Massive sulphide delineation using borehole radar: tests at the McConnell nickel deposit, Sudbury, Ontario

Abstract

Ground-penetrating radar (GPR) surveys were undertaken in three boreholes intersecting the McConnell massive Ni–Cu sulphide deposit near Sudbury, Ontario, Canada. Radar data were acquired using single-hole and crosshole configurations to assess the potential in delineating massive sulphide deposits. Single-hole radargrams acquired with 22 and 60 MHz antennae display reflections from the upper and lower boundaries of the deposit in areas where the contact between the host rock and ore body is sharp. Direct arrival traveltimes selected from crosshole measurements between two shallow boreholes were used for tomographic reconstruction of inter-hole velocities. The crosshole data set also contains late arrival reflections from the ore deposit. The reflections were migrated using the velocity distribution obtained from tomography, to estimate the position of the upper surface of the deposit between the two boreholes. The deposit is imaged over a small area near its intersection with a shallow borehole. The survey geometry could not provide information on the position of the ore body at mid-distance between the boreholes, i.e. in areas of most interest to geologists.