Generation of evolving plate boundaries and toroidal flow from visco-plastic damage-rheology mantle convection and continents

Abstract

Earth's style of planetary heat transport is characterized by plate tectonics which requires rock strength to be reduced plastically in order to break an otherwise stagnant lithospheric lid, and for rocks to have a memory of past deformation to account for strain localization and the hysteresis implied by geological sutures. Here, we explore $\sim$10$^7$ Rayleigh number, visco-plastic, 3-D global mantle convection with damage. We show that oceanic lithosphere-only models generate strong toroidal-poloidal power ratios and features such as a mix of long-wavelength tectonic motions and smaller-scale, back-arc tectonics driven by subduction. Undulating divergent plate boundaries can evolve to form overlapping spreading centers and microplates, promoted and perhaps stabilized by the effects of damage with long memory. The inclusion of continental rafts enhances heatflux variability and toroidal flow, including net rotation of the lithosphere, to a level seen in plate reconstructions for the Cenozoic. Both the super-continental cycle and local rheological descriptions affect heat transport and tectonic deformation across a range of scales, and we showcase both general tectonic dynamics and regionally applied continental breakup scenarios. Our work points toward avenues for renewed analysis of the typical, mean behavior as well as the evolution of fluctuations in geological and model plate boundary evolution scenarios.

Generation of Evolving Plate Boundaries and Toroidal Flow From Visco‐Plastic Damage‐Rheology Mantle Convection and Continents

“…We used the finite element software CitcomS and thank L. Moresi, S. Zhong, A. McNamara, and E. Tan for sharing their code developments, partly supported by the Computational Infrastructure for Geodynamics. Our extensions to CitcomS are available on github.com/geodynamics/citcoms under commit 2bda530, and model input files and movies from our computations at Becker and Fuchs (2023).…”