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- Title
Subduction‐Induced Back‐Arc Extension Versus Far‐Field Stretching: Contrasting Modes for Continental Marginal Break‐Up.
- Authors
Yang, Shuting; Li, Zhong‐Hai; Wan, Bo; Chen, Ling; Kaus, Boris J. P.
- Abstract
Continental break‐up is an ingredient of plate tectonics and the Wilson cycle. During the evolution of the Tethyan Realm since the Paleozoic, a series of ribbon‐like (micro‐)continents are split from the Gondwana and drifted northwards to the Eurasian continent. The initial opening of the Neo‐Tethys Ocean follows a typical continental marginal break‐up of Cimmeria from Gondwana, which is generally considered to be driven by subduction of the Paleo‐Tethyan plate. Yet, the competition between back‐arc extension and far‐field stretching is matter of a long‐standing debate. Therefore, the authors here present the results of systematic 2‐D numerical simulations. The results reveal four types of subduction‐induced continental marginal break‐ups: back‐arc extension, far‐field stretching, double break‐up, and subduction channel opening. A weak relic suture zone is a prerequisite for continental break‐up and an important factor controlling the mode selection. The back‐arc extension mode occurs for relatively short and shallow dipping highly viscous subducted slabs. The far‐field stretching mode, on the other hand, preferably occurs for spatially long and wide subducted slabs without mid‐ocean ridges. Combining the geological observations, numerical simulations and force balance analyses, the authors propose that the northward, single‐sided Paleo‐Tethys oceanic subduction beneath Laurasia, was most likely responsible for the far‐field break‐up of the Cimmerian terranes from Gondwana. This would have required both pre‐existing relic suture zones and the already subducted mid‐ocean ridge, which thus played an important role in the opening of the Neo‐Tethys Ocean. Plain Language Summary: During plate tectonics, continents drift along with ocean floor spreading. Continental collision and assemblage occur when oceanic plates are fully subducted and consumed. On the other hand, oceanic subduction can also drive break‐up of big continental plates and disassemble them into two or more blocks. These processes occurred repeatedly during the evolution of the Tethyan Realm since the Paleozoic, resulting in a series of ribbon‐like (micro‐)continents splitting from Gondwana in the southern hemisphere that drifted toward Laurasia in the north. Subduction‐induced continental break‐up may act in two contrasting ways, that is back‐arc extension and far‐field stretching, the roles of which are widely debated in the context of opening of the Neo‐Tethys Ocean with a typical continental marginal break‐up of Cimmerian blocks from Gondwana. In this study, a series of numerical models are systematically conducted to understand the competition between these contrasting modes. The model results are further compared with geological observations and indicate that the northward, single‐sided Paleo‐Tethys oceanic subduction beneath Laurasia, after the sinking and disappearance of the mid‐ocean ridge, was the most likely cause for the far‐field break‐up of the Cimmerian terranes from Gondwana along the pre‐existing relic suture zones, which thus controls the opening of the Neo‐Tethys Ocean. Key Points: The existence and relative weakness of the relic suture zones control subduction‐induced continental marginal break‐upFar‐field stretching is easier than back‐arc extension for spatially long and wide subducting slabsThe break‐up of Cimmeria from Gondwana was likely driven by the drag from the northward Paleo‐Tethys oceanic subduction
- Subjects
CONTINENTAL drift; SUBDUCTION; SUBDUCTION zones; PALEOZOIC Era; CONTINENTS
- Publication
Geochemistry, Geophysics, Geosystems: G3, 2021, Vol 22, Issue 3, p1
- ISSN
1525-2027
- Publication type
Article
- DOI
10.1029/2020GC009416