Forced Subduction Initiation at Passive Continental Margins: Velocity‐Driven Versus Stress‐Driven

• Published in: Geophysical research letters Vol. 46; no. 20; pp. 11054 - 11064
• Main Authors: Zhong, Xinyi, Li, Zhong‐Hai
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 28.10.2019
• Subjects: Analogs; Continental margins; Convergence; convergent force; convergent velocity; Disasters; Earth; Earth mantle; Geological processes; Lithosphere; Magma; Mathematical models; Natural disasters; Numerical models; Oceans; passive margin; Passive margins; Plate tectonics; Subduction; Subduction (geology); subduction initiation; Subduction zones; Tectonics; Velocity; Southeast Asia
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2019GL084022

Subduction initiation (SI) at passive continental margin plays a key role in the Wilson cycle of plate tectonics; however, the long‐lived, stable Atlantic‐type margin challenges this hypothesis. The spontaneous SI at passive margin is difficult, which could be instead induced by far‐field tectonic forces. Previous analog and numerical models are generally conducted with constant convergent velocity, which may lead to extremely large boundary force in order for SI. In this study, we focus on numerical models with constant convergent force/stress to investigate the conditions for SI at typical passive margin without any type of prescribed weak zones. The result indicates that the SI at young passive margins with thin oceanic lithosphere is much easier than that at old margins. It reveals the dynamics of multiple newly formed subduction zones in the young oceanic plates of Southeast Asia and Southwest Pacific, but generally no SI for the old Atlantic‐type passive margin. Plain Language Summary Subduction, which is a plate moves under another one and sinks into the mantle, is a key process of the Earth. Subduction could cause disasters, shape magnificent natural wonders, and control the long‐term climate. However, our understanding for how and where subduction would begin between continents and oceans is still poor. This is because the beginning of subduction is just a snapshot of long‐lived geological process. Thus, the rock records are rather limited and difficult to observe. In this study, we conducted systematic numerical models to quantify the force required for the formation of a new subduction zone with variable ages of oceanic lithosphere. The result indicates that the force needed to begin subduction increases with the oceanic age, which explains that young oceanic plates in the Southeast Asia and Southwest Pacific are easier to begin subduction; however, the old Atlantic Oceanic plate is hard. Key Points Subduction initiation at passive continental margin is studied by numerical model with convergent force/stress boundary condition Mode selection of subduction initiation and required magnitude of force are dependent on the age of passive marginal oceanic lithosphere Young oceanic lithosphere is easier to initiate subduction with low boundary force, whereas the old Atlantic‐type margin is difficult