A textural study of Archaean peridotites; Ujaragssuit nunât, Ivisârtoq region, southern West Greenland

Abstract

Recent mapping of Ujaragssuit nunât by Chadwick & Crewe (1982) and Chadwick et al. (1983), folIowing reconnaissance work by Allaart et al. (1977), has demonstrated the widespread occurrence of supracrustallithologies. Ujaragssuit nunât is situated immediately to the north-west of Ivisârtoq, which has been described in some detail by Friend & Hall (1977) and Hall (1980, 1981). Friend & Hall (1977) noted that the Akilia association ultramafic rocks can be divided into two groups. The tirst group comprises those rocks rich in olivine or its hydrous alteration products. Ultramafic rocks of the second group are olivine-free, being composed mainly of hornblende with or without clinopyroxene; these rocks are not considered further in this report. A similar division has been proposed for the ultramafic rocks of the Ivisårtoq Amphibolite Complex (Friend & Hall, 1977) which has been correlated with the Malene supracrustal rocks of the Godthåb region. A layered ultrabasic-gabbroic formation has also been reported from Ivisârtoq (Friend & Hal1, 1977). In Ujaragssuit nunåt no unequivocal evidence of a layered complex has been observed but the two-fold division of both the Akilia association and Malene ultramafic rocks is believed to be fundamental.