The Origin of High-Curvature Banda Subduction Zone: Insights from Lithosphere-Scale Analog Modeling

                           The Origin of High-Curvature Banda Subduction Zone: Insights from Lithosphere-Scale Analog Modeling

                                                         Yuwei Liu, Weiwei Ding, Chunyang Wang, Zhengyi Tong, Xiangtian Wen

                              Key Laboratory of Submarine Geosciences & Second Institute of Oceanography, MNR, Hangzhou 31002, China

Abstract:

The Banda Arc is located at the easternmost end of the Southeast Asian circum-subduction system. It is known for its prominent 180° curvature and complex kinematic pattern. The origin of the arc involves various dynamic processes, such as oceanic-continental subduction and arc-continent collision. Previous studies have analyzed and characterized the slab morphology, stagnation depth, deep interactions, and mantle flow of the Banda arc-shaped subducting zone, using a variety of seismological methods, such as seismic tomography, receiver functions and anisotropy analysis. However, there is still a lack of consensus on the formation mechanism and dynamic model of the highly curved subduction zone, i.e., one slab model vs two slab model. Three-dimensional lithosphere-scaled analog modeling is an effective method for studying the deformation mechanisms of subduction zones. In this study, 3-D lithosphere-scaled analog modeling is used to investigate the formation mechanism of the highly curved Banda subduction zone. The experimental process incorporates the morphological, structural, and deformation characteristics of the study area, establishing corresponding models involved continental and oceanic lithosphere, upper mantle. Our preliminary simulation results suggest that the formation of the highly curved Banda subduction zone may be closely related to the arcuate concave morphology of the continental margin on the northern edge of Australia (paleo-Banda embayment). During the rollback of the oceanic slab, the irregular edges of the continental lithosphere significantly influences the geometric evolution of the trench, resulting in the final trench shape similar to the edge morphology of the continental block. The incorporation of continental crust into the subduction processes results in a progressive reduction in the subduction rate, which may ultimately lead to the cessation of subduction. Consequently, the subducted slab retains a relatively steep angle within the mantle. The primary factor contributing to the decreased trench retreat rate and subduction rate is the substantial positive buoyancy of the continental lithosphere. Our models suggest that the Banda subduction zone, characterized by its high curvature, may be formed in the “one slab model”.