Experimental Quantification of 3D Melt Distribution in Partially Molten Rocks

智力优势：本提案描述了部分熔融地幔橄榄岩中熔体分布的实验研究，这将增强我们对海洋扩张脊下上地幔中熔体产生和运输过程的理解。该项目的3个主要目标是：1)生产含有不同数量部分熔体的质地平衡的单矿物和多矿物聚集体，并表征这些样品中熔体的三维分布以及熔体分数的函数变化；2)根据实验确定的三维熔融分布确定部分熔融岩石的渗透率；3)为海洋脊下部分熔融橄榄岩的熔体迁移提供物理约束，从而更好地理解相关的地球化学和地球物理过程。一项初步研究表明，x射线同步加速器微层析成像将提供有价值的熔体拓扑三维信息（如连通性），这是确定部分熔融岩石渗透率的先决条件。高分辨率二维扫描电镜图像将与显微层析成像数据进行比较，以评估后者的保真度。实验将在上地幔条件下使用WHOI的固体介质活塞缸装置进行。x射线同步加速器显微断层扫描（阿贡国家实验室）和扫描电子显微镜（SEM）将用于量化熔体分布。网络建模和晶格玻尔兹曼方法将用于三维复杂流动的建模，并提供宏观尺度输运性质和微观尺度熔体分布之间的定量联系。将实验熔体分布数据纳入模型，将有助于模拟熔体输运及其对实际熔融程度下部分熔融橄榄岩物理性质的影响。拟议活动的更广泛影响：拟议的研究将导致改进模型，以了解许多不同地质系统中的流体流动。因此，这些数据将引起许多学科的科学家的兴趣。这项工作还将建立地幔岩石学团体和同步加速器团体之间的合作，这将导致分析和理论的进步。建议的研究将有助于私家侦探的专业发展，他们都是WHOI的初级教师，并为研究生和本科生提供教育和发展机会。除了在科学期刊上发表论文外，Gaetani和Zhu还将与当地高中生和/或本科生合作，将我们的实验结果以一种更广泛的受众可以访问的形式放在互联网上。通过这些教育和推广活动，拟议的研究不仅可以提高我们在基础科学方面的知识，还可以为培养和培训未来的研究人员提供平台。

Intellectual Merit: This proposal describes an experimental study of melt distribution in partially molten mantle peridotite that will enhance our understanding of the processes of melt generation and transport in the upper mantle beneath oceanic spreading ridges. The 3 main objectives of this project are: 1) to produce texturally equilibrated mono- and polymineralic aggregates containing various amounts of partial melt and to characterize the 3-dimensional (3-D) distribution of melt within these samples and how this changes as a function of melt fraction; 2) to determine the permeability of partially molten rocks based on the experimentally determined 3-D melt distributions; 3) to provide physical constraints on melt migration in partially molten peridotite beneath ocean ridges that will lead to a better understanding of the associated geochemical and geophysical processes. A pilot study indicates that the X-ray synchrotron microtomography will provide valuable 3-D information (such as connectivity) on melt topology, which is a prerequisite for determining the permeability of partially molten rocks. High resolution 2-D SEM microscopy images will be compared to the microtomographic data to assess the fidelity of the latter. Experiments will be carried out at upper mantle conditions using a solid medium piston cylinder device at WHOI. X-ray synchrotron microtomography (Argonne National Laboratory) and Scanning Electron Microscopy (SEM) will be used to quantify melt distribution. Network modeling and the Lattice Boltzmann method will be used to model 3-D complex flow and to provide a quantitative link between the macroscale transport properties and microscale melt distribtution. Incorporation of experimental melt distribution data into the models will facilitate simulation of melt transport and its effects on physical properties of partially molten peridotite at realistic degrees of melting. Broader Impacts of the Proposed Activity: The proposed study will lead to improved models for understanding fluid flow in a number of different geologic systems. Thus, the data will be of interest to scientists in many disciplines. This work will also establish a collaboration between the mantle petrology community and the synchrotron accelerator community that will lead to analytical and theoretical advances. The proposed study will contribute to the professional development of the P.I.s, who are both junior faculty at WHOI, and provide an education and development opportunity for graduate and undergraduate students. In addition to publishing papers in scientific journals, Gaetani and Zhu will work with local high school students and/or undergraduate students to put our experimental results on the internet in a form that will be accessible to a broader audience. Through these education and outreach activities, the proposed research will not only advance our knowledge in basic science, but also serve as platform for cultivating and training researchers of the future.