Experiment Versus Nature: Testing Models of Magma Storage and Movement from the 2006 Eruption of Augustine Volcano, Alaska

实验与自然：测试 2006 年阿拉斯加奥古斯丁火山喷发的岩浆储存和运动模型

• 批准号: 0911694
• 负责人: Jessica Larsen
• 金额: $ 30.27万
• 依托单位: University of Alaska Fairbanks Campus
• 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: 2009-09-01 至 2013-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0911694&HistoricalAwards=false
• 关键词: Experiment; Versus; Nature; Testing; Models

Intellectual Merit: Recent, well-monitored volcanic eruptions serve as excellent "natural laboratories",allowing diverse researchers to collaborate in resolving questions about how to use geophysical precursors to predict eruptive activity. The 2006 eruption of Augustine Volcano, Alaska represents an excellent target for experimental petrology studies to constrain magma storage and ascent dynamics, within a framework of robust geodetic and seismic observations of precursory and syn-eruptive activity and eruptive timescales. Details about the 2006 eruption activity and its deposits will be augmented by experimental studies to develop a petrology- and geochemistry-based model for storage of a largely crystalline, high-silica andesite "mush" body at 4-6 km depth beneath the volcano. Basaltic replenishment and limited hybridization (i.e., magma mixing) produced a low-silica andesite magma, and re-mobilization of the "mush" apparently triggered the eruption. The early explosive phase of the eruption mainly involved the low-silica andesite, which shows petrologic evidence for stalling or storage at ~25 MPa prior to the onset of the eruption. Starting in mid-November, 2005, geodetic data show evidence for dike injection into the shallow crust beneath Augustine, with the eruption ensuing in mid-January. This timescale is also constrained to first order by the widths of amphibole reaction rims found in the low-silica andesite, indicating that ascent to depths shallower than amphibole stability in that magma coincided with the onset of the dike injection. The proposed project would provide experimental constraints on magma storage and ascent rates for the low and high-silica andesite end member magmas: 1. Phase equilibria constraints on magma storage conditions of the high-silica andesite. 2. Continuous rate decompression experiments to constrain plagioclase crystallization kinetics in the low-silica andesite, to decipher the timing of early dike injection leading to the onset of the eruption. 3. Experimentally constrain amphibole breakdown reaction rates, to estimate both magma ascent rates and heating timescales related to magma mixing and hybridization. These tasks will be combined to formulate a model that links the experimental with the geophysical observations, and ultimately to enhance volcano monitoring using precursor geophysical indicators.Broader Impacts: This project support the research activities of one PhD student (Sarah Henton), Ms. Henton's experience with the Montserrat Volcano Observatory and Soufriere Hills Volcano will be beneficial to the project. The project will also support and enhance the research of three females in the geosciences. Through the connections of the PI and collaborator with the Alaska Volcano Observatory, the results will be disseminated to the public living near Augustine, in the Kenai Peninsula. The results will also be used to cross-link with geophysical data from monitoring activities in 2006, to decipher the source mechanisms of geodetic and seismic signals related to specific phases of the eruption.

智力优势：最近监测良好的火山爆发是极好的“天然实验室”，使不同的研究人员能够合作解决如何利用地球物理前兆预测喷发活动的问题。2006年阿拉斯加奥古斯丁火山爆发是一个很好的实验岩石学研究的目标，以限制岩浆储存和上升动力学，在强大的大地测量和地震观测的框架内的火山喷发和同喷发活动和喷发时间尺度。关于2006年喷发活动及其沉积物的详细情况将通过实验研究加以补充，以建立一个基于岩石学和地球化学的模型，用于在火山下方4-6公里深处储存一个主要为结晶的高硅安山岩“泥”体。玄武岩补充和有限的杂交（即，岩浆混合）产生了低硅安山岩岩浆，而“泥浆”的重新流动显然引发了喷发。喷发的早期爆发阶段主要涉及低硅安山岩，这表明在喷发开始前在~25 MPa下停止或储存的岩石学证据。从2005年11月中旬开始，大地测量数据显示有证据表明，在奥古斯丁下面的浅地壳中注入了堤坝，随后在1月中旬爆发。这一时间尺度也被限制到第一顺序的角闪石反应边缘的宽度发现在低硅安山岩，表明上升到深度浅于角闪石稳定性的岩浆相吻合的岩脉注入的开始。拟议的项目将提供实验限制岩浆储存和上升速率的低硅和高硅安山岩端元岩浆：1。高硅安山岩岩浆储存条件的相平衡制约。2.连续率减压实验，以限制斜长石结晶动力学在低硅安山岩，破译早期岩脉注入导致爆发的发病时间。3.实验约束角闪石分解反应速率，估计岩浆上升速率和加热时间尺度有关的岩浆混合和杂交。这些任务将结合起来，制定一个模型，将实验与地球物理观测联系起来，并最终利用前兆地球物理指标加强火山监测，更广泛的影响：本项目支持一名博士生（Sarah亨顿）的研究活动，亨顿女士在蒙特塞拉特火山观测站和苏弗里埃山火山的经验将有助于本项目。该项目还将支持和加强三名女性在地球科学领域的研究。通过PI和合作者与阿拉斯加火山观测站的联系，结果将传播给基奈半岛奥古斯丁附近的公众。其结果还将用于与2006年监测活动的地球物理数据相互联系，以破译与火山爆发具体阶段有关的大地测量和地震信号的来源机制。