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.
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.