Preliminary Rb-Sr whole-rock data for Archean and Nagssugtoqidian rocks from the Søndre Strømfjord area, West Greenland

Abstract

The boundary between the Archaean gneiss block and the Nagssugtoqidian mobile belt (Escher et al., 1976) runs through the area south-east of the inner part of Søndre Strømfjord (fig. 42). The Archaean block here is mainly composed ofbrownish hypersthene gneisses cut by numerous basic dykes, the Kangåmiut dyke swarm. The Nagssugtoqidian mobile belt consists mainly of light grey biotite gneisses, formed by shearing and recrystallisation of gneisses from the Archaean block, together with numerous amphibolite layers, derived from the Kangâmiut dykes.