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首页> 外文学位 >Bathymetry, gravity and magnetic data study between 14° and 16°N, Mid-Atlantic ridge. Evidence for large-scale mechanical extension.
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Bathymetry, gravity and magnetic data study between 14° and 16°N, Mid-Atlantic ridge. Evidence for large-scale mechanical extension.

机译：在大西洋中脊14°至16°N之间进行水深测量，重力和磁数据研究。大规模机械扩展的证据。

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摘要

The completed research targets interpretation of the bathymetric, gravity and magnetic data collected during the Shinkai 6500/Yokosuka cruise during the summer of 1998. The data cover a large offset fracture zone at 15° 20' on the Mid-Atlantic Ridge as well as the spreading segments north and south of the fracture zone.; The extensional models along the Mid-Atlantic ridge (e.g., Karson, 1998) propose two modes of spreading---with magmatic infilling and by mechanical extension. This research objective is to determine evidences for these two extensional modes in the area by processing and interpretation of bathymetry, gravity, magnetic and petrologic data The change in mode of extension is presumably dependent on the availability of basaltic magma in sufficient quantities to allow throughgoing, magma-filled fractures to penetrate the lithosphere. As long as a sufficient rate of magma supply is maintained, initiation of seafloor spreading is likely to terminate an extensive mechanical extension and formation of low-angle detachment faults. However, reduction in the magma supply rate may result in the mode of extension reverting to faulting mechanisms. If this is the case, detachments and strongly rotated tilted blocks may occur in the parts of the oceanic lithosphere. Tectonic core complexes (also known as megamullions) along slow spreading centers have now been recognized in many places where mechanical extension dominates. The study area contains a number of large core complexes, the products of low-angle detachment faulting. Geomorphological, geological, and geophysical characteristics of them are presented.; The dredging and diving results have shown that mantle peridotites are exposed along both flanks of the Mid-Atlantic ridge over a wide area. On the other hand, the geophysical surveys along areas of the ridge that have abundant seafloor outcrops of residual ultramafics yield significant crustal thickness. As serpentinization of peridotites decreases the seismic velocity and density, partial serpentinization can produce rocks with seismic velocities and densities identical to upper crustal rocks. The forward gravity modeling constrained by petrological information and velocity model along the ridge has been conducted to address this issue. Additional forward gravity models have been calculated in the area. The regional crustal thickness estimates have been derived from the gravity data. They show regional thinning of the crust in the areas of the megamullion formations. Crustal age estimates are done based on magnetization linear patterns derived from magnetic anomaly.
机译：完整的研究目标是对1998年夏季在Shinkai 6500 / Yokosuka航行期间收集的测深，重力和磁数据进行解释。这些数据涵盖了中大西洋海脊15°20'处的大偏移断裂带以及在断裂带的北部和南部扩散。中大西洋海脊的伸展模式（例如Karson，1998）提出了两种伸展模式-岩浆充填和机械伸展。本研究的目的是通过处理和解释测深，重力，磁和岩石学数据来确定该地区这两种伸展模式的证据。伸展模式的变化大概取决于玄武岩浆的可用量，以允许其穿过，岩浆充满的裂缝穿透岩石圈。只要维持足够的岩浆供应速率，海底扩张的开始就可能终止广泛的机械伸展并形成低角度的分离断层。但是，岩浆供应速率的降低可能导致延伸模式恢复为断裂机制。如果是这种情况，在海洋岩石圈的某些部分可能会发生分离和强烈旋转的倾斜块。如今，在许多以机械伸展为主的地方，人们已经认识到沿着慢速扩散中心的构造核心复合体（也称为成矿物质）。研究区域包含许多大型岩心复合体，这些是低角度分离断层的产物。介绍了它们的地貌，地质和地球物理特征。疏and和潜水的结果表明，地幔橄榄岩在大范围的中大西洋海脊两侧都暴露出来。另一方面，沿着山脊区域的地球物理勘测，这些区域具有大量残留的超基性海底露头，可产生明显的地壳厚度。由于橄榄岩的蛇纹岩化降低了地震速度和密度，部分蛇纹岩化可以产生具有与上地壳岩石相同的地震速度和密度的岩石。为了解决这个问题，已经进行了受岩石学信息和沿山脊速度模型约束的前向重力建模。该地区还计算了其他的前向重力模型。区域地壳厚度估计值是从重力数据中得出的。它们显示了成团构造区域的地壳区域变薄。地壳年龄的估计是基于从磁异常得出的磁化线性模式进行的。

著录项

  • 作者

    Egorov, Vsevolod I.;

  • 作者单位

    University of Houston.;

  • 授予单位 University of Houston.;
  • 学科 Geophysics.; Geology.
  • 学位 Ph.D.
  • 年度 2004
  • 页码 290 p.
  • 总页数 290
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 地球物理学;地质学;
  • 关键词

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