Phase equilibria experiments to constrain magma storage at Mt Churchill, Alaska; refining the magmatic source of the White River Ash eruptions

阿拉斯加丘吉尔山限制岩浆储存的相平衡实验；

• 批准号: 2308646
• 负责人: Jessica Larsen
• 金额: $ 30.87万
• 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: 2023
• 资助国家: 美国
• 起止时间: 2023-09-01 至 2026-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2308646&HistoricalAwards=false
• 关键词: Phase; equilibria; experiments; constrain; magma

Volcanoes that produce explosive eruptions are very hazardous because they can create widespread ash clouds that are risky for aviation and cause damaging ash fall downwind. The White River ash (WRA) dacite tephra beds found in eastern Alaska and western Canada resulted from three of the most explosive eruptions (VEI 6) from a North American volcano, Mt Churchill, in the past ~2000 years. Those eruptions harmed the indigenous Dene people living in the areas downwind in present day Canada, resulting in a southward migration out of the impacted area. The current global reach of air traffic and the increased human population in downwind regions today mean that a similar-sized eruption from Mt Churchill could potentially cause catastrophic economic and human impacts. Despite its potential hazards, little is known about the source of its explosive, silicic magmas. This study will help us better understand where the magmas that feed Mt Churchill’s eruptions are stored in the crust. Although this volcano does not have a dedicated seismic monitoring network, knowledge of where the magmas live beneath the volcano can help us better estimate what might happen if the volcano becomes restless again in the future. Students will take part in this research during two summer courses taught by the PI at UAF. These courses will involve field trips to learn about the WRA deposits in eastern Alaska, collect samples, and then students will learn how to conduct experiments in the lab. The support from this grant will help cover student fees and field trip costs to encourage broad participation of students from historically excluded groups to help increase diversity in the geosciences. As a member of the Alaska Volcano Observatory, the PI will work closely with AVO colleagues to incorporate the results from this work into AVO operations and outreach efforts.This study will use high pressure and temperature experiments to create a magma plumbing system model for the WRA eruptions. The team will build on petrological data from prior studies, which include mineralogy, temperature, and oxygen fugacity estimates needed for the experiments. They will use plagioclase-hosted melt inclusions to estimate entrapment pressures and volatile compositions by micro-FTIR analyses of H2O and CO2 (if present) and electron microprobe analyses of S and Cl. If reacted amphiboles are found, textural analysis will enable the team to estimate magma ascent rates using prior experimental calibrations. The petrology of the WRA tephra is well-suited for phase equilibria experiments, and the relatively low temperature range constrained by prior work allows for experimental methods that are suitable for student work and have a relatively low failure rate. The experiments will contribute to a magma plumbing system model for the WRA eruptions from Mt Churchill. These results will also be provided to researchers maintaining thermodynamical models to help augment their empirical datasets for increased accuracy applied to plagioclase and amphibole-bearing dacite to rhyolite magmas.This project is jointly funded by Petrology & Geochemistry and the Established Program to Stimulate Competitive Research (EPSCoR).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

产生爆炸性喷发的火山是非常危险的，因为它们可以产生宽度的灰云，这些灰云风险冒险，并导致有害的灰烬下风。在过去〜2000年的北美火山中，在阿拉斯加东部和加拿大西部发现的白河灰分（WRA）Dacite Tephra床是来自北美火山丘吉尔的三起最爆炸性的喷发（VEI 6）。这些爆发损害了当今加拿大阵风中居住在逆风地区的土著人民，导致了受影响地区的向南迁移。当前的全球空中交通范围以及如今的下风地区人口增加意味着，丘吉尔山的类似大小的喷发可能会引起灾难性的经济和人类影响。尽管有潜在的危害，但对其爆炸性，硅岩浆的来源知之甚少。这项研究将有助于我们更好地了解丘吉尔山的爆发储存在哪里。尽管这座火山没有专用的地震监测网络，但知道岩浆居住在火山下的何处可以帮助我们更好地估计如果火山将来再次变得不安，可能会发生什么。学生将在UAF的PI教授的两个夏季课程中参加这项研究。这些课程将涉及实地考察，以了解阿拉斯加东部的WRA矿床，收集样本，然后学生将学习如何在实验室进行实验。这笔赠款的支持将有助于支付学生的费用和实地考察费用，以鼓励从历史上排除的团体中广泛参与，以帮助增加地球科学的多样性。作为阿拉斯加火山天文台的成员，PI将与AVO同事紧密合作，将这项工作的结果纳入AVO运营和外展工作中。这项研究将使用高压和温度实验来为WRA喷发创建岩浆丰满的系统模型。该团队将基于先前研究的岩石学数据，其中包括实验所需的Mineraology，温度和氧气散热性估计。他们将使用斜长石构体的融合物来估计通过对H2O和CO2（如果存在）的微型FTIR分析（如果存在）以及S和CL的电子微探测分析，来估计捕集压力和挥发性组成。如果发现反应的闪石，纹理分析将使团队能够使用先前的实验校准来估计岩浆上升速率。 WRA TEPHRA的岩石学非常适合相等实验，并且先前工作控制的相对低温范围允许适用于学生工作并且具有相对低失败率的实验方法。该实验将为丘吉尔山的WRA爆发有助于岩浆丰满的系统模型。这些结果还将提供给维护热力学模型的研究人员，以帮助增加其经验数据集，以提高适用于斜长石和含有闪石的dacite的精确度，以使岩质岩浆共同资助，该项目由Petrology＆Geochemistry和Geochochemistion和既定计划促进竞争性研究（EPSCOR）。利用基金会的知识分子和更广泛的影响审查标准。