An ultrabasic pipe in the eastern Sukkertoppen region, southern West Greenland

Abstract

An unusual occurrence of ultrabasic material was located in the eastern Sukkertoppen region during the reconnaissance mapping programme of 1977, the findings of which were described by Allaart et al. (1978). It occurs on a small exposure on the west side of a north-pointing peninsula in the middle of the large nunatak Majorqap alangua (65°53'N, 50°40'W), to the north-east of the Majorqaq valley (Hall, 1978, fig. 21). The area is composed predominantly of a suite of granulite facies granitic gneisses which contain numerous enclaves of pyroxene-bearing amphibolites, and locally anorthositic and gabbroic rocks similar to those seen in the Fiskenæsset anorthosite complex (Myers, 1975). The gneisses in the centre af the nunatak are highly irregular in orient at ion, occupying the complex interseclion af closures af at least two major fold phases. A belt af amphibolitcs forms the cliff at the south-west tip af Majorqap alangua. Related rocks occur in arnphibolite facies in the acea around the lakc Qardlit taserssuat immediately to the soulh (Hall, 1978).