The Beiarn Nappe Complex: A record of Laurentian Early Silurian arc magmatism in the Uppermost Allochthon, Scandinavian Caledonides

We report new data on a suite of compositionally variable igneous rocks intruding amphibolite grade schists and marbles of the Beiarn Nappe Complex of the Uppermost Allochthon, Scandinavian Caledonides, to better understand the pre-collisional position and evolution of this exotic continental terrane within the Scandinavian Caledonides. Major and trace element data on bulk samples combined with U–Pb ID–TIMS and Lu–Hf solution-ICP-MS data on zircons from 8 plutons indicate that this suite of magmatic rocks formed in a continental margin arc setting between 434 Ma and 428 Ma, and are characterized by a range of εHf(t)-values between + 5.8 for mafic intrusives to − 5.3 for granites. In terms of age the Beiarn Nappe Complex is correlative to Silurian magmatic rocks i) in the Upper Nappe of the Helgeland Nappe Complex further south within the Uppermost Allochthon, ii) in several complexes of the Upper Allochthon, and iii) in the Caledonides in NE Greenland. A similar source for the magmatic rocks in the Beiarn Nappe Complex and the Hurry Inlet plutonic terrane in Liverpool Land, NE Greenland is supported by a similar range of εHf(t)-values for the two magmatic complexes, also indicating that the magmatic rocks had a mixed juvenile mantle and crustal source, the latter with minimum crustal residence time of 1.75 Ga.