Gabbroic and quartz dioritic intrusions in gneisses on southern Askøy, West Norwegian Caldonides.

Abstract

Light- and dark-coloured biotite gneisses and in part amphibole gneisses, of supracrustal origin have been intruded by a Precambrian basic pluton. Later a quartz diorite was intruded into the basic rocks. By assimilation of basic xenoliths in the quartz diorite rock was formed. The whole area was penetratively folded and metamorphosed during a late Ordovician - early Silurian Caledonian orogenic event. The gneisses were partly migmatized and augen gneisses were formed. Most of the gabbroic and quartz dioritic intrusive rocks were more or less altered, but the basic bodies still have large areas of relatively unaltered rock with primary texture and mineralogy.