Testing for an enhanced metamorphic carbon flux on the Proterozoic Earth, Central Metasedimentary Belt, Ontario, Canada

加拿大安大略省中央变质沉积带元古代地球变质碳通量增强测试

• 批准号: 2247049
• 负责人: Emily Stewart
• 金额: $ 33.63万
• 依托单位: Florida State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-07-01 至 2026-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2247049&HistoricalAwards=false
• 关键词: Testing; enhanced; metamorphic; carbon; flux

When continents collide and mountain ranges are formed, chemical reactions in deeply-buried rocks can release carbon dioxide into Earth’s oceans and atmosphere. While the amount of carbon released in these ‘tectonic fluxes’ is miniscule in comparison to human activities (like the burning of fossil fuels), this carbon can be very important on long geologic timescales (more than one million years). In fact, these geologic carbon cycling processes have been essential to maintaining a habitable planet on which life could evolve and flourish. However, much of the work on geologic carbon cycling has focused on the Phanerozoic Eon, i.e., the last 541 million years since the evolution of complex life; yet, there is reason to suspect that tectonic collisions may have released significantly more carbon on the early Earth. The proposed work is, therefore, a field-based study of tectonic carbon release and mountain building in the ancient rocks from the Central Metasedimentary Belt in Ontario, Canada. These rocks were deposited as sediments and buried in a mountain range more than one billion years ago, long before the evolution of plants, animals, or any kind of multicellular life. A combination of field work, numerical modeling, and geochemical techniques will be used to understand how these tectonically-driven reactions released carbon. This will serve as an essential constraint on our understanding of the interplay between geological, climatic, and biological processes. Furthermore, study of the ancient Earth may serve as an analogue for consideration of planetary habitability both in our solar system and beyond.The proposed work will explore metamorphic decarbonation in an orogenic belt of the middle to late Proterozoic using a combination of detailed petrography, mineral chemistry, bulk rock mass-balance calculations, thermodynamic modeling, and stable carbon and oxygen isotope measurements. The magnitude and mechanisms of CO2 release in the Central Metasedimentary Belt will be reconstructed to test the hypothesis that metamorphic decarbonation was enhanced on the early Earth. Combined with existing geochronology, this work will generate (1) rigorous field-based estimates of the rate, timing, and magnitude of CO2 release in a Proterozoic orogen and (2) a mechanistic understanding of the controls pressure, temperature, protolith composition, and fluid flow exerted in metamorphic decarbonation. This field test will be necessary to account for the complexities introduced by spatially variable open-system fluid flow, metasomatism, and kinetic effects. The work will support at least one PhD student, multiple undergraduates, and high school students in developing scientific skills. In addition, the project will develop an outreach program on plate tectonics for K-8 students and the broader local community.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.

当大陆碰撞和山脉形成时，深埋岩石中的化学反应会将二氧化碳释放到地球的海洋和大气中。虽然与人类活动（如燃烧化石燃料）相比，这些“构造通量”中释放的碳量微不足道，但这些碳在漫长的地质时间尺度（超过一百万年）上可能非常重要。事实上，这些地质碳循环过程对于维持一个生命可以进化和繁荣的可居住星球至关重要。然而，大部分关于地质碳循环的工作都集中在中生代，即，复杂生命演化以来的最后5.41亿年;然而，有理由怀疑构造碰撞可能在早期地球上释放了更多的碳。因此，建议的工作是，在加拿大安大略中央变质沉积带的古岩石构造碳释放和造山作用的实地研究。这些岩石在10亿多年前作为沉积物沉积并埋藏在山脉中，远远早于植物，动物或任何种类的多细胞生命的进化。结合实地工作，数值模拟和地球化学技术将被用来了解这些构造驱动的反应如何释放碳。这将成为我们理解地质、气候和生物过程之间相互作用的一个重要限制。此外，古地球的研究可能作为一个类比，考虑行星的可居住性，无论是在我们的太阳系和beyond.The拟议的工作将探讨变质脱碳作用在造山带的中晚元古代使用详细的岩相学，矿物化学，整体岩石质量平衡计算，热力学模拟，稳定的碳和氧同位素测量相结合。在中央变质沉积带的CO2释放的幅度和机制将被重建，以测试的假设，变质脱碳作用增强了早期地球。结合现有的地质年代学，这项工作将产生（1）严格的基于现场的估计的速率，时间，和规模的二氧化碳释放在元古代造山带和（2）的控制压力，温度，原岩成分，和流体流动施加在变质脱碳作用的机械理解。这个现场测试将是必要的，以解释空间可变的开放系统流体流动，交代作用和动力学效应所带来的复杂性。这项工作将支持至少一名博士生，多名本科生和高中生发展科学技能。此外，该项目将为K-8学生和更广泛的当地社区开发一个关于板块构造的推广计划。该奖项反映了NSF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。