NSFGEO-NERC Quantifying disequilibrium processes in basaltic volcanism (DisEqm)

虽然大多数玄武岩喷发会喷出熔岩，但它们也可能是爆炸性的。了解控制喷发方式的因素将有助于更好地评估危害，例如对航空（爆炸性火山灰）和火山周围环境（喷涌物）的危害。以前关于爆炸性喷发与喷涌式喷发控制的大多数研究都假设，当熔岩从地球深处传播时，晶体和气体与熔岩处于平衡状态。然而，这种假设是错误的，因为晶体和气泡生长得如此之快，以至于它们通常会失去平衡。一种新的x射线成像技术将用于测量真实喷发条件下晶体和气泡的成分和生长速率。该项目涉及一个国际调查小组，每个人将处理这个综合项目的不同部分。美国调查人员将把实验结果整合到计算模型中，以评估岩浆在喷发时是如何碎裂的，以及火山灰是如何在大气中传播的。美国国家科学基金会正在为美国研究人员提供资金，他们是一个国际小组的成员，将评估玄武岩喷发期间不平衡过程的重要性。x射线断层扫描将使用金刚石光源同步加速器对天然岩浆进行减压和冷却。这些测量将在接近自然喷发的条件下量化晶体、气体和熔体相的生长速率、分布和组成。美国研究人员的任务是将这些参数整合到模拟岩浆通过喷发管道输送的计算代码中。真正新颖的方面是，以前的模型假设阶段之间的平衡，但作为该项目一部分的测量将提供必要的参数来模拟非平衡气泡和晶体生长。然后，导管模型将与大气喷发柱模型耦合。这些模型预测了喷发产物的结构和模态含量，以及矿床的分布，允许对数值模型进行现场测试。

Although most basaltic eruptions erupt lava, they can also be explosive. An understanding of what controls the eruptive style will lead to better assessment of hazards, such as those to aviation (explosive ash) and to the environment around the volcano (effusive). Most previous work on the controls of explosive versus effusive eruption assumed that crystals and gas are in equilibrium with the melt as it travels from deep within the Earth. This assumption is faulty, however, because crystals and bubbles grow so fast that they are commonly out of equilibrium. A novel x-ray imaging technique will be used to measure the compositions and growth rates of crystals and bubbles under realistic eruption conditions. The project involves an international team of investigators, each of whom will tackle a different part of this integrative project. The United States investigators will integrate the experimental results into computational models to assess how the magma fragments as it is erupting and how ash is transported in the atmosphere.NSF funding is being provided to U.S. investigators who are part of an international team that will assess the importance of disequilibrium processes during basaltic eruptions. X-ray tomography will be performed on decompressing and cooling natural magmas using a diamond light source synchrotron. These measurements will quantify the growth rates, distribution, and compositions of crystal, gas, and melt phases under conditions that are close to those of a natural eruption. The role of the U.S. investigator is to incorporate these parameters into a computational code that simulates magma transport through an eruptive conduit. The truly novel aspect is that previous models assume equilibrium between the phases, but the measurements made as part of this project will provide the necessary parameters to model disequilibrium bubble and crystal growth. The conduit model will then be coupled to a model of an atmospheric eruptive column. These models predict textures and modal contents of the eruptive products, as well as the deposits' distributions, permitting field tests of the numerical models.