Biological Origin of Precambrian Banded Iron Formations

前寒武纪带状铁地层的生物起源

• 批准号: 34732933
• 负责人: Professor Dr. Andreas Kappler
• 金额: --
• 依托单位: Department of Earth and Atmospheric Sciences
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2006
• 资助国家: 德国
• 起止时间: 2005-12-31 至 2011-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/34732933?language=en
• 关键词: Biological; Origin; Precambrian; Banded; Iron

Banded Iron Formations (BIFs) are Precambrian sedimentary deposits that consist of alternating layers of silica and iron minerals and represent one of the most enigmatic features in the geologic record. Cyanobacterial oxygen is suggested to have caused a chemical oxidation of iron(II) to iron(III), which is followed by the precipitation and deposition of iron minerals. The mechanism responsible for the formation of the earliest BIFs, which were likely precipitated in the absence of molecular oxygen (O2), however, is still unclear. Anoxygenic phototrophic bacteria able to oxidize iron(II) to iron(III) with light as energy source (“photoferrotrophs”) have recently been discovered. The main goal of this project is to evaluate the potential role of these phototrophic iron(II)-oxidizing bacteria in the deposition of Precambrian BIFs by ecophysiological studies with modern bacteria. In the first funding period the rates of phototrophic Fe(II) oxidation were determined under different eco-physiological conditions, the cell-mineral aggregates formed were characterized and the primary mineral precipitates formed by these bacteria were identified leading to the conclusion that these organisms could have been responsible for BIF deposition. Additionally, we suggested ocean water temperature fluctuations as the key trigger responsible for the alternating layering of Si and Fe minerals in BIFs. In the second funding period we intend to determine the dependence of these organisms on biologically important trace metals (Co, Mo, V). From comparison to trace metal dependence in oxygenic photosynthetic microbes (cyanobacteria) and Archean seawater trace metal concentrations (inferred from concentrations in BIFs) we would like to constrain the presence of photoferrotrophs vs cyanobacteria and better understand the potential competition or dominance of one of these organisms vs. the other.

条带状铁建造（BIFs）是前寒武纪沉积矿床，由硅和铁矿物交替层组成，是地质记录中最神秘的特征之一。蓝细菌的氧被认为是导致铁（II）的化学氧化为铁（III），随后是铁矿物的沉淀和沉积。然而，最早的BIF可能是在没有分子氧（O2）的情况下沉淀的，其形成机制仍不清楚。最近发现了能够以光作为能源将铁（II）氧化成铁（III）的不产氧光养细菌（“光养铁菌”）。该项目的主要目标是通过对现代细菌的生态生理学研究来评估这些光养铁（II）氧化细菌在前寒武纪BIF沉积中的潜在作用。在第一个资金周期的光养铁（II）氧化的速率进行了测定，在不同的生态生理条件下，形成的细胞矿物聚集体的特点和主要矿物沉淀物形成的这些细菌被确定导致的结论是，这些生物体可能是负责BIF沉积。此外，我们建议海水温度波动的关键触发器负责交替分层的硅和铁矿物在BIFs。在第二个供资期，我们打算确定这些生物体对生物重要的微量金属（钴，钼，钒）的依赖性。从比较微量金属依赖于产氧光合微生物（蓝细菌）和太古代海水微量金属浓度（推断从BIFs的浓度），我们想限制存在的光养铁细菌与蓝细菌和更好地了解潜在的竞争或优势，这些生物体之一与其他。