Extrusive and intrusive magmatism in the North Rockall Trough

Opacity-rendering techniques applied to 3D seismic data from the North Rockall Trough demonstrate that a range of volcanic features indicative of eruptive style can be recognized. The data reveal a complex terrain containing a range of volcanic features, with lava flows originating from discrete volcanic centres up to 4km wide, contemporaneous normal faults, linear fissures a few kilometres long, ring dykes and inflation ridges. Lava flow morphologies indicative of tube-fed inflated sheet flows, intracanyon flows and elongate subaerial flows that enter water downslope to produce a large hyaloclastic delta are observed. Opacity rendering of doleritic sills reveals a branching hierarchy of magma tubes originating from the centre of the sill and climbing upwards and outwards to produce the distinctive ‘saucer-shaped’ morphology. The results show that magma flow within the area under investigation was complex with magma conduits widely distributed across the region. This suggests that the diagenetic effects associated with contact metamorphism and hydrothermal alteration would be widespread, although reduced in magnitude, compared to an area of similar dimensions surrounding a localized high magma volume conduit such as the Skye Central Complex. Supplementary material: The movies referred to in the article are available at https://doi.org/10.6084/m9.figshare.c.4813002