Continental interior and edge breakup at convergent margins induced by subduction direction reversal: a numerical modeling study applied to the South China Sea margin

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Date
2020-10-06
Authors
Li, Fucheng
Sun, Zhen
Yang, Hongfeng
Lin, Jian
Stock, Joann M.
Zhao, Zhongxiang
Xu, Hehua
Sun, Longtao
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DOI
10.1029/2020TC006409
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Keywords
Continental breakup
Convergent margins
Edge breakup
Subduction direction reversal
Proto‐South China Sea
Numerical modeling
Abstract
The dynamics of continental breakup at convergent margins has been described as the results of backarc opening caused by slab rollback or drag force induced by subduction direction reversal. Although the rollback hypothesis has been intensively studied, our understanding of the consequence of subduction direction reversal remains limited. Using thermo‐mechanical modeling based on constraints from the South China Sea (SCS) region, we investigate how subduction direction reversal controls the breakup of convergent margins. The numerical results show that two distinct breakup modes, namely, continental interior and edge breakup (“edge” refers to continent above the plate boundary interface), may develop depending on the “maturity” of the convergent margin and the age of the oceanic lithosphere. For a slab age of ~15 to ~45 Ma, increasing the duration of subduction promotes the continental interior breakup mode, where a large block of the continental material is separated from the overriding plate. In contrast, the continental edge breakup mode develops when the subduction is a short‐duration event, and in this mode, a wide zone of less continuous continental fragments and tearing of the subducted slab occur. These two modes are consistent with the interior (relic late Mesozoic arc) and edge (relic forearc) rifting characteristics in the western and eastern SCS margin, suggesting that variation in the northwest‐directed subduction duration of the Proto‐SCS might be a reason for the differential breakup locus along the strike of the SCS margin. Besides, a two‐segment trench associated with the northwest‐directed subduction is implied in the present‐day SCS region.
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Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Tectonics 39(11), (2020): e2020TC006409, doi:10.1029/2020TC006409.
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Li, F., Sun, Z., Yang, H., Lin, J., Stock, J. M., Zhao, Z., Xu, H., & Sun, L. (2020). Continental interior and edge breakup at convergent margins induced by subduction direction reversal: a numerical modeling study applied to the South China Sea margin. Tectonics, 39(11), e2020TC006409.
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