Plume-induced crustal convection: 3D thermomechanical model and implications for the origin of novae and coronae on Venus

- First 3D numerical model of Venus novae and coronae formation and evolution.
- Crustal convection induced by plume impingement into thin lithosphere.
- Modeled topography and surface fracturing patterns agree with observations.

Novae and coronae are large volcanotectonic features on Venus, with a contentious and possibly non-unique origin and enigmatic relationship. Their formation is most commonly explained by flexure and fracturing of the strong rigid Venus lithosphere atop mantle upwelling and/or downwelling. Here we present new 3D high-resolution thermomechanical model of mantle plume/diapir impingement into warm and thin lithosphere with Venus-like surface temperature. Numerical results suggests that nova-like and corona-like structures can result from magma-assisted convection of weak ductile crust, induced by decompression melting of the hot rising mantle plume. During the initial stage, nova forms by stellate fracturing of a topographic rise forming atop the growing crustal convection cell. Few million years later, nova can convert to coronae by inward dipping concentric fracturing of the nova rise margins and subsequent outward thrusting of partially molten crustal rocks over the surface. An outer annulus of concentric normal faults forms in the outer rise region of the downbending brittle upper crust, whereas an inner annulus of concentric thrust faults forms in front of the outward thrusting crustal wedge. A trench-like depression forms between these two annuli. Resembling retreating subduction, the rudimentary concentric upper-crustal slab warms up rapidly and recycles into the convection cell. The convection cell remains active for up to 15 million years, fueled by heat and magma from the plume. Predicted surface topography and fracturing patterns agree with some small to moderate size novae and coronae on Venus.

287