...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >Formation-scale hydraulic and mechanical properties of oceanic crust inferred from pore pressure response to periodic seafloor loading
【24h】

Formation-scale hydraulic and mechanical properties of oceanic crust inferred from pore pressure response to periodic seafloor loading

机译：从孔隙压力对周期性海底载荷的响应推论得出的洋壳地层尺度的水力和力学性质

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Observations of fluid pressure variations in young igneous oceanic crust have been made in five sealed and instrumented Ocean Drilling Program boreholes on the flanks of the Mid-Atlantic and Juan de Fuca Ridges. The holes penetrate locally well sedimented, and hence hydrologically well-sealed crust, and are situated 1 to 85 km from areas where water can flow freely through the seafloor at extensive basement exposures. Amplitudes and phases of formation pressure variations have been determined relative to tidal and nontidal pressure variations measured simultaneously at the seafloor for periods ranging from 4.8 hours to 14 days. Formation pressure variations are reduced to amplitudes between 98% and 28% relative to those at the seafloor and shifted in phase by up to 20 degrees. Simple theory for porous media response to periodic loading predicts that the scale of diffusive signal propagation from locations of basement outcrop through buried parts of the igneous crust should be proportional to basement permeability and the inverse square root of the period of the variation. This behavior is consistent with the observations, and the characteristic half wavelength of the diffusive signal defined by the data from the sites near basement exposures is 14 km at diurnal periods. If signals propagate in a simple one-dimensional manner, this requires a formation-scale permeability of 1.7 x 10(-10) m(2). No constraints are provided on the thickness of material characterized by this permeability, but the high-permeability pathway must be laterally continuous. At two sites near basement exposures the bulk modulus of the rock matrix estimated from the elastic component of the pore pressure response is 3 GPa. Where the igneous crust is regionally well sealed by sediment, the elastic response yields a bulk modulus of 16 GPa. The increase in bulk modulus with age and distance from basement outcrop is consistent with an observed increase in crustal alteration, an increase in seismic velocity, and a decrease in permeability. Observed lateral gradients of pressure, coupled with the estimated permeability, suggest that the amplitude of semidiurnal tidal volumetric flux (Darcy velocity) exceeds 10(-6) m s(-1); semidiurnal fluid particle excursions would reach 0.25 m if the full volume of water contained in 10% porosity of the rock matrix were involved. If flow is channelized along discrete pathways, tidally modulated fluid flow velocities and particle excursions would be locally greater. The amplitude of tidal velocity is similar to that estimated fur buoyancy-driven hydrothermal convection, but the direction is generally different. Thus tidal flow may enhance wafer-rock interactions significantly. Energy dissipated in this manner would approach 0.3 mu W m(-3). [References: 47]
机译：在大西洋中部和胡安·德富卡山脊的两侧的五个密封且仪器化的海洋钻探计划钻孔中，观察到了年轻火成的大洋地壳中的流体压力变化。这些孔穿透了局部沉积良好的地壳，因此在水文上也很好地密封了地壳，并且距水可以在广泛的地下室中自由流过海底的区域1至85公里。相对于在海底同时测量4.8小时至14天的潮汐和非潮汐压力变化，已经确定了地层压力变化的幅度和相位。相对于海底压力变化，地层压力变化减小到98％到28％之间的幅度，并且相移最多20度。简单的多孔介质对周期性载荷响应的理论认为，从基底露头位置穿过火成地壳埋藏部分的扩散信号传播规模应与基底渗透率和变化周期的平方根成反比。这种现象与观察结果一致，并且在昼夜周期中，来自地下室附近站点的数据所定义的漫射信号的特征半波长为14 km。如果信号以简单的一维方式传播，则这需要1.7 x 10（-10）m（2）的地层尺度磁导率。对于以这种渗透性为特征的材料的厚度没有提供任何限制，但是高渗透性路径必须在横向上是连续的。在地下暴露附近的两个位置，根据孔隙压力响应的弹性分量估算的岩石基质的体积模量为3 GPa。在火成硬壳被沉积物很好地密封的地方，弹性响应产生的体积模量为16 GPa。堆积模量随年龄和距基底露头距离的增加而增加，这与观察到的地壳变化增加，地震速度增加和渗透率降低相一致。观察到的压力横向梯度，加上估计的渗透率，表明半日潮气量通量（达西速度）的幅度超过10（-6）m s（-1）;如果涉及岩石基质孔隙率10％的全部水分，则半日流体颗粒偏移将达到0.25 m。如果沿离散路径引导流动，则潮汐调制流体流速和颗粒偏移将局部增大。潮汐速度的幅度与估计的由皮草浮力驱动的热液对流相似，但方向通常不同。因此，潮流可以显着增强晶片与岩石的相互作用。以这种方式耗散的能量将接近0.3μW m（-3）。 [参考：47]

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号