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首页> 外文期刊>Geology >What do variable magnetic fabrics in gabbros of the Oman ophiolite reveal about lower oceanic crustal magmatism at fast spreading ridges?
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What do variable magnetic fabrics in gabbros of the Oman ophiolite reveal about lower oceanic crustal magmatism at fast spreading ridges?

机译：Aman Ophiolite的Gabbros中可变磁性织物在快速蔓延的脊时揭示了较低的海洋地壳岩岩

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摘要

The magmatic processes responsible for accretion of the lower oceanic crust remain one of the least-constrained components of the global seafloor spreading system. Samples of gabbroic rocks recovered by scientific ocean drilling are too limited to allow effective assessment of spatial variations in magmatic flow within in situ lower crust. Extensive exposures of gabbros in ophiolites, on the other hand, provide opportunities to study accretion processes in three dimensions across wide areas and at a resolution that allows variations in magmatic fabrics through the crust to be quantified. Here, we show that magnetic anisotropy provides a reliable proxy for lower-crustal magmatic fabrics in the world's largest ophiolite in Oman. Important differences in magnetic fabrics are detected that reflect variations in magmatic processes on a range of scales. Fabrics in layered gabbros are aligned with modal layering and display a consistency in the orientation of maximum principal axes of anisotropy between localities at a regional scale. These fabrics are compatible with subhorizontal preferred alignment of crystals orthogonal to the inferred orientation of the Oman spreading axis, resulting from magmatic flow or deformation of melt-rich crystal mushes during spreading. In contrast, magnetic anisotropy in foliated gabbros at the top of the lower crust reveals for the first time distinctly different linear and anastomosing fabric styles between localities sampled at the same pseudostratigraphic level. These differences reflect spatial variations in the style and trajectory of flow in the crystal mush beneath the axial melt lens during upward melt migration at the spreading axis.
机译：负责低海外壳的吸收的岩浆工艺仍然是全球海底蔓延系统的最低约束部件之一。科学海洋钻井恢复的古桥岩样品过于局限，允许有效评估在原位下地壳内岩浆流动的空间变化。另一方面，在Ophiolites中的广泛暴露，另一方面为在宽区域和分辨率下进行三维的三维过程的机会提供了机会，该分辨率允许岩石织物通过壳化的壳体变化。在这里，我们表明磁各向异性为世界上最大的Ophiolite的低地壳岩浆织物提供了可靠的代理。检测到磁性织物的重要差异，反映了在一系列尺度上的岩浆过程中的变化。层状gabbros的织物与模态分层对齐，并在区域尺度下显示在地方之间的各向异性的最大主要轴线方向的一致性。这些织物与晶体与阿曼扩散轴的推断取向正交的晶体的晶体优选对准兼容，由涂抹过程中富含熔融的水晶糊状物的岩浆流量或变形产生。相反，下地壳顶部的叶片Gabbros中的磁各向异性揭示了在相同伪图形水平上采样的本地的第一次明显不同的线性和吻合织物风格。这些差异反映了在扩散轴上向上熔体迁移期间轴向熔体透镜下方晶体糊状的流动风格和轨迹的空间变化。

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  • 来源
    《Geology》 |2019年第3期|共4页
  • 作者

    Morris Antony; Meyer Matthew; Anderson Mark W.; MacLeod Christopher J.;

  • 作者单位

    Plymouth Univ Sch Geog Earth &

    Environm Sci Plymouth PL4 8AA Devon England;

    Plymouth Univ Sch Geog Earth &

    Environm Sci Plymouth PL4 8AA Devon England;

    Plymouth Univ Sch Geog Earth &

    Environm Sci Plymouth PL4 8AA Devon England;

    Cardiff Univ Sch Earth &

    Ocean Sci Cardiff CF10 3AT S Glam Wales;

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  • 正文语种 eng
  • 中图分类 地质学;
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