CAREER: Experimental Constraints on Carbon-iron Redox Interaction in Earth's Deep Lower Mantle

地球的深层碳循环影响着地球上生命的过去、现在和未来。深层的碳化学作用是碳固存和火山作用的原因。深层钻石的增长不仅推动了一个行业的发展，而且还捕获并保存了我们唯一的地球深层内部样本。地球的下地幔是地球上最大的一层，即使在非常低的浓度下也有很大的碳容量，因此对全球碳收支很重要。该项目将把地幔在地球深层碳循环中的作用的研究与一项教育计划结合起来，该计划包括在密歇根州立大学（MSU）和其他大学招募不同类型的学生到实验室学习地球科学，并改善空间推理的教学，这是地球科学家的一项关键技能。整个地球的碳循环是一个及时的主题，非常适合外展，以吸引对环境问题感兴趣的学生从事地球科学的职业。密歇根州立大学的地质学和全球变化入门课程将开设碳矿物学和地球化学短模块。这些练习的有效性将根据本科专业的招聘和发展地球科学职业的空间推理技能来评估。本科生和研究生的研究助理将参与实验和地球科学教学评估。主要研究目标是确定下地幔条件下岩石学背景下含碳相的稳定性。地幔矿物学和氧逸度（fO2）的深度和区域差异将导致地幔相组合中碳的形态和寄主相的变化。量化含碳相的稳定性与压力、温度、氧化还原条件和主要矿物学之间的关系，对于理解地球内部碳的命运至关重要。在激光加热的金刚石砧细胞中进行的实验将提供一些在岩石学背景下的碳酸盐和碳化物的稳定性和物理性质的实验约束，在压力-温度条件下达到核-幔边界（CMB）。在包括地球化学家、宇宙化学家、火山学家、岩石学家、矿物学家和地球物理学家在内的一个团体中，提出的实验结果对于综合理解碳的起源、储存和通量是必要的。地球的碳循环和对钻石的普遍兴趣提供了一个通过课程作业和研究助教来教学和招收学生的机会。该项目的教育部分是由PI和地理认知专家Julie Libarkin博士合作开发和评估包含深度碳背景和开发3D推理技能的教育模块。模块将通过课堂观察、调查和访谈进行评估，并在网上公开传播。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。

Earth's deep carbon cycle affects the past, present and future of life on our planet. Carbon chemistry at depth is responsible for carbon sequestration and volcanism. The growth of diamonds at depth not only drives an industry, but also traps and preserves our only samples of Earth's deep interior. Earth's lower mantle, the Earth's biggest layer, has great capacity for carbon even at very low concentrations and is thus important to the global carbon budget. The project will integrate research in the role of the mantle in Earth's deep carbon cycle with an education plan that includes recruitment of diverse students to laboratory geoscience and improves teaching of spatial reasoning, a critical skill for Earth scientists, at Michigan State University (MSU) and beyond. The whole-Earth carbon cycle is a timely subject well-suited to outreach to attract students with interest in environmental problems to careers in geosciences. Short modules on carbon mineralogy and geochemistry will be developed for gateway courses in geology and global change at MSU. The effectiveness of these exercises will be assessed in terms of recruitment of undergraduate majors and developing spatial reasoning skills for geoscience careers. Undergraduate and graduate research assistants will participate both in the lab and in geoscience teaching evaluation.The primary research goal is to determine the stability of carbon-bearing phases in petrologic context at conditions of the lower mantle. Depth- and region-dependent differences in mantle mineralogy and oxygen fugacity (fO2) will result in changes in the speciation and host phases of carbon within the mantle phase assemblage. Quantifying the relationship between stability of carbon-bearing phases and pressure, temperature, redox conditions, and major mineralogy is critical to understanding the fate of carbon in Earth's interior. Experiments performed in laser-heated diamond anvil cells will provide some of the first experimental constraints on carbonate and carbide stability and physical properties in petrologic context of mantle phase assemblages at pressure-temperature conditions reaching the Core-Mantle Boundary (CMB). The results of the proposed experiments will be necessary to an integrated understanding of the origin, storage, and flux of carbon among a community including geochemists, cosmochemists, volcanologists, petrologists, mineralogists, and geophysicists. Earth's carbon cycle and popular interest in diamonds offer an opportunity to teach and recruit students through coursework and research assistantships. The education component of this project is a collaboration between the PI and geocognition expert Dr. Julie Libarkin to develop and evaluate educational modules incorporating deep carbon context and developing 3D reasoning skills. Modules will be evaluated by in-class observations, surveys and interviews and disseminated openly online.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.