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

合作研究：部分熔融岩石中反应熔体通道化的实验研究

• 批准号: 1459717
• 负责人: David Kohlstedt
• 金额: $ 32.95万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-15 至 2019-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1459717&HistoricalAwards=false
• 关键词: Collaborative; Research; Experimental; Investigation; Reactive

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.

融化发生在板块构造边界地带以及火山热点地区，如夏威夷和冰岛。迁移的熔体和周围岩石之间的物理和化学相互作用决定了行星如何随时间演变。然而，地球深处形成的熔体向上迁移到地表，要么喷发，要么在地壳岩浆库中缓慢冷却的方式尚不清楚。地质学家想知道，行星的整体组成是如何演变成地壳岩石的，而地壳岩石的矿物学特征与下面的地幔岩石截然不同。这些信息巩固了关于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与知名专家合作实施新的实验室技术为特色，首先，这些技术应该产生与难以接近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，并向学生介绍一些技术，使研究系统的物理和化学之间存在反馈的复杂过程成为可能。熔体的提取影响了地幔、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，熔体必须分离成高渗透率的通道。这些通道必须足够隔离，以保持化学不平衡，并具有足够的渗透性，以允许快速提取熔体，以保持放射性不平衡。在自然界中，熔体偏析是由于反应和变形之间的相互作用而发生的。实验研究提供了对熔体迁移过程的关键见解，并激发了进一步的理论发展。最近发展的一种实验方法再现了反应渗透不稳定性。由于孔隙压力梯度可以在这些实验中控制，因此可以独立控制熔体速度和熔体-固体反应性。因此，随着反应改变岩石微观结构，渗透率随时间的演变可以被探索，熔体通量的增加由于通道化可以被量化，熔体迁移机制可以被记录为物理和化学驱动力的函数。第一组实验将在高温高压下对橄榄石与斜辉石和正辉石的双组分样品进行实验。第二套将橄榄石和两种辉石结合在一个样品中。这项研究还将开发新的方法来分析所得的微观结构和测试/改进参数，以便将实验室数据缩放到自然环境中。