Stratigraphy of the Fiskenæsset anorthosite complex, southern West Greenland, and comparison with the Bushveld and Stillwater complexes

Abstract

The Fiskenæsset complex is a thin layered sheet of deformed and metamorphosed anorthosite, leucogabbro, gabbro, peridotite and dunite, with numerous chromitite layers and lenses. It occurs in an Archaean terrain of amphibolite and granulite facies gneisses as layers up to 500 m thick with outcrop lengths ofup to 25 km and as trains offragments ingneisses, in a belt 50 km wide and 100 km long in the Fiskenæsset region (fig. 28). The Fiskenæsset complexhas given an Rb/Sr whole rock age of 2810 ± 120 m.y. (Alexanderet al., 1973), and gneisses which cut it have given an Rb/Sr whole rock age of 2880 ± 50 m.y. (Moorbath &.. Pankhurst, in press) and a U/Pb zircon age of2835 ± IO m.y. (Pidgeonet al., 1976): A Pb/Pb whole rock age of 2810 ± 70 m. y. from both anorthosite and gneiss from Fiskenæsset has been interpreted as the age of metamorphism (Black et al., 1973).