Collaborative Research: Modes of melt extraction in silicic mushes: processes, efficiency and timescales

地质记录中捕捉到的最危险的喷发与岩浆系统有关，这些岩浆系统喷发出大量富含二氧化硅的岩浆，向大气中爆炸。这种喷发的沉积物通常在化学和物理属性方面都有很好的特征，但岩石学家尚未完全了解这些低晶体含量的大量岩浆在地壳浅层侵位并在喷发前演化的机制。该项目旨在结合实验室对模拟样品和自然样品的实验，并开发物理模型，以限制允许这些系统随其演变的物理条件，以及系统容易发生大规模火山喷发所需的速率(或时间尺度)。熔体与结晶残留物的分离对火山的长期危害具有重要意义。一名研究生的研究将得到资助，并与麻省理工学院建立的一个实验实验室合作。要了解粘性硅熔体如何从它们的结晶货物中分离出来的挑战来自(1)这些相之间的密度上的微小差异，(2)发生熔体提取的大晶体分数(1和2意味着熔体提取过程应该是缓慢的，可能是低效的)和(3)在许多情况下存在被释放的挥发相影响熔体晶体分离。了解和量化晶体泥中相分离的效率取决于了解多相岩浆的流变学，特别是在信息非常有限的条件下(来自岩石记录的实验或明确线索)。将进行新的注射器式压实实验，其中间质流体的提取可以随着时间的推移进行测量，并与残留固体分数的填充变化相关联。这些实验将跨越不同的颗粒尺寸和形状分布，并将与2相和3相压实的数值模拟相结合，以了解重新填充(颗粒的混杂重组而不是变形)如何影响熔体提取。挖掘出的钚的样本将被用来限制实验室中研究熔体提取过程的方式，并从理论上推断自然。这一裁决反映了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。

The most dangerous eruptions captured in the geologic record are related to magmatic systems that erupt large volume of silica-rich magmas explosively into the atmosphere. The deposits of such eruptions are generally well-characterized both chemically and in terms of their physical attributes, however petrologists have yet to fully understand the mechanisms by which these large volume of magma with low crystal content emplace at shallow level in the crust and evolve prior to an eruption. This project aims at combining laboratory experiments on analogs as well as natural samples and developing physical models to constrain the physics that allows for these systems to evolve as they do and the rates (or timescales) required for a system to be susceptible for a large volcanic eruption. The separation of melt from a crystalline residue has implications for long-term volcanic hazards. The research of a graduate student will be funded and collaboration with an experimental laboratory at MIT established.The challenge to understand how viscous silicic melts separate from their crystal cargo comes from (1) the small discrepancy in density between these phases, (2) the large crystal fraction at which melt extraction is occurring (1 and 2 imply that melt extraction should be sluggish and likely inefficient process) and (3) the presence in many cases of an exsolved volatile phase impacting melt-crystal separation. Understanding and quantifying the efficiency of phase separation in crystal mushes is contingent upon understanding the rheology of multiphase magmas specifically over conditions where information is very limited (experimental or unambiguous clues from the rock record). Novel syringe-type compaction experiments will be executed, where interstitial fluid extraction can be measured over time and correlated with changes in packing for the residual solid fraction. These experiments will span various size and shape distributions for particles and will be coupled to numerical simulations of 2 and 3 phase compaction to understand how repacking (mush reorganization rather than deformation of particles) impacts melt extraction. Samples from exhumed plutons will be used to constrain how melt extraction processes studied in the lab and theoretically extrapolate to nature.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.