Premium
Age and origin of the Årdal dike complex, SW Norway: False isochrons, incomplete mixing, and the origin of Caledonian granites in basement nappes
Author(s) -
Lundmark A. M.,
Corfu F.
Publication year - 2007
Publication title -
tectonics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.465
H-Index - 134
eISSN - 1944-9194
pISSN - 0278-7407
DOI - 10.1029/2005tc001844
Subject(s) - nappe , geology , baltica , anatexis , baltic shield , proterozoic , dike , isochron dating , basement , geochemistry , isochron , paleontology , precambrian , tectonics , ordovician , mantle (geology) , partial melting , archaeology , history
Granitic dikes intruding the upper thrust sheets of the Jotun Nappe Complex, southwest Norway, previously assigned a Sveconorwegian age based on Rb‐Sr data, are redated to 427 ± 1 Ma by U‐Pb. The erroneous Rb‐Sr age can be explained by mixing of magmas with different isotopic compositions. Similar geochemical signatures, evidence of Sr mixing, inherited Proterozoic zircons and synkinematic modes of emplacement are also seen in Silurian granites in the Lifjorden Complex as well as in the Lindås Nappe and the Totland unit of the Bergen Arc Complex. We propose that these granites are related and derived from anatexis of Rb‐poor sediments of Baltica affinity overridden by the nappes during Scandian thrusting. This interpretation is compatible with the presence of the granites in nappes of both oceanic and of continental affinities and their absence in the autochthonous basement.