摘要：Dyke swarms are common on Earth and other planetarybodies, comprising arrays of dykes that can extend laterally for tens tothousands of kilometres. The vast extent of such dyke swarms, and theirpresumed rapid emplacement, means they can significantly influence a varietyof planetary processes, including continental break-up, crustal extension,resource accumulation, and volcanism. Determining the mechanisms drivingdyke swarm emplacement is thus critical to a range of Earth Sciencedisciplines. However, unravelling dyke swarm emplacement mechanics relies onconstraining their 3D structure, which is difficult given we typicallycannot access their subsurface geometry at a sufficiently high enoughresolution. Here we use high-quality seismic reflection data to identify andexamine the 3D geometry of the newly discovered Exmouth Dyke Swarm, andassociated structures (i.e. dyke-induced normal faults and pit craters).Dykes are expressed in our seismic reflection data as ∼335–68 m wide, vertical zones of disruption (VZD), in which stratalreflections are dimmed and/or deflected from sub-horizontal. Borehole datareveal one ∼130 m wide VZD corresponds to an ∼18 m thick, mafic dyke, highlighting that the true geometry of the inferreddykes may not be fully captured by their seismic expression. The LateJurassic dyke swarm is located on the Gascoyne Margin, offshore NW Australia,and contains numerous dykes that extend laterally for > 170 km,potentially up to > 500 km, with spacings typically < 10km. Although limitations in data quality and resolution restrict mapping ofthe dykes at depth, our data show that they likely have heights of at least3.5 km. The mapped dykes are distributed radially across a∼39∘ wide arc centred on the Cuvier Margin; weinfer that this focal area marks the source of the dyke swarm. We demonstratethat seismic reflection data provide unique opportunities to map and quantifydyke swarms in 3D. Because of this, we can now (i) recognise dyke swarmsacross continental margins worldwide and incorporate them into models ofbasin evolution and fluid flow, (ii) test previous models and hypothesesconcerning the 3D structure of dyke swarms, (iii) reveal how dyke-inducednormal faults and pit craters relate to dyking, and (iv) unravel how dykingtranslates into surface deformation.
