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Santiaguito火山形成块状流的含水英酸质至流纹酸质熔岩的流变学和热力学性质。它们有可能保持数月至数年的移动，并能延伸很远的距离。它们是重大的危险，近年来在日本的Santiaguito和Unzen都发生了由流锋崩塌引起的阻塞和火山灰流。该项目的结果将包括测量Santiaguito硅块熔岩的实际温度和含水量，以及它们的粘度和热容量作为化学成分、温度和含水量的函数。这些硅成分特别有趣，因为安山岩岩浆不会形成块状熔岩流，我们将确定是否存在这种流变变化发生的“临界熔体结构”。研究结果将直接用于改进现有的慢速移动块状熔岩流侵位模型，并将用于基于构型熵理论的含水（流）英质液体粘度预测模型，为改进当前岩浆和火山过程的物理和热模型提供重要数据。这项工作将与危地马拉的火山观察员密切合作进行，目的是使他们更好地了解与块流安置有关的流变学和热预算，有助于提高危险监测和预测能力。该项目的其他更广泛的影响包括培养粘度和量热技术的研究生，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.