Rheological and Thermodynamic Properties of Subduction Zone Magmas and Lavas - An Integrated Experimental and Observational Study

该项目将研究危地马拉圣地亚吉托火山形成块状流动的含水英安岩-流纹质熔岩的流变性和热力学性质。这些设备有可能保持几个月到几年的移动性，并延伸到很远的距离。它们是重大的危险，最近在圣地亚吉托和温岑(日本)都发生了由流动前锋坍塌引起的阻塞和火山灰流动。该项目的结果将包括测量圣地亚吉托硅块熔岩的实际温度和水含量，以及它们的粘度和热容量随化学成分、温度和水含量的变化。这些硅质成分特别令人感兴趣，因为安山岩浆不会形成阻挡熔岩流，我们将确定是否存在发生这种流变性变化的“临界熔体结构”。这些成果将直接用于改进现有的缓慢移动的块状熔岩流侵位模型，还将用于根据构型熵理论开发含水(流纹状)英安质液体粘度的预测模型，为改进目前岩浆和火山过程的物理和热学模型提供所需的重要数据。这项工作将与危地马拉火山观察员(INSIVUMEH)密切合作开展，目的是使他们更好地了解与块状岩浆流侵位有关的流变学和热预算，有助于改进危险监测和预测能力。该项目的其他更广泛的影响包括培训研究生学习粘度计和量热法技术，并在美国建立第一个将低温粘度测量技术应用于含水硅酸盐液体的实验室。

This project will investigate the rheological and thermodynamic properties of hydrous dacitic to rhyodacitic lavas from Santiaguito volcano in Guatemala, which form block flows. These have the potential to remain mobile for months to years, and to extend great distances. They are significant hazards, and block and ash flows resulting from flow-front collapse have occurred both at Santiaguito and Unzen (Japan) in recent times. Results of this project will include measurements of the actual temperatures and water contents of silicic block-lavas at Santiaguito, and their viscosity and heat capacity as a function of chemical composition, temperature, and water content. These silicic compositions are particularly interesting because andesitic magmas do not form block lava flows, and we will determine whether there is a "critical melt structure" at which this rheological change occurs. The results will be applied directly to refine existing models for the emplacement of slow-moving block lava flows, and will also be used to develop a predictive model of the viscosity of hydrous (rhyo-)dacitic liquids based on configurational entropy theory, providing important data required for improving current physical and thermal models of magmatic and volcanic processes.The work will be carried out in close collaboration with volcano observers in Guatemala (INSIVUMEH), and the aim is to provide them with an improved understanding of rheology and heat budgets related to block flow emplacement, contributing to improved hazard monitoring and prediction capabilities. Other broader impacts of this project include training graduate students in viscometry and calorimetry techniques, and establishing the first laboratory in the USA that will apply low-temperature viscosity measurement techniques to hydrous silicate liquids.