Carta Exploration Ltd

Mineral exploration is the search for mineral deposits by public companies, partnerships, private corporations and individual prospectors.  Exploration is the first step in the mining project pipeline. It may take 5-10 years to discover a mineral deposit and develop it towards the feasibility stage.

Area Selection
Area selection is the process of identifying prospective ground based on ore deposit models, interpretation of geology and structure, proximity of infrastructure, corporate objectives, political stability, taxation incentives and a host of other factors. 

Areas prospective for gold may not be prospective for other metals and commodities.  Companies will differ in their market capitailization or financial reserves and will look for deposits of particular commodity or size.  For example, areas known to host small gold deposits will not be of interest to large gold mining companies because they will not achieve their required internal rate of return from anything but a large gold deposit.

Target Generation
Target generation is the identification of drill targets from the interpretation of mapped geology, trenching, soil or stream sediment sampling, and airborne or ground-based geophysical surveys.

Geophysical Methods
Geophysical surveys idenitfy anomalies, which are variations in gravity, magnetism, electromagnetism (conductivity and resistivity) of rocks in a certain area.  Airborne geophysics is the most economical type of survey for large areas.  Ground-based geophysical surveys are more time consuming and costly.  The most common type of ground-based geophysics is electromagnetics or EM surveys, which detect buried conductive minerals, such as sulfides, within more resistive host rocks.

Geochemical Methods
Geochemical surveys identify anomalies in the commodity sought or in elements associated with the commodity, called pathfinder elements.  Regional geochemical surveys of stream sediments can identify target catchments.  Regional surveys might use a low density of sample points, for example one sample every 100 square kilometres. 

Once an anomaly is identified at a regional scale, a follow-up geochemical survey of soils collected on a grid may reveal anomalies over a smaller area.  In Canada, thick overburden comprising soil, glacial deposits, alluvium or colluvium obscure the bedrock buried beneath.   Geochemical anomalies may be spurious or related to low-grade or sub-grade mineralization. 

Geochemical anomalies are drilled to test for the existence of economic concentrations of mineralization, or even to determine why they exist in the place they exist.

The "Prospector Myth" vs. Systematic Management of Exploration Portfolios: Dealing with the Dilemma, Rose and Citron, October 2000
The Prospector Myth - Coming to Terms with Risk Management in Mineral Exploration
The Science of Exploration Targeting, J.M.A. Hronsky
Introduction to Nickel Sulphide Exploration, Jon Hronsky, June 2007