Physical properties of rocks from the Trans-Hudson orogen, Canada

A physical properties database of rock types from the Trans Hudson orogen is presented. Measurements have been made on 320 samples representing metamorphosed Archaean and juvenile Proterozoic orogenic rocks. Water saturated densities were generally between 2600 and 3100 kg m-3. In most cases the porosity was less than 1 percent. Except for a few samples, magnetic susceptibility ranged from 20 to 4000 x 10 exp-6 SI units. P-wave velocities and S-wave velocities were made under maximum uniaxial stress and triaxial stresses equivalent to depths of ca 4 km. P-wave and S-wave velocities measured were in the range 5-7 km s-1 and 3-4 km s-1 respectively. The velocity data show a wide variation in impedance between neighbouring domains and within domains: seismic reflection coefficients greater than 0.1 would appear to be routinely possible. Thermal conductivity measurements made using a `divided-bar' apparatus, yielded values between 1 and 5 W m-1 K-1. Electrical resistivity measurements were made at room temperature from 5 Hz to 10 kHz after samples were oven dried and after saturation in solutions with salinity up to 1.0 M. The porosity - resistivity data is in reasonable overall agreement with Archie's Law for all rock types. A minimum value for the resistivity of those samples not containing significant sulphide minerals or graphite, was 50 ohm-m. For sulphide and graphite-bearing samples, resistivity was as low as 1 ohm-m. The resistivity data are consistent with the hypothesis that North American Central Plains(NACP) conductivity anomaly is due to the presence in the crust of graphite- and/or sulphide-rich bodies or saline pore fluids.