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

Abstract

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 c. 25 km 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 Mid-Jurassic magmatism exploited pre-existing crustal structural anisotropies established during the Caledonian Orogeny. The lack of large intrusive complexes beneath the Rattray Volcanics indicates that the pre-Middle Jurassic sedimentary sequences (e.g. the Devonian–Carboniferous Old Red Sandstone Group, the Permian Rotliegend and Zechstein groups and the Triassic Skagerrak Formation) extend further than previously supposed and therefore the presence of possible subvolcanic reservoir and source rock units within the triple junction of the Central North Sea may have been overlooked.