Minimisation of the Gravity Response from Mine Infrastructure: An Example from Sons of Gwalia Mine, WA

Abstract

In near mine exploration, gravity surveys are generally detailed and mine infrastructure such as waste dumps, tailings dams and open pits, if not taken into account, can often mask the gravity response from the bedrock geological sources. This was the case at the Sons of Gwalia Mine near Leonora, Western Australia, where a gravity survey on a nominal 100´100m spacing was undertaken to assist in improving the geological framework. Large scale open pit and underground mining activities over the previous 20 years had resulted in significant mine infrastructure. Standard reductions of the gravity data showed a number of anomalous responses that correlated with the waste dumps and tailings dams. Hence there was a requirement to remove the gravity response of the mine infrastructure in order to maximise the response from bedrock sources and thus improve the interpretation. The methodology used to minimise the effect of mine infrastructure on the gravity data involved three-dimensional forward modelling and removal of the gravity response of the waste dumps and tailing dams prior to conventional terrain correction. For the estimated densities adopted, the maximum infrastructure response was 3.6 mgal. The results indicate that the bulk of the effects from mine infrastructure have been removed, allowing a clearer picture of the gravity response from bedrock geological sources. Some residual gravity response from the infrastructure, particularly the southwestern tailings dam, is apparent. Its removal would require a refinement of the forward modelling of the mine infrastructure.