ZTEM airborne tipper AFMAG test survey over a magmatic copper‐nickel target at Axis Lake in northern Saskatchewan

Abstract

An airborne AFMAG demonstration test survey was conducted using the ZTEM™ tipper electromagnetic prospecting system over a known magmatic copper-nickel occurrence in northern Saskatchewan, Canada. These tests were conducted in early 2008 and were flown to test the system's capability to detect the conductive but relatively weakly mineralized sulphide deposits and to define potential extensions at depth. The AFMAG method utilizes naturally occurring audio telluric fields from worldwide sferic activity as its primary field source and is capable of large penetration depths -in the order of hundreds of metres to km. The AFMAG field tests corroborate previously airborne transient electromagnetic, magnetic and ground follow-up EM surveys. 2D forward modelling results agree with the >300m vertical depth extent as defined in subsequent diamond drill testing.

Three-dimensional imaging of a Ag-Au-rich epithermal system in British Columbia, Canada, using airborne z-axis tipper electromagnetic and ground-based magnetotelluric data

“…It was developed through the 1980s (Labson et al, 1985), but technological advances minimizing electric noise from the aircraft and enabling the monitoring of sensor position have only recently allowed large, high-quality data sets to be collected. Applications have included base metal and unconformity uranium 3D ZTEM and MT model of an epithermal system B5 exploration (Lo and Zang, 2008;Legault et al, 2009), as well as geothermal exploration (Devriese et al, 2012). The 2D and 3D inversion techniques developed for MT or controlled-source airborne methods (Siripunvaraporn and Egbert, 2009;Holtham and Oldenburg, 2010;Egbert and Kelbert, 2012) can be applied to ZTEM data to derive models of electric resistivity.…”

“…The airborne z-axis tipper electromagnetic (ZTEM) technique (Lo and Zang, 2008;Legault et al, 2009) measures natural low-frequency (30-720 Hz) EM signals, and it is used for deep mineral exploration extending to depths of up to 2 km in ideal circumstances and resistive terrain, depending on the average electric resistivity of the area (Spies, 1989). The method is closely related to the groundbased magnetotelluric (MT) method, which also uses natural EM signals and has been applied to a wide variety of targets from near-surface to deeper mantle studies (Bastani et al, 2009;Bertrand et al, 2012;Rippe et al, 2013).…”

Metalliferous mining geophysics — State of the art after a decade in the new millennium

“…In the case in which a test site is not readily available, Yin and Hodges (2009) suggested using a wire loop laid out on the ground as a test conductor. Legault (2009a, b) presented two case histories of ZTEM, a heliborne AFMAG system. In one case, an anomalous response was associated with a graphitic conductor at least 500 m deep; in the second case the system was able to map large conductive structures associated with a copper-nickel deposit.…”

ZTEM data inversion and interpretation using the UBC-GIF MTinv3D code: A case history at the Silver Queen project, British Columbia

“…The Z-axis Tipper EM (ZTEM) system, developed by Geotech Ltd (Legault et al, 2009), measures the tipper of the MT field in both the along-line (X) and cross-line (Y) polarizations.…”