俯冲脊的动力学效应：来自三维实验室模式的见解
Dynamical effects of subducting ridges: Insights from 3-D laboratory models
摘要：
我们模拟俯冲的浮力脊和高原，以研究其对板块动力学的影响。平行于海沟的洋脊对俯冲过程的影响更大，因为它们同时影响更长的海沟段。大的浮板段下沉到软流圈的速度较慢，它们的俯冲导致板块俯冲速度的减小。我们观察到这些浮力异常下方的板块变陡，导致板块曲率曲率半径变小，这增加了板块折叠过程中耗散的能量，并进一步降低了俯冲速度。当模拟浮力高原的三维几何形状时，高原上方板块的倾角减小，这是高原两侧致密的“正常”大洋板块俯冲速度加快的结果。在台地完全并入俯冲带之后，板块倾角的这种扰动会维持很长时间。我们将实验与现今南美洲下方的俯冲带进行比较。实验表明，垂直于海沟的适度山脊，如现在的胡安费尔南德斯山脊，浮力不足以改变板的几何形状。相比之下，大洋板块内已经俯冲的浮力异常可能是纳斯卡板块现今深度几何形状的某些方面的原因。
英文摘要：
We model the subduction of buoyant ridges and plateaus to study their effect on slab dynamics. Oceanic ridges parallel to the trench have a stronger effect on the process of subduction because they simultaneously affect a longer trench segment. Large buoyant slab segments sink more slowly into the asthenosphere, and their subduction result in a diminution of the velocity of subduction of the plate. We observe a steeping of the slab below those buoyant anomalies, resulting in smaller radius of curvature of the slab, that augments the energy dissipated in folding the plate and further diminishes the velocity of subduction. When the 3D geometry of a buoyant plateau is modelled, the dip of the slab above the plateau decreases, as a result of the larger velocity of subduction of the dense "normal" oceanic plate on both sides of the plateau. Such a perturbation of the dip of the slab maintains long time after the plateau has been entirely incorporated into the subduction zone. We compare experiments with the present-day subduction zone below South America. Experiments suggest that a modest ridge perpendicular to the trench such as the present-day Juan Fernandez ridge is not buoyant enough to modify the slab geometry. Already subducted buoyant anomalies within the oceanic plate, in contrast, may be responsible for some aspects of the present-day geometry of the Nazca slab at depth.
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