How temperature-dependent elasticity alters host rock/magmatic reservoir models: A case study on the effects of ice-cap unloading on shallow volcanic systems
How temperature-dependent elasticity alters host rock/magmatic reservoir models: A case study on the effects of ice-cap unloading on shallow volcanic systems
复制标题
温度相关弹性如何改变主岩/岩浆储层模型：冰盖卸荷对浅火山系统影响的案例研究
DOI：
10.1016/j.epsl.2016.09.039
复制
发表时间：
2016
影响因子：
5.3
通讯作者：
M. Lupi
中科院分区：
文献类型：
--
作者：
R. Bakker;M. Frehner;M. Lupi
在火山岩系统的地球动力学数值模型中，承载岩浆储集层的火山岩基底通常被假定为具有从寄主岩石到岩浆储集层的急剧过渡的恒定弹性参数。我们通过在200 °C和1000 °C之间进行一组三轴压缩实验，推导出冰岛玄武岩弹性参数与温度之间的经验关系，从而评估这一假设。结果表明，在1000 °C左右，杨氏模量从1.38 GPa显著降低到小于4.7 GPa。基于这些实验室数据，我们开发了一个二维轴对称有限元模型，包括温度依赖的弹性性质的火山basel.As的案例study.As的，我们使用Snæfellsjökull火山系统，冰岛西部的火山沉积物和基底的压力差，由于冰川卸载的火山。首先，我们计算整个模型的温度场，并相应地分配弹性属性。然后，我们评估卸载驱动的压力差在岩浆房在不同的深度模型与温度相关的弹性参数。在弹性参数不变和基底与岩浆房之间的急剧过渡的情况下，我们得到了与其他研究相当的结果。然而，压力变化，由于表面卸载变得更小时，使用更现实的温度依赖性的弹性性能。我们将这种抑制效应归因于岩浆房周围的过渡区，岩浆房仍然是固体岩石，但由于高温而具有相对较低的杨氏模量。我们讨论了我们的研究结果，在岩浆房附近的火山过程，如屋顶坍塌，堤坝注入，或深部热液循环。我们的研究结果旨在量化冰川卸荷对岩浆房动力学和火山活动的影响。
In geodynamic numerical models of volcanic systems, the volcanic basement hosting the magmatic reservoir is often assumed to exhibit constant elastic parameters with a sharp transition from the host rocks to the magmatic reservoir. We assess this assumption by deriving an empirical relation between elastic parameters and temperature for Icelandic basalts by conducting a set of triaxial compression experiments between 200 °C and 1000 °C. Results show a significant decrease of Young's modulus from ∼38 GPa to less than 4.7 GPa at around 1000 °C. Based on these laboratory data, we develop a 2D axisymmetric finite-element model including temperature-dependent elastic properties of the volcanic basement.As a case study, we use the Snæfellsjökull volcanic system, Western Iceland to evaluate pressure differences in the volcanic edifice and basement due to glacial unloading of the volcano. First, we calculate the temperature field throughout the model and assign elastic properties accordingly. Then we assess unloading-driven pressure differences in the magma chamber at various depths in models with and without temperature-dependent elastic parameters. With constant elastic parameters and a sharp transition between basement and magma chamber we obtain results comparable to other studies. However, pressure changes due to surface unloading become smaller when using more realistic temperature-dependent elastic properties. We ascribe this subdued effect to a transition zone around the magma chamber, which is still solid rock but with relatively low Young's modulus due to high temperatures. We discuss our findings in the light of volcanic processes in proximity to the magma chamber, such as roof collapse, dyke injection, or deep hydrothermal circulation. Our results aim at quantifying the effects of glacial unloading on magma chamber dynamics and volcanic activity.