High-Tech Prospecting

High-Tech Prospecting
An important part of mineral exploration in many countries has always been the “boot-and-hammer” prospecting. But exploration has changed drastically with the recent advances in technology, all of which play an important part in the prospecting task.

As is typical, the geological reconnaisance starts the process. In a large amount of countries, government geological surveys hire mapping geologists who examine extensive areas, making note of all the pertinent geological features as shown in outcrops and prominent landforms. The geological maps and reports that they make are a useful source of reference for the person who is trying to find mines. Prospectors with experience plan their search in locations where the geological structures and the rocks suggest that there could be mineralization.

The first order of business for a prospector is the geological mapping on a more detailed scale than that given by the government geologists, and the prospecting of the surface.

What the prospector looks for is for trace amounts of ore minerals, for rock types that are favorable, and for alteration that could have been caused by mineralizing solutions. One very important sign of mineralization is a gossan, an area which has rusty staining on rock formed when sulphide minerals are oxidized. There are other minerals of ore that can also oxidize, they leave a stain in the surface of saecondary minerals on host rocks. The bright yellow and orange of secondary uranium minerals and the light green of nickel bloom are precise examples of this.

If a showing is found, it is sampled, the samples are then sent for a chemical analysis called an assay.

Sampling, which will be better explained and with more detail in chapter five of this article, can be as easy as banging off a piece of rock from an outcrop. The exploration crew will often bring in a bulldozer to strip away overburden or they can also use explosives to blast a trench in the rock.

Another technique that is useful at the reconnaissance stage is remote sensing, the use of radar and photographic images taken by aircraft or satellites. Satellite or aerial imagery are able to show large-scale geological structures like geological contacts or faults in which mineralization often happens. In some zones, like deserts for example, color changes on satellite imagery may denote changes in rock type or show areas of rock alteration.

It is believed in general that the discovery of metals in established mining areas in the future will likely come at greater depths than the known orebodies. There is also the possibility that they might come from areas which are covered by heavy blankets of overburden. Finding these deposits demands more sophisticated technology than the traditional prospecting methods. Targets which are buried can be explored by diamond drilling, but the prospector will be obliged to use geological inference, geochemistry or geophysics to know where to aim the drill.

Geophysics and geochemistry will be examined in this chapter of the article.