2D and 3D fabric quantification of conduit textures to understand eruption dynamics and mechanisms: unique in situ example of Mt Unzen

对导管纹理进行 2D 和 3D 织物量化，以了解喷发动力学和机制：云仙山的独特现场示例

• 批准号: 298894828
• 负责人: Dr. Kai-Uwe Hess
• 金额: --
• 依托单位: Sektion Mineralogie, Petrologie und Geochemie
• 依托单位国家: 德国
• 项目类别: Infrastructure Priority Programmes
• 财政年份: 2016
• 资助国家: 德国
• 起止时间: 2015-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/298894828?language=en
• 关键词: 2D; 3D; fabric; quantification; conduit

The Unzen Scientific Drilling Project (USDP) at Mt Unzen volcano penetrated the magmatic conduit, a key part of the volcanic system; but one that is little studied as it is rarely sampled. In this study we have access to these unique in situ samples, which allows us to investigate what is thought to be the conduit of the last eruption (1991-1995). The system is known to be cyclic and the textural information recorded in these conduit rocks holds key information about magmatic movement, periodic and cyclic dike emplacement, and eruption dynamics that is important for understanding Mt Unzen; and many other dome-building volcanoes at subduction zones. The project focusses on making high resolution 2D and 3D observations in order to quantify the textural information (porosity, mineral alignments etc.) preserved in the conduit samples; textures that can be used to reveal the different stages of magma supply and changes in flow-rate and/or deformation (strain-rates). The project benefits significantly from the breadth of expertise in the project group, and a full multi-disciplinary feasibility study has been performed using all the intended methods. Key of the work is the ability for non-destructive 3D imaging to accurately define the structures in these extremely limited sample volumes, allowing careful placement and minimal destructive analysis to be required. Our analysis will use the latest 2D SEM and 3D X-ray tomographic methods to define the nature of these fabrics in relation to conduit formation, laminar and/or turbulent flow, and the transition from brittle to ductile deformation which all effect eruption mechanisms. By integrating the core textural information we will obtain that from additional magnetic fabric, rock mechanical data and limited geochemical analysis we will gain a better understanding of all conduit processes: from initial intrusion to the later stage hydrothermal alteration. Furthermore, by linking the observed conduit textures to those seen in erupted surface samples, the project will also enable better interpretation of field and geochemical data used to assess eruption mechanisms and volcano stability. The intended outcomes include: a better understanding of the Mt Unzen system, a better framework for interpreting textural information preserved in erupted material (to constrain behavior at depth), and improved conceptual and mechanical-rheological models of the behaviour of magma in conduits. This work focusses on the exceptional and unique samples available from conduit of Mt Unzen, but will have results that are immediately transferable to other dome-building volcanoes at subduction zones.

云仙火山的云仙科学钻探项目（USDP）穿透了岩浆管道，这是火山系统的一个关键部分;但由于很少取样，因此很少进行研究。 在这项研究中，我们有机会获得这些独特的原位样品，这使我们能够调查什么被认为是最后一次喷发（1991-1995年）的管道。该系统是已知的循环和纹理信息记录在这些导管岩石中保存有关岩浆运动，周期性和周期性岩脉侵位的关键信息，和喷发动力学，这是重要的了解云仙山;和许多其他圆顶建设火山在俯冲带。该项目的重点是进行高分辨率的2D和3D观测，以量化纹理信息（孔隙度，矿物排列等）。保存在导管样品中的结构，可用于揭示岩浆供应的不同阶段以及流速和/或变形（应变率）的变化。该项目大大受益于项目小组的广泛专业知识，并使用所有预定方法进行了全面的多学科可行性研究。这项工作的关键是非破坏性3D成像的能力，以准确地定义这些极其有限的样品体积中的结构，允许仔细放置和最小的破坏性分析。我们的分析将使用最新的二维SEM和三维X射线断层摄影方法来定义这些织物的性质，导管形成，层流和/或湍流，以及从脆性到韧性变形的过渡，所有这些都影响喷发机制。通过整合岩心结构信息，我们将获得额外的磁组构，岩石力学数据和有限的地球化学分析，我们将更好地了解所有导管过程：从最初的侵入到后期的热液蚀变。此外，通过将观察到的管道结构与喷发表面样本中看到的结构联系起来，该项目还将能够更好地解释用于评估喷发机制和火山稳定性的实地和地球化学数据。预期成果包括：更好地了解云仙山系统，更好地解释喷发物质中保存的结构信息（以限制深度行为）的框架，以及改进岩浆在管道中行为的概念和力学流变模型。这项工作的重点是从云仙山管道中获得的特殊和独特的样品，但其结果将立即转移到俯冲带的其他圆顶火山。