L. Johansson et al., THE AGE AND REGIONAL CORRELATION OF THE SVECOFENNIAN GEITFJELL GRANITE, VESTRANDEN, NORWAY, Norsk geologisk tidsskrift, 73(2), 1993, pp. 133-143
U-Pb zircon dating of granitoids from the northermost part of the West
ern Gneiss Region (Vestranden) has yielded the oldest ages so far reco
rded in central and southern Norway. The Geitfjell granite, a coarse-g
rained granite near Grong, central Norway yielded a U-Pb zircon age of
1828(-65)+88 Ma, whereas a Rb-Sr determination yielded an age of 1770
+/-62 Ma. Its initial Sr-86/Sr-87 is 0.7094 and epsilon(Nd) (1830 Ma)
value is -0.04. Petrographically similar granites occur also in large
areas in the northern half of the Vestranden region. The petrography,
isotope chemistry, age and chemical composition of dhe Geitfjell grani
te closely resembles that of granites of the Revsund type, which intru
de marine metasedimentary rocks in the Svecofennian Bothnian Basin in
north-central Sweden. A correlation of these granites is thus suggeste
d. The occurrence of this type of granite in the northernmost part of
the Western Gneiss Region suggests that this region reports the wester
ly continuation of the Svecofennian Bothnian Basin rather than a part
of the Southwest Scandinavian orogenic province or the Transscandinavi
an Granite Belt. Precambrian metasedimentary rocks of Bothnian Basin a
ffinity may thus occur in Vestranden.