Exploration can be divided into a number of interlinked and sequential stages which involve increasing expenditure and decreasing risk. Early stages of exploration are planning and prospecting. The planning stage covers the selection of commodity, type of deposit, exploration methods, and the setting up of an exploration entity. Prospecting covers activities leading to the selection of an area for detailed ground work; this is the point at which land is acquired. The subsequent stages involve targeted prospecting and exploration in order to quantify and qualify the mineral resources. Pre-feasibility study is then performed for evaluating the commercial viability of the deposit (Adapted from Moon et al., 2006).
Methods for Mineral exploration may include:
Remote Sensing: Usage of sensors for collecting data about an object or area without being in direct contact with it. These sensors can be on satellites or mounted on aircraft. Geologic mapping, aerial photographs, satellite imagery and airborne geophysical data are some examples of this category.
Geophysics: Usage of measurements associated with physical properties made at or above the ground surface and in boreholes to draw conclusions about concealed geology. Geophysical methods can be classified as passive (naturally existing fields) or active (fields generated by some stimulus). Geophysic exploration may be based on resistivity (measuring potential differences between two or more electrodes generated by a current introduced into the ground), gravity (measuring differences in specific gravity of rock masses), spontaneous polarization (measuring differences in spontaneous electrical potential caused by electrochemical reactions), induced polarization (measuring changes in double-layer charge within a mineral interface), magnetic susceptibility (measuring changes in structure or magnetic susceptibility in certain near-surface rocks), among others properties.
Geochemistry: Usage of superficial material, such as soil, till, or vegetation, that can be analyzed for identifying a geochemical anomalies. Regional geochemical exploration has traditionally based on top soil or water stream sampling. Also, there may be an association between the presence of some chemical elements and the occurrence of certain mineral resources.
Pitting and trenching: Usage of shallow excavation for deep sampling material. They also provide continuous exposure of material, facilitating localized geological interpretations.
Drilling: Usage of material extracted from a small diameter hole. Several methods are available according different objectives, ground conditions and cost (e.g. auger drilling, percussion drilling rotary drilling etc.)
The selection of the exploration methods are based on a set of variables associated with level of detail required, stage of exploration, characteristics of the mineral deposit (type, size, location, etc.) and time-frame. Also, technical and economic factors should guide the development of the final exploration plan.
The choice of exploration strategy varies considerably and depends on the objects of the company and its wiliness to take risks. Potential projects for mineral exploration can be associated with well-known geological districts (e.g. vicinity of existent operations) or geological district still to be understood. Companies may choose acquisition of existing prospects or operational sites (e.g. producers with economic constraints). Also, mineral exploration may be performed within current operations in order to capture untapped mineral resources (e.g. new market opportunity). Lastly, joint venturing can be an alternative for sharing risk and enhancing synergies with prospective partners (Adapted from Moon et al., 2006).
In summary, mineral exploration projects are typically complex and risky. Therefore, it is critical to have a systematic approach that incorporates the uncertainties ingrained to this important phase of the mining cycle. Moreover, by having a combination of qualified and motivated team and robust adaptive resource management plan, exploration projects should increase significantly the likelihood of successful outcomes.
Do you know that some of the exploration methods are used in civil engineering and archaeology?
Please provide your thoughts about other potential applications for exploration methods.
Moon, C.J. et al. “Introduction to Mineral Exploration”, Blackwell Publishing, second edition, Malden, MA, USA (2010).