Deformation of accretionary wedges in response to seamount subduction: Insights from sandbox experiments
Deformation of accretionary wedges in response to seamount subduction: Insights from sandbox experiments
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DOI：
10.1029/1999tc900055
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发表时间：
2000-02
期刊：
影响因子：
4.2
通讯作者：
S. Dominguez;J. Malavieille;S. Lallemand
中科院分区：
文献类型：
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作者：
S. Dominguez;J. Malavieille;S. Lallemand
采用二维和三维方法进行沙盒实验，研究海山俯冲引起的边缘变形。在锥形海山俯冲过程中，连续的变形机制被激活。首先，观察到锋面逆冲断层的重新激活和加积楔的压实。随后，在俯冲海山前缘斜坡之上发育逆冲推覆和共轭走滑断层作用。基底滑脱体在俯冲高压的作用下向上偏转，在海山后缘斜坡的后面形成一个巨大的阴影带。因此，锋面加积受到抑制，部分锋面边缘被拖入俯冲带。当主滑脱层在海山之后返回到其基准面时，边缘记录了快速沉降，并形成新的加积楔，关闭边缘凹部。沉积物在海山尾流下冲到阴影区，底侵在增生楔的后部之下。观察到与基底侵蚀有关的上板块基底的可变形向海终端的大幅缩短和增厚。海山俯冲导致增生楔内部物质的显著转移，有利于前缘的大规模构造侵蚀和后缘的增厚。相对未变形的、充满水的沉积物的俯冲和底侵作用，以及沿影响边缘的断裂沿着的流体排出，可能会改变沿沿着基底滑脱的流体压力。因此，在俯冲海山周围，两个板块之间的有效基底摩擦力和局部机械耦合预计会有很大变化。
Sandbox experiments, using a two‐dimensional and a three‐dimensional approach, are used to study the deformation of margins in response to seamount subduction. Successive mechanisms of deformation are activated during the subduction of conical seamounts. First, reactivation of the frontal thrusts and compaction of the accretionary wedge is observed. Then, back thrusting and, conjugate strike‐slip faulting develops above the leading slope of the subducted seamount. The basal decollement is deflected upward in the wake of the subducting high, and a large shadow zone develops behind the seamount trailing slope. Consequently, frontal accretion is inhibited and part of the frontal margin is dragged into the subduction zone. When the main decollement returns to its basal level in the wake of the seamount, the margin records a rapid subsidence and a new accretionary wedge develops, closing the margin reentrant. The sediments underthrusted in the wake of the seamount into the shadow zone, are underplated beneath the rear part of the accretionary wedge. Substantial shortening and thickening of the deformable seaward termination of the upper plate basement, associated with basal erosion is observed. Seamount subduction induces significant material transfer within the accretionary wedge, favors large tectonic erosion of the frontal margin and thickening of the rear part of the margin. The subduction and underplating of relatively undeformed, water‐ladden sediments, associated with fluid expulsion along the fractures affecting the margin could modify the fluid pressure along the basal decollement. Consequently, significant variations of the effective basal friction and local mechanical coupling between the two plates could be expected around the subducting seamount.