Basaltic fissure eruptions, which are the most common type of eruption on Earth, are fed by dykes which mediate magma transport through the crust. Dyke propagation processes are important because they determine the geometry of the transport pathway and the nature of any geophysical signals associated with magma ascent. Here, we investigate small-scale (mm–cm wide) banding features at the margins of dykes in the Teno Massif (Tenerife, Spain) and the Columbia River Basalt Province (CRBP) (USA). Similar marginal bands have been reported for dykes in numerous localities around the world. Dyke margins record valuable information about propagation because they are the first material to solidify against the host rock at the propagating dyke tip. We find that the marginal bands are defined by cyclic variations in phenocryst concentration and vesicularity, and we infer that these cyclic variations in texture are a product of cyclic variations in magma flow rates and pressures within the dyke tip. This indicates that dyke emplacement occurs in pulses, with propagation repeatedly hindered by the rapid cooling and solidification of magma in the narrow dyke tip. Using a 1D conduction model, we estimate the time taken for each band to cool and solidify, which provides a timescale of several minutes to tens of minutes for the pulses. The occurrence of similar bands in various volcanic settings suggests that pulsatory propagation is a common, if not ubiquitous, process associated with dyke emplacement.

中文翻译：

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玄武岩岩脉边缘的条带表明就位期间的脉动传播

玄武岩裂缝喷发是地球上最常见的喷发类型，由介导岩浆穿过地壳输送的岩脉供给。岩脉传播过程很重要，因为它们决定了输送路径的几何形状以及与岩浆上升相关的任何地球物理信号的性质。在这里，我们调查了特诺地块（西班牙特内里费岛）和哥伦比亚河玄武岩省（CRBP）（美国）堤坝边缘的小规模（毫米-厘米宽）带状特征。据报道，世界各地许多地方的堤坝也存在类似的边缘带。岩脉边缘记录了有关传播的有价值的信息，因为它们是第一个在传播的岩脉尖端与主岩凝固的材料。我们发现边缘带是由斑晶浓度和囊泡度的循环变化定义的，并且我们推断这些结构的循环变化是岩浆流速和岩脉尖端内压力的循环变化的产物。这表明岩脉侵位以脉冲形式发生，传播过程反复受到狭窄岩脉尖端岩浆的快速冷却和凝固的阻碍。使用一维传导模型，我们估计每个带冷却和凝固所需的时间，这为脉冲提供了几分钟到几十分钟的时间尺度。在各种火山环境中出现的类似带表明，脉动传播是与岩脉就位相关的常见过程（即使不是普遍存在）。