Electrical conductivity of NaCl-H2O fluid in the crust

Hiroshi Sakuma, Masahiro Ichiki

Research output: Contribution to journalArticlepeer-review

24 Citations (Scopus)

Abstract

Ionic electrical conductivity of NaCl-H2O fluid as a function of pressure (0.2-2.0 GPa), temperature (673-2000 K), and NaCl concentration (0.6-9.6 wt %) was investigated using molecular dynamics (MD) simulations. Conductivity versus NaCl concentration has a nonlinear relationship due to the presence of electrically neutral ion pairs in concentrated solutions. The calculated conductivity at 0.6 wt % NaCl is consistent with the available experimental data, and the calculated conductivity at higher temperatures shows a greater degree of pressure dependence. The major factors controlling the conductivity are the density of the NaCl-H2O fluid and the permittivity of solvent H2O. A purely empirical equation for deriving the conductivity was proposed. Highly conductive zones below a depth of 35 km in the middle portion of the continental crust can be interpreted by the presence of NaCl-H2O fluid with the salinity ranging from 0.2 to 7.0 wt %. A highly conductive zone observed at a depth of 20 to 40 km above the subducting oceanic crust in Cascadia can be explained by the presence of low-salinity (0.5 wt %) NaCl-H2O fluid possibly generated by the dehydration of basalt.

Original languageEnglish
Pages (from-to)577-594
Number of pages18
JournalJournal of Geophysical Research: Solid Earth
Volume121
Issue number2
DOIs
Publication statusPublished - 2016 Feb 1

Keywords

  • aqueous fluid
  • dielectric constant
  • ion association
  • magnetotellulic
  • molecular dynamics

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

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