Strike‐Slip Enables Subduction Initiation Beneath a Failed Rift: New Seismic Constraints From Puysegur Margin, New Zealand
Strike‐Slip Enables Subduction Initiation Beneath a Failed Rift: New Seismic Constraints From Puysegur Margin, New Zealand
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DOI：
10.1029/2020tc006436
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发表时间：
2020-03
期刊：
影响因子：
4.2
通讯作者：
B. Shuck;H. V. Van Avendonk;S. Gulick;M. Gurnis;R. Sutherland;J. Stock;J. Patel;E. Hightower;S. Saustrup;Thomas Hess
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文献类型：
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作者：
B. Shuck;H. V. Van Avendonk;S. Gulick;M. Gurnis;R. Sutherland;J. Stock;J. Patel;E. Hightower;S. Saustrup;Thomas Hess
俯冲作用的发生往往利用了先前弱化的岩石圈，并可能优先沿沿着先前存在的板块边界成核。为了评估过去的构造体制和继承的岩石圈结构如何导致自我维持的俯冲，我们对Puysegur海沟进行了分析，这是一个具有快速演化构造历史的年轻俯冲带。新西兰南部的Puysegur边缘经历了从裂谷到海底扩张到走滑的转变，最近又经历了早期俯冲，所有这些都发生在过去的1.45亿年中。在这里，我们提出了深穿透多通道反射和海底地震仪断层图像记录地壳结构沿着边缘。我们的图像显示，索兰德盆地下方覆盖的太平洋板块包含拉伸的大陆地壳和岩浆侵入体，这些侵入体是由坎贝尔和挑战者高原之间的始新世-渐新世裂谷形成的。裂谷作用向南发展得更快，但从未像以前认为的那样在索兰德盆地继续分裂和海底扩张。随后的走滑变形使大陆地壳向北移动，形成斜向碰撞带，并留下了距今1.1亿年的大洋岩石圈。早期的俯冲作用发生在大洋岩石圈从南部强行向大陆碰撞带俯冲的过程中。我们认为，俯冲开始在Puysegur海沟是由继承浮力对比和结构弱点，在早期阶段的大陆裂谷和走滑沿沿着板块边界印入岩石圈。Puysegur边缘表明，强制成核沿着走滑边界是一个可行的俯冲起始方案，并应考虑在整个地球的历史。
Subduction initiation often takes advantage of previously weakened lithosphere and may preferentially nucleate along pre‐existing plate boundaries. To evaluate how past tectonic regimes and inherited lithospheric structure might lead to self‐sustaining subduction, we present an analysis of the Puysegur Trench, a young subduction zone with a rapidly evolving tectonic history. The Puysegur margin, south of New Zealand, has experienced a transformation from rifting to seafloor spreading to strike‐slip, and most recently to incipient subduction, all in the last ∼45 million years. Here we present deep‐penetrating multichannel reflection and ocean‐bottom seismometer tomographic images to document crustal structures along the margin. Our images reveal that the overriding Pacific Plate beneath the Solander Basin contains stretched continental crust with magmatic intrusions, which formed from Eocene‐Oligocene rifting between the Campbell and Challenger plateaus. Rifting was more advanced to the south, yet never proceeded to breakup and seafloor spreading in the Solander Basin as previously thought. Subsequent strike‐slip deformation translated continental crust northward causing an oblique collisional zone, with trailing ∼10 Myr old oceanic lithosphere. Incipient subduction transpired as oceanic lithosphere from the south forcibly underthrust the continent‐collision zone. We suggest that subduction initiation at the Puysegur Trench was assisted by inherited buoyancy contrasts and structural weaknesses that were imprinted into the lithosphere during earlier phases of continental rifting and strike‐slip along the plate boundary. The Puysegur margin demonstrates that forced nucleation along a strike‐slip boundary is a viable subduction initiation scenario and should be considered throughout Earth's history.