Back to the future: silicate weathering through time and space

On geological timescales, Earth’s climate is closely linked to the silicate weathering feedback through the coupled silica-carbon cycles. Weathering of silicate minerals on land sequesters atmospheric CO₂. This process is counteracted by marine authigenic clay formation (also known as reverse weathering), which consumes alkalinity and releases the beforehand sequestered CO₂ back into the ocean and atmosphere. Despite the significance and first description already decades ago, the balance between the terrestrial and marine silicate weathering feedback remains difficult to quantify and is mainly attempted indirectly via elemental and isotopic shifts in fluid composition.

In this talk, I will give an overview of controlling processes on silicate weathering from the Archean to the present day, with special emphasis on the close coupling of the terrestrial and marine weathering regimes. I will show, how silicon isotopes (δ³⁰Si) and Ge/Si ratios can be used to decipher weathering and reverse weathering processes and how early diagenesis impacts originally-inherited signatures, hampering the interpretation of authigenic clay geochemistry in the geological record. As an outlook, I will discuss the approach of enhanced silicate weathering in the marine environment as a tool to mitigate climate change through ocean alkalinisation.