Ultrabasic intrusives from Narssaq and Tugtutôq

Abstract

On the Panernaq peninsula [now named Ungussivik] north of Narssaq, five small outcrops of ultrabasic rock occur, the largest being some 200 m across. Conceivably these are connected at depth and should be regarded as probably comprising a single intrusion. The smallest (southernmost) of the outcrops is now, unfortunately, obscured by a Narssaq municipal refuse-tip. Two small bodies of similar ultrabasic material have been found on the eastern part of Tugtutôq island. All these ultrabasic masses are associated with the large olivine gabbro intrusions (Upton, 1964) and are held to represent younger intrusions into, or adjacent to, the latter. They are themselves cut by the big feldspar dykes and by the trachyte and comendite dykes of the regional WSW-ENE swarms.