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

地质记录中记录的最危险的喷发与岩浆系统有关，这些岩浆系统将大量富含二氧化硅的岩浆爆炸性地喷入大气中。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大量低晶体含量的岩浆在地壳浅层就位并在喷发前演化的机制。该项目旨在结合对类似物和天然样品的实验室实验，并开发物理模型，以限制允许这些系统发展的物理学以及系统易受大规模火山爆发影响所需的速率（或时间尺度）。从结晶残留物中分离出的熔融物对长期的火山灾害有影响。一名研究生的研究将得到资助，并与麻省理工学院的一个实验室建立合作。理解粘性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）发生熔体提取的大晶体分数（1和2意味着熔体萃取应该是缓慢的并且可能是低效的过程）和（3）在许多情况下存在影响熔体-晶体分离的溶出挥发相。理解和量化晶体浆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条件下（来自岩石记录的实验或明确的线索）。将执行新的压密型压实实验，其中可以随时间测量间隙液提取，并与残留固体部分的填充变化相关。这些实验将涵盖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（糊状物重组而不是颗粒变形）如何影响熔体提取。从挖掘出来的岩体中提取的样品将用于限制熔体提取过程如何在实验室中进行研究，并从理论上推断自然界。该奖项反映了NSF的法定使命，并被认为是值得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的支持。

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.