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Rethinking the Genesis of Banded Iron Formations: Simulating Partial Fe(II) Oxidation and Secondary Reactions of Iron-Silica Precipitates

重新思考带状铁形成的成因：模拟铁-二氧化硅沉淀物的部分 Fe(II) 氧化和二次反应

基本信息

批准号：
2142509
负责人：
Jena Johnson
金额：
$ 33.13万
依托单位：
Regents of the University of Michigan - Ann Arbor
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=2142509&HistoricalAwards=false
关键词：
Rethinking Genesis Banded Iron Formations

项目摘要

The original minerals from Earth’s primordial ocean preserve signals of the evolution of early life and ocean chemistry. To fully understand the implications of these minerals, it is necessary to recreate these phases in controlled laboratory conditions. This study focuses on the formation of iron silicates, recently identified as early minerals from marine sediments deposited during the first two billion years of Earth’s history. We will simulate the ancient ocean surface water in which a portion of iron is oxidized, the descent of the particulate products through the deep ocean, and the hypothesized respiration of the oxidized iron by microbial life in the sediments, characterizing the solid products of each step. This project will support two graduate students to lead this research and receive training in experimental geobiology. Researchers will additionally demonstrate how it is possible to recreate ancient iron precipitates in the lab and perform electron microscopy of ancient sediments with students in U-Michigan’s Earth Camp program, a summer program to expose underserved high school students to Earth and Environmental Sciences. An alum of this program who attends U-Michigan will receive a paid opportunity to assist with the proposed research, giving them valuable lab experience and a supportive laboratory community to assist in the retention of underrepresented students in the department.This project will identify likely (bio)chemical reactions that occurred in the ancient ocean and sediments, enabling to update the investigator’s model of the early iron (bio)chemical cycle. Iron-rich silicates appear to be early minerals in marine Archean (4.0 – 2.5 Ga) chemical sediments known as ‘Banded Iron Formations (BIFs)’. However, it is unknown whether reduction-oxidation (redox) processes, hypothesized to be present in the Archean ocean and often mediated by life, promoted the formation of such silicates. The proposed work will investigate what solid products are formed from plausible processes in the Archean ocean, thereby generating predictions as to which of these pathways contributed to the Archean iron cycle and how BIF minerals, particularly iron silicates, may reflect ancient (bio)chemical reactions. Specifically, researcher will answer the questions: 1) What are the initial solid products of partial Fe(II) oxidation under hypothesized Archean ocean conditions? 2) How are the initial solid products of partial iron oxidation chemically modified under Archean oceanic water column conditions? 3) How does microbial respiration of Fe(II,III)-silica products transform their chemistry and mineralogy? The experiments will address these questions by replicating Archean water column environments with trace levels of O2, then exposing these solids to anoxic water column conditions to simulate exposure during particle descent, followed by simulating early diagenesis by feeding these precipitates to an iron-reducing bacterial strain. This process-based, mechanistic approach will determine which plausible redox reactions in the Archean ocean produce iron silicates or other minerals found in BIFs, yielding insights into the interplay between life and geochemistry in the Archean Eon.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.

来自地球原始海洋的原始矿物保存了早期生命和海洋化学进化的信号。为了充分了解这些矿物的含义，有必要在受控的实验室条件下重建这些相。这项研究的重点是硅酸铁的形成，这是最近从地球历史的前20亿年期间沉积的海洋沉积物中发现的早期矿物。我们将模拟古代海洋表面水，其中一部分铁被氧化，颗粒产物通过深海下降，以及沉积物中微生物生命假想的氧化铁的呼吸作用，表征每一步的固体产物。该项目将支持两名研究生领导这项研究，并接受实验地球生物学方面的培训。研究人员还将演示如何在实验室中重建古代铁沉淀物，并与密歇根大学地球营计划的学生一起对古代沉积物进行电子显微镜检查。地球营计划是一个暑期计划，旨在让服务不足的高中生接触地球和环境科学。参加密歇根大学这个项目的校友将获得一个有偿机会协助拟议的研究，为他们提供宝贵的实验室经验和支持的实验室社区，以帮助留住该系未被充分代表的学生。该项目将识别在古代海洋和沉积物中发生的可能的(生物)化学反应，使研究人员能够更新研究人员对早期铁(生物)化学循环的模型。富含铁的硅酸盐似乎是海相太古宙(4.0-2.5Ga)化学沉积物中的早期矿物，被称为“带状铁建造(BIF)”。然而，尚不清楚还原-氧化(氧化还原)过程是否促进了这种硅酸盐的形成，这种过程假设存在于太古宙海洋中，通常受生命的影响。这项拟议的工作将调查太古宙海洋中可能的过程形成了哪些固体产物，从而预测这些途径中的哪些对太古宙的铁循环做出了贡献，以及BIF矿物，特别是铁硅酸盐，可能如何反映古代的(生物)化学反应。具体地说，研究人员将回答以下问题：1)在假设的太古代海洋条件下，部分Fe(II)氧化的初始固体产物是什么？2)在太古代海洋水柱条件下，部分Fe(II)氧化的初始固体产物是如何被化学修饰的？3)Fe(II，III)-SiO_2产物的微生物呼吸作用如何改变其化学和矿物学？这些实验将通过复制具有微量O2水平的太古代水柱环境来解决这些问题，然后将这些固体暴露在缺氧水柱条件下以模拟颗粒下降期间的暴露，然后通过将这些沉淀物喂给铁还原细菌菌株来模拟早期成岩作用。这种基于过程的机械论方法将确定太古代海洋中哪些看似合理的氧化还原反应会产生BIF中发现的铁、硅酸盐或其他矿物，从而深入了解太古宙生命与地球化学之间的相互作用。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。