<p>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 <em>ε</em>Hf<sub>(313 Ma)</sub> 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 <em>c</em>. 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.
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