CASE STUDY
Innovating geophysics surveys in mining
Geophysical surveys are crucial in mineral exploration activities, as they give detailed information about the mineral potential of a geographical area. Over the years, the way in which geophysical surveys are conducted has improved significantly, making it possible for efficient and accurate results. By Dineo Phoshoko
D Specialist aircraft are used for geophysical surveys. They fly low and slow to improve data quality, and in this example carry magnetic sensors in wingtip pods (Credit: Reid Geophysics)
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uring 2019, Reid Geophysics collaborated with Sierra Leone’s Ministry of Mines and Mineral Resources, along with the National Minerals Agency, to commission the nationwide airborne geophysical survey. Speaking to Inside Mining, Tim Archer, managing director of Reid Geophysics, explains that the main objective of the nationwide survey is to obtain integrated geophysical data that will form the basis for a review of the country’s geology and mineral resources and their distribution. “The ultimate goal is to gain improved knowledge of the quantity and distribution of the country’s mineral resources so as to ensure their sustainable exploitation in future,” he says. Archer explains that the survey was conducted in Sierra Leone because the country has a long history of mining commodities and is home to various minerals, including diamonds, gold, iron ore, rutile and bauxite. “The government now wants to attract further international mining investment, and has secured funding from the World Bank for a nationwide airborne geophysical survey.”
The survey was unique in that more than 543 000 line km of magnetic and radiometric data was collected. The data was collected at a flight line spacing of 150 m and a nominal terrain clearance (subject to safety constraints) of 50 m. “As far as we are aware, this is the highest-resolution nationwide dataset ever collected,” Archer said. Another important aspect of the survey is that a customised aircraft was used to conduct the actual survey. The aircraft had eye-level navigation display and wingtip magnetic sensors. In addition, the aircraft also had high-volume radiometric crystals.
Survey advantages and limitations Conducting an airborne geophysics survey has major advantages. Archer explains that airborne geophysics is a rapid and cost-effective means of surveying large areas of ground for mineral exploration. “The survey model adopted in Sierra Leone can be successfully applied to other African countries, to map mineral resources and attract foreign investment,” he adds. At the 2020 Investing in African Mining Indaba, a
