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Hydrothermal Venting-Induced Structural Compartmentalization in Vøring Basin, Norwegian North Sea

Abstract

Three-dimensional seismic reflection data corroborated by borehole data from the volcanic-rich margin offshore Norway have been employed to characterize the subsurface morphology of hydrothermal vent complexes. Here we aim to unravel the three-dimensional geometry of the hydrothermal vent complex and its associated deformation dynamics within the host-succession and the supra-vent stratigraphy, which has remained poorly constrained. Using multiple seismic attributes such as variance and chaos, the geometries of the hydrothermal vents are systematically mapped across varied stratigraphic levels. Hydrothermal vents complexes in the study area affected Paleogene sediments and exemplified on seismic sections as thin vertical zones of low amplitude to chaotic reflections, with a dome or eye-shaped upper part that is often plagued with smaller and variably shaped volcanic sills and a lower part that corresponds to the tips of saucer-shaped volcanic sills. The nine hydrothermal vent complexes here evolved from the explosive release of fluids and fluidized sediments associated with the emplacement of volcanic sills emplaced at depth of about 4000-5000 ms two-way travel time (TWTT). Structures associated with venting include forced folds with wavelengths of about 1.5 km and distinctive radial faults, which counteract the trends of tectonic and polygonal faults in the study area. The E-W and N-S tectonic faults in the study area show marked intersection geometries with vent-induced radial faults. Faulting or extension due to venting is preponderant at depths of 2000-3000 ms, and the degree at which the vents structurally partition the overburden decreases at shallow depths terminating below the Neogene sediments. Hydrothermal vents complexes are products of Eocene and Oligocene volcanism associated with the opening of the Norwegian and Greenland Seas. Our initial finding suggests the emplacement of hydrothermal vents complexes results in the structural deformation and compartmentalization of overburden succession in parts of the Vøring Basin. This has wider implications for understanding the role of venting of hydrothermal fluids and fluidized materials associated with magmatic plumbing at depth in deforming the overburden succession.