What do iron silicates signify about the chemistry and biology of the ancient ocean?

Iron silicate inclusions discovered in Archean cherts signal a major difference in early Earth biogeochemistry that is not yet understood. We are performing laboratory experiments in an anoxic glovebox to synthesize similar iron-silicates under various plausible conditions for the 2.5 Ga ocean. These experiments will help us constrain the aqueous geochemistry of the iron-silicate producing ancient ocean, including the silica and ferrous iron activity, pH, and pO2 levels, as well as constrain the metabolic activities of ancient life.

Relevant publications:

Johnson JE, Muhling JR, Cosmidis J, Rasmussen B, Templeton AS (2018) Low-Fe(III) Greenalite Was a Primary Mineral From Neoarchean Oceans, Geophysical Research Letters, doi: 10.1002/2017GL076311.