Collaborative Research: Bubble Trouble - Re-evaluating olivine melt inclusion barometry and trace-element geochemistry in the Cascades

确定熔岩(岩浆)在地壳中储存和处理的深度对于解释导致喷发的火山动荡以及了解地球大陆的化学演化至关重要。尽管它们很重要，但向地表供应岩浆的区域的结构和运作仍然知之甚少。例如，目前尚不确定岩浆是分布在横跨整个地壳的“混泥带”，还是储存在不同的“岩浆室”中。该项目将重新评估喀斯喀特火山系统中的岩浆储存深度和化学变异性的来源，这种方法利用了被困在喷发的晶体中的小块岩浆，称为熔融包裹体。至关重要的是，除了周围的熔体外，还将直接测量这些熔体包裹体内小气泡的二氧化碳含量。该项目将有助于科学了解喀斯喀特弧线上的火山活动，该火山活动对社会构成重大危害。它还将促进两个早期职业PI、两个研究生和多个本科生之间的密切合作和多层次、点对点的指导结构。这笔赠款还将支持残疾科学家的指导计划和一个虚拟论坛，供患有慢性病和隐形残疾的学者分享他们关于适应野外工作、会议和工作室的故事。橄榄石承载的熔体包裹体的挥发性成分对喀斯喀特火山喷发的镁铁质岩浆喷发的深度提供了重要的限制。然而，绝大多数(97%，N=410)之前发表的来自级联的橄榄石寄主熔体包裹体数据没有测量到蒸汽泡中的二氧化碳(S)。对N=339级联汽泡的初步拉曼分析表明，如果没有这些测量，存储深度被低估了2-5X倍。测量熔体包裹体挥发分含量，同时考虑蒸汽泡中的二氧化碳和碳酸盐(使用现场加热实验)，将更好地约束瀑布不同区域的岩浆存储深度，并提供对存储深度沿走向的任何变化的洞察(可能是由于熔体H2O含量、地壳应力状态或岩浆流量速率)。虽然全岩微量元素分析通常用于评估地壳和地幔中的岩浆作用，但全岩样品通常是在很大范围内未知深度上组装和修改的材料的融合。对已知捕获深度的熔体包裹体进行微量元素测量，将更好地限制影响液体成分的同化和混合过程，并可以揭示这些过程在地壳中发生的位置。来自相同样品的等量橄榄石的同位素数据将进一步限制地壳物质对最镁铁组分的贡献程度。总而言之，这些数据将为大陆弧岩浆丰度标志的起源提供独特的见解。这项研究还将评估地幔熔融条件、导致镁铁质岩浆在地壳中失速的过程，以及与世界各地熔体包裹体研究相关的其他主题(例如，确定在蒸汽泡中形成碳酸盐的过程和测试气泡生长模型)。研究生和本科生将获得各种实际操作的地球化学技术、数据解释、编码和软件开发方面的技能。学生们将通过前往不同的实验室，与学术和政府机构的合作者互动，并在专业会议上展示他们的发现来建立网络。这笔赠款还将支持开发和改进开源软件工具，帮助火山学社区转向可查找、可访问、可互操作和可重复使用(公平)的数据处理和建模工作流程。PIS还将协调一个由小组成员组成的虚拟论坛和一个问答活动，与更广泛的受众分享隐形残疾人士的声音和经验，重点放在实验室和现场工作上。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Determining the depths at which molten rock (magma) is stored and processed in the crust is vital for interpretations of volcanic unrest in the lead up to eruptions and for understanding of the chemical evolution of the Earth’s continents. Despite their importance, the structure and operation of the regions which supply magma to the surface remain poorly understood. It is currently uncertain, for example, whether magma is distributed across “mush zones” spanning the entire crust or stored in distinct “magma chambers”. This project will re-evaluate magma storage depths and the origin of chemical variability in volcanic systems in the Cascades using an approach that makes use of small pockets of magma trapped within erupted crystals, termed melt inclusions. Crucially, the CO2 contents of small bubbles within these melt inclusions will be measured directly, in addition to the surrounding melt. This project will contribute to the scientific understanding of volcanism along the Cascade arc, which presents a significant hazard to society. It will also foster close collaborations and a multi-tiered, peer-to-peer mentoring structure between two early career PIs, two graduate students, and multiple undergraduate students. The grant will also support a mentoring program for scientists with disabilities and a virtual forum for academics with chronic illnesses and invisible disabilities to share their stories about adapting to fieldwork, conferences, and workshops.The volatile contents of olivine-hosted melt inclusions provide important constraints on the depths at which mafic magmas erupting in the Cascades were stored and staged prior to eruption. However, the vast majority (97%, N=410) of previously published olivine-hosted melt inclusion data from the Cascades did not measure CO2 in vapor bubble(s). Preliminary Raman analyses of N=339 Cascade vapor bubbles indicates that without these measurements, storage depths have been underestimated by factors of 2-5X. Measuring melt inclusion volatile contents while accounting for CO2 and carbonate in the vapor bubble (using in situ heating experiments) will better constrain magma storage depths in different regions of the Cascades and provide insights into any variations in storage depth along strike (perhaps due to melt H2O contents, crustal stress state, or magma flux rate). While whole-rock trace element analyses are commonly used to assess magmatic processes in both the crust and mantle, whole-rock samples are generally an amalgamation of materials assembled and modified over a great range of unknown depths. Trace element measurements from melt inclusions with known entrapment depths will better constrain assimilation and mixing processes affecting liquid compositions and can reveal where in the crust these processes occur. He isotope data from aliquots of olivine from the same samples will further constrain the extent to which crustal materials have contributed to the most mafic components. Together, these data will provide unique insights into the origins of enriched signatured of continental arc magmas. This study will also assess mantle melting conditions, the processes causing mafic magmas to stall in the crust, and other topics relevant for melt inclusion studies worldwide (e.g., identifying processes forming carbonate in vapor bubbles and testing bubble growth models). Graduate and undergraduate students will acquire skills in a wide variety of hands-on geochemical techniques, data interpretation, coding, and software development. Students will build networks by travelling to different laboratories, interacting with collaborators at academic and government institutions, and presenting their findings at professional conferences. The grant will also support the development and improvement of open-source software tools, helping the volcanological community move to data processing and modelling workflows which are findable, accessible, interoperable, and reusable (FAIR). The PIs will also co-ordinate a virtual forum with panelists and a Q&A to share the voices and experiences of individuals with invisible disabilities with a broader audience, with a focus on laboratory and field work.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.