The helicopter borne time-domain VTEM system has been in constant development since 2002 through complex and multicomponent technical improvements in an effort to satisfy exploration and mining industry requirements. Progress in the geoelectrical informational level of data obtained with different VTEM systems is illustrated with the results of test surveys over the Caber VMS deposit. Forward plate modeling with different systems for the Caber deposit geometry target with changing conductance, as well as resistivity-depth transforms of the real data, both serve to illustrate significant broadening of the conductance aperture and increasing depth of investigation over time. Most of all the increasing sensitivity of the VTEM system is highlighted.

SUMMARYIn 2016, Geotech completed a test of a helicopter-borne GT-2A gravimeter combined with ZTEM™ (Z-Axis Tipper Electromagnetics) and aeromagnetic towed bird system over the Vredefort Dome impact structure in South Africa. The survey consisted of nine (9) approx. 70 km long NW-SE oriented flight lines, totalling 640 km, acquired at a nominal spacing of 500 m over an area of approximately 650 km 2 . The successful test demonstrates the feasibility of integrating density measurements using airborne gravimetry on a helicopter platform while combining the superior depth of investigation of ZTEM™ and aeromagnetics for regional geophysical survey applications.