Stromatolites as archive for metal cycling and early life: uranium and molybdenum isotope studies of modern and Archean stromatolites

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.

The key-questions, related to the investigation of recent stromatolites planned in this proposal are i) do they record Mo and U isotopic signatures associated with metal reduction or ii) do they rather archive the isotopic signatures of their water source? In case i) stromatolites may represent a tool to reconstruct the appearance of metal-reducing metabolisms, while in case ii) 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: I) are the isotopic signatures generated during their deposition preserved in these stromatolites and II) what can they tell us about the redox-evolution of the oceans and/or the first appearance of metal reducing organisms?