PLUME-INDUCED SUBDUCTION: LOCALIZED ON VENUS NOW, HELPING THE ONSET OF PLATE TECTONICS ON EARTH IN THE ARCHEAN

We recently observed plume-induced subduction in laboratory experiments where a brittle viscous-elasto-plastic lithosphere was self-consistently developing on top of a convecting mantle. Necessary conditions were derived as a function of the mechanical properties and thermal structure of the lithosphere and mantle, the buoyancy of the lithosphere and the buoyancy and size of the mantle plume. They show that plume-induced subduction could currently occur on Venus. Observations were gathered to show that it could indeed be the case at two coronae, Artemis and Quetzalpetlatl. However, subduction remained localized and this regime is not only different from plate tectonics (which implies continuous subduction and renewal of the surface), but also different from stagnant lid and episodic complete resurfacing, as had been proposed for Venus. This new regime is more consistent with models that predict ongoing resurfacing of Venus.

Our scalings further suggest that the hot lithosphere of Venus could be an analogue for early Earth, when conditions may have been favourable for the plume-induced subduction identified nowadays on Venus. Inspection of the geological record on Earth suggests that such a strong association between plumes and subduction may have been instrumental in the nucleation and growth of cratons. In this framework, the big peak in continental crust growth observed at 2.7 Gyr could have originated from a global plume event due to the sudden destabilization of a denser layer at the bottom of the mantle. The simultaneous nucleation of subduction all over our planet would then greatly contribute to the establishment of continuous plate tectonics.