Collaborative Research: Characterizing and quantifying carbon sequestration processes across the Andean Convergent Margin

合作研究：描述和量化安第斯汇聚边缘的碳封存过程

• 批准号: 2121670
• 负责人: Karen Lloyd
• 金额: $ 50.08万
• 依托单位: University of Tennessee Knoxville
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-01-01 至 2024-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2121670&HistoricalAwards=false
• 关键词: Collaborative; Research; Characterizing; quantifying; carbon

Subduction zones are the interface between Earth’s interior (crust and mantle) and exterior (atmosphere and oceans), where carbon and other volatile elements are actively moved between terrestrial reservoirs by plate tectonics. The efficiency of volatile transfer controls the chemical state of Earth’s interior and exterior, including the atmospheric composition. In turn, the distribution of carbon and other volatiles in Earth’s surface reservoirs has enabled conditions favorable for life on Earth. Despite the importance of carbon, its fluxes, sources, and sinks remain under-constrained in subduction-related fluids, with an almost complete absence of studies linking it to underground biological processes. The deep carbon mass balance has previously been estimated by comparing subducting slab inputs to arc volcano degassing outputs, with the difference representing the amount of carbon that is transported into Earth’s deep mantle. However, slab and mantle-derived carbon can also be sequestered in the form of hydrothermal minerals (e.g., calcite, aragonite) and by microbial uptake in the crust of the overriding plate, effectively masking an unknown portion of the carbon output from the subduction zone. The lack of constraints on these key processes, however, limits the understanding of the overall efficiency of the deep carbon cycle. This project involves substantive collaboration with colleagues in Chile, including an international workshop, and the work of several U.S. students will be supported.This project will characterize the extent of mineralogical and biological carbon sequestration along the geologically well-studied Andean Convergent Margin (ACM). The PIs hypothesize that calcite precipitation sequesters significant amounts of carbon in the ACM, particularly where the crust is thickest in the Central Volcanic Zone (CVZ). Furthermore, this project will test if subsurface microbial communities sequester carbon into biomass through chemosynthesis, forming an additional sink for carbon. Finally, the PIs will systematically assess how geochemical transformations and microbial communities vary as a function of subduction parameters (i.e., carbon input from the slab, upper plate thickness and lithology, as well as slab dip angle), which can then be used to compare results to a range of global convergent margins. To accomplish these goals, the PIs will conduct a field expedition to the CVZ in 2022 to collect fluid and gas samples from ~15 natural springs, seeps and fumaroles in the forearc and arc. They will measure helium and carbon isotopes, microbial chemosynthesis rates, and contributions of chemosynthesis to total microbial biomass in all samples. CVZ results will be interpreted alongside published and unpublished datasets from the ACM and other convergent margins globally (i.e., Central America). If subsurface geochemical and biological carbon sinks are found to be substantial in the ACM, it will add to growing evidence that carbon sequestration is widespread in the overlying crust of convergent margins. Such a finding could fundamentally alter the canonical understanding of deep carbon cycling between Earth’s surface and mantle. This project involves substantive collaboration with colleagues in Chile, including an international workshop, and the work of several U.S. students will be supported.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.

俯冲带是地球内部（地壳和地幔）和外部（大气和海洋）之间的界面，在板块构造中，碳和其他挥发性元素在地面储层之间积极移动。挥发性转移的效率控制着地球内部和外部的化学状态，包括大气成分。反过来，地球表面储层中碳和其他挥发物的分布使得有利于地球生命的条件。尽管碳的重要性，但其通量，来源和水槽在俯冲相关的烟道中仍然不受限制，几乎完全没有将其与潜在的生物学过程联系起来的研究。以前，通过将俯冲板输入与电弧火山脱气输出进行比较，量的碳质量平衡已估算出来，而差异代表了传输到地球深地幔中的碳量。然而，板和地幔衍生的碳也可以以热液矿物质（例如方解石，后者）的形式隔离，并通过在压层板的外壳中通过微生物摄取来隔离，从而有效地掩盖了俯冲板的碳输出的未知部分。但是，对这些关键过程的缺乏限制限制了对深碳循环总体效率的理解。该项目涉及与智利的同事（包括国际研讨会）的实质性合作，将支持几名美国学生的工作。该项目将表征沿着地质良好的安第斯融合边缘（ACM）沿矿物学和生物碳固换的程度。 PI假设钙降水隔离了ACM中的大量碳，尤其是在中央火山区（CVZ）中的地壳最厚的情况下。此外，该项目将测试地下微生物群落是否通过化学合成将碳静止在生物质中，从而形成碳的额外水槽。最后，PIS将系统地评估地球化学转化和微生物群落如何随俯冲参数的函数而变化（即，来自平板，上板厚度和岩性的碳输入，以及平板倾角，以及可以将其用于将结果比较的结果与全球融合率的范围进行比较。为了实现这些目标，PIS将在2022年对CVZ进行一次实地考察，以在前臂和ARC中从约15个天然弹簧，See和Fumaroles收集流体和气体样品。他们将测量氦和碳同位素，微生物化学合成率以及化学合成对所有样品中总微生物生物量的贡献。 CVZ结果将与全球ACM和其他收​​敛利润率（即中美洲）的发表和未发表的数据集一起解释。在ACM中发现地下地球化学和生物碳汇水很大，它将增加越来越多的证据，表明碳固醇在融合边缘的上覆的外壳中广泛存在。这样的发现从根本上可以改变对地球表面和地幔之间深碳循环的规范理解。该项目涉及与智利的同事（包括国际研讨会）的实质性合作，将支持几位美国学生的工作。该奖项反映了NSF的法定任务，并通过使用该基金会的知识分子优点和更广泛的影响来审查标准，通过评估来诚实地支持。