EGU2020-16952, updated on 26 Feb 2024
https://doi.org/10.5194/egusphere-egu2020-16952
EGU General Assembly 2020
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

The role of transform faults during back-arc spreading centre jumps

Nicholas Schliffke1, Jeroen van Hunen1, Frederic Gueydan2, Valentina Magni3, and Mark B. Allen1
Nicholas Schliffke et al.
  • 1Durham University, Earth Sciences, Durham, United Kingdom of Great Britain and Northern Ireland (nicholas.j.schliffke@durham.ac.uk)
  • 2Géosciences Montpellier, Université Montpellier 2, place E. Bataillon 34095 Montpellier cedex 5, France
  • 3cThe Centre for Earth Evolution and Dynamics (CEED), University of Oslo, SemSaelandsvei 24, PO Box 1048, Blindern, NO-0316 Oslo, Norway

Jumps in the location of back-arc spreading centres are a common feature of back-arc basins, but the controlling factors are not understood. In several narrow subduction zones with a long subduction history, such as the Scotia arc or Tyrhennian Sea, several spreading centres have been active in the course of history with regular, quasi-instantaneous jumps towards the retreating trench. A prominent feature of these regions are large bounding transform (‘STEP’) faults. However, whether STEP faults influence the (unknown) dynamics spreading centre jumps remains to be explored.

 

We therefore run 3D-models to simulate a long narrow subducting slab, bound by continents, which retreats and creates necessary STEP-faults self-consistently. The results offer a new mechanism for back-arc spreading jumps: After the creation of a back-arc spreading centre in the retreating subduction system, transform faults between trench and back-arc basin form. Spreading jumps are thus a consequence of the fact that these constantly elongating transform faults, which decouple the overriding plate from neighbouring plates, fail to remain active once a threshold length (~1.3x plate width) is reached. Subsequently, the back-arc basin and neighbouring plates are strongly coupled, and ongoing trench retreat localizes stresses and rapidly ruptures the overriding plate closer to the trench while the old spreading centre is abandoned.  In a parameter study, the results further explain why the narrowest subduction zones, such as the Calabrian Arc, experience more frequent and closer spreading jumps than the long-period jumps of a wider subduction zone such as the Scotia Arc. The widest subduction zones should not undergo any back-arc spreading jumps with this mechanism, consistent with other natural examples.

How to cite: Schliffke, N., van Hunen, J., Gueydan, F., Magni, V., and Allen, M. B.: The role of transform faults during back-arc spreading centre jumps, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16952, https://doi.org/10.5194/egusphere-egu2020-16952, 2020.

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