Shell vs. plate tectonics: numerical stress quantification in a shortening lithosphere with strain localization

The mechanical characteristics of a shell, having a double curvature, are fundamentally different to the characteristics of a plate, having no curvature in its undeformed state. Geometrically, the Earth’s lithosphere is a shell rather than a plate. However, most geodynamic numerical models applied to study the deformation of the lithosphere do not consider this curvature. It is currently unclear whether the shell-type geometry of the lithosphere has a significant impact on lithosphere deformation on the scale of few 1000 kilometers. This study investigates the importance of considering lithospheric shells and compares numerical results of a shortening shell-type and plate-type lithosphere. We apply the two-dimensional state-of-the-art thermo-mechanical code MDoodz (Duretz et al. 2021). We consider a shortening lithosphere in an initially curved and in an initially rectangular geometry and calculate the spatio-temporal stress distribution inside the deforming lithosphere. We further present preliminary results on the effects and relative importance of various softening mechanism, leading to strain localization and subduction initiation, such as thermal softening, grain size reduction, or anisotropy generation due to fabric development.

 

REFERENCES

Duretz T., R. de Borst and P. Yamato (2021), Modeling Lithospheric Deformation Using a Compressible Visco-Elasto-Viscoplastic Rheology and the Effective Viscosity Approach, Geochemistry, Geophysics, Geosystems, Vol. 22 (8), e2021GC009675