RAPID: The effusive to explosive transition of La Soufrière, St. Vincent: Insights from petrology and hygrometry

快速：圣文森特拉苏弗里耶尔从热情洋溢到爆炸性的转变：来自岩石学和湿度测量的见解

• 批准号: 2132566
• 负责人: Holli Frey
• 金额: $ 1.57万
• 依托单位: Union College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-06-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2132566&HistoricalAwards=false
• 关键词: RAPID; effusive; explosive; transition; La

The on-going eruption of La Soufrière provides the unique opportunity to understand and evaluate a volcanic event as it is occurring and evolving in almost real-time. Unique to this study, mineral hygrometry will be applied to assess the pre-eruptive water content dissolved in the melt, as recorded by the crystallization of phenocryst rims and/or microlites in scoria from the first eruptive phases on April 9th and 10th. If a buildup of volatiles is driving the eruption, one would expect to see that reflected in the water content recorded by the mineral phases. One can also readily determine if magma mixing was an eruption trigger by comparing the zoning profiles of co-existing minerals, as magma mixing and degassing result in contrasting patterns. Using crystal size distribution and textures of microlites will enable decompression pathways to be estimated and ascent rates of the explosive phase better understood. The magma chamber conditions just prior to the eruption can also be estimated. When combined with similar data from the effusive 2021 lava dome or lithics entrained in the explosive deposits, the causes of the differences in eruptive style can be established. This effort will be useful to the authorities monitoring the eruption. It is a substantive international collaboration and will fund the research of undergraduates.In late December 2020, a lava dome began extruding in the summit crater of La Soufrière, a stratovolcano on the eastern Caribbean island of St. Vincent, after exhibiting no volcanic activity since 1979. On April 9th, 2021, the eruptive style transitioned to an explosive phase, with multiple Plinian events in the first few hours of eruption. Based on the recommendation of the UWI Seismic Research Centre (UWI-SRC), the official agency for monitoring the ongoing eruption, the government of St. Vincent issued an evacuation of the red zone (16,000 people) less than 24 hours prior to the eruption. The transition from effusive to explosive behavior was abrupt and it is unclear what mechanism triggered the ash venting phase, which has severely affected St. Vincent with significant ashfall (also affecting neighboring Barbados and St. Lucia), pyroclastic density currents, and lahars. Throughout the changing eruption styles, La Soufrière has been extensively monitored using seismicity, ground deformation, gas emissions, and remote sensing by the UWI-SRC. Based on gas emission and water geochemistry data obtained by the PIs during the effusive phase, we hypothesize that the magmatic system was not degassing, leading to a buildup of volatiles which eventually triggered the eruption. Using various petrologic tools, this hypothesis shall be tested and the likelihood of similar behavior in the future shall be assessed. This effort will be useful to the authorities monitoring the eruption. It is a substantive international collaboration and will fund the research of undergraduates.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.

正在进行的拉苏弗里埃火山喷发提供了一个独特的机会，可以了解和评估火山事件，因为它几乎是实时发生和演变的。这项研究的独特之处在于，矿物测湿法将被应用于评估溶解在熔体中的喷发前水含量，如4月9日和10日第一次喷发阶段的火山渣中斑晶边缘和/或微晶的结晶所记录的。如果挥发物的积累是火山喷发的驱动力，人们会期望看到矿物相记录的水含量反映出来。人们也可以通过比较共存矿物的分区剖面来确定岩浆混合是否是喷发的触发因素，因为岩浆混合和脱气导致了对比鲜明的模式。使用微晶的晶体尺寸分布和纹理将使减压路径被估计和爆炸阶段的上升率更好地理解。火山爆发前的岩浆房条件也可以估计。结合2021年喷发的熔岩穹丘或爆炸性沉积物中夹带的岩屑的类似数据，可以确定喷发风格差异的原因。这一努力将有助于当局监测火山爆发。这是一项实质性的国际合作，将资助本科生的研究。2020年12月下旬，位于加勒比海东部圣文森特岛的成层火山拉苏弗里埃尔（La Soufrière）的山顶火山口开始出现熔岩圆顶，该火山自1979年以来一直没有火山活动。2021年4月9日，喷发风格过渡到爆炸阶段，在喷发的最初几个小时内发生了多起普林尼事件。根据UWI地震研究中心（UWI-SRC）的建议，圣文森特政府在火山爆发前不到24小时发布了红色区域（16，000人）的疏散。火山灰从喷发到爆发的转变是突然的，目前还不清楚是什么机制触发了火山灰喷发阶段，这严重影响了圣文森特岛，产生了大量的火山灰（也影响了邻国巴巴多斯和圣卢西亚）、火山碎屑密度流和火山泥流。在整个不断变化的喷发风格中，拉苏弗里耶尔火山一直受到UWI-SRC使用地震活动，地面变形，气体排放和遥感的广泛监测。基于气体排放和水的地球化学数据获得的PI在喷出阶段，我们假设，岩浆系统不脱气，导致挥发物的积累，最终引发喷发。应使用各种岩石学工具对这一假设进行检验，并评估未来发生类似行为的可能性。这一努力将有助于当局监测火山爆发。这是一个实质性的国际合作，将资助本科生的研究。这个奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

项目成果

Petrology of the 2020-21 effusive to explosive eruption of La Soufrière volcano, St Vincent: Insights into plumbing system architecture and magma assembly mechanism

圣文森特拉苏弗里耶尔火山 2020-21 年喷发至爆炸性喷发的岩石学：深入了解管道系统架构和岩浆聚集机制

• DOI: 10.1144/sp539-2022-177
• 发表时间: 2023
• 期刊: Special Publications
• 作者: Weber, Gregor;Blundy, Jon;Barclay, Jenni;Pyle, David M.;Cole, Paul;Frey, Holli;Manon, Matthew;Davies, Bridie V.;Cashman, Katharine
• 通讯作者: Cashman, Katharine

2021 EXPLOSIVE ERUPTION AT LA SOUFRIÈRE, ST. VINCENT: CONSTRAINTS ON ERUPTION TRIGGERS FROM MONITORING AND PETROLOGY

2021 年圣路易斯拉苏弗里埃尔火山爆发

• DOI: 10.1130/abs/2021am-367910
• 发表时间: 2021
• 期刊: Geological Society of America Abstracts with Programs
• 作者: Frey, Holli;Christopher, Thomas E.;Manon, Matthew R.;Walters, Sydney;Wright, Joanna;Levins, Grace;Joseph, Erouscilla P.
• 通讯作者: Joseph, Erouscilla P.

Petrology of the explosive deposits from the April 2021 eruption of La Soufrière volcano, St Vincent: a time-series analysis of microlites

圣文森特拉苏弗里埃尔火山 2021 年 4 月喷发的爆炸性沉积物的岩石学：微晶石的时间序列分析

• DOI: 10.1144/sp539-2022-291
• 发表时间: 2023
• 期刊: Special Publications
• 作者: Frey, H. M.;Manon, M. R.;Barclay, J.;Davies, B. V.;Walters, S. A.;Cole, P. D.;Christopher, T. E.;Joseph, E. P.
• 通讯作者: Joseph, E. P.