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

云仙火山科学钻探工程（USDP）穿透了火山体系的关键部分岩浆导管；但这个问题很少被研究，因为它很少被采样。在这项研究中，我们有机会获得这些独特的原位样本，这使我们能够调查被认为是最后一次喷发（1991-1995）的管道。该系统是旋回的，其结构信息记录了岩浆运动、周期和旋回岩脉侵位、喷发动力学等重要信息，对认识云仙山具有重要意义；以及其他许多位于俯冲带的圆顶火山。该项目侧重于进行高分辨率的2D和3D观测，以量化管道样本中保存的纹理信息（孔隙度、矿物排列等）；纹理可以用来揭示岩浆供应的不同阶段以及流动速率和/或变形（应变速率）的变化。该项目从项目组的广泛专业知识中受益匪浅，并且已经使用所有预期的方法进行了全面的多学科可行性研究。这项工作的关键是能够在这些极其有限的样本量中准确地定义非破坏性3D成像的结构，从而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扫描电镜和三维x射线层析成像方法来定义这些结构的性质，这些结构与管道形成、层流和/或湍流以及从脆性变形到韧性变形的转变有关，这些变形都会影响喷发机制。通过整合岩心结构信息，我们将从额外的磁性结构、岩石力学数据和有限的地球化学分析中获得这些信息，我们将更好地了解所有管道过程：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的管道结构联系起来，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现场和地球化学数据。预期的结果包括：更好地了解云禅山系统，更好地解释保存在喷发物质中的结构信息的框架（以约束深度的行为），以及改进管道中岩浆行为的概念和机械流变模型。这项工作的重点是从云仙山的导管中获得的特殊和独特的样本，但其结果将立即转移到俯冲带的其他圆顶状火山。

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.