Modern Mining September 2015

DIAMONDS

the south of the Jwaneng diamond mine. In his presentation at the conference, Daniels recounted how De Beers in the 1950s and 60s, under the guidance of the late Dr Gavin Lamont, changed from panning samples to grid samples. This change, he said, initially resulted in the dis- covery of Orapa and Jwaneng. Falconbridge introduced aero- magnetic surveys over areas where there were indicator anomalies but with thick sand, an approach which subsequently resulted in the discovery of the in the discovery of the Gope (GO25) pipe in 1981 (which has now been developed by Gem Diamonds as the Ghaghoo diamond mine). According to Daniels, the discoveries of the KX36 kimberlite in the Central Kalahari (by Petra) and the Thankane-01 kimberlite to the west of Jwaneng (by De Beers) were a result of increasing the sample sizes from the standard 20 litres to 200 litres and 100 litres respectively. He pointed out that the easy days of finding sig- nificant concentrations of kimberlite indicator minerals (KIMs) were probably over. He also showed (using examples from Botswana) that the minimum lead time from commencing an exploration programme to making a kimberlite discovery was five years, and often much lon- ger. The only exceptions to this were GO25 and the Martin’s Drift (Lerala) kimberlites. Refuting the conventional wisdom that geophysics and drilling were the most signifi- cant aspects of diamond exploration, Daniels predicted that future kimberlite discoveries would largely depend on soil sampling rather than the application of regional geophysics. The key to future discoveries he said would be a greater understanding of the surface textures of individual KIMs as opposed to significant numbers of KIMs in individual samples. He commented that a single KIM with primary surface textures constituted an anomaly that warranted following up. Four historical KIM soil anomalies of sig- nificance in Botswana remained unexplained, said Daniels. He told conference delegates that Pangolin Diamonds held the exploration rights Tsabong and Kokong kimber- lite fields. This was followed up by large scale regional soil sampling using a heli- copter over the central parts of Botswana which resulted

Selection of picroilmenite from a single Malatswae soil sample, showing fragile reaction rims partially to completely preserved on the grains. The largest grains exceed 2 mm.

over three of these anomalies and was currently conducting extensive soil sample programmes over these areas. He noted that Pangolin had announced the recovery of four diamonds, numerous picro-ilmenites, garnets, clinoprox- enes and a mantle xenolith fragment from soil samples from the Malatswae project, which is situated to the south-east of the OKF. The recovery of diamonds from soil samples in Botswana is a rare occurrence and Pangolin believes it is on the right track for the discov- ery of diamondiferous kimberlites. Speaking to Modern Mining at the conference and elab- orating on his presentation, Daniels said that a large number of the KIMs recently reported had primary surface textures suggesting close proximity to source. He said the chemical com- position of the ilmenites recovered from the Malatswae area was distinct from the ilmen- ites from Orapa and indicated that Pangolin was sampling a different kimberlite field. He told Modern Mining that he was “quietly confi- dent” that the detailed sampling grids currently underway at the Malatswae project would lead to several kimberlite discoveries in the near future for Pangolin. Since the Gaborone conference was held, Pangolin has provided further updates of its progress at Malatswae, the latest (dated 12 August) reporting that it has received posi- tive results from a ground penetrating radar (GPR) survey over its palaeo-alluvial diamond target within the project area and from two GPR surveys over two kimberlite targets. Photos courtesy of Pangolin Diamonds

The key to future discoveries will be a greater understanding of the surface textures of individual KIMs as opposed to significant numbers of KIMs in individual samples.

September 2015  MODERN MINING  47