Interpretation of Nd,Sr and Pb isotope data from Archean migmatites in Lofoten-Vesterålen,Norway

Sm-Nd data for the Archean granulite and amphibolite facies migmatites of Langøy and Hinnøy in Vesterålen are presented which indicate that their protoliths formed ～2.6 AE ago. Rubidium and U loss during a granulite facies metamorphism at ～1.8 AE caused serious disturbance of total-rock U-Pb and Rb-Sr systems. Therefore these systems do not provide any precise age information for the granulite facies migmatites. For the amphibolite facies migmatites of Vesterålen both SmNd, RbSr and PbPb total-rock systems give model ages of ～2.6 AE. The results on both granulite and amphibolite facies rocks are thus in agreement. Previous interpretations based on PbPb data, which indicated an age of 3.41 AE for the Archean terrane of Vesterålen, are not valid.One SmNd model age from the granulite facies migmatites at Moskenesøy in Lofoten indicates that the protoliths of these migmatites formed ～2.0 AE ago and are thus not related to the Vesterålen migmatites.