Three-dimensional (3-D) seismic imaging of conduits and radial faults associated with hydrothermal vent complexes (Vøring Basin, Offshore Norway)

Here, we document a suite of radial faults associated with hydrothermal vent complexes in the Vøring Basin, offshore Norway. These complexes have pyramid-shaped, cylindrical- and conical-shaped conduits, with a dome-, or eye-shaped morphology at their summit, intruding on Paleogene sedimentary rocks. Hydrothermal vents are intimate with the tips of magmatic sills that were emplaced at depths ranging between 1800 and 5800 ms Two Way Travel Time (TWTT). At shallower depths of 1800 to 3000 ms TWTT and intermediate depths of 3000 to 5000 ms TWWT, magmatic sills regularly intersect the lower parts of the vent conduits, which are characterized here as pipes. An important parameter that is used to characterize the morphology of a hydrothermal vent conduit is the width of the conduit, which is defined as the longest axis marking the extent of the vents' conduit within the surrounding host-rock strata. Our findings reveal that radial faults are commonly associated with the summits of hydrothermal vents, implying the existence of local stress fields around the vents, where the maximum compressive stress is radial and minimum stress is circumferential, which overrides the regional stress field and indicate variable stress regimes as opposed to tectonic faults. Importantly, circumferential stretching due to catastrophic plumbing of hydrothermal fluids, differential compaction and intensive fracturing enabled the polygonal faults to realign in a radial pattern resulting in the formation of radial faults at the vent summit. As a corollary of this work, we hypothesize that pyramid-shaped hydrothermal conduits are possibly markers of protracted sill emplacement in sedimentary basins.