17 Aug 2023
 | 17 Aug 2023
Status: this preprint is open for discussion.

How a volcanic arc influences back-arc extension: insight from 2D numerical models

Duo Zhang and Huw Davies

Abstract. Investigating plate tectonics through the lens of back-arc extension in subduction systems, this study introduces a 'hot region' on the overriding plate (OP) in 2D thermo-mechanical models, simulating the role of an arc. The models identified two extension locations on the OP: at the hot region (Mode EH) or surprisingly at a far-field location which is about 750 km from the trench (Mode EF). The study also found that extension could occur at the same far-field location without a hot region when the OP is young and thin, or the subducting plate (SP) is old and strong. Our models suggest that EH mode is common, occurring in many cases like Mariana Trough and Lau Basin, while the EF mode is rare, potentially occurring in scenarios like the Japan Sea. The primary driving mechanism in our models is poloidal flow beneath the OP, and the extension process is the competition of basal drag which thins the OP versus thermal healing which thickens it, and also a competition of thermal weakening at the hot region and at the far-field location. Increased trench retreat rates, facilitated by increased hot region temperature and width, encouraged this flow and consequently promoted back-arc extension.

Duo Zhang and Huw Davies

Status: open (until 26 Oct 2023)

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Duo Zhang and Huw Davies

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Fluidity staffs at Imperial College London, University of Oxford, University of Reading, National Oceanography Centre Southampton, Herriot Watt University, Numerical Algorithms Group, Museum für Naturkunde Berlin, Florida State University, Columbia University, Chinese Academy of Sciences, The University of Edinburgh, and the Australian National University

Duo Zhang and Huw Davies


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Short summary
We numerically model the influence of an arc on back-arc extension. The arc is simulated by emplacing a hot region in the overriding plate. We investigate how plate ages and properties of the hot region affect back-arc extension and present regime diagrams of the nature of back-arc extension for these models. We find that back-arc extension not only at the hot region but surprisingly also away from it, and a hot region facilitates extension of the overriding plate.