Results of experimental and test TEM surveys, Elura deposit, Cobar, NSW

Abstract

The Bureau of Mineral Resources (BMR) has carried out a series of TEM test surveys at Elura to investigate the advantages of various loop sizes and configurations, and to assess the application of recent developments in quantitative methods of interpretation. The use of multi-component and in-loop systems can be useful in extracting extra spatial information on anomaly sources, but care must be taken with interpretation. Model studies offer a valuable aid in interpretation. The design of multi-turn TEM receiving coils should ensure that the coil does not distort the shape of the transient decay curve. In assessing methods of interpretation it was found that SIROTEM data could not be used quantitatively in the coincident loop mode for signal levels below 10 mV/A There is a need for accurate calibration facilities for low signal levels, as parameters such as loop size and inductance are varied. This calibration is also necessary for systems such as the Crone PEM if they are to be used quantitatively. It is possible that a separated-loop configuration (e.g. the in-loop geometry) will have to be employed to reduce effects such as self-inductance, to allow accurate recording at low signal levels.