Superdeep Diamonds from the Transition Zone and Lower Mantle

钻石是一种非凡的材料，其终极物理性能和技术应用。天然钻石还揭示了地球深部地幔中的物理和化学过程，那里几乎没有直接样品。钻石中的矿物包裹体反映了涉及高压、高温、流体、熔体以及地球表面和内部之间的动态相互作用的反应。该项目将支持研究钻石中微小矿物包裹体的技术开发。将对一套新的150多颗深源钻石进行调查，这些钻石形成于过渡区和下地幔超过410公里的深度。寄主包裹体的3D成像、衍射和光谱将在国家X射线和红外设施中进行。将通过快速、高通量的方法识别和表征多达1000个微矿物包裹体。这项研究的结果将提高我们对地球内部矿物多样性的理解，特别是对水和含水相的了解。其目的是揭示水通过板块构造在地壳和地幔之间循环的机制，这一过程是许多自然灾害的根源。该项目将促进与两名当地高中教师的合作，在他们的物理课程中引入地球物理课程。它还将促进对几名研究生的培训，为未来在学术界、联邦机构、工业和国家实验室的职业生涯做准备。钻石的高强度和稳定性使其成为将矿物和地球化学信息从深部地幔传输到地表的完美容器，作为壳幔碳循环的一部分。这项研究将研究来自巴西Juina的一套新的超深钻石，其中包含来自过渡带和下地幔的矿物包裹体。主要挑战之一涉及确定钻石的深度来源，这些钻石往往缺乏一套完整的矿物包裹体来确定其形成条件。将对多达1000个包裹体进行分析，可能会促进新矿物相的发现，并提供有关水进入地幔的深度的信息。新的显微分析技术将提高可研究包裹体的速度和减小包裹体的大小，从而扩大地幔矿物学的数据库。光谱方法将探测钻石中各种原子尺度的缺陷，作为其来源深度的追踪器。另外，将在高压下测量钻石在结构各个方向的声速，以确定钻石的弹性性质。这将改进大陆以下深层地壳根部地震波速的地球物理模拟。其他实验将研究含水矿物在上地幔温度下的减压行为，以阐明钻石的上升路径。最终，这项研究将改进并有可能修改教科书中关于地球内部结构和动力学的图景。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Diamond is a remarkable material for its ultimate physical properties and technological applications. Natural diamonds also reveal physical and chemical processes in the Earth's deep mantle from where there are few direct samples. Mineral inclusions in diamond reflect reactions involving high pressure, high temperature, fluids, melts, and dynamic interactions between the Earth's surface and interior. This project will support technological development to investigate tiny mineral inclusions in diamonds. A new suite of more than 150 diamonds of deep origin, which formed at depths greater than 410 km in the transition zone and the lower mantle, will be investigated. 3D imaging, diffraction, and spectroscopy of the hosted inclusions will be carried out at national X-ray and infrared facilities. Up to a thousand micro-mineral inclusions will be identified and characterized by fast, high-throughput methods. Results of this research will improve our understanding of the mineral diversity in the Earth's interior, with special focus on water and hydrous phases. The goal is to reveal the mechanisms by which water recycles between the crust and mantle through plate tectonics, a process at the origin of numerous natural hazards. This project will foster collaboration with two local high-school teachers to introduce a geophysics curriculum to their physics courses. It will also promote the training of several graduate students for future careers in academia, federal agencies, industry, and the national laboratories. The high strength and stability of diamond make it a perfect vessel for transporting minerals and geochemical information from the deep mantle to the surface as part of the crust-mantle carbon cycle. This study will examine a new suite of superdeep diamonds from Juina, Brazil, which host mineral inclusions from the transition zone and lower mantle. One of the major challenges pertains to determining the depth origin of the diamonds which often lack a complete suite of mineral inclusions to pinpoint their formation conditions. Up to a thousand inclusions will be analyzed potentially promoting the discovery of new mineral phases and providing information about how deeply water is transported into the mantle. New micro-analysis techniques will increase the rate and decrease the size of inclusions that can be studied, thus broadening the database of mantle mineralogy. Spectroscopic methods will probe various types of atomic-scale defects in diamonds as tracers for their depth of origin. Separately, the sound velocity of diamond will be measured at high pressure in all directions of the structure to determine diamond elastic properties. This will improve the geophysical modeling of seismic wave velocity in the deep, crustal roots below continents. Other experiments will examine the decompression behavior of hydrous minerals at upper mantle temperatures to elucidate diamond ascent pathways. Ultimately this research will improve and potentially modify the textbook picture of the structure and dynamics of Earth's interior.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.