据研究人员介绍，在快速扩张的中心，断层发育在轴向顶槽(AST轴周围0-250m)主要是由源于岩浆透镜体(AML)的岩脉诱发变形引起的。在轴向高点(＞2,000m)以外，突出的深海山边界断层的形成通常与岩石圈冷却并远离AST时的不弯曲有关。断层的存在很少被绘制在这两个热性质不同的区域之间，岩石圈仍然太热，以至于无法将断层与热冷却过程联系起来，而在AST外，增生岩脉作用主导控制着脊轴。
研究人员通过比较在东太平洋隆起(EPR) 9°50′N采集的三维地震图像和测深数据，发现岩浆体的独特形态特征与这些断层的方向之间存在显著的垂直一致性。测绘断层的空间重合和不对称成核模式，是岩浆诱发断裂在脊轴附近的最直接证据，为热液作用和岩浆侵位提供了通道，有助于在AST外形成地壳。
高分辨率的海底和地下图像也使修正的构造应变估计成为可能，这表明EPR海底扩张的近轴构造分量比以前认为的要小一个数量级，熔岩埋藏断层对扩张的贡献几乎可以忽略不计。
附：英文原文
Title: Magma-induced tectonics at the East Pacific Rise 9°50’N: Evidence from high-resolution characterization of seafloor and subseafloor
Author: Marjanovi, Milena, Chen, Jie, Escartín, Javier, Parnell-Turner, Ross, Wu, Jyun-Nai
Issue&Volume: 2024-6-14
Abstract: At fast-spreading centers, faults develop within the axial summit trough (AST; 0 to 250 m around the axis) primarily by diking-induced deformation originating from the axial magma lens (AML). The formation of the prominent abyssal-hill-bounding faults beyond the axial high (>2,000 m) is typically associated with the unbending of the lithosphere as it cools and spreads away from the AST. The presence of faults is rarely mapped between these two thermally distinct zones, where the lithosphere is still too hot for the faults to be linked with the process of thermal cooling and outside of the AST where the accretional diking process dominates the ridge axis. Here, we reveal a remarkable vertical alignment between the distinct morphological features of the magma body and the orientation of these faults, by comparison of 3-D seismic imagery and bathymetry data collected at the East Pacific Rise (EPR) 9°50’N. The spatial coincidence and asymmetric nucleation mode of the mapped faults represent the most direct evidence for magmatically induced faulting near the ridge axis, providing pathways for hydrothermalism and magma emplacement, helping to build the crust outside of the AST. The high-resolution seafloor and subsurface images also enable revised tectonic strain estimates, which shows that the near-axis tectonic component of seafloor spreading at the EPR is an order of magnitude smaller than previously thought with close to negligible contribution of lava buried faults to spreading.
DOI: 10.1073/pnas.2401440121
Source: https://www.pnas.org/doi/abs/10.1073/pnas.2401440121