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.

“该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。“火山给全世界数百万人带来危险，包括许多生活在美国部分地区的人。科学家现在可以预测许多监测良好的火山爆发的时间。不幸的是，目前不可能准确预测喷发的爆炸性，因为这取决于大量因素，如火山管道的形状和岩浆的成分，其中大多数取决于深层地下的过程，因此在喷发之前无法直接观察到。更好的预测取决于我们对控制地下火山管道内岩浆流动的条件的理解。该项目旨在通过调查犹他州南部圣拉斐尔沙漠中被深度侵蚀的古火山的地质情况，提供关键数据，以提高对这一问题的认识。这种独特的地质环境，火山在数百万年内没有爆发，提供了关于火山爆发期间地下运作过程的基本见解。我们不能直接观察到这些过程，但我们可以从地质记录中保存的特征中解释这些过程。康纳、韦特莫尔及其同事将联合收割机地质测绘与三维地面激光雷达成像、地球化学和岩石学建模以及寄主岩石弹性特性分析相结合，以详细了解控制圣拉斐尔沙漠火山管道形成的侵蚀和混合过程。进行这些观测的基本目标是对管道流和火山爆发模型所共有的一组输入参数进行地质和地球化学约束。这将通过以下方式实现：（1）利用地面激光雷达通过地质测绘生成各个火山管道的3D模型。这将基本上将管道带入计算机，并允许项目团队测量横截面积，形状和半径随高度的变化，直接测量管道流动和发展的数值模型中所需的管道几何形状。这种方法将允许研究岩脉和管道之间的详细三维关系，以及角砾岩（寄主岩石-岩浆）混合带，以及其他特征，这些特征足够详细，可用于管道模型。(2)对从这些管道系统采集的样品进行详细的结构和地球化学分析，将有助于深入了解管道两侧和沿着岩浆的矿物学和化学变化。这些数据将约束模型中使用的喷发参数，如岩浆温度，初始挥发分含量（从原始镁铁质矿物中的熔融包裹体获得），粘度，结晶深度，以及这些参数中的跨导管梯度。(3)将仔细描述导管所在围岩的特性。该描述将包括微观结构研究，旨在量化围岩中的变形机制、应变类型和强度，作为与管道距离的函数。