Autochthonous granodiorites north-west of Frederikshåbs Isblink, Fiskenæsset region

Abstract

The gneiss complex immediately north-west of Frederikshåbs Isblink is composed mostly of amphibolite facies, grey, streaky, quartzo-feldspathic, biotite and hornblende gneisses. Subordinate amphibolites, homblendites, thin anorthosites, peridotite lenses up to 200 m across, rare concordant marble bands and associated calc-silicate gneisses and kyanite and sillimanite gneisses make up the bulk of the remainder, and the whole has been complexly deformed. Occupying the higher ground within the complex, and comprising the largest single lithological unit there is a considerable volume of massive weathering, porphyroblastic granodiorite and granodiorite gneiss. Field relationships show this to be unquestionably autochthonous and almost certainly of palingenetic origin and while on a small scale the 'contact' with the surrounding gneisses may be locally discordant, overall it follows closely the large scale structure and this suggests its control by preexisting lithology.