Subduction dynamics driven by crustal heterogeneities in the subducting plate

Subduction zones play a fundamental role in shaping Earth’s surface. Their dynamics are responsible for forming deep-sea trenches, orogens, volcanic arcs and basins. However, subducting plates are not homogeneous; they contain crustal heterogeneities such as seamounts, oceanic plateaus, and depocenters that influence slab dynamics when they enter the subduction interface. In this study, we use 2D geodynamic models to explore how variations in the strength, size, and position of these heterogeneities, affect trench migration and slab geometry. These parameter variations allow us to investigate how crustal heterogeneities controls subduction processes. Our results show that strong heterogeneities representing cold oceanic plateaus or seamounts, aseismic ridge slow down subduction and trench motion, increase slab dip, and can ultimately halt subduction. In contrast, weak rheological heterogeneities analogous to sedimentary depocenters accelerate trench retreat velocity up to ∼ 2 times faster than the homogeneous model and promote back-arc basin formation in some cases. Our results demonstrate that inherited weak crustal heterogeneities within subducting plates can trigger slab break off even in the absence of continental collision. We identify a negative correlation between slab breakoff depth and both the heterogeneity’s length and its distance to the trench. We demonstrate that the obtained variety of breakoff depths leads to a variety of post-breakoff geodynamic evolution, including resumed subduction, overriding plate extension, back-arc opening and polarity reversal by overriding lithosphere continental delamination. Episodicity in trench retreat velocity observed in the models resembles natural examples such as the Calabrian and Hellenic arcs. These findings highlight that relatively small inherited structures or sediment accumulations in the oceanic crust could exert a major control on subduction dynamics, influencing slab geometry, trench migration, and the evolution of the overriding plate, contributing to the tectonic complexity of the system.