Electrical conductivity and dissociation of fluids in crust and mantle

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The electrical conductivity of fluids in the system H2O-NaCl has been measured to 1 GPa and 600 ˚C. These data more than double the pressure range of available conductivity data in this system. A simple numerical model was developed that allows predicting the conductivity of saline fluids in the entire crust and the shallow upper mantle. The elevated conductivity in the forearc region of subduction zones can be explained by not more than 1 % of a saline fluid forming a continuous film or network. The present extension proposal request funding for extending the conductivity measurements in the systems NaCl-H2O, KCl-H2O, HCl-H2O, and NaOH-H2O to 3 GPa and 1000 ˚C. These data would provide firm constraints on dissociation constants of dissolved species and of the pH of fluids in the upper mantle and would allow testing various predictions by thermodynamic models. Moreover, the data would allow modeling the conductivity of complex fluids, which would allow distinguishing hydrothermal systems from magma chambers below volcanoes and therefore aid in volcanic risk assessment.