Early Paleogene offshore igneous activity to the northwest of the UK and its relationship to the North Atlantic Igneous Province

Abstract

Abstract Offshore occurrences of Early Tertiary igneous rocks to the northwest of Britain are allocated to seven major categories using criteria such as geographical location, structure, age and genetic relationship. The categories are: (1) Faeroe Plateau Lava Group; (2) North Rockall Trough-Hebrides Lava Group; (3) central igneous complexes; (4) volcaniclastic rocks; (5) Faeroe-Shetland Intrusive Complex; (6) the Minch; and (7) Wyville-Thomson Ridge. An igneous chronology is presented based on radiometric age dating (mainly K-Ar whole rock), biostratigraphical data and seismic relationships. Most landward central complexes (i.e. Skye, Rhum, Ardnamurchan, Mull, Arran) pre-date those which are more oceanward (i.e. Erlend, Darwin, St Kilda, Rockall). Exceptions to this trend (i.e. Rosemary Bank, Anton Dohrn, Hebrides Terrace) are probably genetically linked to crustal thinning in the Rockall Trough. The age of the Faeroe Plateau Lava Group, and especially the contiguous Rockall Trough-Hebrides Lava Group, are not particularly well constrained. The main intrusive phase on, and to the southeast of, the Faeroe Islands (i.e. Faeroe-Shetland Intrusive Complex) was a relatively late stage magmatic event, coeval with the opening of the North Atlantic between Greenland and NW Europe.