Collaborative Research: Geophysical and geochemical investigation of links between the deep and shallow volatile cycles of the Earth

合作研究：地球深层和浅层挥发性循环之间联系的地球物理和地球化学调查

• 批准号: 2333102
• 负责人: Katherine Kelley
• 金额: $ 40.62万
• 依托单位: University of Rhode Island
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-02-01 至 2027-01-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2333102&HistoricalAwards=false
• 关键词: Collaborative; Research; Geophysical; geochemical; investigation; Collaborative; Research; Geophysical; geochemical; investigation

Since its formation billions of years ago, Earth has been slowly cooling via convection, where warmer material rises to the surface and cold tectonic plates plunge deep into the interior. Understanding this process is important for a wide range of problems, such as determining the factors that drive plate tectonics to sustaining deep water and carbon cycles that stabilize the atmosphere, hydrosphere, and climate throughout Earth’s history. This is particularly relevant for society, both because plate tectonic processes are the driving forces behind hazards such as earthquakes and volcanoes and because our climate and atmosphere make Earth habitable. This project studies large scale convection and volatile pathways in the solid Earth by using earthquake data recorded at global seismic stations paired with geochemical estimates of volatiles from rocks collected at mid-ocean ridges where oceanic plates are diverging. Although the mantle must rise in these locations to replace the mass of the plates as they diverge, the upwellings are typically considered to be small in scale, not necessarily tied to the larger whole Earth convective system. However, recent seismic imaging and the researcher's own comparisons between geochemical data and geophysical data suggest that in some regions upwellings beneath mid-ocean ridges may connect to the lower mantle with broad implications for the understanding of volatiles on Earth, their pathways, and abundances. An outreach program will increase diversity in the Earth Sciences by designing an interactive digital tool that explores and explains Earth’s deep volatile cycle and its connection to physical rocks samples. It will be designed for various levels, useable by experts, tour guides, K-12 school groups, self-directed students, the public, and explorers online. The tool will be delivered via large portable touchscreen interfaces in the marine sample repositories at U. Rhode Island and Woods Hole Oceanographic Institution, which store many of the rock samples to be studied by this project. Together the facilities reached ~15,000 visitors in the past 5 years, which included the COVID pandemic. The content will also be displayed at the WHOI Discovery Museum in the rotating exhibit section and will be made available on a website hosted through Volcano@URI. Finally, the project will provide training for 2 graduate students in cutting-edge methodologies in geochemical analyses and global seismic analyses. Water is essential to life on Earth. It also plays a large role in studies of Earth’s deep interior and its evolution. It is thought to be an important factor in the existence of plate tectonics, the formation of the continents, and the initiation of volcanism and earthquakes. The mantle transition zone (MTZ), which separates the upper from the lower mantle from ~410 to ~660 km depth, is key to Earth’s hydration cycle in that it is thought to have the capacity to store ocean(s) of water. Yet, determining the exact locations and pathways of the hydration across the transition zone has proven challenging. Plumes and subduction zones are thought to be the main conduits of hydration between the upper and the lower mantle. Ridges are typically assumed to be relatively independent of Earth’s large-scale whole mantle convection patterns. However, ridges do release water from the mantle during mid-ocean ridge basalt (MORB) emplacement. Although MORB water contents are relatively low, ridges represent the longest continuous plate boundaries on the planet, and so the total mass of water passing through the ridge system is substantial. Ridges also represent an accessible window into the water content of much of the upper mantle. The researchers have made some preliminary comparisons of available information, namely global seismic models and compiled water contents from previously analysed ridge samples. They find that in some locations MORB samples with higher water content correspond to locations where seismic observables may suggest enhanced hydration in the MTZ. They also find many ridge segments have too little geochemical data to constrain any trend. This preliminary work is promising and demands additional attention and investigation. This project is jointly funded by the Geophysics program in the Division of Earth Sciences and the Marine Geology and Geophysics program in the Division of Ocean Sciences.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.

自数十亿年前的地球形成以来，地球一直通过会议缓慢冷却，温暖的材料升至表面和冷构造板板在内部深处。了解这一过程对于各种问题很重要，例如确定驱动板块构造的因素，以维持深水和碳循环，从而稳定整个地球历史的大气，水流和气候。这与社会尤其重要，这既是因为板块构造过程都是地震和火山等危害背后的驱动力，并且因为我们的气候和大气使地球变得可居住。该项目通过使用在全球地震台上记录的地震数据以及在海洋板上收集的岩石中收集的岩石的地球化学估计的地震估计，研究了固体地球中的大规模转换和挥发性途径。尽管地幔必须在这些位置上升才能替换板的质量，但通常认为上升的范围在规模上很小，不一定与较大的整个地球对流系统息息相关。然而，最近的地震成像以及研究人员在地球化学数据和地球物理数据之间的比较表明，在某些区域中，海脊下方的某些区域上升可能与下层层相连，对对地球上挥发物的理解，其途径和抽象的理解具有广泛的影响。外展计划将通过设计一种交互式数字工具来探索和解释地球深层挥发性周期及其与物理岩石样品的联系，从而提高地球科学的多样性。它将为各种级别设计，可由专家，导游，K-12学校团体，自我指导的学生，公众和探险家在线使用。该工具将通过U. Rhode Island和Woods Hole Oceanographic Institution的海洋样品存储库的大型便携式触摸屏接口进行交付，该机构存储了许多由该项目研究的岩石样品。在过去的5年中，这些设施共同吸引了约15,000名游客，其中包括COVID大流行。该内容还将在旋转展览部分的Whoi Discovery博物馆展出，并将在通过Volcano@Uri托管的网站上提供。最后，该项目将在地球化学分析和全球地震分析中为两名研究生提供培训。水对地球生命至关重要。它在研究地球深内部及其演变的研究中也起着重要作用。人们认为这是板块构造，大陆的形成以及火山和地震的主动性的重要因素。地幔过渡区（MTZ）将上层与〜410至〜660 km深度分开，是地球水合周期的关键，因为它被认为具有存储海洋水的能力。但是，确定跨过渡区的水合的确切位置和途径已被证明是挑战。羽毛和俯冲带被认为是上层和下地幔之间水合的主要管道。通常认为脊相对与地球大规模的整个地幔转换模式相对独立。但是，脊确实在中山脊（MORB）扩增过程中从地幔中释放水。尽管MORB水的含量相对较低，但脊代表了行星上最长的连续板边界，因此通过脊系统的水总质量很大。山脊还代​​表着大部分地幔的水含量的可访问窗口。研究人员已经对可用信息进行了一些初步比较，即全球地震模型，并从先前分析的山脊样品中编译了水内容物。他们发现，在某些位置，具有较高水分含量的病态样品，与地震观测的位置相对应，可能表明MTZ中的水合增强。他们还发现许多山脊段的地球化学数据太少，无法限制任何趋势。这项初步工作是有希望的，需要额外的关注和调查。该项目由地球科学部的地球物理学计划和海洋科学系的海洋地质与地球物理学计划共同资助。该奖项反映了NSF的法定任务，并被认为是通过基金会的知识分子和更广泛的影响来评估的，被认为是珍贵的支持。