Geochemical Exploration

Geochemical Exploration is defined as, "The systematic measurement of one or more chemical properties of naturally occurring materials to identify abnormal chemical patterns or geochemical anomalies related to mineralization". In simple words it means, the identification of mineral deposits by the use of chemical methods. Although geochemical exploration alone is insufficient to detect and pinpoint ore reserves, it is used in conjunction with geologic and geophysical exploration methods. However when the effectiveness of geologic or geophysical methods become limited due to certain reasons, geochemical prospecting becomes a useful tool to confirm the presence of mineral deposits.

The term "Mineral deposit" is defined as an abnormal concentration of a naturally occurring material(Note that "economic viablity of extraction" is not included in the definition anymore). Since an abnormal concentration of any naturally occurring material is bound to leave behind traces, the objective of geochemical exploration is to identify these clues left by the mineral deposit and to use them to locate it.

Geochemical exploration usually includes the measurement of concentrations of group elements, trace elements, and single elements in,
- Soil, rock, Sediment
- Water, (sea/river)
- Plant material
- Glacial Debris
to determine geochemical anomalies that might indicate a mineralization. Before carrying out the investigation it is essential to have an idea about the behaviour and characteristics of the chemicals involved, the exploration methods to be used and the analytical techniques to be used. Once these factors are considered, proper planning and preparation will help optimize the exploration.

Depending upon the ways of sampling and analysis several methods of Geochemical exploration or surveys can be defined.

Stream sediment surveys - this is of two types, stream sediment panned concentrate surveys and stream sediment surveys. this method is used when heavy minerals and chemicals that bond with clay are involved.

Soil Geochemical surveys - used when looking for surface mineralizations especially in sedimentary environments.

Hydro Geochemical surveys - in analyses for highly soluble and mobile chemical elements.

Bedrock Geochemical surveys - This is usually done during  the last stages of the exploration in order to confirm the mineralization.

Biogeochemical surveys - Although rarely used, in certain cases of mineralization, plants that grow in the area show certain characteristics that point to the mineralization - in the case of copper the leaves of a certain plant that grows in the vicinity turns to a brownish colour due to the absorption of copper.

Considering the conditions and expected methods of mineralization, a suitable geochemical exploration methods can be adopted if required along with geologic and geophysical methods in order to identify areas of mineralization.