The Rattray Volcanics: Mid-Jurassic fissure volcanism in the UK Central North Sea

The Middle Jurassic Rattray Volcanic Province is located at the triple junction of the North Sea continental rift system. It has previously been thought to be sourced from three large central volcanoes: the Glenn, Fisher Bank and Ivanhoe Volcanic Centres. Re-interpretation using 3D seismic and well data shows that no volcanic centres are present and the Rattray Volcanics were instead sourced in fissure eruptions from linear vents including the Buchan Glenn Fissure System, a ~25km-long zone of WSW-ENE striking linear fissure vents and associated small volcanic edifices across the Buchan-Glenn Horst. The orientation of the fissures is broadly parallel to the Highland Boundary Fault which intersects the Rattray Volcanics at the Buchan-Glenn Fissure System, implying that Middle Jurassic magmatism exploited pre-existing crustal structural anisotropies established during the Caledonian Orogeny. The lack of large intrusive complexes beneath the Rattray Volcanics indicates pre-Middle Jurassic sedimentary sequences (e.g. Devonian-Carboniferous Old Red Sandstone Group, Permian Rotliegend and Zechstein Groups and Triassic Skagerrak Formation) extend further than previously supposed, and therefore the presence of possible sub-volcanic reservoir and source rock units may have been overlooked within the triple junction of the Central North Sea.