An application of airborne GEOTEM* in Australian conditions

Abstract

The transition to fully digital data acquisition systems has been the major advance in virtually all areas of geophysics. In 1985, GEOTEM*, the first fully digital airborne EM system, was introduced into commercial operation. Geoterrex commissioned an Australian based GEOTEM system in 1989. Over 250,000 line kilometres of survey have now been flown with the system allowing a greater appreciation of the advantages of a fully digital operation. Data acquired over the Freddie Well massive sulphide deposit, near Mt Magnet in Western Australia, provide a good example of the advantages of new technology applied to the detection of difficult targets. The deposit was undetected by the early versions of the Mark V and Mark VI INPUT? receivers. The enhanced Mark V receiver detected the deposit though the response never dominated the high amplitude response of the adjacent overburden. The GEOTEM survey, which employed dual transmitter frequencies of 75 Hz and 125 Hz, clearly detected the deposit with late channel response exceeding the amplitude of the surrounding conductive cover.