What lies beneath: feeding a basaltic volcanic eruption.

下面是什么：为玄武岩火山喷发提供动力。

• 批准号: 2401682
• 金额: --
• 依托单位: Durham University
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2020
• 资助国家: 英国
• 起止时间: 2020 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2401682
• 关键词: What; lies; beneath; feeding; basaltic

Basaltic volcanic eruptions span a wide spectrum of styles, from relatively gentle effusion of lava, to violent explosions that produce lofting ash plumes. The eruption style, and its evolution in time and space, depends to a large extent on multiphase fluid dynamic processes that occur within the magma as it travels through the sub-volcanic plumbing system. Most basaltic eruptions are fed by dykes, which are a ubiquitous feature of eroded basaltic volcanoes. When a dyke intersects the surface, it first forms a fissure eruption. Usually, the eruption localizes to a single vent within a few days, and often builds a scoria cone or shield, depending on its vigour.Beneath the vent, the conduit retains a dyke geometry, and various lines of evidence indicate that complex magma flow patterns develop within the dyke. Understanding the magma flow pattern within a dyke, and how it changes with time, is crucial because it controls the nature of the eruption at the surface. In particular, localization of gas-rich magma into rapidly upwelling jets is expected to promote more explosive eruption styles.The main goals of this project are:1. to collect field evidence and use laboratory experiments and/or numerical models to reconstruct magma flow processes in volcanic conduits from textural evidence in dykes;2. to interpret magma flow patterns in exposed volcanic conduits in the UK and Tenerife.Bubbles and crystals are very common in dykes, and often show preferential alignment that is imposed by the magma flow. These textures provide a record of the flow history through an eruption, however, their interpretation has been hindered by a lack of understanding of the processes that create them. In this project we will investigate and quantify the process of marginal accretion of crystal- and bubble-bearing magma as it flows along a conduit, using laboratory experiments and/or numerical modelling, depending on the skills of the applicant. Results will be used to analyse and interpret field samples from dykes exposed at different depths within the subvolcanic plumbing system, allowing us, for the first time, to reconstruct dyke flow processes through time and space.Experiments:Suspensions of bubbles and particles in molten wax will be pumped through a model dyke (a high-aspect-ratio duct) with one cooled wall. The wax will solidify against the wall, producing a marginally-accreted facies that will be texturally analysed using x-ray computed tomography. Experimental parameters will be systematically varied, including: size, shape and concentration of particles; size and concentration of bubbles; wax flow rate; cooling rate; duct geometry. Parameters will be scaled to the natural system.Fieldwork:Textures exposed in dykes of the British Tertiary Igneous Province will be mapped at the crystal/vesicle scale in the field, and samples will be collected for XRCT and SEM analysis. The samples will inform laboratory experimental parameters. Later fieldwork in the Teno Massif in Tenerife will focus on mapping spatial and temporal changes in textural indicators of magma flow, in order to reconstruct 4D flow patterns.

玄武质火山爆发的风格范围很广，从相对温和的熔岩流出，到产生蓬松的火山灰柱的剧烈爆炸。喷发方式及其在时间和空间上的演变在很大程度上取决于岩浆在次火山管道系统中流动时发生的多相流体动力学过程。大多数玄武岩喷发都是由岩墙提供的，这是侵蚀玄武岩火山的普遍特征。当岩脉与表面相交时，它首先形成裂缝喷发。通常情况下，喷发会在几天内局限于一个喷口，并根据其活力形成火山渣锥或盾。在喷口下方，通道保持着岩墙的几何形状，各种证据表明岩墙内形成了复杂的岩浆流动模式。了解岩脉内的岩浆流动模式及其随时间的变化是至关重要的，因为它控制着地表喷发的性质。特别是富气岩浆局部化为快速上涌的喷流，有望促进更多的爆发式喷发。收集现场证据，并使用实验室实验和/或数值模型，从岩脉中的纹理证据重建火山管道中的岩浆流动过程;2.解释英国和特内里费岛暴露的火山管道中的岩浆流动模式。气泡和晶体在堤坝中非常常见，并且通常显示出由岩浆流施加的优先排列。这些纹理提供了通过喷发的流动历史的记录，然而，由于缺乏对创建它们的过程的理解，它们的解释受到了阻碍。在这个项目中，我们将调查和量化的过程中的晶体和气泡轴承岩浆的边缘增生，因为它沿着沿着管道流动，使用实验室实验和/或数值模拟，这取决于申请人的技能。结果将用于分析和解释次火山管道系统内不同深度暴露的堤坝的现场样本，使我们能够首次重建堤坝在时间和空间中的流动过程。实验：气泡和颗粒的悬浮液将被泵入熔融蜡中通过具有一个冷却壁的模型堤坝（高纵横比管道）。蜡将靠着墙壁凝固，产生边缘增生的相，将使用x射线计算机断层扫描进行纹理分析。实验参数将系统地变化，包括：颗粒的大小，形状和浓度;气泡的大小和浓度;蜡流速;冷却速率;管道几何形状。参数将按比例缩放到自然system.Fieldwork：暴露在英国第三纪火成岩省的堤坝纹理将映射在现场的晶体/囊泡规模，并将收集样品进行XRCT和SEM分析。样本将提供实验室实验参数。后来在特内里费岛的特诺地块的实地考察将集中在绘制岩浆流的纹理指标的空间和时间变化，以重建4D流动模式。