Geological investigations in East Greenland (Part XI). The minor peripheral intrusions, Kangerdlugssuaq, East Greenland.

Abstract

The minor peripheral syenitic and granite intrusions associated with the main Kangerdlugssuaq alkaline intrusion are described. The earlier intrusions-Peak 2005 Syenite; Krerven Syenite; Augite Syenite; and Bagnresset Syenite-and the later Granite and Snout Series generally have the compositions of slightly oversaturated nordmarkites. They differ chemically from the syenites of the main intrusion, especially in their contents of alumina, total iron, and alkalis. The ferromagnesian minerals include aegirine, ferroaugite, magnesioarfvedsonite, and katophorite, and the accessory mineral chevkinite, together with perthitic alkali feldspar, quartz, and minor minerals. The Snout Series, Krerven Syenite, and, especially, the Augite Syenite are heavily contaminated by basaltic inclusions. The overall composition of the main and minor peripheral intrusions, including the Granite, is that of a slightly oversaturated nordmarkite, differing little from that of the main intrusion. The minor intrusions are · generally regarded as early and late pulses emanating from the same magma source as that which supplied the main intrusion, although there is evidence that the later Snout Series and Granite, and possibly the earlier Bagnresset Syenite, were emplaced at a higher temperature, or cooled more quickly, and may have derived from differentiated liquid fractions.