Geochemical Methods

Geochemical methods involve the measurement of the chemistry of the rock, soil, stream sediments or plants to determine abnormal chemical patterns which may point to areas of mineralisation.

When a mineral deposit forms, the concentration of the ore "metals" and a number of other elements in the surrounding rocks is usually higher than normal. These patterns are known as primary chemical halos. When a mineral deposit is exposed to surface processes, such as weathering and erosion, these elements become further distributed in the soil, groundwater, stream sediments or plants and this pattern is called a secondary chemical halo. Secondary halos aid in the search for deposits as they normally cover a greater area and therefore the chance of a chemical survey selecting a sample from these areas is greater than from a primary halo area.

Different elements have different "mobility" in the environment based on their readiness to dissolve in water, their density, their ability to form compounds with other elements and the acidity (pH) of the environment. Subsequently, the secondary halo may not contain the "metal" for which a geochemical survey is searching but other "marker" elements.

Minerals Downunder Exploration Contents