The control of Phanerozoic atmosphere and seawater composition by basalt–seawater exchange reactions |
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Authors: | Rolf S Arvidson Michael Guidry Fred T Mackenzie |
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Institution: | aDepartment of Earth Science MS-126, Rice University, P.O. Box 1892, Houston TX 77251-1892, USA;bDepartment of Oceanography, SOEST, 1000 Pope Road, University of Hawaii, Honolulu HI 96822, USA |
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Abstract: | We present results from a long term geochemical cycling model, with a focus on the sensitivity of atmospheric carbon dioxide, oxygen, and the major element composition of seawater to seafloor spreading rates. This model incorporates rock weathering, basalt–seawater exchange reactions, and the formation and destruction of chemical sediments and organic matter. Hydrothermal reactions between seafloor and seawater involving calcium, magnesium, sodium, potassium, sulfate and carbon are the high temperature counterparts to low temperature redox, weathering, precipitation and diagenetic reactions. A major source of uncertainty is the extent to which these exchange fluxes are controlled by seafloor spreading rate. In addition, the return fluxes of these components to the atmospheric and primary silicate reservoirs reflect not only the overall rates of subduction and metamorphism, but the distribution of the overlying sedimentary burden and authigenic minerals formed during basalt alteration as well. In particular, we show how the stoichiometry of exchange fluxes (Mg/Ca and SO4/Ca) may buffer atmospheric CO2 and O2 concentrations. |
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Keywords: | Phanerozoic CO2 Seawater composition Seafloor spreading |
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