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Oceanic crust recycling controlled by weakening at slab edges
Jessica Munch1, Taras Gerya2, Kosuke Ueda2
1Department of Earth Sciences, Institute of Geophysics, ETH Zürich, Zürich, Switzerland. jessica.munch@erdw.ethz.ch.
Nature Communications
|April 26, 2020
Summary
Subduction zones retreat by faulting, but mechanisms are unclear. Strain-induced weakening of fractures controls oceanic lithosphere recycling, influencing slab shape and fault propagation in subduction zones.
Area of Science:
- Geodynamics
- Tectonics
- Geophysics
Background:
- Retreating subduction zones migrate oceanward, cutting through oceanic crust.
- Faults at slab edges enable spontaneous retreat, but propagation mechanisms are unknown.
Purpose of the Study:
- Investigate physical mechanisms controlling fault propagation and direction in retreating subduction zones.
- Determine the role of strain-induced weakening in oceanic lithosphere recycling.
Main Methods:
- Utilized 3D numerical subduction models.
- Simulated various intensities of strain-induced weakening of fractures.
Main Results:
- Oceanic lithosphere recycling is primarily controlled by strain-induced weakening of slab edge fractures.
- Intense weakening promotes brittle faulting, slab narrowing, and detachment.
- Lack of weakening leads to ductile propagation and slab widening.
- This rheological control is independent of passive continental margins.
Conclusions:
- Strain-induced weakening is a key factor in subduction zone dynamics.
- Slab edge behavior (brittle vs. ductile) is dictated by fracture weakening intensity.
- Natural subduction zone paths may be guided by deep-water-induced fracture weakening.
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