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Extensional tectonics and two-stage crustal accretion at oceanic transform faults

机译：海洋变换故障的延长构造和两阶段地壳吸收

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摘要

Oceanic transform faults are seismically and tectonically active plate boundaries(1) that leave scars-known as fracture zones-on oceanic plates that can cross entire ocean basins(2). Current descriptions of plate tectonics assume transform faults to be conservative two-dimensional strike-slip boundaries(1,3), at which lithosphere is neither created nor destroyed and along which the lithosphere cools and deepens as a function of the age of the plate(4). However, a recent compilation of high-resolution multibeam bathymetric data from 41 oceanic transform faults and their associated fracture zones that covers all possible spreading rates shows that this assumption is incorrect. Here we show that the seafloor along transform faults is systemically deeper (by up to 1.6 kilometres) than their associated fracture zones, in contrast to expectations based on plate-cooling arguments. Accretion at intersections between oceanic ridges and transform faults seems to be strongly asymmetric: the outside corners of the intersections show shallower relief and more extensive magmatism, whereas the inside corners have deep nodal basins and seem to be magmatically starved. Three-dimensional viscoplastic numerical models show that plastic-shear failure within the deformation zone around the transform fault results in the plate boundary experiencing increasingly oblique shear at increasing depths below the seafloor. This results in extension around the inside corner, which thins the crust and lithosphere at the transform fault and is linked to deepening of the seafloor along the transform fault. Bathymetric data suggest that the thinned transform-fault crust is augmented by a second stage of magmatism as the transform fault intersects the opposing ridge axis. This makes accretion at transform-fault systems a two-stage process, fundamentally different from accretion elsewhere along mid-ocean ridges.
机译：海洋变换故障是地震性和构造的主动板边界（1），使疤痕称为骨折区域 - 在可以交叉整个海洋盆地（2）的海洋板上。板构造的目前的描述假设变换故障是保守的二维防滑边界（1,3），岩石圈既不产生也不摧毁，岩石圈冷却和加深作为板的年龄的函数（ 4）。然而，最近汇编了来自41个海洋变换故障及其相关的骨折区域的高分辨率多阵线碱基数据，涵盖所有可能的传播率的相关骨折区域表明这种假设是不正确的。在这里，我们表明，与基于板冷却争论的期望相比，沿着变换故障沿着变换故障的海底沿着它们的相关骨折区域更深入（高达1.6公里）。海洋山脊和变换故障之间的交叉点的吸积似乎是强烈的不对称：交叉口的外角表现出浅薄的浮雕和更广泛的岩浆广告，而内角有深层节奏盆地，似乎是磁性饥饿的。三维粘胶塑料数值模型表明，变形区内变形区内的塑料剪切失效导致板边界在海底下方的深度越来越斜剪切。这导致围绕内角的延伸，在变换故障中围绕地壳和岩石圈，并与沿着变换故障的海底加深。浴权数据表明，随着变换故障与相对的脊轴相交，减少了变换的变换故障地壳。这使得变换故障系统的增值是两级过程，从根本上不同于中海脊的其他地方的吸收。

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  • 来源
    《Nature》 |2021年第7850期|402-407|共6页
  • 作者

    Grevemeyer Ingo; Ruepke Lars H.; Morgan Jason P.; Iyer Karthik; Devey Colin W.;

  • 作者单位

    GEOMAR Helmholtz Ctr Ocean Res Kiel Kiel Germany;

    GEOMAR Helmholtz Ctr Ocean Res Kiel Kiel Germany;

    Southern Univ Sci & Technol Shenzhen Peoples R China;

    GEOMAR Helmholtz Ctr Ocean Res Kiel Kiel Germany|GeoModeLLing Solut Zurich Switzerland;

    GEOMAR Helmholtz Ctr Ocean Res Kiel Kiel Germany;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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