Metamorfe og eruptive bergarter på Hitra.

Abstract

The area investigated comprises the northern part of the island of Hitra with surrounding smaller islands, situated west of Trondheim, Norway. North of a line between Strømfjorden and Fillan strongly metamorphosed sediments and volcanics predominate. Here a largescaled granitization has taken place, leading to the formation of massive trondhjemitic and graodioritic rocks. Several dioritic bodies are intruded, most of them in lava. The diorites are partly gneissic. South of this line, there are predominantly massive, igneous rocks, varying in composition from gabbroic to granodioritic. Gabbro is rare: diorite, quartzdiorite, trondhjemite and granodiorite predominate. West of Barmfjord one may distinguish the following 9 zones from N to S: 1. The outermost islets: Granodiorite. 2. Dolmøy: Migmatites with mica gneiss, amphibolite, marble and foliated granodiorite. 3. The northernmost part of Hitra: Migmatite with the same components as on Solmøy, but with an unfoliated trondhjemite as massive component. 4. Diorite. 5. Amphibolite and hornblende gneiss. 6. Finegrained gneisses, amphibolite and red, foliated granodiorite. 7. Diorite. 8. Trondhjemite and granodiorite. 9. Diorite in a large, southern massif. To the west trondhjemite and granodiorite.