Did an impact event contribute to North Atlantic igneous province flood basalt volcanism?

Large igneous provinces represent short-lived high-volume magmatic events that have had profound influence on Earth’s climate and are often associated with continent disassembly. The Paleogene North Atlantic igneous province is one such magmatic event, with well-preserved and accessible volcanic remnants in the British and Irish Paleogene igneous province. Recent evidence for a possible meteoritic ejecta layer beneath some of the oldest British and Irish Paleogene igneous province lava flows has been used to suggest a causal link between impact and volcanism. Here it is shown that two deposits previously reported to variably contain unmelted impactor fragments, including osbornite, reidite, barringerite, baddeleyite, alabandite, and native iron spherules, are lithologically distinct from one another, with no definitive geochemical traces of impact. The deposits are poor in highly siderophile (Re, Os, Ir, Ru, Pt, Pd) and siderophile elements, with radiogenic 187Os/188Os61.5Ma 36% to >400% higher than in chondrites. Possible origins as a distal density current deposit resulting from an impact are inconsistent with distinct major- and trace-element chemistries of the deposits. Instead, both deposits have volcanic origins, with extensive reworking and incorporation of underlying sediments and crustal rocks. There is no outstanding evidence for an impact contributing to North Atlantic igneous province flood basalt volcanism, and mantle plume impingement during continental breakup is the most likely cause for the inception of the magmatism.