Collaborative Research: An Experimental Investigation of Reactive Melt Channelization in Partially Molten Rocks

熔融发生在板块构造边界地带以及夏威夷和冰岛等火山热点地区的下方。迁移中的熔体和周围岩石之间的物理和化学作用决定了行星如何随着时间的推移而演化。然而，地球深处形成的熔体向上迁移到地表，在地壳岩浆室中喷发或缓慢冷却的方式还没有被很好地理解。地质学家想知道大量的行星组成是如何演化而产生的地壳岩石，这些岩石的矿物学与下面的地幔岩石有着根本的不同。这些信息支撑了有关地球内部和表面之间化学交换程度的知识。这项研究将以一位早期职业科学家为特色，与老牌专家合作，实施新的实验室技术，第一次，应该会产生与难以进入的自然系统相关的结果。随着实验程序的完善，新的本科生实验练习将被开发出来。他们将使用玻璃珠和盐，并向学生介绍使研究复杂过程成为可能的技术，在这些过程中，系统的物理和化学之间存在反馈。熔体提取影响地幔、地壳和大气之间的大部分化学交换。地球化学、地球物理和地质证据表明，在熔体提取的某个阶段，熔体必须分离到高渗透性通道中。这些通道必须足够隔离，以保持化学不平衡和足够的渗透性，以允许快速熔融提取，以保持辐射成因的不平衡。在自然界中，熔体分离是由于反应和变形之间的相互作用而推断出来的。实验研究提供了对熔体迁移过程的关键见解，并推动了进一步的理论发展。最近开发的一种实验方法重现了反应渗透不稳定性。由于在这些实验中可以控制孔隙压力的梯度，因此有可能独立地控制熔体速度和熔体-固体反应性。因此，当反应改变岩石微结构时，渗透率随时间的演变可以被探索，由于沟道化而导致的熔体流量的增加可以被量化，熔体的迁移状态可以作为物理和化学驱动力的函数被记录下来。第一组实验将在高温高压下橄榄石与单斜辉石和斜辉石的双组分样品上进行。第二组将在一个样品中将橄榄石和两种辉石结合起来。这项研究还将开发新的方法来分析由此产生的微结构和测试/改进参数，以便将实验室数据与自然环境进行比对。

Melting occurs beneath the plate tectonic boundary zones as well as volcanic hotspots, such as Hawaii and Iceland. The physical and chemical interactions between the migrating melt and the surrounding rock determine how planets evolve over time. However, the means by which melt formed deep in the Earth migrates upward to the surface to either erupt or cool slowly in a crustal magma chamber are not well understood. Geologists want to know how bulk planetary composition evolves to produce crustal rocks that have fundamentally different mineralogy than the underlying mantle rock. Such information underpins knowledge about the extent of chemical exchange between the Earth's interior and surface. This study will feature an early career scientist working with established experts to implement new laboratory techniques that, for the first, should produce results that can be related to the inaccessible natural system. As the experimental procedures are honed, new undergraduate lab exercises will be developed. They will employ glass beads and salt and introduce students to techniques that make is possible to investigate complex processes where there are feedbacks between the physics and chemistry of the system.Melt extraction affects much of the chemical exchange between mantle, crust and the atmosphere. Geochemical, geophysical and geological evidence suggests that, at some stage of melt extraction, melt must segregate into high permeability channels. These channels must be isolated enough to preserve chemical disequilibrium and permeable enough to allow fast melt extraction in order to preserve radiogenic disequilibrium. In nature, melt segregation is inferred to occur due to an interplay between reaction and deformation. Experimental investigations provide key insights into the processes occurring during melt migration and motivate further theoretical developments. A recently developed experimental methodology has reproduced the reaction infiltration instability. Since the gradient in pore pressure can be controlled in these experiments, it is possible to independently control melt velocity and melt-solid reactivity. Thus, the evolution of permeability with time can be explored as the reaction modifies the rock microstructure, the increase in melt flux due to channelization can be quantified, and melt migration regimes can be documented as a function of physical and chemical driving forces. A first set of experiments will be conducted on dual composition samples of olivine with clinopyroxene, and with orthopyroxene at high temperature and pressure. A second set will combine olivine with both pyroxenes in a single sample. This study will also develop new methods for analyzing the resulting microstructures and test/refine parameters that allow for scaling of laboratory data to natural environments.