The Successful Prediction of Non-Magnetic Dykes Using a Dighem Survey

In South Africa, subsequent to the deposition of the coal seams, the formations have been<br>invaded by dolerite dykes and sills. These present considerable problems during<br>underground mining, and can also affect resource calculations, thus their reliable<br>prediction is very important. The use of airborne and ground magnetic surveys together<br>with drilling to detect dykes has been an established practice for many years. However,<br>the location of non-magnetic dykes has presented a serious challenge to the exploration<br>geophysicist and geologist. A Dighem survey together with limited angle drilling has<br>proven to be a cost-effective solution in certain situations.