Kimberlite exploration using integrated airborne geophysics

Abstract

Airborne magnetic and electromagnetic surveys together with kimberlite indicator mineral geochemistry have been standard practice in the search for kimberlites. The recent advent of the airborne gravity gradiometer (AGG) showed that airborne gravity gradiometry could also be a successful tool in kimberlite exploration. The installation of a digital AGG system on a helicopter led to the first airborne gravity gradient cum magnetic cum electromagnetic survey. The survey was flown over the central part of the Ekati tenement within the Lac de Gras kimberlite province. Each of these three geophysical methods relies on a different physical property contrast for its success. A selected sub-area shows that no one method would have identified all known pipes. But all known pipes would have been discovered by integrating all three data sets. The pipes in the selected area are associated with conductivity and/or gravity gradient anomalies; a few with magnetic anomalies. New data alone are not sufficient to guarantee success in a mature exploration environment. The geophysical data were individually inverted to create 3D density, magnetic susceptibility and electrical conductivity models. Integrating and applying classification techniques to the three 3D models was used in the generation of new targets. Drill testing of the targets has begun leading to the discovery of a new pipe.