Metamorphic decarbonation, silicate weathering and the long-term carbon cycle

The seawater Sr-87/Sr-86 curve implies a 50-100 Myr episodicity in weathering rate which requires a corresponding variation in CO2 degassing from the solid earth to the atmosphere. It is proposed that this is caused by orogenesis, which both produces CO2 as a result of metamorphic decarbonation reactions, and consumes extra CO2 as a consequence of erosion-enhanced weathering. Global climate on the geological time-scale is therefore controlled by the difference between the relatively large and variable orogenic-moderated degassing and weathering CO2 fluxes.