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

学术价值：最近，监测良好的火山喷发充当了优秀的“自然实验室”，允许不同的研究人员合作解决如何使用地球物理前兆来预测火山喷发活动的问题。2006年阿拉斯加州奥古斯丁火山的喷发为岩石学实验研究提供了一个极好的目标，该实验研究在对喷发前和同步喷发活动以及喷发时间尺度进行强大的大地测量和地震观测的框架内，限制了岩浆的储存和上升动力学。关于2006年火山喷发活动及其沉积物的详细信息将通过实验研究得到补充，这些实验研究将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公里深的地方储存大量结晶的高硅安山岩“泥状”体。玄武岩的补充和有限的杂交（即岩浆混合）产生了低硅安山岩岩浆，“糊状”的再动员显然是引发喷发的原因。喷发早期主要发育低硅质安山岩，岩石学证据表明，在喷发开始前，低硅质安山岩在~25 MPa处发育迟滞或储存。从2005年11月中旬开始，大地测量数据显示奥古斯丁地下浅层地壳中有岩脉注入的证据，1月中旬火山爆发。在低硅安山岩中发现的角闪洞反应边缘的宽度也限制了这个时间尺度的一级，这表明岩浆上升到比角闪洞稳定性更浅的深度与岩脉注入的开始时间一致。建议的项目将为低硅质安山岩和高硅质安山岩端元岩浆的岩浆储存和上升速率提供实验约束：高硅安山岩岩浆储存条件的相平衡约束。2. 通过连续速率减压实验对低硅安山岩中斜长石结晶动力学进行了约束，并对早期岩脉注入导致火山爆发的时间进行了破译。3. 通过实验约束角闪洞击穿反应速率，估算岩浆上升速率和与岩浆混合和杂交有关的加热时间尺度。这些任务将结合起来，形成一个将实验与地球物理观测联系起来的模型，并最终利用地球物理前兆指标加强对火山的监测。更广泛的影响：该项目支持一名博士生（Sarah Henton）的研究活动，Henton女士在蒙特塞拉特火山观测站和苏弗里埃尔火山的经验将对该项目有益。该项目还将支持和加强三位女性在地球科学方面的研究。通过PI和合作者与阿拉斯加火山观测站的联系，结果将传播给居住在基奈半岛奥古斯丁附近的公众。研究结果还将用于与2006年监测活动的地球物理数据交叉联系，以破译与火山喷发特定阶段有关的大地测量和地震信号的来源机制。

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.