Technical Papers - Airborne Electromagnetics

The MEGATEM Fixed-Wing Transient EM System Applied to Mineral Exploration: A Discovery Case History

Richard Smith and David Fountain of Fugro Airborne Surveys (Ottawa, Canada) and Michel Allard of Canadian mining company, Noranda (Laval, Quebec), describe the development of a new airborne electromagnetic survey system for mineral exploration

Erratum: on page 76, second column, second paragraph, The sentence "Figure 5 shows the response collected in 1983 on an INPUT profile over Caber", should read "Figure 5 shows the response collected in 1983 on an INPUT profile over Perseverance".

Introduction

In the mid 1980s, Geoterrex (now part of Fugro Airborne Surveys) introduced the GEOTEM system, a fully digital airborne electromagnetic (AEM) receiver, using the same transmitter that had previously been used, very successfully, on the INPUT system (Annan, 1990). The GEOTEM system is mounted on a twin engine CASA 212 aircraft, and the transmitter loop is wound around the nose, wing tips and the tail of the aircraft. This transmitter excites eddy currents in the subsurface with periodic pulses of the 'primary' magnetic field. The decay of these currents is measured with a receiver towed behind the aircraft in a 'bird'. When the eddy currents decay slowly, this is generally indicative of material in the subsurface that is conductive.

Published in First Break, July, 2003, Volume 21, pages 73-77.
© 2003 European Association of Geoscientists & Engineers. Single copies of the article may be printed - visit First Break online.

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