A new occurrence of gabbro in the Oslo Rift, South Norway
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- Artikler 
Xenoliths made up of an assemblage of gabbro, diorite and biotite monzonite in syenite and granite and veined by these rocks have been found within a small area at the south end of lake Mykle in the southern part of the Oslo Rift. The xenoliths most probably represent the remains of a former gabbroic neck similar to those occurring elsewhere in the Oslo Rift. The Mykle occurrence is located about 50 km to the south and in prolongation of a linear belt of gabbroic necks in the northern part of the rift zone. Gabbro, diorite and biotite monzonite may represent remnants of a composite neck, or the biotite monzonite and perhaps also the diorite may be gabbro modified by infiltration of fluids from the enclosing syenites and granites. Xenolites og larvikite in xenoliths of biotite monzonite indicate that gabbroic rocks in this region were later than larvikite and older than syenite and granite.