Collaborative Research: Exploring the Magmatic, Crustal, and Conduit Conditions Required for Mafic, Plinian Volcanism

合作研究：探索镁铁质、普林尼式火山活动所需的岩浆、地壳和管道条件

• 批准号: 1831143
• 负责人: Brittany Brand
• 金额: $ 51.93万
• 依托单位: Boise State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-08-15 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1831143&HistoricalAwards=false
• 关键词: Collaborative; Research; Exploring; Magmatic; Crustal

Low-silica 'mafic' magmas are the most common magmas to erupt on Earth. Because their viscosity is low, they usually form lava flows or weak explosive eruptions. However, mafic-composition volcanoes can produce much stronger, Plinian-style eruptions capable of dispersing ash fall over thousands of square kilometers, and producing deadly, landscape-altering ash flows that travel tens of kilometers from source. Despite their potential impact, the mechanisms responsible for generating mafic, Plinian eruptions are not understood. This project will benefit society by constraining the causes and consequences of such eruptions, which has global implications for the millions of people living at risk from mafic volcanic centers including the currently active Kilauea volcano in the USA. Two Boise State University (BSU) PhD students will be trained by the five participating scientists on the team, advancing discovery and understanding while promoting teaching, training, and learning. Undergraduate geoscience students from the Universidad de Concepcion (Chile) will be included in the field work and research, broadening participation of under-represented groups. The results and experience of the research team will be shared on the BSU magmatic and volcanic studies group Facebook page through a series of blog post and short videos of our field work that document the key elements of discovery associated with the project. Finally, the investigators and students will incorporate samples, stories, images and videos from the work in Chile into local and regional outreach efforts.This project targets the 13.4_ka (~12 km3 DRE) and ~12.6 ka (1 km3 DRE) mafic eruptions at Volcan Llaima, Chile, which produced extensive ash flow deposits found radially around the volcano. The difference in eruption sizes permits investigation of processes that promote large-volume, caldera forming mafic eruptions versus smaller volume Plinian mafic eruptions. A full suite of diverse but complimentary methods, including petrology, geochemistry, physical volcanology, decompression experiments, and rheology experiments, allows the research team to address the broad, fundamental research question of what magmatic and crustal conditions promote and trigger mafic, Plinian eruptions. More specifically, spatially and stratigraphically constrained petrologic and geochemical studies will allow us to investigate magmatic conditions during and prior to eruption, such as compositional variability of the magma and changes in chamber temperatures, pressures, and gas content. Establishing variability in these conditions will permit reconstruction of the magma plumbing system. A combination of all methods are used to constrain conduit conditions that promote high explosivity for mafic melts, including the interplay between ascent rate and degassing of the magma, as well as changes in magma rheology that prevent gas loss, promoting higher explosivity. The results of this work will have implications for understanding explosive mafic eruptive processes that extend to mafic centers worldwide, including both large-volume and small-volume mafic, Plinian eruptions.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.

低硅基性岩浆是地球上最常见的岩浆喷发。由于它们的粘度低，通常形成熔岩流或微弱的爆炸性喷发。然而，镁铁质组成的火山可以产生更强烈的普林尼式喷发，能够将火山灰分散到数千平方公里的范围内，并产生致命的、改变火山灰流的火山灰流，这些火山灰流从源头传播数十公里。 尽管有潜在的影响，但导致镁铁质普林尼式喷发的机制尚不清楚。该项目将通过限制此类火山爆发的原因和后果来造福社会，这对生活在镁铁质火山中心（包括美国目前活跃的基拉韦厄火山）风险中的数百万人具有全球影响。两名博伊西州立大学（BSU）的博士生将接受团队中五名参与科学家的培训，在促进教学、培训和学习的同时推进发现和理解。孔塞普西翁大学（智利）的地球科学本科生将参加实地工作和研究，扩大代表性不足群体的参与。研究团队的成果和经验将通过一系列博客文章和我们实地工作的短视频在BSU岩浆和火山研究小组的Facebook页面上分享，这些视频记录了与该项目相关的发现的关键要素。最后，研究人员和学生将把智利工作中的样本、故事、图像和视频纳入当地和区域的外联工作。该项目针对智利Volcan Llaima的13.4_ka（~12 km 3 DRE）和~12.6 ka（1 km 3 DRE）镁铁质喷发，这些喷发产生了火山周围放射状的大量灰流沉积物。喷发大小的差异允许调查的过程，促进大容量，破火山口形成的镁铁质喷发与小容量普林尼基性喷发。一整套多样但互补的方法，包括岩石学，地球化学，物理火山学，减压实验和流变学实验，使研究团队能够解决广泛的，基础的研究问题，即岩浆和地壳条件促进和触发镁铁质，普林尼火山爆发。更具体地说，空间和地层约束的岩石学和地球化学研究将使我们能够调查岩浆喷发期间和之前的条件，如岩浆成分的变化和室内温度，压力和气体含量的变化。确定这些条件的可变性将允许重建岩浆管道系统。所有方法的组合被用来限制导管条件，促进高爆炸性的镁铁质熔体，包括上升速率和脱气的岩浆之间的相互作用，以及防止气体损失，促进更高的爆炸性岩浆流变学的变化。这项工作的结果将对理解扩展到全球镁铁质中心的爆炸性镁铁质喷发过程产生影响，包括大体积和小体积的镁铁质，普林尼火山爆发。该奖项反映了NSF的法定使命，并被认为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来支持。