Megadyke propagation down dynamic topography

Tim Davis¹, Yuan Li², Adina Pusok² and Richard Katz²

• Affiliations: ^ 1^School of Earth sciences, University of Bristol, UK. ²University of Oxford, UK

• Presentation type: Poster

• Presentation time: Thursday 16:30 - 18:30, Room Poster Hall

• Poster Board Number: 191

• Programme No: 1.8.22

• Theme 1 > Session 8

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Abstract

Magmatic dykes that extend laterally for hundreds to thousands of kilometres are known as megadykes. These are fundamental features of both Earth and Venus's crust whose formation mechanisms remain poorly understood. Megadyke structures typically form swarms that originate from a common source and that propagate laterally without eruption. The challenge lies in explaining why dykes eventually terminate with a characteristic length in a given swarm. Here we show that megadyke propagation is driven by the dynamic topography (and gravitational potential energy, GPE) created by underlying mantle plumes, with dyke length controlled by gradients in gravitational potential energy associated with domal uplift. Using a mathematical model of fluid-driven fracture that incorporates magma solidification and turbulent flow dynamics, we demonstrate that dykes perched at their level of neutral buoyancy can propagate laterally to distances comparable to or exceeding the size of the underlying plume head. Moreover, we show that such dykes  require lower source pressures than previously thought. The GPE mechanism explains both the characteristic lengths of megadyke swarms. It also explains their variable extent:small changes in source pressure can significantly affect propagation distance. Our findings provide a new framework for understanding the formation of these massive geological structures and suggest that plume-induced dynamic topography may play a crucial role in controlling radial dyke systems within Earth's crust.