Refining the understanding of Earth's oxygenation through the paleo-redox geochemistry of redbeds

通过红层的古氧化还原地球化学加深对地球氧合的理解

• 批准号: RGPIN-2017-05028
• 负责人: Babechuk, Michael
• 金额: $ 1.97万
• 依托单位: Memorial University of Newfoundland
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=644402
• 关键词: Refining; understanding; Earth; oxygenation; through

Establishing when free oxygen (O2) first appeared in Earth's atmosphere and how levels of O2 subsequently accumulated, fluctuated, and stabilised at levels capable of supporting animal life have motivated researchers for decades. A key strategy to unravel these issues is to investigate the redox-sensitive element geochemistry of ancient terrestrial rocks, such as paleosols (fossil “soils”) and redbeds, which formed in direct contact with the paleo-land surface and atmosphere. Redbeds are siliciclastic sedimentary rocks bearing Fe(III)-oxides that, in many cases, formed from the oxidation of Fe(II) in soils or surface waters during their deposition. Redbeds appeared for the first time only in the Paleoproterozoic, following the onset of Earth's Great Oxidation Event (GOE) that began approximately 2.45 billion years ago (Ga). However, redbeds are vastly understudied using state-of-the-art geochemical techniques that could provide quantitative information on their formation mechanisms, evaluate whether redox-sensitive trace metals (e.g., Cr, V, Mo, U) were scavenged by the Fe(III)-oxides, and establish how redbeds may have been influenced by post-depositional diagenesis and metamorphism.******This research will provide the first detailed investigation of redbeds that integrates textural and mineralogical data with major element, high-precision ultra-trace element, and Cr stable isotope geochemistry. The heart of the research will be the first in-depth study of Earth's oldest redbeds, which are preserved in the ca. 2.45-2.32 Ga Huronian Supergroup (Ontario), but complementary insight will come through the study of younger redbeds (Triassic, Lower Fundy Group, Nova Scotia/New Brunswick) and modern river sediments (Newfoundland, Costa Rica). Bulk rock geochemistry will be used to constrain the provenance lithology and fluvial process baseline characteristics of the sediments and sedimentary rocks, and a sequential Fe extraction strategy will be used to target the geochemical characteristics of the Fe(III)-oxides. The research strategy is structured to evaluate, for the first time, what paleo-redox proxy information can be established from the geochemistry of redbeds and how these data fit into the wider framework of Earth's redox evolution. This strategy could shed new light on Earth's critical stages of atmospheric O2 evolution. The research is also relevant to redbed-hosted deposits (e.g., U, Cu) and the oxidation of the Martian surface. The research will provide in-depth, multi-disciplinary training to numerous students, preparing them for impactful careers in a wide range of Earth science sectors. The research program will produce high-impact scientific contributions (publications and conference presentations) and is structured to evolve into an extensive network of global collaborations that will foster the growth of Canada and MUN as an Earth Science research hub.****** **** **** **** ****

建立何时自由氧（O2）首先出现在地球大气中，以及随后在能够支持动物生命的水平上积累，波动和稳定的O2水平如何使研究人员成熟数十年。解开这些问题的一个关键策略是研究古代陆地岩石的氧化还原敏感元素地球化学，例如古溶（化石“土壤”）和红床，这些岩石是直接与古地的表面和大气层接触而形成的。红床是载有Fe（III） - 氧化物的硅细沉积岩，在许多情况下，它们是由土壤或地表水沉积过程中的Fe（II）氧化形成的。在地球上大约24.5亿年前（GA）开始的地球大氧化事件（GA）之后，红床首次仅在古元中出现。 However, redbeds are vastly understood using state-of-the-art geochemical techniques that could provide quantitative information on their formation mechanisms, evaluate whether redox-sensitive trace metals (e.g., Cr, V, Mo, U) were scavenged by the Fe(III)-oxides, and established how redbeds may have been influenced by post-depositional diagenesis and metamorphism.******This research will provide the first detailed对将纹理和矿物学数据与主要元素，高精度超轨道元素和CR稳定同位素地球化学相结合的红床的调查。该研究的核心将是对地球最古老的红床的深入研究，该研究保存在大约。 2.45-2.32 GA人类超级群（安大略省），但完整的见解将通过研究年轻的红床（Triassic，Lower Fundy Group，Nova Scotia/New Brunswick）和现代河流沉积物（Newfoundland，Costa Rica）来实现。体积岩石地球化学将用于限制沉积物和沉积岩石的出处岩性和河流过程基线特征，并将使用顺序的FE提取策略来针对Fe（III） - 氧化物的地球化学特征。该研究策略的结构是首次评估从红床的地球化学以及这些数据如何拟合到地球氧化还原进化的更广泛框架中的首次评估。这种策略可以为地球大气O2进化的关键阶段提供新的启示。该研究还与红床托管沉积物（例如U，Cu）和火星表面的氧化有关。这项研究将为许多学生提供深入的多学科培训，为他们在广泛的地球科学领域的有影响力的职业做准备。该研究计划将产生高影响力的科学贡献（出版物和会议演讲），并结构发展为全球合作的广泛网络，将促进加拿大和MUN作为地球科学研究中心的增长。**** **** **** ************