Stromatolites as archives for metal mobilization and early life metabolisms? Uranium and Mo isotope studies of modern and Archean stromatolites and carbonates.

叠层石作为金属动员和早期生命代谢的档案？

• 批准号: 404682152
• 负责人: Professor Dr. Stefan Weyer, Ph.D.
• 金额: --
• 依托单位: Institut für Mineralogie
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/404682152?language=en
• 关键词: Stromatolites; archives; metal; mobilization; early

In the proposed project, we aim to investigate the suitability of stromatoilites as archive for I) the redox evolution of early oceans and atmosphere and II) for the appearance of microorganism that were capable to reduce metals. In order to reach these aims, we want to investigate the trace element- and Mo- and U-isotope compositions of recent and ancient (Permian, Neoproterozoic and Neo- to Paleoarchean) stromatolites. Many carbonates directly record the Mo and U isotope composition of their water source. However, stromatolites appear to consist of microbial communities, including beside cyanobacteria also a variety of metabolisms that are capable to reduce metals, such as sulfate and iron reducers and potentially also denitrification-performing organisms. Several modern stromatolites show significant enrichment of redox-sensitive metals in the deeper anoxic layers, such as Mo. Thus, in contrast to other carbonates, stromatolites may bear characteristic isotopic signals of Mo and U reduction. Recent experimental studies imply that the characteristically strong U isotope fractionation during U reduction (between UIV and UVI) may be limited to biotic U reduction, which is likely the dominant mechanism in modern near-surface anoxic environments, such as the deep Black Sea and Cariaco Basin. As a result, sediments of such restricted ocean basins frequently show a correlation of Mo and U isotope signatures. The key-questions, related to the investigation of recent stromatolites planned in this proposal are R1) do they record Mo and U isotopic signatures associated with metal reduction or R2) do they rather archive the isotopic signatures of their water source? In case R1) stromatolites may represent a tool to reconstruct the appearance of metal-reducing metabolisms, while in case R2) they may represent recorders for the redox evolution of seawater (and the atmosphere). The key-questions, related to the investigation of the early Proterozoic and Archean stromatolites are: A1) are the isotopic signatures generated during their deposition preserved in these stromatolites and A2) what can they tell us about the redox-evolution of the oceans and/ or the first appearance of metal reducing organisms? Ancient samples are selected in order to represent a variety of early Earth key intervals, but also to investigate effects of diagenetic alteration (incl. dolomitisation and silification) on the Mo and U isotope signatures. Furthermore, the signatures of the stromatilites will be compared with signatures recorded in other carbonates and organic-rich shales from the same period, in order to optimize reconstructions of the paleo-redox evolution.

在拟议的项目中，我们的目标是研究叠层石作为 I）早期海洋和大气的氧化还原演化和 II）能够还原金属的微生物出现的档案的适用性。为了实现这些目标，我们想要研究近代和古代（二叠纪、新元古代和新至古太古代）叠层石的微量元素、钼和铀同位素组成。许多碳酸盐直接记录其水源的钼和铀同位素组成。然而，叠层石似乎由微生物群落组成，除了蓝藻之外，还包括各种能够还原金属的代谢物，例如硫酸盐和铁还原剂，以及可能具有反硝化作用的生物体。几种现代叠层石在较深的缺氧层中显示出显着富集的氧化还原敏感金属，例如钼。因此，与其他碳酸盐相比，叠层石可能具有钼和铀还原的特征同位素信号。最近的实验研究表明，在 U 还原过程中（UIV 和 UVI 之间）特征性强的 U 同位素分馏可能仅限于生物 U 还原，这可能是现代近地表缺氧环境（例如黑海深海和卡里亚科）的主导机制。盆地。因此，此类受限海洋盆地的沉积物经常显示出钼和铀同位素特征的相关性。与本提案中计划的近期叠层石调查相关的关键问题是 R1）它们是否记录与金属还原相关的 Mo 和 U 同位素特征或 R2）它们是否宁愿存档其水源的同位素特征？在R1）的情况下，叠层石可能代表重建金属还原代谢外观的工具，而在R2）的情况下，它们可能代表海水（和大气）氧化还原演化的记录器。与早期元古代和太古代叠层石研究相关的关键问题是：A1）这些叠层石中保存的沉积过程中产生的同位素特征，A2）它们能告诉我们有关海洋氧化还原演化的什么信息和/还是金属还原生物的首次出现？选择古代样本是为了代表早期地球的各种关键区间，同时也是为了研究成岩蚀变（包括白云石化和硅化）对钼和铀同位素特征的影响。此外，叠层岩的特征将与同期其他碳酸盐和富含有机物页岩中记录的特征进行比较，以优化古氧化还原演化的重建。