Reutilisation of hydrothermal vent complexes for focused fluid flow on continental margins (Modgunn Arch, Norwegian Sea)

• Published in: Basin research 2021-04, Vol.33 (2), p.1111-1134
• Main Authors: Roelofse, Chantelle, Alves, Tiago M., Omosanya, Kamal’deen O.
• Format: Article
• Language: English
• Subjects: Arches; Complex formation; Conduits; Continental margins; Cretaceous; Diameters; Eocene; Fluid dynamics; Fluid flow; fluid migration; Fluids; focused fluid flow; Historical structures; hydrothermal vent complexes; Lava; Magma; magma‐rich margins; North Atlantic Ocean; Ocean floor; Palaeocene; Paleocene; Seismic data; Sills; Strata; Vents
• ISSN: 0950-091X; 1365-2117
• DOI: 10.1111/bre.12507

Conventional three‐dimensional (3D) seismic data reveal abundant igneous activity on the Modgunn Arch, mid‐Norwegian margin. Magmatic sills and associated hydrothermal vent complexes located at various depths prove the repeated utilisation of Paleocene‐Eocene magmatic conduits. In total, 125 sills and 85 hydrothermal vent complexes were identified and mapped, with vent complexes ranging in diameter from 300 to 3,100 m and sills from 0.5 to 50 km. Three examples of stacked vent complexes are presented, revealing large eruptions of hydrothermal fluids vertically through the same conduit, from sills to the palaeo‐sea floor. The vent complexes are found throughout Paleocene strata (66–56 Ma), whilst at least ten (10) vents were active during the Eocene. This study emphasises the importance of characterising ancient magmatic structures, as hydrothermal conduits and vent structures were, and may still be, reutilised as preferential fluid flow pathways to shallower strata. A minimum of four phases of hydrothermal vent complex formation are inferred. Cretaceous faults are both bypassed and used for magma and fluid flow. The reutilisation of magmatic structures here described may bring to light previously overlooked plays and renew interest in exploring magma‐rich continental margins. Amplitude anomalies and stacked hydrothermal vent complexes (HTVCs) indicate reutilisation of HTVCs for fluid flow. (a) High‐amplitude anomaly shown in plan view, located above a hydrothermal vent complex (HTVC), indicating possible gas and fluid flow across the HTVC. (b) Seismic section showing an HTVC with the high‐amplitude anomaly identified and mapped in (a). (c) Seismic section with two stacked HTVCs and seismic dimming in between, indicating two episodes of hydrothermal venting. Bright amplitudes above suggest subsequent fluid flow across the HTVCs.