MINERAL EXPLORATION UNDER DEEP COVER

To resource future generations, new mineral deposits must be found to replace deposits currently being mined, and to meet anticipated increases in the global consumption rates of many mineral commodities. Throughout the 20^th century there has been a growing trend in the discovery of buried deposits (generally within a few hundred meters of the surface), and the trend is predicted to grow as the stock of near-surface mineral deposits further diminishes.

Finding deep mineral deposits is difficult, and the exploration methods used to find new deposits at or near the surface will not all be useful for discovering deposits under deep cover. What is required are: better tools and techniques to accurately describe the geology of the Earth’s crust in four dimensions (the three dimensions of space plus time); new and improved targeting models to guide ground selection; new insights into the geophysical characteristics of mineral systems and mineral deposits; more powerful geophysical exploration tools to directly detect possible mineralization of a wide variety of types at depth; and more cost effective drilling technologies to test for deep mineralization.

Good progress is being made to overcome some of these challenges, but more needs to be done. For example, current ore deposit models are useful in identifying prospective terrains at a regional scale, but are of little use in predicting the location of deposits at the local scale. A new generation of predictive targeting models is needed, based as much on the geophysical characteristics of ore types and their host rocks as on the ore-type mineralogy and chemistry emphasised in current deposit models.

The discovery in 1975 of the giant iron oxide copper-gold mineral system at Olympic Dam, South Australia will be used to illustrate the likely future directions and challenges of deep undercover exploration.