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SZI: mid-ocean ridges vs. passive margins

Antoine Auzemery and colleagues study under what conditions SZI is more likely to occur at passive margins than at mid-ocean ridges:

We perform numerical modelling to simulate the shortening of an oceanic basin and the adjacent continental margins. We find that, upon compression, subduction initiation at passive margin is favoured for thermally thin (Palaeozoic or younger) continental lithospheres (<160 km) over cratons (>180 km), and for oceanic basins younger than 60 Myr (after rifting). The results also highlight the importance of convergence rate that controls stress distribution and magnitudes in the oceanic lithosphere. Slow convergence (<0.9 cm/yr) favours strengthening of the ridge and build-up of stress at the ocean-continent transition allowing for subduction initiation at passive margins over subduction at mid-oceanic ridges.

Antoine Auzemery, Ernst Willingshofer, Philippe Yamato, Thibault Duretz, Fred Beekman (2021). Kinematic boundary conditions favouring subduction initiation at passive margins over subduction at mid-oceanic ridges . Front. Earth Sci. 9:765893. doi: 10.3389/feart.2021.765893

Synopsis of hindering and facilitating parameters in plume-induced subduction initiation. Note that aging of the lithosphere has a dual effect; aging increases lithospheric strength, which hinders subduction initiation, but it can also facilitate subduction initiation because it increases lithospheric density.
(A) Geodynamic processes that potentially contribute to the transfer of stress to a passive margin. (B) Passive margin SZI and (C) intra-oceanic SZI for slow and fast converging systems, respectively.

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