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对沉积物成岩作用在化学物质平衡和始新世气候中的作用的约束——来自IODP Expedition 396的高分辨率孔隙流体。海洋沉积物中硅酸盐的化学变化（或成岩作用）可能在现代和地质时间尺度上对海水化学的调节起关键作用。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都很重要，也可以作为了解海洋在地质时期变化的代用物。例如，用Mg、Sr、Li和B作为古气候指标来代表温度（Mg/Ca）、风化（Sr/Ca、Li/Ca）和碳酸盐体系（B/Ca）。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，并结合建模技术来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，以及在过去6500万年中硅酸盐成岩作用是否影响了全球气候过程。这项研究将在罗格斯大学和普林斯顿大学进行。该项目的主题（例如，溶质源和汇，气候变化）将被纳入PI将在新泽西社区大学进行的公开讲座中。PI还将开发夏季研究项目，作为罗格斯大学在校本科生和全国大学中代表性不足群体学生的指导项目的一部分。我们利用一系列古海洋学代用指标（例如Mg/Ca、Sr/Ca、Li/Ca和B/Ca）重建过去气候过程的能力依赖于对海洋元素来源和汇的基本理解。尽管这些元素在不同的成岩过程中大量交换，但对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，但基于这些模型假设的数据约束是有限的。利用最近实施的IODP 396远征队对中挪威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)确定硅酸盐成岩作用控制孔隙流体化学的模式；(2)利用基于数据和模型的方法确定硅酸盐成岩作用过程（如灰分蚀变、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)阐明了古近系温室时期硅酸盐成岩作用对气候变化的影响程度。孔隙流体将使用罗格斯大学和普林斯顿大学的海王星MC-ICP-MS设备分析其同位素（𝛅26Mg, 87Sr/86Sr，𝛅7Li，𝛅11B）组成。采样分辨率和提出的分析方案将对海洋沉积物中硅酸盐成岩作用调节海水化学和促进环境变化的程度提供前所未有的限制。重要的是，这项工作将为基于代理和基于代理的模型重建地球历史上较暖的气候提供关键的见解。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。

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.