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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演化的信号。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现这些相。这项研究的重点是铁硅酸盐的形成，最近被确定为地球历史前20亿年海洋沉积物中的早期矿物。我们将模拟古代海洋表层水，其中一部分铁被氧化，颗粒产品通过深海的下降，以及沉积物中微生物生命对氧化铁的假设呼吸，表征每一步的固体产品。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的培训。研究人员还将展示如何在实验室中重现古代铁沉淀物，并与密歇根大学地球夏令营项目的学生一起对古代沉积物进行电子显微镜检查，该项目是一项暑期项目，旨在让服务不足的高中生接触地球和环境科学。参加U-Michigan的该计划的校友将获得有偿机会来协助拟议的研究，为他们提供宝贵的实验室经验和支持性的实验室社区，以帮助保留在部门中代表性不足的学生。该项目将确定可能发生在古代海洋和沉积物中的（生物）化学反应，从而更新早期铁（生物）化学循环的研究者模型。富铁硅酸盐似乎是太古代（4.0 - 2.5 Ga）海洋化学沉积物中的早期矿物，称为“带状铁建造（BIFs）”。然而，目前尚不清楚是否还原-氧化（氧化还原）过程，假设存在于太古代海洋中，并经常由生命介导，促进了这种硅酸盐的形成。拟议的工作将调查太古代海洋中可能的过程形成了什么样的固体产品，从而预测这些途径中的哪一个有助于太古代铁循环，以及BIF矿物，特别是铁硅酸盐，如何反映古代（生物）化学反应。具体而言，研究人员将回答以下问题：1）在假设的太古代海洋条件下，Fe（II）部分氧化的初始固体产物是什么？2)在太古代海洋水体条件下，铁部分氧化的初始固体产物是如何发生化学变化的？3)Fe（II，III）-二氧化硅产品的微生物呼吸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的太古代水柱环境来解决这些问题，然后将这些固体暴露于缺氧水柱条件下以模拟颗粒下降过程中的暴露，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方法将确定太古代海洋中哪些合理的氧化还原反应产生铁硅酸盐或在BIF中发现的其他矿物，从而深入了解太古代生命和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。