3D Numerical modelling of induced subduction initiation by transference

Subduction initiation remains one of the critical unsolved problems of modern plate Tectonics (e.g., Stern, 2004; Stern and Gerya, 2018). At passive margins, oceanic lithosphere is old and negatively buoyant, but also thick and very strong. Thus, spontaneous foundering of this lithosphere at these locations requires forces higher than the ones driving tectonic plates in nature (slab-pull and ridge-push, e.g., Cloething et al., 1982, 1989; Mueller and Phillips, 1991). Therefore, different authors have proposed different conceptual processes of induced subduction initiation, in which pre-existent, inherited (mechanical and/or chemical) lithospheric weaknesses, including older subduction zones, might trigger the formation of a new one.

One of these processes is the so-called subduction initiation by transference (Stern, 2004), in which it is argued that a crustal buoyant obstacle (e.g., a continental terrane) could arrive at a subduction zone, causing it to shut down, and triggering a new subduction at the back-end of such a terrane, i.e., causing the subduction zone to be transferred there from its original (frontal) position.

In the present paper, we present new preliminary results of 3D numerical models (LaMEM code of Kaus, 2016) to understand the (geo)dynamic viability of subduction initiation by transference, and to gain new insights on the main parameters governing the possibility of its occurrence in nature. We use buoyancy driven models of continental terrane accretion against the overriding plate (OP) of a subduction zone, to find out if subduction transference is “caused” by the scrapping-off of the continental crustal portion of the terrane against the OP (e.g., Tetreault and Buiter, 2012), or if true front-to-back transference of subduction, critically implying rupture of the lithosphere at the back margin of the terrane, is really possible. Our still preliminary results seemingly suggest that the scrapping-off scenario is more viable, while the true transference one might depend on two key factors: 1) the trench-parallel width of the continental terrane relatively to the width of the oceanic subducting slab; and 2) the existence vs. absence of a weakened (faulted and serpentinized?) zone in the back-end margin of the accreting terrane.

 

 

Acknowledgements:

This work is supported by the Portuguese Fundação para a Ciência e Tecnologia, FCT, I.P./MCTES through national funds (PIDDAC): UID/50019/2023, LA/P/0068/2020 https://doi.org/10.54499/LA/P/0068/2020) and https://doi.org /10.54499/UID/PRR/50019/2025