Sub-Audio Magnetics (SAM) – Ground-based and HeliSAM FLEM Trials at the Forrestania EM Test Range

Abstract

Sub-Audio Magnetics (SAM) is a rapid sampling survey technique capable of simultaneous acquisition of data related to the magnetic and electrical properties of the earth. SAM surveys have historically been used for the acquisition of high resolution magnetometric resistivity (MMR) and total magnetic intensity (TMI) data. Recent developments in SAM receiver instrumentation and signal processing have now made the extraction of electromagnetic (EM) data possible due to the exceptionally high data quality now being achieved. SAM data are acquired from a moving platform which makes the technique amenable to applications ranging from ultra-detailed, man-carried or vehicle-towed ground surveys to helicopter-borne acquisition. This paper describes ground-based and helicopter-borne SAM Fixed Loop EM (FLEM) trials conducted over the Forrestania EM Test Range in Western Australia and compares the results with conventionally-acquired (stationary) SAMSON surveys. The trials have demonstrated that SAM FLEM surveys are able to detect high conductance ore bodies at significant depth from a moving survey platform. In either ground or airborne acquisition mode, the SAM technique is shown to be a significant advance toward reducing the cost of deep exploration for high conductance orebodies.