Pathways for degassing during the lava dome eruption of Mount St. Helens 2004-2008
Pathways for degassing during the lava dome eruption of Mount St. Helens 2004-2008
复制标题
DOI：
10.1130/g35940.1
复制
发表时间：
2014-11-01
期刊：
影响因子：
5.8
通讯作者：
Pallister, John S.
中科院分区：
文献类型：
--
作者：
Gaunt, H. Elizabeth;Sammonds, Peter R.;Pallister, John S.
挥发物逃离上升岩浆的能力调节了火山系统的爆炸性。在岩浆上升过程中，在熔岩穹丘喷发，应变局部化在管道边缘发生，造成损害晕与气体逃逸的影响。本文首次系统地研究了塔里木盆地边缘剪切带渗透率网络各向异性。D. 2004-2008年圣海伦火山熔岩圆顶（华盛顿州，美国）。结果表明，越来越大的渗透率各向异性多达四个数量级（超过类似4米）从内部的脊柱通过损伤晕移动。我们发现，渗透率基本上是各向同性的脊柱内部，但高度各向异性的损伤区和故障核心。我们的圆顶岩石的检查表明，渗透率各向异性强烈依赖于垂直定向剪切层的存在。在这里，我们表明，挥发物的逃逸率将是几个数量级更高的垂直通过导管边缘剪切带比水平进入导管壁。
The ability of volatiles to escape rising magma regulates the explosivity of a volcanic system. During silicic lava dome eruptions, strain localization at the conduit margin occurs during magma ascent, creating a damage halo with implications for gas escape. Here we report the first systematic study of permeability network anisotropy across the marginal shear zone of the A. D. 2004-2008 lava dome at Mount St. Helens (Washington State, USA). The results show increasingly large permeability anisotropy of as much as four orders of magnitude (over similar to 4m) moving from the interior of the spine through the damage halo. We find the permeability to be essentially isotropic in the spine interior but highly anisotropic in the damage zone and fault core. Our examination of the dome rocks reveals that the permeability anisotropy depends strongly on the presence of vertically oriented shear layers. Here we show that the rate of escape of volatiles will be several orders of magnitude higher vertically through a conduit margin shear zone than horizontally into the conduit wall.