Aeromagnetic gradiometer program of the Geological Survey of Canada

Abstract

During the past two decades, the Geological Survey of Canada Aeromagnetic Survey Group, consisting of geophysicists, electronic engineers, technicians, and computer scientists, developed the aeromagnetic gradiometer technique for mineral exploration. The same group ran the aeromagnetic survey program in Canada, perhaps the largest such continuing aeromagnetic survey program in the world. In 1973, fabrication commenced on an inboard vertical gradiometer system on the GSC Queenair aeromagnetic survey aircraft. During the period 1978–1981, a number of experimental gradiometer surveys were carried out by the Geological Survey of Canada to demonstrate the efficacy of the aeromagnetic gradiometry technique as a geologic mapping tool in mineral exploration programs. Because of a need for aeromagnetic gradiometer surveys in the topographically rugged Gaspé Peninsula of Quebec, the GSC began in 1983 to foster the development of helicopter‐borne gradiometer systems through R and D contracts. Four companies responded and built towed‐boom helicopter gradiometer systems which have now been used in surveys in four eastern provinces. It is clear that the aeromagnetic gradiometer technique combined with VLF EM is an excellent geophysical tool to improve the accuracy of detailed geologic mapping for mineral exploration programs. VLF EM is an inexpensive add‐on that materially improves the geologic mapping capability of the airborne system. The product in color pixel form is in essence a pseudogeologic map and it is presently being employed as such.