Dynamics of crystal mush: Insight from 2D and 3D analysis of drill cores from Kilauea Iki lava lake, Hawaii

钻探热熔岩听起来像科幻小说，但它不仅是一种清洁能源的建议来源，而且在1960年至1988年期间实际上已经进行了多次。然后夏威夷火山观测站的科学家们探测了1959年火山爆发时形成的熔岩湖。他们的目标是通过收集岩芯样本来“观察”湖水的冷却和凝固。早期的钻探岩心只采集了湖的上地壳，其中包括完全结晶的岩石和晶体“糊状物”，晶体中含有高达45%的熔化物（在取芯过程中被水淬火成玻璃）。后来，在整个湖泊中钻取岩心，对上层和下层的固体地壳以及内部的淤泥进行取样。对由此产生的岩芯进行的化学分析表明，在凝固过程中，熔岩湖内的熔体、气泡和晶体在流动。了解是什么过程控制这些运动可以提高我们对火山下岩浆系统中融化、气泡和晶体如何、何时以及为何重新排列的理解。它还可能揭示气泡和晶体的运动如何为火山爆发做准备并引发火山爆发。该团队将使用X射线扫描技术来获得核心的3D图像，这些图像将显示自1959年以来玻璃加上晶体加上气泡的空间分布，作为湖泊位置和时间的函数。单个岩心图像可用于模拟控制熔体运动的特性，如熔体百分比、连通性和渗透率。通过空间和时间跟踪这些过程不仅可以提供前所未有的火山研究，还有助于未来的钻探工作。世纪以来，（1）岩浆系统中的熔体演化和（2）可喷发（富含熔体）岩浆体形成的概念模型都是围绕大型、长寿、熔体主导的岩浆房的概念构建的。然而，地球物理成像和岩浆系统的岩石学分析表明，他们占主导地位的结晶岩，含有熔体透镜体。这两个观点的调和是关键，以提高我们的岩浆系统，饲料火山爆发的理解，并需要更好地了解控制的物理过程，和化学后果，熔体，晶体和挥发物的再分配mush为主的系统。该项目将通过对夏威夷凝固的基拉韦厄伊基熔岩湖钻探获得的一套岩心进行µCT扫描来解决这个问题。在1960年至1988年期间收集的18个岩心包括高达45%的熔体（现在是玻璃）样本，跟踪冷却地壳的初始生长，后来横切上地壳和下地壳以及中间的晶体泥。对岩芯的岩石学研究记录了湖中熔体、晶体和气泡的复杂多样的运动。新的3D数据将用于绘制晶体糊在空间和时间上的物理特性。额外的2D分析将检查熔体和晶体分布的化学后果，特别是寻找与不同类型的熔体通道相关的反应性流动的证据。伴随的2D模拟实验和建模将跟踪颗粒-颗粒相互作用时，气体通过粘性液体+光弹性固体颗粒悬浮液流动。综合工作的结果将提高对熔岩湖（和岩床）凝固的理解，并有助于解释部分熔融系统的地球物理信号。钻探火山的想法也抓住了公众的想象力，并在开发“清洁”热液能源方面有实际应用。研究人员将在史密森学会的虚拟展览中开发这些主题，主题是钻探热熔岩。该奖项反映了NSF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。

Drilling hot lava sounds like science fiction, but it is not only a suggested source of clean energy but was actually done multiple times between 1960 and 1988. Then scientists at the Hawaiian Volcano Observatory probed a lava lake that formed during an eruption in 1959. The goal was to ‘watch’ the lake cool and solidify by collecting drill core samples. Early drill cores sampled only the upper crust of the lake, which comprised both fully crystalline rock and crystal ‘mush’ comprising crystals with up to 45% melt (quenched to glass by water during coring). Later cores were drilled through the entire lake, sampling both upper and lower solid crust as well as interior mush. Chemical analysis of the resulting drill cores showed that during solidification, melt, bubbles and crystals were moving around within the lava lake. Knowing what processes control those movements could improve our understanding of how, when and why melt, bubbles and crystals are rearranged in magmatic systems under volcanoes. It may also reveal how the movement of bubbles and crystals prepare for and trigger volcanic eruptions. The team will use x-ray scanning technology to get 3D images of the cores that will show the spatial distribution of glass plus crystals plus bubbles as a function of position in the lake and time since 1959. Individual core images can be used to model properties - such as melt percentage, connectivity and permeability - that control melt movement. Tracking these processes through space and time will not only provide an unprecedented look into a volcano but also aid future drilling efforts. For a century, conceptual models of (1) melt evolution in magmatic systems and (2) formation of eruptible (melt-rich) magma bodies were framed around the concept of large, long-lived, melt-dominated magma chambers. However, both geophysical imaging and petrologic analysis of magmatic systems suggest that they dominated by crystal ʻmushʻ that contains lenses of melt. Reconciliation of these two perspectives is key to improving our understanding of the magma systems that feed volcanic eruptions and requires improved understanding of the physical processes that control, and the chemical consequences of, redistribution of melt, crystals and volatiles within mush-dominated systems. This project will address this problem using µCT scans of a suite of cores obtained by drilling into the solidifying Kilauea Iki lava lake, Hawaii. 18 cores collected between 1960 and 1988 include samples with up to 45% melt (now glass), track the initial growth of a cooling crust and later transected both the upper and lower crust as well as intervening crystal mush. Petrologic studies of the cores have documented complex and diverse movements of melt, crystals and bubbles within the lake. New 3D data will be used to map the physical properties of crystal mush in space and time. Additional 2D analysis will examine the chemical consequences of melt and crystal distribution and, specifically, look for evidence of reactive flow associated with different types of melt channels. Accompanying 2D analog experiments and modeling will track particle-particle interactions when gas is fluxed through suspensions of viscous liquid + photoelastic solid particles. The results of the combined work will improve understanding of lava lake (and sill) solidification and aid interpretation of geophysical signals from partially molten systems. The idea of drilling into volcanoes also captures the public imagination and has practical applications to the development of “clean” hydrothermal energy. The researchers will develop these themes in a virtual exhibit for the Smithsonian Institution on the topic of Drilling Hot Lava.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.