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

地质记录中记录到的最危险的喷发与岩浆系统有关，它们将大量富含硅的岩浆爆炸性地喷发到大气中。这些火山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，然而，岩石学家还没有完全了解这些大量低晶含量的岩浆在地壳浅层沉积并在火山喷发前演化的机制。该项目旨在结合模拟物和自然样本的实验室实验，并开发物理模型，以约束允许这些系统进化的物理特性，以及系统容易受到大型火山爆发影响所需的速率（或时间尺度）。熔体与结晶残留物的分离意味着长期的火山危险。研究生的研究将得到资助，并与麻省理工学院的一个实验实验室合作建立。了解粘性硅熔体如何从其晶体货物中分离的挑战来自(1)这些相之间的密度差异很小，(2)熔体萃取发生时的大晶体分数（1和2意味着熔体萃取应该是缓慢且可能效率低下的过程）以及(3)在许多情况下存在影响熔体-晶体分离的挥发相。理解和量化晶体中相分离的效率取决于对多相岩浆流变学的理解，特别是在信息非常有限的情况下（实验或来自岩石记录的明确线索）。新型注射器型压实实验将被执行，其中可以随时间测量间隙流体萃取，并与残余固体组分的填充物变化相关。这些实验将跨越颗粒的各种尺寸和形状分布，并将与2相和3相压实的数值模拟相结合，以了解重新包装（糊状重组而不是颗粒变形）如何影响熔体提取。从挖掘出的钚中提取的样本将用于约束实验室研究的熔体提取过程，并从理论上推断出自然界。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。

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.