In this case, all of the above prospecting methods apply except for direct observation, method 1. Geology is still a useful tool to outline the appropriate regional environment for the occurrence of the target deposit type, but direct ore associations and alteration are usually hidden. In addition, because of the thicker overburden cover, the proportion of ore related boulders, such as mineralisation or alteration, unmineralised boulders is much smaller. Geochemical methods can be successfully applied to narrow down the target search area, but they seldom provide an actual drill target. As a result, prospecting in such areas tends to rely more heavily on geophysical methods to outline drill targets and ultimately on drilling to make the initial discovery.
Costs are usually much higher and out of the range of individual prospectors.