Abstract
Subduction style is controlled by a variety of physical parameters. Here we investigate the effect of subducting plate length on subduction style using laboratory experiments of time-evolving buoyancy-driven subduction in 3-D space. The investigation includes two experimental sets, one with a lower (~740) and one with a higher (~1,680) subducting plate-to-mantle viscosity ratio (ηSP/ηM). Each set involves five models with a free-trailing-edge subducting plate and variable plate length (20–60 cm, scaling to 1,600–4,800 km), and one model with a fixed-trailing-edge subducting plate representing an infinitely long plate. Through determining the contact area between subducting plate and underlying mantle, plate length affects the resistance to trenchward motion of the subducting plate and thus controls the partitioning of the subduction velocity (vS) into the subducting plate velocity (vSP) and trench velocity (vT). This subduction partitioning thereby determines the subduction style by controlling the dip angle of the slab tip once it first touches the 660 km discontinuity. The low ηSP/ηM models display two subduction styles. Short plates (≤40 cm) induce a higher subduction partitioning ratio (vSP/vS), promoting trench advance and slab rollover geometries, whereas longer plates (≥50 cm) lead to a lower vSP/vS, producing continuous trench retreat and backward slab draping geometries. In contrast, the high ηSP/ηM models exclusively show trench retreat with draping geometries, as the high ηSP/ηM enables less slab bending before its tip touches the 660 km discontinuity. Our study indicates that future modeling work should consider the effects of plate length on the style and evolution of subduction.
Original language | English |
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Article number | e2020JB020514 |
Pages (from-to) | 1-23 |
Number of pages | 23 |
Journal | Journal of Geophysical Research: Solid Earth |
Volume | 125 |
Issue number | 11 |
Early online date | 18 Oct 2020 |
DOIs | |
Publication status | Published - Nov 2020 |
Funding
We would like to thank Arijit Laik for his help in preparing one experiment in the lab. We would like to thank Anouk Beniest for providing comments and discussion on an early draft of the paper, and two anonymous reviewers for providing constructive comments that improved the contents of the paper. W. P. Schellart was funded by a Vici grant (016. VICI.170.110) from the Dutch National Science Foundation (NWO).
Keywords
- geodynamics
- plate kinematics
- slab bending
- slab dip
- subduction
- trench migration