Gardar mantle xenoliths: Igdlutalik, South Greenland

Abstract

A dyke of presumed Gardar age on Igdlutalik island near Narsaq contains an abundance of ultramafic xenoliths. Both host rock and xenoliths have been metamorphosed and the original mineral assemblages largely replaced by tremolite, chlorite and magnetite. Textural and geochemical evidence suggests: (a) that the host rock was a part of the ultramafic lamprophyre suite known throughout the Tugtut6q-Ilimaussaq-nunataq lineament, and (b) that the xenoliths were mantle-derived peridotites (possibly garnetiferous), together with some glimmerites that may be analogues of MARID-suite xenoliths known from kimberlite occurrences.