Fe Isotopes and Biological Processing of Fe in the Pre-Oxygenated Earth: Archean to Mid-Proterozoic Banded Iron Formations

9903252约翰逊拟议的研究将侧重于使用铁（Fe）同位素来追踪微生物在太古代至中元古代铁的地球化学循环中的作用，涵盖最早的地球（38亿年前），到大约20亿年前大气条件快速变化的时期。 我们的目标是开发一种“同位素指纹”，它可以独特地记录生物活动，但相对不受后期变化的影响，例如较年轻的地质过程对岩石的改变。 “同位素指纹”将依赖于观察到微生物通过选择性偏好较轻的质量来破碎Fe的四种稳定同位素（54Fe，56Fe，57Fe和58Fe）的相对丰度。 我们建议，铁的同位素组成将提供一个强有力的手段来评估微生物在铁的地球化学循环中的作用，在前寒武纪，这是准确地解释前寒武纪的大气条件的岩石记录的关键。

9903252Johnson The proposed research will focus on using iron (Fe) isotopes to trace the role of microorganisms in the geochemical cycle of Fe in the Archean to Mid-Proterozoic, covering the earliest Earth (3.8 billion years ago), to a period of rapid change in atmospheric conditions about 2 billion years ago. Our goals are to develop an "isotopic fingerprint" that uniquely records biologic activity, but is relatively immune to later changes, such as alteration of rocks by younger geologic processes. The "isotopic fingerprint" will rely on the observation that microorganisms fractionate the relative abundances of the four stable isotopes of Fe (54Fe, 56Fe, 57Fe, and 58Fe) through selective preference for the lighter masses. We propose that the isotope composition of Fe will provide a powerful means to evaluate the role of microbes in the geochemical cycling of Fe in the Precambrian, which is critical for accurately interpreting Precambrian atmospheric conditions from the rock record.