近日，法国巴黎文理研究大学教授Bickert, Manon及其团队的最新研究，报道了岩浆侵入揭示洋中脊不断裂。相关论文于2024年4月10日发表在《自然》杂志上。

研究表明，在脊轴线上的构造伸展可以被山脊两侧的构造缩短而部分抵消。大西洋中脊和嘉士伯海脊离轴约15km的逆断层地震序列证明了这一过程。研究使用力学模型，以表明脊侧翼线浅压缩至脆性破坏点之前，是岩石圈远离轴向起伏伸直的自然结果。岩浆充填裂缝的侵入，表现为沿脊轴线迁移的伸展地震活动群，可以提供触发逆断层地震的微小压应力增量。

通过水深分析，研究进一步发现，MOR正断层的反向再激活是一个广泛发生的过程，它可以将深海山丘在脊轴线形成后不久的振幅减少多达50%。这种“非断裂”机制对全球海底结构施加了一级影响，并为伸展环境中的逆断层地震提供了物理解释。

据了解，洋中脊(MORs)是构造伸展的典型场所，在那里，岩石圈板块之间的分裂形成了覆盖地球表面约三分之二的深海山丘。

附：英文原文

Title: Mid-ocean ridge unfaulting revealed by magmatic intrusions

Author: Olive, Jean-Arthur, Ekstrm, Gran, Buck, W. Roger, Liu, Zhonglan, Escartn, Javier, Bickert, Manon

Issue&Volume: 2024-04-10

Abstract: Mid-ocean ridges (MORs) are quintessential sites of tectonic extension, at which divergence between lithospheric plates shapes abyssal hills that cover about two-thirds of the Earth’s surface. Here we show that tectonic extension at the ridge axis can be partially undone by tectonic shortening across the ridge flanks. This process is evidenced by recent sequences of reverse-faulting earthquakes about 15km off-axis at the Mid-Atlantic Ridge and Carlsberg Ridge. Using mechanical models, we show that shallow compression of the ridge flanks up to the brittle failure point is a natural consequence of lithosphere unbending away from the axial relief. Intrusion of magma-filled fractures, which manifests as migrating swarms of extensional seismicity along the ridge axis, can provide the small increment of compressive stress that triggers reverse-faulting earthquakes. Through bathymetric analyses, we further find that reverse reactivation of MOR normal faults is a widely occurring process that can reduce the amplitude of abyssal hills by as much as 50%, shortly after they form at the ridge axis. This ‘unfaulting’ mechanism exerts a first-order influence on the fabric of the global ocean floor and provides a physical explanation for reverse-faulting earthquakes in an extensional environment.

DOI: 10.1038/s41586-024-07247-w

Source: https://www.nature.com/articles/s41586-024-07247-w