Hydrothermal Vent Complexes Associated With the Infinity Sill (Vøring Basin, Offshore Norway)

Abstract

The emplacement of igneous sill intrusions induces rapid heating of host rocks, generating fluids that migrate through structures known as hydrothermal vent complexes (HTVCs). While sill geometry and permeability are considered important factors controlling fluid migration around igneous sill intrusions, the precise mechanisms controlling vent distribution remain unclear. To improve the understanding of the primary controls on the final distribution of HTVCs, we are using a 3D seismic data set from the Mid‐Norwegian margin to analyze HTVCs associated with the ∼56 Ma Infinity Sill. The sill covers 237 km ² and is associated with 79 HTVCs, 25 of which are classified as mini‐vents. The HTVCs have outer diameters ranging between ∼0.1–2.7 km, are separated by spacings between ∼1.2–4.8 km, have conduit heights ranging between ∼0.6–1.1 km, and variable upper terminations. Our analysis reveals a large‐scale fluid migration pattern dominated by venting along the sill margins and above the sill interior, controlled by factors such as the fluid generation potential around the sill, the density of local highs in the sill interior as well as the mode and heights of sill transgression. Sill geometry is thus found to affect the formation, size and spacing of HTVCs, and is interpreted to constitute a primary control on the final distribution and morphological characteristics of HTVCs. Our findings contribute to a better understanding of subsurface fluid dynamics associated with sill intrusions emplaced in organic‐rich strata and have broader implications for understanding the climatic effects of hydrothermal venting at the Paleocene‐Eocene transition.