Simulating iron mineral precipitation in Early Earth oceans and their role in controlling phosphorous bioavailability

Green rust (GR) and greenalite are highly reactive, redox-sensitive iron (Fe) phases that are believed to have played a crucial role in cycling of Fe, key nutrients (e.g., P) and toxins (e.g., As) in Fe2+- and Si-rich deep Early Earth oceans ~2.4 billion years ago. Using an analogue of the Early Earth ‘seawater’, we followed the formation and transformation of GR and greenalite in the absence and presence of As and P. The combination of As and P is crucial because As(V) is a key competitor for phosphate, but highly toxic to all living cells. To assess to what extent the formation pathways of GR and greenalite in these early oceans would have shaped As toxicity and thus P bioavailability can tell us about how these processes affected the evolution of microbial processes (photosynthesis) and, ultimately, life as we know it today.