Electrical conductivity of fluid-bearing quartzite under lower crustal conditions

Akira Shimojuku, Takashi Yoshino, Daisuke Yamazaki, Takamoto Okudaira

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)

Abstract

The electrical conductivity of fluid-bearing quartzite was determined as function of temperature and fluid fraction at 1GPa in order to assess the origin of the high conductivity anomalies observed in the middle to lower crustal levels. Dihedral angles of quartz-fluid-quartz determined from recovered samples were below 60°, suggesting that fluid forms an interconnected network through the quartz aggregate. The electrical conductivity of quartzite increases with increasing temperature, which can be approximately expressed by Arrhenius equation. The apparent activation enthalpy decreases from 0.70 to 0.25eV with increasing fluid fraction in volume from 0.00043 to 0.32. The electrical conductivity (σ) of the fluid-bearing quartzite increased with fluid fraction (φ) proportionally to a power law (σ∝φ0.56-0.71) within the temperature range of 900-1000K. The electrical conductivity of the aqueous fluid-bearing quartzite with the maximum fluid fraction (0.32) was found to be about three orders of magnitude higher than that of dry quartzite at 1000K. However, its electrical conductivity was definitely lower than the geophysically observed values of high-conductivity anomalies, even if the quartzite contained large fluid fractions (0.32). The present results suggest that fluid-bearing quartzite is unable to account for the high-conductivity anomalies in terms of fluid fraction. A significant amount of other ionic species, such as Na, Cl, and Al in aqueous fluid, in addition to silica phases dissolved in fluid, is required to increase conductivity.

Original languageEnglish
Pages (from-to)1-8
Number of pages8
JournalPhysics of the Earth and Planetary Interiors
Volume198-199
DOIs
Publication statusPublished - May 1 2012

Keywords

  • Crust
  • Electrical conductivity
  • Fluid
  • Quartz

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Geophysics
  • Physics and Astronomy (miscellaneous)
  • Space and Planetary Science

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