Prospecting using Geophysics

The rapid expansion of technological knowledge following the Second World War has permitted great advances in geo physics, the study of the physical properties of the Earth. It’s not a new science – as early as the seventeenth century, Swedish prospectors were using magnetized iron bars to locate magnetic bodies of iron ore but it developed rapidly during the post-war boom. And computerization has meant the amount of data we can acquire and process on site has increased dramatically.

In all geophysical surveys, what is sought is an anomaly — an exception to the norm. A geophysical anomaly is an area where the earth has unusual physical properties.

In a typical geophysical survey, a physical property like the gravitational or magnetic field is measured on a grid of locations over the survey area. The value found at each grid position is plotted on a plan view of the property. Lines are then drawn through points having equal value, in exactly the same manner that isobars are drawn on a weather map or elevation con tours on a relief map. This map of the geophysical data allows the prospector to pick out areas with the geophysical characteristics that suggest there may be mineralization.

Another approach is to compile the data as profiles, giving a section view if the anomaly. These are commonly used by both geo physicists and geologists, who use them is guides in selecting the most appropriate means of further investigating the anomaly.