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，但这不仅是一种建议的清洁能源，而且在1960年至1988年期间实际上已经进行了多次。随后，夏威夷火山观测站的科学家探测了1959年火山喷发期间形成的熔岩湖。目的是通过收集岩心样本来“观察”湖泊的冷却和凝固。早期的岩心只取样了湖的上部地壳，其中既有完全结晶的岩石，也有高达45%熔融的晶体“糊状”（在取心过程中被水淬成玻璃）。后来的岩心钻穿了整个湖泊，采样了上部和下部的固体地壳以及内部的糊状。对钻芯的化学分析表明，在凝固、融化过程中，气泡和晶体在熔岩湖中四处移动。了解控制这些运动的过程可以提高我们对火山岩浆系统中融化、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是如何为火山爆发做准备并引发火山爆发的。该团队将使用x射线扫描技术获得岩心的3D图像，这些图像将显示玻璃、晶体和气泡的空间分布，作为1959年以来在湖中位置和时间的函数。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。通过空间和时间追踪这些过程，不仅可以让我们对火山有一个前所未有的了解，还有助于未来的钻井工作。一个世纪以来，(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着大型、长寿命、以熔体为主的岩浆房的概念建立起来的。然而，岩浆系统的地球物理成像和岩石学分析表明，它们主要是由含有熔融透镜的结晶i - mush - i构成的。这两种观点的协调是提高我们对岩浆系统的理解的关键，它为火山爆发提供了动力，需要我们更好地理解控制熔融物、晶体和挥发物在以糊状为主的系统中重新分配的物理过程及其化学后果。该项目将利用微CT扫描夏威夷基拉韦厄伊基熔岩湖（Kilauea Iki lava lake）的一套岩心来解决这个问题。1960年至1988年间收集的18个岩心包括高达45%熔融（现在是玻璃）的样本，跟踪冷却地壳的初始生长，随后对上下地壳以及中间的晶体糊状物进行了截切。岩心的岩石学研究记录了湖中复杂多样的熔体、晶体和气泡运动。新的3D数据将用于绘制晶体糊状物在空间和时间上的物理性质。额外的二维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流动的证据。伴随的二维模拟实验和建模将跟踪气体通过黏性液体+光弹性固体颗粒悬浮液流动时粒子-粒子之间的相互作用。联合工作的结果将提高对熔岩湖（和still）凝固的理解，并有助于解释部分熔融系统的地球物理信号。钻入火山的想法也吸引了公众的想象力，并在开发“清洁”热液能源方面具有实际应用。研究人员将在史密森学会关于钻探热熔岩主题的虚拟展览中发展这些主题。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。

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.