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

• Published in: Earth and Planetary Science Letters
• Main Authors: Jacobsen, Stein B., Wasserburg, G. J.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Elsevier 1978
• Subjects: Lofoten; Norway; Patience
• Online Access: https://doi.org/10.1016/0012-821X(78)90181-4

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 Sm-Nd, Rb-Sr and Pb-Pb 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 Pb-Pb data, which indicated an age of 3.41 AE for the Archean terrane of Vesterålen, are not valid. One Sm-Nd 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. © 1978 Elsevier Scientific Publishing Company. Received May 16, 1978. Revised version received July 25, 1978. Einar Tveten of the Norwegian Geological Survey (NGU) was most helpful in assisting us with the fieldwork and discussing the field relations in Vesterålen. We also appreciate the patience of his wife Laila and her younger assistant. We are grateful to K.S. Heier and W.L. Griffin for discussions and for making some of the arrangements for us to go there. Samples GS-5, GS-23 and TL-39 were supplied by I.K. Iden who also kindly made unpublished REE data available to us as a guidance for sample selection. Some of the Sm-Nd results and our interpretation of the U-Pb and Rb-Sr systematics were first presented in a seminar at the Mineralogical-Geological Museum in Oslo, August 1977, and we appreciate the discussion with W.L. Griffin and coworkers on that occasion. After this work was completed, we received from W.L. Griffin a revised preprint of [8] that reports the new Pb-Pb age by P.N. Taylor for the amphibolite facies migmatites and a revision ...