Collaborative Research: Volcanism on the Edge - Basaltic Volcanism from Source to Surface across the Colorado Plateau/Basin & Range Transition in SW Utah

美国西南部有近40个玄武岩火山区，总共有2000多座第四纪火山，其中许多火山是最近才喷发的（过去5万年）。这些火山大多被认为是“单生”的（即，它们只喷发一次），它们通常产生相对较小的喷发量（1立方千米）。然而，最近已经清楚的是，这种喷发可能造成重大危害，因为它们的喷发方式多种多样，包括爆炸行为，而且未来任何喷发的地点都是未知的。在美国西南部，火山活动的原因和最近爆发的频率都没有得到很好的了解。该项目将重点研究位于科罗拉多高原与盆地和山脉省之间的犹他州西南部的火山活动，该地区对火山活动的成因尤其神秘，对近期火山活动的性质和频率也知之甚少。通过整合详细的野外观测和测绘、放射性测年、物理火山学和地球化学分析，该项目将提供岩浆上升和储存导致喷发的来源、过程和时间尺度的关键约束，以及与喷发方式和危害的联系。除了提供有关危害公众的信息外，这项工作还包括指导和培训两名博士生和几名本科生在野外，分析和成像技术方面的研究人员。与此同时，pi还将开展以K-12学生和教师为对象的研究性教育活动、公开演讲、初高中学生暑期课程等与该事业相关的各种活动。美国西南部至少有2229座第四纪火山，其中大部分是单成因火山。重要的问题围绕着火山作用的原因和来源，年龄和喷发的复发间隔，以及喷发风格的范围和控制。了解控制美国西南部单一成因火山活动的过程，以及这些过程运作的时间尺度，对危害和风险评估至关重要。此外，许多这些单成因火山场的基性使它们成为它们所挖掘的地幔源的理想探针，因此，时空成分变化可以提供该地区复杂构造历史的独特记录。我们提出了一个综合的物理火山学和岩石学/地球化学研究在西南犹他火山场第四纪火山作用，跨越从盆地和山脉到科罗拉多高原的过渡，以阐明构造，岩浆来源，和喷发风格和危害之间的联系。主要目标包括：1)建立年龄范围和系统的年龄进展（如果存在）；2)评估喷发类型的范围和相关危害；3)确定喷发活动与局部构造特征的潜在关系；4)限定喷发中地幔源的性质（岩石圈vs软流圈）、位置（深度）和空间异质性；5)评估地幔与地壳控制对岩浆组成和喷发方式的相对重要性，以及岩浆含水量的影响；6)限定时间尺度和岩浆储存系统在岩浆从源头上升到地表过程中的重要性。我们的综合方法将包括详细的野外测绘，40Ar/39Ar测年，喷发产物的结构分析，以及整个岩石和矿物尺度的元素和同位素分析。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。

The American Southwest is home to nearly forty basaltic volcanic fields that collectively contain more than 2,000 Quaternary volcanoes, including many that have erupted relatively recently (past 50,000 years). Most of these volcanoes are considered to be “monogenetic” (i.e., they erupt only once), and they generally produce relatively small volume eruptions (1 km3). Nevertheless, it has recently become clear that such eruptions can pose significant hazards due to their wide variety of eruptive styles, including explosive behavior, and the fact that the location of any future eruption is unknown. In the southwest US, neither the cause of this volcanism nor the frequency of recent eruptions is well understood. This project will focus on volcanism in SW Utah, in the transition between the Colorado Plateau and the Basin and Range provinces, an area that is particularly enigmatic with regard to the causes of volcanism, and poorly constrained with regard to the nature and frequency of recent volcanic activity. By integrating detailed field observations and mapping, radiometric dating, physical volcanology, and geochemical analyses, this project will provide key constraints on the sources, processes, and timescales of magma ascent and storage leading to eruption, and the link to eruptive style and hazards. In addition to providing information about hazards to the public, this work includes mentoring and training of two PhD students and several undergraduate researchers in field, analytical and imaging techniques. PIs will also engage in a variety of outreach activities related to the project, including research-based educational activities for K-12 students and teachers, public talks, and a summer course for middle and high school students.The Southwest US contains at least 2229 Quaternary volcanoes, most of which are monogenetic. Significant questions surround the causes and sources of the volcanism, the ages and eruptive recurrence intervals, and the range of – and controls on – eruptive styles. Understanding the processes that govern monogenetic volcanism in the Southwest US, and the time scales over which these processes operate, is critical for hazard and risk assessment. In addition, the mafic nature of many of these monogenetic volcanic fields makes them ideal as probes of the mantle sources that they tap, and spatial-temporal-compositional variations can thus provide a unique record of the complex tectonic history in this area. We propose an integrated physical volcanology and petrology/geochemistry study of Quaternary volcanism in the SW Utah volcanic field, spanning the transition from the Basin and Range to the Colorado Plateau, to elucidate links between tectonics, magma sources, and eruptive styles and hazards. Primary objectives include: 1) establishing age ranges and systematic age progressions, if extant; 2) evaluating the range of eruptive styles and associated hazards; 3) determining potential relationships of eruptive activity to local tectonic features; 4) constraining the nature (lithospheric vs. asthenospheric), location (depth), and spatial heterogeneity of the mantle sources tapped in the eruptions; 5) assessing the relative importance of mantle versus crustal control on magma composition and eruptive style, and the influence of magmatic water content; and 6) constraining timescales and the importance of magma storage systems in ascent from source to surface. Our integrated approach will involve detailed field mapping, 40Ar/39Ar dating, textural analysis of eruptive products, and elemental and isotopic analyses at both the whole-rock and mineral scales.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.