Discovery of Lower Cretaceous hydrothermal vent complexes in a late rifting setting, southern North Sea: insights from 3D imaging

We present data for 31 kilometre-scale hydrothermal vent complexes and associated sand remobilization that have formed as a consequence of magmatic intrusions within salt strata (southern North Sea, Dutch Sector). This study uses 3D seismic data tied to three wells and artificial neural networks to describe conical and cylindrical vent structures located in the NE part of the Broad Fourteens Basin. The structures are composites of 58 subvertical pipes that form complexes, and are 951 ± 364 m in height and 487 ± 426 m in diameter. Interactions of magma and fluids at depth triggered successive fluid pressure build-ups in Triassic sandstones, resulting in upward-propagated ruptures, followed by the collapse of overlying deposits and the injection and extrusion of fluidized sand. The relationship between vent tops and their overlying deposits indicates a Mid- Hauterivian age, unusual for volcanic activity in the North Sea area. This event could have a significant impact on hydrocarbon exploration, as the hydrothermal vent complexes bypass a regional source-rock and seal, offering new migration routes and connectivity between potential reservoirs. The intrusions also raise questions about the influence of transform tectonics on the focusing of volcanic activity during the late rifting phase of the North Sea.