Regional geology of early Precambrian high-grade metamorphic rocks in West Greenland. Part 1: Kângnaitsoq to Ameralik

Abstract

Within this region three types of area are distinguished: 1. Amphibolite-grade areas which did not reach a granulite grade. 2. Granulite-grade areas. 3. Amphibolite-grade areas, many of which have been retrogressed from the earlier granulite grade. The main rocks are hypersthene-biotite gneisses, biotite-hornblende gneisses, amphibolites with or without orthopyroxene, sillimanite mica schists, rare marbles, skarns and quartzites, layered calcic anorthosites, a great variety of meta-ultramafic rocks including rare zoned talc lenses, abundant pegmatites, several generations of dolerite dykes locally amphibolitised by deep-seated fauIts. The fold structure of the region is characterised by abundant large-scale interference patterns. The history of the region is interpreted on the basis of a deformed cover/basement relationship, all major units being now mutually conformable.