Conductivity-Depth Image (CDI) showing thick conductive crater in-fill
C.L. (Tiaan) Le Roux and W.H.B. (Billy) Steenkamp have written a paper about Xcalibur Airborne Geophysics’ project for Catoca in Angola using the SkyTEM’s airborne EM and magnetic surveys for finding diamonds.
Airborne geophysical techniques are widely accepted and routinely used in the search for diamondiferous kimberlite intrusions, particularly if large areas need to be explored or if the kimberlites are covered by more recent Tertiary or Kalahari sediments and do not penetrate to the present day surface.
Since its inception about 12 years ago Xcalibur Airborne Geophysics has flown many high-resolution airborne geophysical surveys in a number of African countries for various diamond exploration companies. Among these are a number of recent surveys flown for Sociedade Mineira de Catoca LDA (Catoca) in 2013 in Angola.
Angola is the world’s fourth-largest diamond producing country after Botswana, Russia and South Africa. Apart from the well-known Catoca diamond mine in the Lunda Sul province, which is one of the largest kimberlite pipes in the world, Catoca together with partners Endiama and Prescol,hold a number of large very prospective exploration licenses in Angola. In spite of being in ‘elephant country’ for kimberlites, it remains a challenge to cost-effectively and successfully explore for economically viable prospects. The correct application of both magnetic and electro-magnetic (EM) airborne geophysical surveys forms an integral part of Catoca’s exploration strategy for finding kimberlites that contain diamonds.
The most cost-effective technique for first-pass exploration of large areas, particularly where access on the ground is difficult, is still airborne magnetic surveying. The key is to use state-of-the-art geophysical instruments on a robust, low-noise airborne platform and acquire good quality data along adequately spaced flight lines at the lowest safe flying height. Follow-up with airborne EM helps to differentiate, delineate and confirm targets for direct drilling.
Airborne EM data is acquired using the proven world-leader high-resolution helicopter-borne
SkyTEM system from SkyTEM Surveys Aps., Denmark. This system is mounted on a large
non-metallic hexagonal frame which is slung 35m below a standard Eurocopter B3 helicopter.
Read the entire paper from Xcalibur here.