Electrical conductivity of two-pyroxene granulite, collected from north margin of North China craton, was measured at 1.0 similar to 2.0 GPa and 523 similar to 1173 K by using three different methods at the same time.  The three methods are an impedance spectroscopy for a broad frequency range of 0.05 to 10(-6) Hz, a single lower frequency (0.1 Hz), and the DC-method.  The experiments were carried out in a measurement system of electrical conductivity, which consisted of an YJ-3000t multi-anvil apparatus, a Solartron IS-1260 Impedance/Gain-Phase analyzer, an Agilent 34401A Multimeter, and a computer.

The experimental results indicate that within the range of experimental temperature and pressure, the electrical conductivity of two-pyroxene granulite changes from 2.66 X 10(-5) S center dot m(-1) to 0.056 S center dot m(-1) and hardly has a dependence on the given pressure.  With increasing temperature, the electrical conductivity increases.  The conductivity-temperature relation follows an Arrhenius behavior.  The pre-exponential factor and activation energy of the Arrhenius formula are 8.95 similar to 17.9 S center dot m(-1) and 0.569 similar to 0.605 eV, respectively. 

The comparison of the results obtained by the three methods indicates that the result measured by the impedance spectroscopy is always higher than that of the 0.1 Hz's and the result determined by the DC-method is always the lowest.  Nevertheless the difference among the data points is less than 0.20 lg (S/m) except for two low-temperature points.  Based on the experimental results, the regional crust model and the geothermal gradient, we constructed the profiles of conductivity versus depth.  The comparison of the calculated results with the electrical structure of this area reveals that the electrical conductivity of two-pyroxene granulite intersects the range of the electrical conductivity of the lower middle crust and the lowermost crust beneath this area. 

Combining with the conclusion of the in situ seismic velocity measurement and the seismic refraction profile, we can conclude that the two-pyroxene granulite could be a constituent of the lower crust in the northern margin of North China craton.

Publication name	CHINESE JOURNAL OF GEOPHYSICS-CHINESE EDITION Volume: 53 Issue: 10 Pages: 2386-2395 Published: OCT 2010
Author(s)	Li P, Zhou WG, Gong CY, Fan DW, Wei SY, Xie HS
Corresponding author	LI Peng niaolp@163.com,　Chinese Acad Sci, Lab Earths Interior & Geofluid Geochem, Inst Geochem, Guiyang 550002, Peoples R China

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