The effects of plate interface rheology on subduction kinematics and dynamics
The effects of plate interface rheology on subduction kinematics and dynamics
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板块界面流变学对俯冲运动学和动力学的影响
DOI：
10.1093/gji/ggac075
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发表时间：
2022
影响因子：
2.8
通讯作者：
Faccenna, Claudio
中科院分区：
文献类型：
--
作者：
Behr, Whitney M;Holt, Adam F;Becker, Thorsten W;Faccenna, Claudio
构造板块运动主要是俯冲板片势能变化与地幔、弯曲岩石圈和板片-上板界面粘性耗散平衡的结果。对活动俯冲带和折返岩石的广泛观测表明，俯冲界面剪切带流变学对俯冲地壳物质的组成很敏感，例如，沉积物与镁铁质火成岩洋壳。在这里，我们使用2-D数值模型的动力学一致的俯冲系统地研究俯冲界面粘度如何影响大规模的俯冲运动学和动力学。我们的模型包括一个大洋板块俯冲到一个覆盖大陆板块之下。板片包括控制界面流变学的海洋地壳/软弱层。我们实现了一系列的板和接口的强度，并探讨如何运动学响应的初始上地幔板阶段，以及随后的准稳态附近的660公里的不连续性的粘度跳跃积水。如果材料的性能进行适当的平均，我们的结果证实了界面强度对板块运动的影响，简化的粘性耗散分析的基础上：一个0.02数量级的界面粘度增加可以减少收敛速度的0.01数量级。然而，完整的动态解决方案显示了一系列有趣的行为，包括界面强度和覆盖板的地形和端部成员弱界面弱板的情况下，导致板断裂/撕裂之间的相互作用。此外，对于模型的空间有限，弱沉积物带嵌入在定期的界面材料，可以预期的不同类型的海洋物质的俯冲通过地球的历史，增强回滚和俯冲速度的瞬态响应是不同的强和弱板。我们的工作证实了早期的建议，板块界面的重要性，并扩大了板块重组，传入和覆盖板块的性质和潜在的地质记录之间的可量化的联系的范围。
Tectonic plate motions predominantly result from a balance between the potential energy change of the subducting slab and viscous dissipation in the mantle, bending lithosphere and slab–upper plate interface. A wide range of observations from active subduction zones and exhumed rocks suggest that subduction interface shear zone rheology is sensitive to the composition of subducting crustal material—for example, sediments versus mafic igneous oceanic crust. Here we use 2-D numerical models of dynamically consistent subduction to systematically investigate how subduction interface viscosity influences large-scale subduction kinematics and dynamics. Our model consists of an oceanic slab subducting beneath an overriding continental plate. The slab includes an oceanic crustal/weak layer that controls the rheology of the interface. We implement a range of slab and interface strengths and explore how the kinematics respond for an initial upper mantle slab stage, and subsequent quasi-steady-state ponding near a viscosity jump at the 660-km-discontinuity. If material properties are suitably averaged, our results confirm the effect of interface strength on plate motions as based on simplified viscous dissipation analysis: a ∼2 order of magnitude increase in interface viscosity can decrease convergence speeds by ∼1 order of magnitude. However, the full dynamic solutions show a range of interesting behaviour including an interplay between interface strength and overriding plate topography and an end-member weak interface-weak slab case that results in slab break-off/tearing. Additionally, for models with a spatially limited, weak sediment strip embedded in regular interface material, as might be expected for the subduction of different types of oceanic materials through Earth’s history, the transient response of enhanced rollback and subduction velocity is different for strong and weak slabs. Our work substantiates earlier suggestions as to the importance of the plate interface, and expands the range of quantifiable links between plate reorganizations, the nature of the incoming and overriding plate and the potential geological record.
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