Global mantle convection models produce transform offsets along divergent plate boundaries

Abstract

The presence of offsets, appearing at intervals ranging from 10s to 100s of kilometres, is a distinct characteristic of constructive tectonic plate margins. By comparison, boundaries associated with subduction exhibit uninterrupted continuity. Here, we present global mantle convection calculations that result in a mobile lithosphere featuring dynamically derived plate boundaries exhibiting a contrasting superficial structure which distinguishes convergence and divergence. Implementing a yield-stress that governs the viscosity in the lithosphere, spreading boundaries at the top of a vigorously convecting mantle form as divergent linear segments regularly offset by similar length zones that correlate with a large degree of shear but comparatively minimal divergence. Analogous offset segments do not emerge in the boundaries associated with surface convergence. Comparing the similarity in the morphologies of the model plate margins to the Earth’s plate boundaries demonstrates that transform-like offsets are a result of stress induced weakness in the lithosphere owing to passive rupturing.

Craton Formation in Early Earth Mantle Convection Regimes

“…Additionally, the models' aspect ratio may strongly affect the temperatures and heat flow (Lowman et al., 2001); however, for a ratio above 6 (Lowman et al., 2001) and for large Ra the mean temperatures converge (O’Farrell & Lowman, 2010). We have neglected the role of three‐dimensional structures, such as strike‐slip tectonics (Langemeyer et al., 2021). However, comparisons of spherical and Cartesian models show that the tectonic regimes characterized by divergent and convergent margins are consistently reproduced in both geometries (Crameri & Tackley, 2014).…”

Tectonics is a hologram

“…With pseudo-plasticity, the planform of convection involves sheet-like downwellings with properties consistent with subduction on Earth (Crameri and Tackley, 2014;Coltice et al, 2019) and cylindrical plumes (Arnould et al, 2020). The surface pattern is a network of divergent, convergent and possibly transform boundaries (Langemeyer et al, 2021). These boundaries are sharp or diffuse, making them sometimes hard to automatically identify (Mallard et al, 2017).…”

Looking beyond kinematics: 3D thermo-mechanical modelling reveals the dynamics of transform margins

“…Whether transform faults originate pre-or syn-rifting or even post-continental break-up is still a matter of debate. However, some oceanic transform faults can form without any continental inheritances as shown by the presence of many transform faults along mid-oceanic ridges due to the plate kinematics and oceanic lithosphere rheology (Langemeyer et al, 2021). More recently, based on natural examples, Bellahsen et al (2013) and Basile (2015) highlighted the fact that transform faults can form synchronously with syn-rift structures and may reactivate or cross-cut inherited structures (e.g.…”