How have dissolved metal concentrations changed with the evolution of metabolisms and rise of oxygen?

Dissolved metal concentrations in the ocean have changed considerably over our planet’s 4.6-billion-year-old history, but the concentrations are hard to quantify. Yet chemically-precipitated carbonate rocks contain evidence of changing ocean chemistry in their trace element contents (see below!). We aim to reconstruct the evolution of seawater chemistry using a combination of (1) modern experiments studying how metals like Mn and Fe can substitute into calcites, and (2) measurements of well-preserved carbonate rocks over time, selected using isotopic proxies for diagenesis.

Red staining on Archean carbonates from S. Africa,
due to their high iron content!