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

点击翻译按钮获取中文摘要

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.