Archaean ultramafic rocks with relict spinifex textures in the Umanak area, central West Greenland

Conspicuous olivine and serpentine textures were found in a number of ultramafic bodies in the Umanak area while it was being mapped on a scale of 1:20000. The rocks in the area mapped by the writer are mainly a suite of quartzo-feldspathic gneisses (Pulvertaft et al., this report) in which there are distinct amphibolite-dominated supracrustal horizons which enable the major structures of the area to be recognised. The structure which dominates the area is a large recumbent/rec1ined fold plunging ESE at a low angle and closing to the NNE. Isoclinal folds belonging to an earlier phase, and late open folding have also been recognised in the area.