The 2021 Virtual Outstanding Student and PhD candidate Presentation (vOSPP) Award is awarded to Zhibin Lei for the poster/PICO entitled:
Impact of trench retreat rate on initiating focused back-arc extension within a mobile overriding plate (Lei, Z.; Davies, J. H.)
Click here to download the poster/PICO file.
Zhibin Lei is a PhD candidate at Cardiff University, UK, under the supervision of Prof. J. Huw Davies. His general research interest lies in understanding the geodynamic origin and governing parameters accounting for different degrees of deformation observed within the lithosphere during plate tectonic events of subduction, rifting, pluming, delamination, initiation of new plate boundaries etc.
The awarded poster investigates the role of high trench retreat rate on initiating focused back-arc extension within a mobile overriding plate. We find that it takes a minimum trench retreat rate to initiate rifting or further extension in the back-arc region for models with a free mobile boundary condition. The extension is driven by the non-uniform basal drag of the trenchward mantle wedge flow due to rapid trench retreat. The results could potentially be used to explain the southward decreasing stretching state along the Lau-Havre-Taupo back-arc system where trench retreat rate decreases southward as well. On the other hand, in the models we find that an older subducting plate leads to faster trench retreat rate, but this correlation only exists before the slab approaches the lower mantle. This matches well with the observation that the subducting plate age is always old (>55 Ma) in subduction zones with back-arc extension. It also explains why there is a poor correlation between the age of subducting plate and trench retreat rate because most slabs have already reached the lower mantle.