Simulation of iron mineral diagenesis in ancient iron formations by P/T-treatment of biogenic and abiogenic iron minerals

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Precambrian Banded Iron Formations (BIFs) are ancient sedimentary deposits consisting of silica and iron minerals. It is heavily debated whether the deposition of the oldest BIFs (>3 Gyr) are a result of chemical oxidation of dissolved iron(II) by cyanobacterial oxygen (O2) leading to the formation of abiogenic iron(III) minerals or whether the oldest iron formations are a direct product of anoxygenic phototrophic Fe(II)-oxidizing bacteria (leading to biogenic iron(III) minerals). A possible approach to distinguish these two processes is to study the transformation of iron(III) minerals over geological time, since in contrast to abiogenic iron(III) minerals, biogenic iron(III) minerals are directly associated with microbial cells. The goal of this project is to study diagenetic processes of biogenic and abiogenic iron minerals and to identify features in the diagenetic mineral products indicative for either biogenic or abiogenic iron minerals. To this end we intend to expose iron minerals and cell-iron-mineral aggregates produced by phototrophic Fe(II)-oxidizers to temperatures and pressures experienced by BIFs and couple this to mineral identification, Fe-isotope and organic biomarker analysis. This study will help to constrain the processes with regard to BIF deposition and will improve our understanding of iron biogeochemistry in modern environments.