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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Effects of mechanical layering of host rocks on dike growth and arrest
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Effects of mechanical layering of host rocks on dike growth and arrest

机译：基岩机械分层对堤防生长和停滞的影响

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Many dikes intruding the layered host rock of Miyakejima and Piton de la Fournaise are arrested, segmented, and show variation in thickness. These geometric factors can be largely attributed to the mechanical layering of the host rocks that constitute these volcanoes. Some dikes are arrested at the base of stiff (high Young's modulus) rock layers, whereas others are segmented in the layers. We use finite-element models (FEM) to simulate a typical dike arrest at the base of a stiffer layer. The dike may become arrested when it reaches at the base of the suffer layer for several reasons. First, the dike-induced tensile stress may not be high enough to break the rock. Second, the stiff layer may act as a "stress barrier". Third, the material toughness of the layers may be unfavorable for vertical dike propagation and result either in dike arrest or dike deflection. When the magmatic overpressure (driving pressure) is sufficiently high dike can intrude into the overlying layer. Some deflected dikes resume their vertical propagation, thereby generating offset segments. The layering of a volcano thus commonly controls the dike propagation paths and if and where the dikes become arrested. Our measurements show that the dikes in these volcanoes tend to be comparatively thick where they dissect "soft" pyrodastic layers, and thin where they dissect stiff lava flows and sills. Numerical FEM simulations indicate that the variation of dike thickness observed in Miyakejima and Piton de la Fournaise can be broadly explained in terms of layer-stiffness differences of one or two orders of magnitude.
机译：许多侵入Miyakejima和Piton de la Fournaise的层状主岩的堤坝被逮捕，分割并显示出厚度变化。这些几何因素在很大程度上可归因于构成这些火山的基岩的机械分层。一些堤坝被阻滞在坚硬（高杨氏模量）岩石层的底部，而另一些则被细分在这些层中。我们使用有限元模型（FEM）来模拟在较硬层底部的典型堤防。当堤坝到达受灾层的底部时，出于多种原因，堤坝可能会被阻止。首先，堤坝引起的拉应力可能不够高，无法破坏岩石。第二，硬质层可以充当“应力屏障”。第三，各层的材料韧性可能不利于垂直堤防的传播，并导致堤防或堤防变形。当岩浆超压（驱动压力）足够高时，堤坝会侵入上覆层。一些偏转的堤坝恢复其垂直传播，从而产生偏移段。因此，火山的分层通常控制堤防的传播路径，以及堤防是否在何处停止。我们的测量结果表明，这些火山的堤坝在剖析“软”的火山岩层时往往比较厚，而在剖析坚硬的熔岩流和坎ill处则比较薄。数值有限元模拟表明，在Miyakejima和Piton de la Fournaise中观察到的堤厚度的变化可以用一到两个数量级的层刚度差异来广义地解释。

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