Equation-of-state and electrical conductivity of NaCl-bearing fluids in the deep Earth: insights from molecular simulations

Summary The next generation of mineral and energy system discoveries in Australia will be made under deeper cover or water and require knowledge of the deep earth. Primarily, these discoveries will be driven by understanding the lithospheric properties and resource transport that underpin the systems. Nevertheless, our lack of good understanding of the physical-chemical properties of lithospheric scale mineral systems hinders our interpretation of available data and makes predictive models difficult to use. These properties are very difficult to measure in the laboratory but are accessible through molecular dynamic simulations. We used molecular dynamics simulations to investigate the chemical and physical properties of the NaCl-bearing fluids over wide range of temperature (25-1000 °C), pressure (1-60 kbar) and salinity (0-10 m) using high-performance computers. The equation-of-state, ion association and diffusion constant of NaCl solutions were predicted and fitted into an electrical conductivity model. By integrating predictive geophysical properties with large-scale models, this study will develop essential guides that underpin interpretation of geophysical data for mineral exploration.