Estimating Eruption Model Input Parameters From Direct Observations of Deeply Eroded Basalt Conduits, San Rafael, UT

根据深度侵蚀玄武岩管道的直接观察估算喷发模型输入参数，犹他州圣拉斐尔

• 批准号: 0910696
• 负责人: Charles Connor
• 金额: $ 17.88万
• 依托单位: University of South Florida
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-07-01 至 2012-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0910696&HistoricalAwards=false
• 关键词: Estimating; Eruption; Model; Input; Parameters

"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)." Volcanoes create hazards for millions of people worldwide, including many living in parts of the USA. Scientists can now forecast the timing of many eruptions at well-monitored volcanoes. Unfortunately, it is currently not possible to accurately forecast how explosive an eruption might be, because this depends on a large number of factors, such as the shape of volcano conduits and the composition of magma, most of which depend on processes operating in the deep subsurface and so are not directly observable prior to eruptions. Better forecasts depend upon improving our understanding of the conditions that govern magma flow within volcanic conduits in the subsurface. This project aims to provide crucial data to improve this understanding through investigation of the geology of deeply eroded ancient volcanoes in the San Rafael desert of southern Utah. This unique geologic environment, where volcanoes have not erupted in millions of years, provides essential insight about processes operating in the subsurface during volcanic eruptions. We cannot observe these processes directly at currently erupting volcanoes, but we can interpret them from the features preserved in the geologic record. Connor, Wetmore and colleagues will combine geologic mapping with 3D terrestrial LiDAR imaging, geochemistry and petrological modeling, and analysis of the elastic properties of host rocks to develop a detailed understanding of the erosion and mixing processes that controlled formation of volcanic conduits of the San Rafael desert. The basic goal of making these observations is to place geological and geochemical constraints on a set of input parameters common to models of conduit flow and volcanic eruptions. This will be accomplished by: (1) generating 3D models of individual volcano conduits through geologic mapping utilizing terrestrial LiDAR. This will essentially bring conduits into the computer and allow the project team to measure cross-sectional areas, shapes, and change in radius with height, direct measures of conduit geometry needed in numerical models of conduit flow and development. This approach will allow study of the detailed 3D relationships between dikes and conduits, and breccia (host rock - magma) mixing zones, among other features in sufficient detail to be useful in conduit models. (2) Detailed textural and geochemical analyses of samples systematically collected from these conduits will yield insights into variations in mineralogy and chemistry of magmas across and along conduits. These data will constrain eruption parameters used in models, such as magma temperature, initial volatile content (obtained from melt inclusions in primary mafic minerals), viscosity, depth of crystallization, and across conduit gradients in these parameters. (3) The properties of the wall rock that hosts conduits will be carefully described. This description will include microstructural studies aimed at quantifying deformation mechanisms, strain type and intensity in the wall rocks, as a function of distance from the conduits.

“该裁决是根据2009年《美国复苏与再投资法》（公法111-5）资助的。”火山为全球数百万人造成了危害，其中包括许多居住在美国部分地区的人。科学家现在可以预测监视良好的火山的许多爆发时间。不幸的是，目前无法准确预测喷发的爆炸性，因为这取决于大量因素，例如火山凝聚力的形状和岩浆的组成，大多数依赖于在深层地下运行的过程，因此在喷发之前并不直接观察。更好的预测取决于我们对地下火山导管内岩浆流量的条件的理解。该项目旨在通过调查犹他州圣拉斐尔沙漠深处侵蚀的古代火山的地质来提供关键数据，以提高这种理解。这种独特的地质环境，在数百万年内没有爆发火山，它为火山喷发期间在地下运行的过程提供了基本的见解。我们无法直接在目前爆发的火山上直接观察这些过程，但是我们可以从地质记录中保留的特征来解释它们。 Connor，Wetmore及其同事将将地质映射与3D陆地激光雷达成像，地球化学和岩石学建模以及对宿主岩石的弹性特性进行分析，以对控制侵蚀和混合过程的详细理解，这些过程控制了San Rafael沙漠的火山管道形成的侵蚀和混合过程。进行这些观察结果的基本目标是将地质和地球化学约束放在导管流和火山喷发模型共有的一组输入参数上。这将通过以下方式完成：（1）通过陆地雷达通过地质映射生成单个火山导管的3D模型。这实质上将将导管带入计算机，并允许项目团队通过高度，直接测量导管流量和开发的数值模型中所需的导管几何形状的直接测量。这种方法将允许研究堤防和导管之间的详细3D关系，以及Breccia（寄主岩石 - 岩浆）混合区域以及其他足够详细的特征，可用于导管模型。 （2）从这些导管中系统收集的样品的详细质地和地球化学分析将产生对跨导管岩浆和岩浆化学的变化的见解。这些数据将限制模型中使用的喷发参数，例如岩浆温度，初始挥发性含量（从原发性镁铁质矿物中的熔体夹杂物获得），粘度，结晶深度以及这些参数中的导管梯度。 （3）将仔细描述托管导管的壁岩的特性。该描述将包括旨在量化墙壁岩石中的变形机制，应变类型和强度的微观结构研究，这是距离导管距离的函数。