UC Berkeley

The chemical weathering of sulfide-bearing rocks can result in the dissolution of carbonate rocks leading to degassing of (Formula presented.) to the atmosphere. While this process has been argued to be a significant geologic source of (Formula presented.), it also perturbs the geological cycles of oxygen and sulfur, triggering a cascade of geochemical feedbacks. Using a numerical model of geochemical cycles and climate, we found that due to feedbacks on atmospheric oxygen associated with the organic carbon cycle, an increase of sulfide weathering leads to a limited source of (Formula presented.) followed by a longer sink of (Formula presented.). This result is due to the stoichiometry of sulfide weathering where more (Formula presented.) is consumed than (Formula presented.) is released. If sulfide weathering increases progressively on a geological timescale, the duration of the carbon source is extended, but its magnitude is negligible before it becomes a carbon sink.