The Earth's mineral deposits fall into two groups: those that have been discovered and those that await discovery. Of those waiting discovery in Australia we can further divide these into three types:
- those outcropping at the surface,
- those which outcrop but are covered by soil and decaying rock material (called regolith) and
- those not outcropping but may be close to the surface
Only about 15% of the Australian continent has potentially prospective rocks outcropping at the surface. Almost all of the mineral deposits that outcrop in these rocks have already been discovered. The rest of the continent is either under soil and/or regolith or is currently considered to be unprospective. These regions require sophisticated exploration techniques that penetrate the surface layers to view what is hidden below.
The role of looking for mineral deposits falls to the exploration companies. These may be units of much larger mining corporations or separate companies who find deposits then sell the rights for mining. Despite a century of exploration, Australia remains relatively under-explored, particularly beneath areas covered by soil, sand and vegetation.
The first step in exploring for a mineral deposit is to establish an area in which the possibility of finding a deposit is higher than other areas. These areas can be placed into two groups:
- Those that are known to be mineral bearing ie. other deposits are known.
- Those where minerals have not yet been recognised (mainly due to the area being covered by sediments, sand, soil etc.) but have favourable geological conditions.
The risks involved in exploration are high in both cases, but even higher for the second. Obviously, companies would be interested in looking in areas with the highest prospectivity but to assess which area has this, they need broader regional information.
