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

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.

Automated summary

The study in mid-Norwegian margin reveals abundant igneous activity, with magmatic sills and hydrothermal vent complexes being repeatedly utilised in the Paleocene-Eocene period. The vent complexes show large eruptions of hydrothermal fluids vertically through the same conduit, highlighting the importance of characterising ancient magmatic structures. The reutilisation of magmatic structures may lead to new plays and renew interest in exploring magma-rich continental margins.