Identification of Massive Sulphide on the Basis of Conductivity

S. J. Balch, D. K. Stickles, D. Blohm, G. M. McDowell

In the early 1980's, INCO began using a borehole induction probe to identify the contact between rock and pyrrhotite-rich massive sulphide. This technique of conductivity mapping has helped reduce mining costs by providing a better estimate on the amount of massive sulphide present between closely spaced blastholes from which core is not available.

In an effort to improve this technology, a number of Canadian mining companies joined together in 1994 to support the development of a new conductivity probe designed by IFG Corporation of Brampton, Canada. The design objectives have been a high dynamic range to allow discrimination within massive sulphide without saturation, good sensitivity to enable its use in disseminated zones and areas with weakly conductive sulphide, and to be able to separate areas with high concentrations of magnetic minerals from conductive zones.

The theory of the new conductivity probe is discussed. Results are shown from several holes which contain massive and disseminated pyrrhotite-rich sulphide, and massive chalcopyrite. One problem that still exists and will be discussed is in the separation of magnetic and conductive effects.

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