Exploration methods
Before drilling, explorers narrow down where to look with mapping, geochemistry, geophysics and remote sensing. Each method finds different clues.
2 min read
Exploration methods are the tools used to decide where to drill. They find clues, not deposits: only drilling proves what is there.
What it is
Drilling is expensive, so explorers first use cheaper methods to find and rank targets. Most work moves from broad and cheap to narrow and more costly: from a whole region down to a few drill targets.
The methods
Geological mapping
Geologists walk the ground, record rock types, structures such as faults, and signs of alteration, where hot fluids changed the rock. Mapping turns scattered observations into a picture of where a deposit might sit. It is cheap and always comes first.
Geochemistry
looks for unusual amounts of metal at the surface.
| Method | What is sampled | Scale |
|---|---|---|
| Stream sediment sampling | Sand and silt from streams | Regional: points to a catchment |
| Soil sampling | Soil on a grid | Local: outlines an anomaly |
| Rock-chip sampling | Pieces of outcrop | Specific: shows grades at surface |
| Channel sampling | A continuous cut across outcrop or a trench | Gives representative grades over a width |
Explorers also analyse pathfinder elements, such as arsenic near gold, that travel further than the metal itself.
Geophysics
measures physical properties of the ground to see below the surface. Surveys can be flown from aircraft or drones, or run on the ground.
| Method | Measures | Good for |
|---|---|---|
| Magnetics | Magnetism of rocks | Mapping geology under cover, intrusions, faults |
| Gravity | Rock density | Dense bodies such as massive sulphides, buried structures |
| Induced polarisation (IP) | How rocks hold an electrical charge | Scattered sulphides, typical of porphyry copper |
| Electromagnetics (EM) | Electrical conductivity | Massive sulphides, such as VMS and nickel deposits |
| Radiometrics | Natural radioactivity (potassium, thorium, uranium) | Alteration and rock types at the surface |
A geophysical anomaly is only a hint. Many are caused by barren rocks such as graphite or magnetite.
Remote sensing
Satellite and aircraft images can show alteration minerals, structures and landforms across large areas. Drones and laser surveys (LiDAR) give detailed terrain maps.
Trenching
Where soil covers the rock, an excavator digs a trench across the target so geologists can map and sample fresh rock beneath.
How the methods compare on cost
| Method | Relative cost |
|---|---|
| Mapping, stream and soil sampling | Low |
| Airborne magnetics and radiometrics | Low per square kilometre |
| Ground IP, EM and gravity | Medium |
| Trenching | Medium |
| Drilling | High |
Why it matters
Good targeting decides how efficiently money is spent. Most anomalies do not lead to a deposit, which is why grassroots exploration has the longest odds. See the stage guide.
Ranges are indicative and vary by deposit and region. This is educational material, not investment advice.
Key terms
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Educational material only. Nothing here is investment advice or an offer to buy or sell any security or mineral interest.