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

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.

Determining magma flow in sills, dykes and laccoliths and their implications for sill emplacement mechanisms

“…The sills are predominantly dolerites and olivine dolerites (Gibb and Kanaris-Sotiriou 1988), with the major and trace element geochemistry matching that of the Faroes Upper Formation lavas (Waagstein 1988). The vast majority of the sills were intruded between 55 and 53 Ma (Ritchie and Hitchen 1996), close to the age of the geochemically similar Faroes Upper Formation lavas.…”

Geochemical study of lower Eocene volcanic ash layers from the Alpine Anthering Formation, Austria.

“…Ashes of a similar composition are long known from the North Sea region (Bøggild, 1918), in particular from the Fur Formation in Denmark. Ritchie and Hitchen (1996) suggested sub-aerial volcanism with possible seamounts as source for the phreatomagmatic eruption.…”

Regional controls on Lower Tertiary sandstone distribution in the North Sea and NE Atlantic margin basins

“…This long-lived feature continued southwestwards to form the faulted margins of the West Shetland and Outer Hebrides platforms. Igneous activity was initiated in the Hebrides province with the emplacement of volcanic centres on Skye, Mull, Ardnamurchan and Rhum (Mussett et al 1988;Ritchie & Hitchen 1996).…”