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

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Thorsten W. Becker , Lukas Fuchs


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.



Geology, Geophysics and Seismology, Tectonics and Structure



Published: 2023-08-17 01:38

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CC BY Attribution 4.0 International

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