海洋板块俯冲作用下上覆大陆岩石层减薄机制的动力学模拟

几乎所有大陆岩石层的减薄现象，可能都与海洋板块的俯冲作用相关，但是两者之间的内在联系迄今仍不十分明确，为此，我们设计了一系列包含洋-陆俯冲系统的二维数值模型，来探讨海洋板块的俯冲作用对上覆大陆岩石层变形行为的影响，尤其对大陆岩石层减薄效应的制约.模型结果表明，海洋板块俯冲过程中的地幔楔熔体对大陆岩石层地幔的热侵蚀以及由熔体上升所诱发的地幔局部对流的强烈扰动会导致上覆大陆岩石层的减薄效应.这种效应不仅表现在横向上的向陆内蔓延，还表现在垂向上的向浅部发展.且多类动力学参数都能制约大陆岩石层的减薄效应.具体地，随着汇聚速率和洋壳厚度的增加，上覆大陆岩石层在横向上的减薄范围越大，在垂向上的减薄程度也越深；而随着俯冲海洋板块年龄的增加，上覆大陆岩石层在横向上的减薄范围增大，但在垂向上的减薄程度会减小；随着上覆大陆岩石层厚度的增加，其横向减薄范围会减小，但在垂向上的减薄程度会加深.本文研究成果能为揭示华北克拉通减薄/破坏的动力学过程提供一定的理论参考依据.

Dynamics of thinning of overriding continental lithosphere induced by oceanic plate subduction: Numerical modeling

Much evidence from geophysical, geochemical and geological studies have suggested that the thinning of continental lithosphere is generally related to oceanic subduction. While the dynamic process of such thinning remains in debate. Using a 2-D thermo-mechanical model, we systematically investigated the mechanisms of continental lithospheric thinning under oceanic subduction and explored their key constraints. The numerical models indicate that the erosion by partial melting in the mantle wedge and by the small-scale mantle convection could induce lithospheric thinning both horizontally and vertically. Moreover, the convergence velocity, thickness of oceanic crust, the age of subducting oceanic plate and the thickness of overriding continental lithosphere play important roles in the dynamics of lithospheric thinning. Specifically, with the increase of convergence velocity and the thickness of oceanic crust, the range of lithospheric thinning increases both horizontally and vertically. Besides, the range of lithospheric thinning increases horizontally and decreases vertically with the growing age of the subducting oceanic plate. Nevertheless, with increasing the thickness of overriding continental lithosphere, the range of lithospheric thinning decreases horizontally and increases vertically. Our model results could provide some insights into the dynamic processes of the thinning and destruction of the North China Craton during geologic epochs.