The Effect of Temperature-dependent Strength of Lithosphere on the Earth's Tectonic Evolution

Plate tectonics is a characteristic feature of Earth, but its initiation and early evolution remain debated. Geological and geochemical evidence suggests that plate tectonics was initiated from a stagnant-lid regime in the Archaean, however mechanisms associated with this transition are unclear. Previous geodynamic models, which typically assume fixed lithospheric strength, require a low effective yield-stress rheology to obtain plate-like behaviour, inconsistent with laboratory measurements. Here, we apply a global-scale mantle convection model that incorporates a temperature-dependent friction coefficient, representing thermodynamic weakening on fault planes during rapid slip (Brantut & Platt, 2017), to study the tectonic evolution of Earth-like planets. As the timescales of geodynamic models and fault motion differ by several orders of magnitude, a simplified step-function approach is adopted, where reduced friction coefficients of 0.01~0.1 are applied below the temperature threshold to mimic unstable fault motion (Karato & Barbot, 2018). Our results show that temperature-dependent weakening does not systematically promote stagnant-to-mobile lid transitions. Instead, plume-induced subduction serves as the dominant process to transition from an initial stagnant phase to plate-like lithospheric behaviour (mobile lid). We find that temperature-dependent friction coefficients can act as an additional weakening mechanism to promote subduction even at high lithospheric strengths. Unlike earlier models, which produced mobile-lid behaviour only under lithospheric strengths much lower than laboratory estimates, these findings demonstrate that more realistic rheological parameters can sustain mobile-lid behaviour when dynamic weakening is considered. We also find that subduction-zone locations are stabilised over time in cases with temperature-dependent friction coefficients. This behaviour is associated with localised lithospheric weakening in cold downwellings, and consistent with the stability of trench locations in plate reconstructions (Müller et al., 2019) as well as of seismically-observed lower-mantle structures (Torsvik et al., 2010). Our results provide a possible explanation for why plume-induced subduction on Venus, where high surface temperatures inhibit dynamic weakening, remains short-lived and localised, preventing plate tectonics.

References

Brantut, N., & Platt, J. D. (2017). https://doi.org/10.1002/9781119156895.ch9

Karato, S., & Barbot, S. (2018). https://doi.org/10.1038/s41598-018-30174-6

Müller, R. D., Zahirovic, S., Williams, S. E., Cannon, J., Seton, M., Bower, D. J., Tetley, M. G., Heine, C., Le Breton, E., Liu, S., Russell, S. H. J., Yang, T., Leonard, J., & Gurnis, M. (2019). https://doi.org/10.1029/2018TC005462

Torsvik, T. H., Burke, K., Steinberger, B., Webb, S. J., & Ashwal, L. D. (2010). https://doi.org/10.1038/nature09216