As greater portions of geologically prospective land evolve into mature exploration terrain, mineral explorers are relying less on surface mapping and prospecting and more on modern exploration techniques that can “see” underground to generate worthwhile projects.
But looking for buried deposits can be beyond the reach of many exploration companies simply because probing beneath the surface, whether using geophysical equipment or drilling, is considerably more expensive than looking for deposits that outcrop at surface.
Companies working in countries with strong government-sponsored geological surveys, such as Canada and Australia and parts of the United States, have a head start with access to comprehensive datasets of free geological, geochemical and geophysical information that can be compiled to find anomalies at depth that might otherwise go unnoticed. In this case, a good part of the prospect generation can take place at a desk with the help of a 3D mapping program, a reasonably powerful computer, and a trained eye.
Conceptually intriguing prospects can also be candidates for further probing given a joint venture partner with the cash to fund a variety of geophysical surveys and drilling. Take Nevada, for instance, where most of the remaining gold deposits are blind from surface. Junior explorers working in the State generally have either a major gold company supporting them or are splitting the costs with a joint venture partner of similar size.
Miranda Gold has been one of the most successful at generating and selling prospects along Nevada’s Cortez Gold trend in Nevada using this JV model. Though the junior has yet to make a significant discovery, Miranda has come up with results compelling enough to hold the interest of current and potential partners. As a result, this “project generator” has 15 projects on the go without diluting its share structure or treasury and currently has about $10 million in the bank.
For example, at Coal Canyon, a sediment-hosted deposit in the heart of the Cortez trend, Miranda and a former partner used geophysics to determine that fault-controlled gold mineralization correlated with gradient resistivity and self-potential geophysical anomalies. The correlation led to a conceptual target of broad zones of silicification enveloping oxidizing sulfides that could be pyritic dikes within gold-bearing fault zones. Finally, by compiling geophysical data, surface mapping, and geochemical sampling results the partners were able to generate drill targets.
Although initial drilling was unsuccessful in finding significant gold mineralization, a subsequent joint venture partner did find the first subsurface, Carlin-style, disseminated gold mineralization ever discovered on the Coal Canyon property. The project awaits follow-up.
Today’s explorers need tools more powerful than a pick, compass, and hand lens to generate new prospects. Perhaps the most powerful tool of all is the ability to conceptualize a prospective target at depth using the best of modern software, then convince those with deeper pockets that the target is worth probing.
Miranda’s story on their use of 3D for prospect generation appears in this month’s Earth Explorer magazine – Miranda Gold: Cutting Edge Prospects .