Effect of Partial Melting on Elastic Properties of Rocks at Mantle Conditions

地球内部的温度高到足以融化岩石，火山和火山岩就是证据。因此，地壳和地幔的部分部分可能是熔融的，尽管它们主要是固态的。本建议的目的是提高对部分熔融状态与介质弹性性能变化之间关系的理解。焦点将是地球的上地幔。由于弹性特性定量地定义了地震波在介质中传播的速度，因此这项研究的结果将使地震速度变化图与部分熔化程度之间的联系更加紧密。该计划的方法是探索熔化和力学的物理和化学基础知识，从而更深入地了解其基本原理，以便提供一个强大的模型，然后可以应用于各种环境。虽然该提议的重点是地球的上地幔区域，但一个改进的模型也将与地壳相关。事实上，该结果也可以应用于在工业环境中定义这种关系，以检测各种材料熔化的初始阶段。该计划为学生提供了一个尖端的学习经验，包括研究生在准备他们的博士学位和本科生在暑期研究项目的重点。这些结果将被用于整个地球科学，作为地球内部行为的基本信息。开发的工具将提供给其他研究人员用于研究材料的强度相关特性。这些工具（软件和硬件）将立即成为压缩操作同步加速器设施的一部分，并可供所有希望使用它们的社区使用。这里开发的工具将有助于研究极端环境下的材料性能，并将有助于开发更好的工业材料。作者最近证明了目前的固体/熔体组合力学性能模型是不充分的，并提出固体和熔体之间的相互作用对弹性性能有显著影响。新模型“动态熔炼”改变了熔炼对体模量和剪切模量关系的预测影响。在动态熔炼模型中，熔炼动力学引入了弹性特性频率依赖性的变化。目前的建议是通过研究材料更广泛的化学性质来仔细测试动态熔化模型，并改变实验条件和方案，以便将预测的变化与实验观察到的变化进行比较。在同步加速器光源上安装的多砧高压装置具有新的高压能力，使实验成为可能。这些系统能够在样品上产生上地幔的压力和温度，然后可以轴向压缩，同步加速器产生具有非常高精度长度测量的样品图像，以及产生应力状态的衍射剖面。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 temperature within the Earth is high enough to melt rocks as evidenced by volcanoes and volcanic rocks. It is thereby probable that parts of the Earth's crust and mantle are partially molten even though they are dominantly solid. The goal of this proposal is to improve the understanding of the relationship between the state of partial melting and changes in elastic properties of the media. The focus will be the upper mantle of the Earth. Since elastic properties quantitatively define the speed that seismic waves propagate through the media, the results of this research will enable better associations between maps of seismic speed variations and degrees of partial melting. The approach of this program is to probe the physics and chemistry basics of melting and mechanics yielding a deeper understanding of the underlying principles in order to provide a robust model that can then be applied to a wide variety of environments. While the focus of the proposal is the upper mantle region of the Earth, an improved model will also be relevant to the crust. Indeed, the results could also have applications in defining this relationship in industrial settings in detecting incipient stages of melting of various materials. This program provides a cutting-edge learning experience for students including graduate students in the preparation of their PhD and undergraduate students in the focus of a summer research project. The results will be used throughout the Earth sciences as fundamental information on the behavior of the Earth's interior. The tools that are developed will be made available to other researchers for studying strength related properties of materials. These tools (software and hardware) will immediately become part of the COMPRES-operated synchrotron facility and available to all in the community that wish to use them. The tools developed here will be useful for studying material properties under extreme environments and will be useful to develop better industrial materials.The authors have recently demonstrated that the current models of the mechanical properties of solid/melt combinations are inadequate and have proposed that the interaction between the solid and melt has a significant effect on the elastic properties. The new model, "dynamic melting," changes the predicted effect of melting on the relationship between the bulk modulus and the shear modulus. In the dynamic melting model, the kinetics of melting introduces a change in the frequency dependence of the elastic properties. The current proposal is to carefully test the dynamic melting model by studying a broader range of chemistry of the material and alter the experimental conditions and protocols in order to compare the predicted changes with the experimentally observed changes. The experiments are made possible by new high pressure capabilities on multi-anvil high pressure apparatus installed at synchrotron light sources. These systems enable the generation of pressure and temperature of the upper mantle on samples that can then be axially compressed, with the synchrotron yielding images of the sample with very high precision measurements of length, and diffraction profiles that yield state of stress.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.