformed towards the south; these dykes are correlated with the 'MD' dykes in the Archaean block further north (Bridgwater et al, 1976); dolerite dykes which are presumed to be part of the MD swarm are found cutting the Archaean orthogneisses in the coastal outcrop of the foreland in South-East Greenland; the dolerite dykes are cut by appinite dykes which occur in the foreland gneisses up to c. (a) a Border Zone in the north consisting of the Archaean foreland which, in the west, is overlain imconformably by Ketilidian sedimentary and mafic vo1canic rocks; the underlying Archaean gneisses are cut by Early Proterozoic dolerite dykes which are increasingly metamorphosed and deformed towards the south; these dykes are correlated with the 'MD' dykes in the Archaean block further north (Bridgwater et al, 1976); dolerite dykes which are presumed to be part of the MD swarm are found cutting the Archaean orthogneisses in the coastal outcrop of the foreland in South-East Greenland; the dolerite dykes are cut by appinite dykes which occur in the foreland gneisses up to c. 80 km north of the bound-
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