Tourmaline in Precambrian supracrustal rocks from Aasiaat, central West Greenland

Abstract

Close to the town Aasiaat/Egedesminde supracrustal rocks outcrop on some small islands situated around the position 68°46'N and 52°38'W. The largest of these islands, Isuamiut, is barely a few kilometres long and the islands are situated more than 10 km from the mainland. an Isuamiut two tourmaline-rich layers or tourmalinites have been found (Ellitsgaard-Rasmussen, 1954). Tourmalinite is a peculiar rock type consisting mainly of tourmaline together with quartz, feldspar or mica, sometimes with appreciable amounts of sulphides andlorscheelite. The chemical composition of the tourmaline in tourmalinites is to some extent indicative of the genesis of the boron. I therefore decided to collect some samples of tourmaline on Isuamiut when passing the area on a boat journey along the west coast of Greenland during July 1987.