Melt segregation in a deforming partially molten rock - an experimental investigation of the consequences of viscous anisotropy

在变形的部分熔岩中熔化分离？从固体颗粒加1%或2%的熔体组成的地幔岩石中提取熔体的粘性各向异性后果的实验研究？S地表岩浆喷发。这个过程控制着我们星球的化学和物理演化。由于在很深的地方发生的过程不能直接观察到，我们对地球部分熔融区域的动力学的理解很大程度上依赖于对部分熔融岩石行为的数值/计算机模型。在坚硬但可变形的岩石中建立机械弱熔体模型的起点被称为两相流理论。将这一理论应用于发生在地球深处的大规模过程？S地表需要描述熔体流经岩石的粘度(强度)和速率的方程。用来描述地幔中变形、熔体分布和熔体迁移相互作用的模型的有效性的一个重要检验是它们解释在部分熔岩的实验室实验中观察到的现象的能力。描述部分熔岩动力学的理论在2009年发表了三篇基础论文，这是一个根本性的突破。这些论文探讨了变形过程中各向异性粘度(即岩石强度的方向依赖性)对熔体分布的影响。它假设粘度(强度)应该是各向异性的，因为熔体的口袋在变形时会排列成一条直线。基于这种各向异性的颗粒尺度熔体分布，预测在变形岩石中应该会形成富熔体带，这与以前的实验观察一致。这一分析还预测，固体和熔体应该从低应力区域分离到高应力区域。事实上，我们最近的实验在我们实验室的部分熔融样品中证明了这种行为。我们研究的一个关键方面是与牛津大学(计算机模型)和东京大学(理论)的科学家进行协同合作。通过我们的合作，基于两相流理论的模型将与实验观测结果进行验证，以促进我们对地球上熔体如何在地幔中流动的理解--S地幔。虽然理论和实验之间的一致性显然很重要，但差异代表着改进理论的一条途径。理论预测和实验观测之间的差异为我们提供了一个机会来加深我们对部分熔融岩石的颗粒尺度力学的理解。因此，设计良好的实验，对熔体分布、熔体偏析和机械性能进行详细分析是至关重要的。这项研究的一个独特方面是我们参与了STEM在墨西哥的外联活动-Clubs de Ciencia México？，这是一个为墨西哥高中生和本科生提供科学外联和指导的组织。科学俱乐部是为期一周的互动性很强的研讨会，旨在引导学生进行科学和研究；特别关注科学推理和伦理。最近的一个研讨会？岩石是如何流动的？？说明了了解我们星球的实验研究的必要性？S的演化。将通过一个网站和外联讲习班继续进行宣传，利用我们目前的实验调查来解释实验研究对了解我们星球的大规模动态的影响。

Melt segregation in a deforming partially molten rock ? An experimental investigation of the consequences of viscous anisotropy Kohlstedt - Extraction of melt from mantle rocks composed of solid grains plus 1 or 2% melt results in eruption of magma at Earth?s surface. This process controls the chemical and physical evolution of our planet. Since processes occurring at great depths are not directly observable, much of our understanding of the dynamics of partially molten regions of Earth?s interior relies on numerical/computer models of the behavior of partially molten rocks. The starting point for models of a mechanically weak melt in a strong but deformable rock is known as two-phase flow theory. Application of this theory to large-scale processes occurring far below Earth?s surface requires equations describing the viscosity (strength) and the rate at which melt flows through a rock. An important test of the validity of models used to describe the interactions of deformation, melt distribution, and melt migration in the mantle is their ability to explain phenomena observed in laboratory experiments on partially molten rocks.A fundamental breakthrough in the theory describing the dynamics of partially molten rocks occurred with the publication of three fundamental papers in 2009. These papers explored the implications of anisotropic viscosity (i.e., the directional dependence of the strength of a rock) on melt distribution during deformation. It was hypothesized that viscosity (strength) should be anisotropic because pockets of melt become aligned during deformation. Based on this anisotropic grain-scale melt distribution, it was predicted that melt-rich bands should develop in deforming rocks, consistent with previously experimental observations. This analysis also predicted that solid and melt should segregate from regions of low stress to regions of high stress. Our recent experiments, in fact, demonstrated this behavior in partially molten samples deformed in torsion in our laboratory. A key aspect of our research is a synergistic collaboration with scientists at the University of Oxford (computer models) and Tokyo (theory). Through our cooperative efforts, models based on two-phase flow theory will be tested against experimental observations in order to advance our understanding of how melt flows in Earth?s mantle. While agreement between theory and experiment is clearly important, discrepancies represent an avenue for progress in refining theory. Discrepancies between theoretical prediction and experimental observation represent an opportunity to refine our understanding of the grain-scale mechanics of partially molten rocks. Thus, well-designed experiments with detailed analysis of melt distribution, melt segregation, and mechanical properties are essential. A unique aspect of this research is our involvement in STEM outreach in Mexico though ?Clubes de ciencia México?, an organization of science outreach and mentoring for high school and undergraduate students in Mexico. The science clubs are one-week long, very interactive workshops designed to initiate students to science and research; special focus is given to scientific reasoning and ethics. A recent workshop on ?How do rocks flow?? illustrated the necessity of experimental studies for understanding our planet?s evolution. Outreach will continue through a website and outreach workshops, using our current experimental investigations to explain the implications of experimental research for understanding large-scale dynamics of our planet.