Acid and intermediate intrusions, deformation and gneiss formation, north-east of Fiskenæsset

Abstract

The sequence of acid and intermediate intrusions and of deformation provides the chronological framework of the geology of an area of 500 km2 north of inner Fiskenæsfjorden and around inner Grædefjord (Plate 1). The oldest recognisable rocks are amphibolites and ultramafite derived from volcanics, irregular doleritic intrusions and layered, gravity-stratified sills; metasediments, chiefly quartz+ biotite±garnet±sillimanite±magnetite gneisses; and layered, gravity-stratified bodies of anorthosite, leucogabbro and gabbro. These rocks were already partly deformed before the sequence of acid and intermediate igneous intrusions and deformation described below and summarised in Table 1.