Hydrothermal Metal Fluxes over the Cenozoic

热液喷口是一种水下间歇泉，它向海洋中喷出的水与河流一样多。这些喷口可以改变海水的化学成分，并在百万年的时间尺度上改变气候。然而，有多少水通过这些喷口循环，或者它如何随着时间的推移而变化，这是未知的。在喷发过程中，铁和锰等金属从喷口喷出，在深海中运输，并沉积在海洋沉积物中。这些沉积物是地质记录中过去火山爆发的证据。该项目将收集、扩展、比较和分析在海洋沉积物中发现的多种化学线索。我们的目标是弄清楚这些喷口的流动在数百万年来是如何变化的。最终，该项目将计算来自热液喷口的金属流量，并绘制地图，显示这些金属现在和过去的沉积位置。锰、钴、铜和锌等金属的海底分布对现代技术和可再生能源至关重要。此外，该项目还支持K-12外联活动，涉及在地球科学中代表性不足的社区，由于整个海洋体积每几千年在下面的海洋地壳中循环一次，全球热液流量与全球河流流入海洋的流量相当。热液循环对海水化学平衡、长期气候、地球化学循环、古海水成分和俯冲入地幔的地壳成分有重要影响。尽管热液通量很重要，但其约束性很差。该项目将汇编、扩充、比较和综合海洋沉积物中热液金属沉积的示踪剂，以重建百万年时间尺度内全盆地热液通量空间分布的变化。集中在太平洋板块，热液沉积的四个示踪剂将进行比较：铁锰氧化物丰度从涂抹幻灯片，多元建模的元素浓度，铅同位素和稀土元素模式。该项目检验的假设是，可以将追踪热液喷口金属沉积的海洋沉积物记录结合起来，并扩展到整个海洋盆地，以重建从现代到新生代大部分时间的热液通量变化。沿着估算通量，该项目将绘制现在和过去热液金属沉积的地图，说明热液羽流从大洋中脊迁移到何处和多远。这一结果对过去微量营养素（铁）的循环以及对受热液作用影响的新型同位素系统的限制都有影响。鉴于将对Mn、Co、Cu和Zn进行调查，该项目与关键矿物研究有关。该项目支持早期职业科学家和K-12外展活动，其中涉及来自地球科学领域代表性不足的社区的人们。该奖项反映了NSF的法定使命，并且通过使用基金会的知识价值和更广泛的影响进行评估，被认为值得支持审查标准。

Hydrothermal vents are underwater geysers that spew about as much water into the ocean as rivers. These vents can change the chemistry of seawater and change the climate on million-year timescales. However, how much water circulates through these vents or how it has changed over time is unknown. During eruptions, metals like iron and manganese are erupted from the vents, transported within the deep ocean, and deposited in the marine sediment. These deposits serve as evidence of past eruptions in the geologic record. This project will gather, expand, compare, and analyze multiple chemical clues found in marine sediments. The goal is to figure out how the flow of these vents has changed over millions of years. Ultimately, the project will calculate the flow of metals from hydrothermal vents and create maps that show where these metals are deposited now and in the past. The seafloor distribution of these metals such as manganese, cobalt, copper, and zinc are critical to modern technology and renewable energy. Additionally, the project supports K-12 outreach activities involving communities underrepresented in the geosciences.With the entire ocean volume cycling through the underlying ocean crust every few thousand years, the global hydrothermal fluid flux is comparable to the global riverine flux to the ocean. Hydrothermal circulation significantly affects the chemical balance of seawater chemistry, long-term climate, biogeochemical cycles, paleo-seawater compositions, and the composition of crust subducted into the mantle. Despite the importance, hydrothermal fluxes are poorly constrained. This project will compile, expand, compare, and synthesize tracers of hydrothermal metal deposition in marine sediment to reconstruct variations in the basin-wide spatial distribution of hydrothermal fluxes over million-year timescales. Focusing on the Pacific Plate, four tracers of hydrothermal deposition will be compared: Fe-Mn oxide abundances from smear slides, multivariate modeling of element concentrations, Pb isotopes, and rare earth element patterns. The project tests the hypothesis that marine sediment records tracing metal deposition from hydrothermal vents can be combined and expanded across ocean basins to reconstruct changes in hydrothermal fluxes for the modern back through much of the Cenozoic. Along with estimating fluxes, the project will produce maps of present and past hydrothermal metal deposition that will illustrate where and how far hydrothermal plumes are transported away from mid-ocean ridges. The outcome has implications for the cycling of micronutrients (iron) in the past as well as adding constraints to novel isotope systems affected by hydrothermalism. Given that Mn, Co, Cu, and Zn will be investigated, the project is pertinent to critical minerals research. The project supports early career scientists and K-12 outreach activities involving people from communities underrepresented in the geosciences as well.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.