Zircon U–Pb age for the Orkney lamprophyre dyke swarm, Scotland, and relations to Permo-Carboniferous magmatism in northwestern Europe

posted on 21.06.2016 by A.Mattias Lundmark, Roy H. Gabrielsen, John Flett Brown

Magmatic zircon in the syenite (bostonite) part of a composite NE–SW-trending cogenetic bostonite–camptonite dyke in Orkney, Scotland, yields a laser ablation inductively coupled plasma mass spectrometry age of 313 ± 4 Ma and εHf(313 Ma) values of +6 to +11. This suggests that the NE–SW-, east–west- and NW–SE-trending Scottish lamprophyre dyke swarms were emplaced during one late Carboniferous magmatic event, contrasting with published K–Ar dates ranging between c. 325 and 250 Ma. This magmatism is interpreted as a response to late Variscan regional extension or an early response to the Skagerrak mantle plume. Lamprophyre magmatism was initiated some 10 Ma earlier in Scotland than in the Oslo Rift.