Tracking ascent rates in an open-vent volcano: Testing textural and geochemical ascent speedometers

火山爆发来源于地壳中的岩浆房。岩浆储存的深度和喷发前向地表移动的速度对于评估单个火山的危险性非常重要。露天火山特别危险，因为它们在喷发前缺乏动荡信号。该项目特别关注2018年阿拉斯加半岛上的Veniaminof火山喷发，该火山通过火山灰排放对当地社区和航空构成重大风险。在上升过程中溶解的挥发性元素（尤其是H2O）是爆炸性喷发的驱动因素。因此，限制这些岩浆中挥发性元素的收支以及挥发物损失的速度为火山喷发模型和火山喷发行为以及类似火山的喷发行为提供了重要的约束。各种各样的技术被用来估计岩浆上升，在本研究中，这些技术将进行比较，以提高它们的稳健性，并测试它们的潜在假设。除了科学上的好处，这个项目将促进美国地质勘探局/AVO和学术界之间的合作，而这种合作将确保现有的数据集和样本将继续被利用。阿拉斯加半岛是地质研究（GeoPRISMS）的重点地点，我们的工作将补充正在进行的地球物理研究活动（两栖阵列）。挥发性元素数据对地球物理学具有重要意义，并将为地壳和上地幔地震和大地电磁研究提供信息。该项目支持与新闻界同事的合作，以改善科学传播并帮助培养新一代具有科学素养的记者。研究2018年Veniaminof火山喷发玄武岩安山岩岩浆上升与结构演化的相互作用。对2018年火山喷发期间岩浆上升速率的现有估计来自于微岩，将与独立确定的橄榄石熔体上升速率进行比较。为了解释沉积和构造记录，我们还将收集熔体包裹体挥发性数据，以限制上升前地壳储存区的挥发性元素收支。这项工作包括一系列分析技术（拉曼、x射线计算机断层扫描、SIMS、FTIR、EPMA、LA-ICPMS），以充分表征和纠正不稳定的预算。与弹坑研究有关的基本假设将得到检验：1)弹坑上升速率的一致性，2)爆发事件过程中的变化，3)弹坑颈部效应。该项目将辅以热力学模型的发展，该模型通过计算任何优选的p -t - x -时间路径上的化学亲合力来捕获结晶和溶解的驱动力。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Volcanic eruptions are sourced from magma chambers in the crust. At what depth magmas are stored and how fast they move to the surface prior to an eruption is of great importance to assess the hazards associated with individual volcanoes. Open-vent volcanoes are particularly hazardous for their lack of unrest signals prior to an eruption. This project specifically focuses the 2018 eruption of the open-vent volcano Mt Veniaminof on the Alaska Peninsula, which poses substantial risk to local communities and aviation through ash emissions. Volatile elements that exsolved on ascent (especially H2O) are the drivers of explosive eruptions. Thus, constraining the volatile element budget in these magmas as well as how fast the volatiles are lost provide important constraints for eruption models and the eruptive behavior of this and similarly behaving volcanoes. A variety of techniques are used to estimate magma ascent and in this study, those techniques will be compared to improve their robustness and test their underlying assumptions. In addition to the scientific benefits, this project will foster collaboration between the USGS/AVO and the academic community, while this collaboration will ensure that existing data sets and samples will continue to be exploited. The Alaska Peninsula is a focus site of geologic research (GeoPRISMS) and our work will complement ongoing geophysical research activities (Amphibious Array). Volatile element data is of importance for geophysics and will inform crustal and upper mantle seismic and magnetotelluric studies. The project supports a collaboration with journalism colleagues to improve science communication and help build a new generation of science-literate journalists. The interplay between magma ascent and textural evolution of basaltic andesites of the 2018 Veniaminof eruption will be studied. Existing estimates for magma ascent rates during the 2018 eruption derived from microlites, will be compared against independently determined ascent rates from melt embayments hosted in olivine. To interpret the embayment and textural record, we will also collect melt inclusion volatile data to constrain the volatile element budget in the crustal storage region prior to ascent. The work includes a series of analytical techniques (Raman, x-ray computed tomography, SIMS, FTIR, EPMA, LA-ICPMS) to fully characterize and correct the volatile budget. Fundamental assumptions related to embayment studies will be tested: 1) the uniformity of ascent rates among embayments, 2) changes over the course of an eruptive episode, 3) the effect of embayment necking. The project will be complemented with the development of a thermodynamic model that captures the driving forces for crystallization and dissolution through the calculation of chemical affinities along any preferred P-T-X-time path.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.