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Influence of lava flows on the global evolution of Venus

Diogo L. Lourenço , Paul J. Tackley, Maria Grünenfelder

Abstract

Lava flows on Venus can be exceptionally long, far surpassing those on Earth. Radar data from NASA's Magellan mission revealed flows extending hundreds to thousands of kilometres. Previous numerical models have shown that magmatism and crustal production significantly influence planetary tectonics. For example, extrusive volcanism helps breaking tectonic plates facilitating plate tectonics on rocky planets (Lourenço et al., EPSL 2016), while intrusive magmatism has been found to lead to a new global tectonic mode entitled "plutonic-squishy lid". This mode divides the lithosphere into small blocks that move across the surface due to lithospheric drippings and delaminations, even in the absence of active subduction (Lourenço et al., G3 2020). Notably, this regime might apply to Venus (e.g., Byrne et al., PNAS 2021; Smrekar et al., Nat. Geo. 2022). However, previous numerical models of lithospheric and mantle evolution have not considered lateral lava spreading, instead assuming that crust is always formed above eruption sites. Here, we extend the global mantle convection code StagYY (Tackley, PEPI 2008) to incorporate lateral lava spreading and analyse its effects on Venus' evolution. We study how varying lateral lava spreading angles impact crust and lithospheric thickness, mantle temperature, surface heat flow, eruption rates, and outgassing history. Additionally, we explore how lava flows influence Venus' tectonic regime, a subject of ongoing debate (e.g., Rolf et al., Space Sci. Rev., 2024). Our models produce a range of predictions that can be tested by future missions to Venus, including EnVision measurements by the VenSpec spectrometers, comprising outgassing and surface composition.