A Resistivity Tomography Test Survey in the Toyoha Mine, ? Hokkaido, Japan

Resistivity tomography was intensively developed from the mid 1980’s to early 1990’s. The technical development department of the Metal Mining Agency of Japan(MMAJ) had conducted research on the application of resistivity tomography to mineral exploration until the end of 1993.

The MMAJ has adopted the McOHM-21 system as the data acquisition system for resistivity tomography. The McOHM-21 is a DC transmitter and receiver combined unit manufactured by OYO Corporation, and can be programmed to simultaneously measure three potentials as well as injected current wave forms.

Using the McOHM-21, the MMAJ executed a resistivity tomography test survey in the Toyoha Mine, Hokkaido, Japan, in August 1993, in order to delineate the location and shape of the known lead-zinc sulphide vein as a low resistivity anomaly.

Electrodes were set up with 5m separation along three sides(90m-110m-60m) of the mine development encircling the inclined vein whose maximum width was 2m. Two sets of data obtained by pole-pole and dipole-dipole configurations were analyzed by the alpha centers method and a combination of the finite element method and nonlinear least-squares method respectively. The reconstructed resistivity images show the vein as a low resistivity zone, though there are some differences in the location and width between the expected vein and the reconstructed image. The resistivity image, corrected for the high temperature(95 degrees centigrade) of the rock in the survey area, coincides with the resistivity values(20 degrees centigrade) of rock and ore samples taken from the walls of the mine development.

Such resistivity data is a great support in solving the exploration problems in mines, where information on the target(e.g. veins) is only partly exposed in the mine development.