Crustal carbonate build-up as a driver for Earth’s oxygenation

Abstract

Oxygenation of Earth’s atmosphere and oceans played a pivotal role in the evolution of the surface environment and life. It is thought that the rise in oxygen over Earth’s history was driven by an increasing availability of the photosynthetic limiting nutrient phosphate combined with declining oxygen-consuming inputs from the mantle and crust. However, it has been difficult to assess whether these processes alone can explain Earth’s oxygenation history. Here we develop a theoretical framework for the long-term global oxygen, phosphorus and carbon cycles, incorporating potential trajectories for the emergence of continents, the degassing of mantle volatiles and the resulting increase in the size of the crustal carbonate reservoir. We find that we can adequately simulate the Earth’s oxygenation trajectory in both the atmosphere and oceans, alongside reasonable reconstructions of planetary temperature, atmospheric carbon dioxide concentration, phosphorus burial records and carbon isotope ratios. Importantly, this is only possible when we include the accumulation of carbonates in the crust, which permits ever-increasing carbon recycling rates through weathering and degassing. This carbonate build-up is a missing factor in models of Earth’s coupled climate, nutrient and oxygen evolution and is important for reconstructing Earth’s history and potential exoplanet biogeochemistry. The accumulation and subsequent recycling of carbonate in the crust may have helped to drive the oxygenation of the early Earth, according to an ocean and atmosphere box model incorporating the inorganic carbon cycle.