Use of airborne hyperspectral and soil geochemical surveys in diamond exploration at Terowie, southern Flinders Ranges, South Australia

Abstract

Two new kimberlite intrusions in the Pine Creek area, east of Terowie, South Australia were located by soil sampling across anomalies identified from airborne hyperspectral data. The area includes the state?s largest kimberlite diatreme and has been widely prospected in the past using diamond indicator minerals, airborne and ground magnetics, and follow-up drilling. Thin soil cover on kimberlite contains Fe-Mg smectite and talc, which provide the target spectral anomaly. While not unique to kimberlite, the mineral combination produces a relatively small number of constrained anomalies in this area of dominantly clastic sedimentary rocks. Soil geochemical traverses were used to test spectral anomalies, with elevated levels of Ni, Cr and Nb confirming the presence of ultrabasic intrusions. The newly identified kimberlites are associated with subtle highs in the magnetic data that were not recognised as priority targets in previous investigations. In this region of the Flinders Ranges, spectral methods are capable of locating weathered kimberlite in residual and erosional terrains. The combination of detailed magnetic and spectral data offers an approach to prioritising anomalies, from either data set, that will help to locate kimberlite at or near the surface, and accessible to shallow sampling to test their diamond content.