En geologisk undersøkelse på den nordvestlige del av kartblad Børgefjell.

Abstract

A geological investigation of the Caledonid of the Majavatn-Kvigtindregion, Nordland, Norway. The northwestern part of the map area Børgefjell, Nordland, was investigated during the summers of 1957 and 1958, seven weeks each summer.1. Mica gneisses and metaschists. This group of rocks comprises plagioclase-bearing rocks rich in biotite and\/or muscovite. Rocks with little or no plagioclase are found in the Kvigtind nappe. The most abundant types are: Mica-plagioclase gneiss, biotite-hornblende gneiss, biotite-garnet gneiss, cyanite-staurolite gneiss and muscovite gneiss. The schistosity is very distinct in these rocks. The field observations indicate a sedimentary origin, but he high Na and Ca content is not in accordance with such an origin. A metasomatic introduction of these elements is therefore suggested. This suggestion is supported by the occurence of plagioclase-pegmatites in the gneisses. The mica schists in the Kvigtind nappe seem to have their original composition unchanged. The mica- gneisses probably represent meta-morphic and metasomatized pelitic sediments. In the staurolite-cyante gneisses the paragenesis staurolite-cyanite-almandite suggests a state of nonequilibrium in the rock.