Modeling inherited structures and their effects on strain localization during continental rifting 

Abstract

Continental rifting is a fundamental process of plate tectonics and the Wilson Cycle where weak zones within the continental lithosphere are exploited by both far-field and near-field forces to break-up the continental lithosphere (e.g Molnar et al., 2019). These pre-existing weak-zones are remnants of past tectonic deformation, delineated by shear zones, faults, and/or mobile belts. Reactivation of such inherited structures from previous tectonic phases has been attributed to several continental rift systems, for example, the Rhine graben, Rio Grande rift, Main Ethiopian Rift, Malawi Rift, and the Red Sea. In geodynamic modeling of continental rifts, these weak zones are often approximated by lithospheric thermal perturbation or a weak seed/fault to facilitate strain localization and initiate rifting in response to uniform stretching of the lithosphere. Here, we adopt a different approach building upon models by Salazar-Mora and Sacek (2022) and Peron-Pinvidic et al. (2022) to implement the inherited structures. We start with a geodynamic simulation of continental collision and orogenesis prior to extension but include the effect of temperature-dependent strain healing in the mantle (e.g. Fuchs and Becker, 2021) and time dependent plastic strain healing in the crust (e.g. Olive et al., 2016). We use a 2D geodynamic model ThermoMech (e.g. Xue et al., 2023) coupled to a landscape evolution model FastScape (Yuan et al., 2019), to explore the parameter space in an effort to understand the longevity of weak zones and their implications for rift initiation.   Fuchs, L. & Becker, T. W. (2021). Deformation Memory in the Lithosphere: A Comparison of Damage-dependent Weakening and Grain‐Size Sensitive Rheologies. J. Geophys. Res.: Solid Earth 126. Molnar, N. E., Cruden, A. R., & Betts, P. G. (2019). Interactions between propagating rifts and linear weaknesses in the lower crust. Geosphere, 15(5), 1617–1640. Olive, J.-A., Behn, M. D., Mittelstaedt, E., Ito, G. & Klein, B. Z. (2016). The role of elasticity in simulating long-term tectonic extension. Geophys. J. Int. 205, 728–743. Peron-Pinvidic, G., Fourel, L. & Buiter, S. J. H.  (2022). The influence of orogenic collision inheritance on rifted margin architecture: Insights from comparing numerical experiments to the Mid-Norwegian margin. Tectonophysics 828, 229273. Salazar-Mora, C. A. & Sacek, V. (2023). Effects of Tectonic Quiescence Between Orogeny and Rifting. Tectonics 42. Xue, L., Muirhead, J. D., Moucha, R., Wright, L. J. M. & Scholz, C. A. (2023). The Impact of Climate-Driven Lake Level Changes on Mantle Melting in Continental Rifts. Geophys. Res. Lett. 50. Yuan, X. P., Braun, J., Guerit, L., Rouby, D., & Cordonnier, G. (2019). A New Efficient Method to Solve the Stream Power Law Model Taking Into Account Sediment Deposition. J. Geophys. Res.: Earth Surface, 124(6), 1346–1365.