En hornblenderik sone i Seiland-peridotitten. Foreløbig meddelelse.

Abstract

A hornblende-rich zone in the peridotite of Seiland: In the island of Seiland the presence of an extensive peridotite mass was known from earlier investigations. This rock proved to be of a varying mineral composition, the more common type being hornblende-pyroxene-peridotite. As shown on the map, a zone of hornblende-rich rock crosses the peridotite mass. This rock has about 50 percent hornblende, the rest being olivine and pyroxene. There are poikilitic inclusions of olivine and pyroxene in the large hornblende crystals and there are pocket-like inclusions of peridotite in the hornblende- rich rock. The impression was gained that the hornblende-rich rock was formed by metasomatic alteration of the peridotite in a tectonic zone of weakness.