Collaborative Research: Reconstructing the geometry of magmatic plumbing systems using fluid inclusions

合作研究：利用流体包裹体重建岩浆管道系统的几何形状

• 批准号: 2217371
• 负责人: Penelope Wieser
• 金额: $ 31.1万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-09-01 至 2025-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2217371&HistoricalAwards=false
• 关键词: Collaborative; Research; Reconstructing; geometry; magmatic

Constraining the depth at which magma feeding volcanic eruptions is stored in the crust is critical both for volcano monitoring agencies to interpret unrest signals during volcanic crises, and for our understanding of the formation of energy-critical metal deposits and the evolution of the Earth’s crust. However, popular techniques using earthquakes and ground deformation to obtain storage depths cannot be used at many potentially hazardous volcanoes which show little activity at present, or have limited monitoring networks. More widely applicable methods which measure the chemistry of erupted crystals are associated with large uncertainty. This team will investigate a powerful but under-used approach in volcanology, by measuring the densities of pockets of gas-rich fluids trapped within growing crystals, known as fluid inclusions (FI). This method has the potential to be significantly more precise and accurate, placing very tight constraints on where magma is stored in the crust. After investigating the strengths and weaknesses of depths from FIs using eruptions from Hawai’i and Canary Islands as a case study (where storage depths have been determined by other methods), magma storage depths will be investigated in a series of explosive eruptions that occurred several centuries ago at both locations where future eruptions of this type present a significant hazard. A rapid response simulation will be carried out in collaboration with Hawaiian Volcano Observatory (HVO) to determine just how quickly estimates of magma storage depths can be obtained during the next large eruptive crisis, and how this information can be used to inform decision making to mitigate societal risk. This proposal will foster close collaborations between three PIs with complimentary scientific expertise at different career levels, and support several students and a postdoc in a multi-tiered mentoring structure spanning three institutions. The team will develop and distribute synthetic and natural fluid inclusions to be used as calibration standards, and a workshop will promote collaboration and synergy between different research groups using Raman spectroscopy.This award will capitalize on recent advances in the spectral and spatial resolution of confocal Raman spectroscopy, allowing highly precise and accurate measurements of the densities of CO2-rich fluids trapped within fluid inclusions down to ~ 1 µm in size. The simple physical relationship between the density and pressure of a CO2-rich fluid means that distributions of FI densities can be converted into magma storage pressures with very small errors (~5-10%), and then magma storage depths using known crustal density profiles. First, detailed comparisons of depths obtained from FIs will be compared to published work investigating melt inclusion saturation pressures in samples from Kīlauea Volcano, Hawai’i, and Timanfaya, Canary Islands. This will permit assessment of sources of uncertainty affecting FI barometry such as decrepitation (when the inclusion explodes) using high-resolution electron backscatter diffraction (HR-EBSD), and the presence of additional volatile species (e.g., S, Cl, H) using synthetic FIs equilibrated with different fluid compositions. After determining the strengths and weaknesses of fluid inclusion barometry, new constraints will be placed on changes in magmatic plumbing during explosive to effusive transitions at Kīlauea Volcano (a significant societal hazard), evolution from shield to post-shield in the Galápagos, and from unknown samples during an eruption simulation in collaboration with HVO. Synthetic FIs with different concentrations of CO2 will be synthesized and characterized with an experimentally calibrated Raman system to distribute to laboratories around the world to use as standard reference materials for calibration of Raman Spectrometers. This will eliminate systematic offsets between densities determined in different laboratories.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.

限制火山喷发岩浆在地壳中储存的深度，对于火山监测机构解释火山危机期间的动荡信号，以及我们对能量关键金属矿床的形成和地壳演化的理解都至关重要。然而，利用地震和地面变形来获得储存深度的流行技术不能用于许多潜在的危险火山，这些火山目前几乎没有活动，或者监测网络有限。更广泛应用的测量爆发晶体化学性质的方法具有很大的不确定性。这个团队将通过测量被困在生长晶体中的富含气体的流体口袋的密度，来研究火山学中一种强大但未被充分利用的方法，这种方法被称为流体包裹体（FI）。这种方法有可能更加精确和准确，对岩浆在地壳中的储存位置施加非常严格的限制。在以夏威夷和加那利群岛的喷发为例研究了岩浆储存深度的优缺点之后（储存深度是通过其他方法确定的），岩浆储存深度将在几个世纪前发生在这两个地方的一系列爆炸性喷发中进行调查，未来这种类型的喷发会带来重大危险。将与夏威夷火山观测站（HVO）合作进行快速反应模拟，以确定在下一次大爆发危机期间如何快速获得岩浆储存深度的估计，以及如何利用这些信息为决策提供信息以减轻社会风险。该提案将促进三个具有不同职业水平的互补科学专业知识的pi之间的密切合作，并在三个机构的多层次指导结构中支持几名学生和一名博士后。该团队将开发和分发用作校准标准的合成和天然流体包裹体，并举办研讨会，促进不同研究小组之间使用拉曼光谱的合作和协同作用。该奖项将利用共聚焦拉曼光谱和空间分辨率的最新进展，允许高度精确和准确地测量流体包裹体中富含二氧化碳的流体的密度，最小尺寸为~ 1 μ m。富二氧化碳流体的密度和压力之间的简单物理关系意味着，FI密度分布可以以很小的误差（~5-10%）转换成岩浆储存压力，然后利用已知的地壳密度剖面计算岩浆储存深度。首先，从FIs获得的深度的详细比较将与已发表的研究夏威夷k<e:1>劳厄火山和加那利群岛提曼法亚样品中熔体包裹体饱和压力的工作进行比较。这将允许评估影响FI气压计的不确定性来源，例如使用高分辨率电子背散射衍射（HR-EBSD）来评估老化（当包裹体爆炸时），以及使用不同流体成分平衡的合成FI来评估额外挥发性物质（例如S， Cl， H）的存在。在确定流体包裹体气压测定法的优缺点后，将对k<e:1>劳埃亚火山爆发到喷涌过渡期间岩浆管道的变化（一个重大的社会危害）、Galápagos从屏蔽层到后屏蔽层的演变以及与HVO合作进行的喷发模拟期间未知样本的变化施加新的限制。不同CO2浓度的合成fi将通过实验校准的拉曼系统进行合成和表征，并分发给世界各地的实验室，作为拉曼光谱仪校准的标准参考物质。这将消除在不同实验室测定的密度之间的系统偏移。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。