A database of physical properties of rocks from the Trans-Hudson Orogen, Canada

Abstract

A physical properties database of rock types from the Trans-Hudson Orogen provides information for interpretation of geophysical surveys over the Trans-Hudson Orogen. Measurements have been made on 320 samples (all reduced to core) 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 < 1%. Except for a few samples, magnetic susceptibility ranged from 20 to 4000 × 10–6 SI units. P- and S-wave velocities were made under maximum uniaxial stress and triaxial stresses equivalent to depths of ca. 4 km. P- and S-wave velocities measured were 5–7 km s–1 and 3–4 km s–1, respectively. 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 between 0.0 and 1.0 mol/L. Increasing salinity caused a reduction in resistivity. The porosity–resistivity data is in reasonable overall agreement with Archie's Law for all rock types. A minimum value of 50 Ω m was obtained from samples not containing significant sulphide minerals or graphite. For sulphide and graphite-bearing samples, resistivity was as low as 1 Ω m. The resistivity data are consistent with the hypothesis that North American Central Plains (NACP) conductivity anomaly could be due to the presence of graphite- and (or) sulphide-rich bodies or saline pore fluids in the crust. Thermal conductivity measurements made using a "divided-bar" apparatus yielded values between 1 and 5 W m–1 K–1.