MINING IN AFRICA SPECIAL — Airborne geophysics applied to

The West African country of Ghana is undergoing aerial geophysical survey work, courtesy of Aerodat Inc.

The Mississauga, Ont.-based company, which has been flying both non-exclusive fixed-wing and exclusive helicopter-borne surveys, expects to have most of the data in-house by late spring.

The fixed wing survey involves a high-sensitivity magnetic, multi-channel radiometric and VLF-EM geophysical system. The helicopter-borne survey includes a 5-frequency electromagnetic and high-sensitivity vertical magnetic gradiometer geophysical system.

The fixed-wing survey is covering about 22,000 sq. km (encompassing all the major gold belts in southern Ghana), employing a 200-metre line spacing and 100-metre terrain clearance. About 115,000 line km of data will be recorded. The electromagnetic technique of the helicopter-borne survey should prove useful for delineating conductive structures — gold deposits associated with massive and disseminated sulphides. The geophysical system of this survey will also be used for porphyry copper, diamond and alluvial deposit exploration.

Lode gold deposits have been responsible for about 75% of Ghana’s gold production to date. These deposits are closely linked to major northeast-trending regional structures which can be traced along strike for more than 100 km and which are usually situated along the transition zone between metasediments and metavolcanics.

The lode deposits feature quartz veins and vein systems of all sizes. They are commonly associated with more massive, gold-bearing sulphide mineralization in the metasedimentary hostrocks. Much of the vein gold is free but when in excess of 50%, it usually is intimately associated with an arsenopyrite and pyrite.

In addition to its project in Ghana, Aerodat is currently flying a survey in Ivory Coast.