Malene amphibolites and related anorthosites from Akugdlerssuaq, inner Godthåbsfjord, with komatiite affinities

Abstract

Mapping by helicopter reconnaissance in 1976 (Allaart et al. 1977) and subsequent more detailed mapping in 1981 (Nutman, 1982) showed that there are several units of anorthosite with associated amphibolite on Akugdlerssuaq, inner Godthåbsfjord. The anorthosite and amphibolite units are interspersed with units ofstrongly deformed Amitsoq gneisses (identified by the presence of basic dyke remains and by enclaves of banded iron formation) sheeted by younger gneisses. Most of the contacts between anorthosite and amphibolite units and the Amitsoq gneisses are clearly tectonic, whilst the remaining contacts could also be tectonic or are modified primary contacts (Nutman, 1982). The younger gneisses are of late Archaean age (Bridgwater & Nutman, unpublished Rb-Sr isotopic data).