OCE-PRF: Constraints on the role of sediment diagenesis in chemical mass balance and Eocene climate using high-resolution pore fluids from IODP Expedition 396

OCE-PRF使用IODP Expedition 396高分辨率孔隙流体对沉积物成岩作用在化学质量平衡和始新世气候中的作用的限制硅酸盐是海洋沉积物和地壳中的重要矿物。在现代和地质时间尺度上，海洋沉积物中硅酸盐的化学变化（或成岩作用）可能在调节海水化学方面发挥关键作用。然而，我们对硅酸盐成岩作用如何影响海水中的特定元素，如镁（Mg）、锶（Sr）、锂（Li）和硼（B）的理解是不完整的。这些元素在现代海洋中很重要，也是理解海洋在地质时期变化的代表。例如，Mg、Sr、Li和B被用作温度（Mg/Ca）、风化（Sr/Ca、Li/Ca）和碳酸盐体系（B/Ca）的古气候代用指标。PI Clementi将对从北大西洋新沉积物岩心中挤出的流体进行化学分析，并采用建模技术，以确定海洋沉积物中发生了哪些成岩过程，这些过程如何影响海水化学，以及硅酸盐成岩作用是否影响了过去6500万年的全球气候过程。这项研究将在罗格斯大学和普林斯顿大学进行。本项目的主题（例如，溶质源和汇，气候变化）将被纳入公共讲座，PI将在新泽西社区学院。PI还将开发夏季研究项目，作为目前罗格斯大学本科生和来自全国各地大学代表性不足群体的学生的辅导计划的一部分。我们使用一系列古海洋学代理重建过去气候过程的能力（例如，Mg/Ca、Sr/Ca、Li/Ca和B/Ca）依赖于对海洋中元素的源和汇的基本理解。尽管这些元素在各种成岩过程中大量交换，但是，对Mg、Sr、Li和B的化学质量平衡的限制仍然不完整。此外，海洋沉积物中的硅酸盐成岩作用被认为影响了古近纪气候，但这些模型假设的数据基础上的限制是有限的。使用最近实施的IODP Expedition 396到挪威中部边缘的一套新的高分辨率孔隙流体样品，结合数值模拟，本文提出的工作将：（1）识别控制孔隙流体化学的硅酸盐成岩作用的模式;（2）使用基于数据和模型的方法来确定硅酸盐成岩作用过程的影响（例如，灰蚀变、逆风化、海相硅酸盐风化和地壳蚀变）对Mg、Sr、Li和B地球化学收支的影响;（3）阐明硅酸盐成岩作用对古近纪温室气候变化的贡献程度。将使用罗格斯大学和普林斯顿大学的Neptune MC-ICP-MS设施分析孔隙流体的同位素（Mg26、87 Sr/86 Sr、Li 77、Li 11 B）组成。采样分辨率和拟议的分析计划将在海洋沉积物中的硅酸盐成岩作用调节海水化学和促进环境变化的程度上提供前所未有的限制。重要的是，这项工作将为基于代理和代理启用模型的地球历史上温暖气候的重建提供重要的见解。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估。

OCE-PRF Constraints on the role of sediment diagenesis in chemical mass balance and Eocene climate using high-resolution pore fluids from IODP Expedition 396Silicates are important minerals in ocean sediments and Earth’s crust. The chemical changes (or diagenesis) of silicates in marine sediments may play a key role in regulating seawater chemistry at modern and geological timescales. Yet, our understanding of how silicate diagenesis influences specific elements, such as magnesium (Mg), strontium (Sr), lithium (Li) and boron (B), in seawater is incomplete. These elements are important in both the modern ocean and as proxies for understanding changes in the ocean over geologic time. For example, Mg, Sr, Li, and B are used as paleoclimate proxies for temperature (Mg/Ca), weathering (Sr/Ca, Li/Ca), and the carbonate system (B/Ca). PI Clementi will pair chemical analysis of fluids squeezed from new sediment cores from the North Atlantic Ocean with modeling techniques to determine which diagenetic processes are occurring in marine sediments, how these processes influence seawater chemistry, and whether silicate diagenesis has influenced global climate processes over the last 65 million years. The research will be conducted at Rutgers University and Princeton University. Themes from this project (e.g., solute sources and sinks, climate change) will be incorporated into public lectures that the PI will give at New Jersey community colleges. The PI will also develop summer research projects as part of mentoring programs for current Rutgers undergraduate students and students from under-represented groups at colleges across the country.Our ability to reconstruct past climate processes using a range of paleoceanographic proxies (e.g., Mg/Ca, Sr/Ca, Li/Ca, and B/Ca) is reliant on a fundamental understanding of the sources and sinks of elements in the ocean. Despite substantial exchange of these elements during various diagenetic processes, however, constraints on chemical mass balance for Mg, Sr, Li, and B remains incomplete. Further, silicate diagenesis in marine sediments has been suggested to have influenced Paleogene climate, but data-based constraints on these model hypotheses is limited. Using a new suite of high resolution pore fluid samples from recently implemented IODP Expedition 396 to the Mid-Norwegian Margin, combined with numerical modeling, the work proposed here will: (1) identify the mode(s) of silicate diagenesis controlling pore fluid chemistry; (2) use data- and model-based approaches to determine the influence of silicate diagenesis processes (e.g., ash alteration, reverse weathering, marine silicate weathering, and crustal alteration) on the geochemical budgets of Mg, Sr, Li, and B; and (3) elucidate the extent to which silicate diagenesis contributed to climate changes during the Paleogene hothouse. Pore fluids will be analyzed for their isotopic (𝛅26Mg, 87Sr/86Sr, 𝛅7Li, 𝛅11B) composition using the Neptune MC-ICP-MS facilities at Rutgers University and Princeton University. The sampling resolution and proposed analytical plan will offer unprecedented constraints on the extent to which silicate diagenesis in marine sediments regulates seawater chemistry and facilitates environmental change. Importantly, the work will provide critical insight for proxy-based and proxy enabled model-based reconstructions of warmer climates in Earth’s history.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.