Overriding Plate Deformation and Topography During Slab Rollback and Slab Rollover: Insights From Subduction Experiments

• Published in: Tectonics (Washington, D.C.) D.C.), 2022-02, Vol.41 (2), p.n/a
• Main Authors: Xue, K., Schellart, W. P., Strak, V.
• Format: Article
• Language: English
• Subjects: Analog models; Analogs; Deformation; Dynamic topography; Experiments; mantle flow; Modes; overriding plate deformation; Subduction; Subduction zones; Topography; trench migration; Uplift
• ISSN: 0278-7407; 1944-9194
• DOI: 10.1029/2021TC007089

Some subduction zones in nature show mainly overriding plate (OP) extension and low topography, and others show mainly shortening and elevated topography. Here we investigate how end‐member subduction modes (trench retreat with slab rollback and trench advance with slab rollover) affect overriding plate deformation (OPD), topography, and mantle flow with time‐evolving three‐dimensional fully‐dynamic analog models using particle image velocimetry. We conduct two sets of experiments, one of which is characterized by trench retreat, and the other characterized by trench advance. Experiments showing continuous trench retreat experience overall OP extension, while experiments dominated by trench advance experience overall shortening. Both subduction modes present fore‐arc shortening and intra‐arc extension. Our experiments indicate that the overall OPD is mainly driven by the horizontal mantle flow at the base of the OP inducing a viscous drag force (FD), and is determined by the horizontal gradient of the horizontal mantle shear rate dγ˙/dx $d\dot{\gamma }/dx$, which controls the horizontal trench‐normal gradient in FD. Furthermore, a large‐scale trenchward OP tilting and overall subsidence are observed in the experiments showing continuous trench retreat, while a landward OP tilting and an overall uplift are observed during long‐term trench advance. The two types of topography during the two different subduction modes can be ascribed to the downward component of the large‐scale trenchward mantle flow and the upward component of the landward mantle flow, respectively, and thus represent forms of dynamic topography. Our models showing trench advance provide a possible mechanism for OPD and topography at the Makran subduction zone. Key Points 4D dynamic analog subduction models investigate how end‐member subduction modes affect the overriding plate deformation and topography Continuous trench retreat produces overall overriding plate extension, while long term trench advance promotes overall shortening Continuous trench retreat facilitates trenchward overriding plate tilting, while long term trench advance promotes landward tilting