ZTEM tipper AFMAG and 2D inversion results over an unconformity uranium target in northern Saskatchewan

Abstract

An airborne AFMAG demonstration test survey was conducted using the ZTEM™ tipper electromagnetic prospecting system over an unconformity uranium occurrence in northern Saskatchewan, Canada. These tests were conducted in early 2008 and were flown to test the system's capability to penetrate and define the basement geology below a thick sequence of Athabasca sandstones, as well as defining resistivity structure relating to possible fault-controlled alteration zones. 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 previous airborne transient electromagnetic and magnetic surveys, and the inferred geology. A 2D inversion algorithm has been developed to account for the air layer required for the ZTEM tipper data. The results agree with the known geology to below >500m.

ZTEM airborne AFMAG survey results over low sulphidation epithermal gold-silver vein systems at Gold Springs, south eastern Nevada

“…ZTEM tipper results can be readily converted to an equivalent resistivity-depth section using computer 2D or 3D inversion. In this case a new version of the Zvert2d program, described in Legault et al (2009) and based on the 2D code of de Lugao and Wannamaker (1996), called Av2dtopo, was implemented that accounts topography and bird altitude. The 2D inversions were performed on the Tzx (in-line) component data along the west-east flight direction using all 6 available frequencies (30,45,90,180,360 and 720 Hz).…”

ZTEM airborne tipper AFMAG results over the Copaquire porphyry, northern Chile

“…This suggests that the Sulfato zones may be responding to a surficial potassic alteration zone and a surrounding pyritic phyllic-propyllitic altered halo and/or geological structures at depth. Figures 6-7 present the 2D inversion results for the In-Line (Tzx) ZTEM tipper data, using the Zvert2d code, which accounts for the ZTEM mobile Hz and fixed Hx approximation and also for the air-layer below the receiver (Legault et al, 2009). Figure 6 shows the 2D resistivity cross-section obtained from the inversion of a line directly over the Cerro Moly and Marta Area, proximal to the MT survey line, presented in Figure 2.…”

Helicopter EM (ZTEM-VTEM) Survey Results over the Nuqrah Cu-Pb- Zn-Au Sedex massive sulphide deposit in the Western Arabian Shield

“…Ltd, Midland, AU). The ZTEM survey results were interpreted using the Av2Dtopo inversion code (Legault et al, 2012b) that was adapted for the ZTEM airborne AFMAG system from standard 2d MT inversion code (c.f., Legault et al, 2009). Figure 4 presents the resistivity-depth slices obtained from RDI imaging of the VTEM dBz/dt results 150m below the surface, with approximately 350m being the nominal estimated depth of investigation for the VTEM survey.…”