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March 8, 2012: Ingassing, Storage, and Outgassing of Terrestrial Carbon through Geologic Time

Posted on Mar 8, 2012 in Seminars

Raj Dasgupta
Rice University


The Earth is unique among the terrestrial planets in our solar system in having a fluid envelope that fosters life. The key behind Earth’s habitable climate is well-tuned cycles of carbon (C) and other volatiles. While on ten to thousands of year time-scales the chemistry of fluids in the atmosphere, hydrosphere, and biosphere is dictated by fluxes of carbon between the near surface reservoirs, over million to billion years this is maintained by chemical interactions of carbon between the Earth’s interior, more specifically the Earth’s mantle, and the exosphere. This is because of the fact that the estimated total mass of C in the mantle is greater than that observed in the exosphere and the average residence time of carbon in the mantle is on the ≥1 Ga. But how did the Earth’s mantle attain and maintain the inventory of mantle carbon over geologic time and is the residence time of carbon in the mantle as constrained by the present-day fluxes a true reflection of the carbon ingassing and outgassing rates throughout the history? Also, when in the history of the planet carbon inventory of the mantle got established and how did it change through geologic time? The answers to these questions are important because understanding the origin and chemistry of carbon and how they regulate feedbacks between the planet’s interior and the atmosphere is of fundamental importance owing to far-reaching implications for a number of fields of natural sciences, such as the thermal history of the Earth, internal differentiation, long-term evolution of climate, and origin and evolution of life. Because the abundance and mode of storage of mantle carbon are central to carbon’s role in global geodynamics, it is critical to constrain the processes that modulated the carbon inventory of the Earth’s mantle through time. In this talk, I will try to review ingassing, outgassing, and storage mechanisms of terrestrial carbon, from the time period of early planetary differentiation and magma ocean in the Hadean to the plate tectonic cycles of the modern Earth through Phanerozoic.