Precambrian structures of the Ikorfat peninsula, Agto region, West Greenland

Abstract

A supracrustal sequence of biotite gneisses, light coloured garnet-biotite gneisses (metasediments) and metabasite rocks is bounded to the north-west and south-east by basement rocks of biotite (± hornblende) gneisses and metabasites. The supracrustal sequence lies in the core of a major F₃ synform. Metabasite horizons are used as marker horizons to elucidate the structure of the area. Hornblende-granulite subfacies metamorphism accompanied the F₃ folding; later retrograde metamorphism only affected the rocks along master joints and thrusts. Structural analysis of the basement rocks indicates at least two folding phases older than the F₃ folding of the supracrustal sequence; the supracrustals also show minor folds of a fourth phase.