Chemical relations between metabasaltic lavas and metadolerites in the Ivigtut area, South-West Greenland

Chemical analyses of representative samples from a swarm of metadolerite dykes which penetrates the pre-Ketilidian basement in the Ivigtut area indicates that the earlier and main part of the intrusives have tholeiitic compositions and that the latest dyke intrusions are more alkaline. Analyses of rocks representing different metamorphic facies conditions produced in one and the same dyke indicates that the Ketilidian metamorphic reactivation of the basement took place under isochemical conditions in the northern part of the Ivigtut area. Comparison between the chemical composition of the metadolerites and the Ketilidian metavolcanics shows that they are slightly different, and it is concluded that the metadolerites and the metavolcanics cannot have been derived at the same time from the same source. The dykes are ascribed to a pre-Ketilidian age.