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Flat subduction versus big mantle wedge: contrasting modes for deep hydration and overriding craton modification
  • Zhong-Hai Li
Zhong-Hai Li
University of Chinese Academy of Sciences

Corresponding Author:[email protected]

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Subduction-induced deep hydration and water cycling may play significant roles in the modification and destruction of the overriding cratonic lithosphere. Two contrasting modes are generally proposed: (1) flat subduction (FS) regime with slab subducting sub-horizontally beneath the overriding lithosphere, and (2) big mantle wedge (BMW) regime with slab flattening in the mantle transition zone. Here, systematic petrological-thermomechanical models are conducted to investigate the fluid/melt activities in the contrasting subduction regimes as well as their effects on the modification of overriding lithosphere. The model results indicate that the dehydration process in the FS regime can significantly modify the overriding lithosphere for a region of about 600 km from the trench. During the progressive flat subduction, the partial melting and magmatism migrate towards the inner land of the overriding plate, which will be reversed and backward to the trench during the transition from flat to steep subduction. On the other hand, the deep hydration in the BMW regime is strongly dependent on the sub-crustal serpentinite layer in the subducting slab, whereas the oceanic crust cannot carry water to the transition zone. The modification of the overriding lithosphere in the BMW regime occurs in a larger region of >1000 km from trench, which is however generally slower and weaker. The modification and destruction of North China Craton is more likely to be controlled by the flat subduction of paleo-Pacific plate in the late Jurassic to early Cretaceous, which may be accompanied by the effects of deep water cycling in the BMW regime.
Aug 2020Published in Journal of Geophysical Research: Solid Earth volume 125 issue 8. 10.1029/2020JB020018