DEEP CARBON CYCLE The ways in which the near surface carbon cycle are connected to the deep Earth are fundamental to the short and long-term geologic cycle of carbon. Carbon is transported to the deep Earth in subduction zones and returned to the near surface by metamorphic and volcanic activity. However, little is known about the species of carbon and their fluxes. Our program at Johns Hopkins University is a part of the Deep Carbon Observatory based at the Carnegie Institution of Washington.
INTERACTIONS BETWEEN C-BEARING FLUIDS AND ROCKS IN THE DEEP CRUST AND MANTLE Isabelle Daniel (Lyons), Craig Manning (UCLA) & Dimitri Sverjensky (Johns Hopkins) The Earths deep carbon cycle is strongly influenced by the reactivity of carbonate minerals along the P-T paths at which they are transported into the deep crust and mantle. Yet major questions remain unanswered: What happens to these carbonate minerals in the presence of aqueous fluids? In what form is dissolved CO2 in the deep carbon cycle? Is it present as molecular CO2, bicarbonate (HCO3-), carbonate (CO3--) or metal complexes of these ions (e.g. MgHCO3+)? Are there new unexpected carbonate-bearing species in aqueous fluids at high temperatures and pressures? It is also expected that the form of CO2 and the solubility of carbonate minerals will depend strongly on the salinity of the fluids and the pH imposed by silicate mineral assemblages. However, experimental data and theoretical geochemical models addressing these issues are lacking under deep crust and mantle conditions. Knowing the solubility and speciation of carbonate is vital to quantification of the transfer of CO2 between reservoirs, understanding the variability of the fluxes of CO2 in the deep carbon cycle, and deciphering the chemical environments of deep life and of hydrocarbon generation. Our research provides information that is important to all four directorates of the Deep Carbon Observatory (DCO).
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