Exploration methods have seen great changes in past 25 years

The past twenty-five years have seen substantial changes within the mining industry in terms of geological theories, technical procedures, equipment design, interpretation techniques and data presentation.

One example is the evolution of airborne surveying over the past quarter century. MPH Consulting, for example, supervised thousands of kilometres of airborne radiometric surveying during the uranium boom of the late 1970’s, but relatively little such surveying is carried out today in Canada. Also, most of the airborne geophysical surveying of 10 to 20 years ago was carried out with large, fixed-wing aircraft. Now, the bulk of this work is carried out by the more versatile helicopter and, in terms of the EM, at a much greater range of operating frequencies.

A great deal of IP surveying has also been conducted in the 1980’s in response to the explosion in gold exploration. Borehole IP (and EM) surveys are now accepted exploration approaches.

The evolution of IP hardware over the past 25 years has been impressive. In 1967 IP gear was cumbersome and the surveying tedious. Calculations were performed with a slide rule. Now, with built-in microprocessors, IP receivers can simultaneously read up to six dipoles, instantaneously calculate parameters of interest and plot pseudosections in the field. Likewise, in terms of ground magnetic surveying, the eye-numbing, nightly diurnal corrections are now a thing of the past with state-of-the-art, microprocessor-linked base station and field magnetometers.

Geologically, we have witnessed considerable evolution in ore deposit models over the last 25 years. For example there was still considerable debate over the syngenetic versus epigenetic origin of Noranda-type base metal massive sulphide deposits 25 years ago. The synvolcanic origin of such deposits is now universally accepted.

Conversely, these were a number of strong proponents in the 1970’s of a syngenetic origin for Archean Iode and Carlin-type gold deposits. The epigenetic nature of such mineralization is now generally accepted. Exploration for diamondiferous kimberlites was shrouded in secrecy and mystery up until relatively recently. Now, there is a great deal of information in the public realm as to the chemistry of potentially productive pipes.

One geochemical technique that has virtually disappeared is the heavy minerals geochemistry of glacial overburden via the reverse circulation drilling method. Tens of thousands of RC holes were drilled throughout Canada from about 1970 to the 1980s. Very little, if any, of this work is going on at present. In retrospect, with a couple of exceptions, the RC method hasn’t been a particularly effective mine-finding tool. The fundamental approach seems sound enough but the vagaries of glacial processes have greatly complicated the useful interpretation of the heavy minerals results. Of all the innovations in the mining industry in the past 25 years, the most revolutionary has been the introduction of the computer into virtually every facet of the exploration and mining industry. The major impact of the microprocessor technologies has been to provide the exploration and mining engineer with the ability to routinely manipulate and process data such that many of the more tedious and repetitive calculations can be relegated to automation.