Dullstroom Platts – Borehole DP001 – Summary of Drilling

Borehole DP001 was collared on the farm Mapochsgronde 500JS approximately 2km north of the village/hamlet of Tonteldoos. The borehole only deviated by 1.3 degrees (dip of –89.7 degrees @ 732.95 metres) from the vertical on reaching 733.39 metres final depth.

The core recovered from collar to a depth of 586.82 metres is dominated by a massive, medium to coarse-grained gabbronorite, with local development of leuco and mela gabbronorite. The lithologies are characteristic of the Main Zone of the Bushveld Complex.

Three distinct zones or “packages” of anorthosite were encountered intercalated with the gabbronorite. The upper anorthosite package was encountered between 70.26 and 85.00 metres and has a distinctly spotted appearance. The middle anorthosite package, between 282.80 and 295.21 metres, is not as well developed. The lower anorthosite package is very narrow and was encountered between 419.14 and 419.84 metres.

A fine grained igneous intrusive is intersected between 461.50 and 552.94 metres and is a younger basic dyke cutting the core axis at approximately 18 degrees. This dyke can be projected to surface and equates very well with a north-south trending linear negative relief feature some 150 metres east of the drill collar, and is therefore a 25 metre wide dyke dipping some 20 degrees to the west.

The “Tennis Ball Marker” was encountered between 554.61 and 561.82 metres, and is a distinctive horizon encountered during surface mapping consisting of well-rounded autoclasts or xenoliths of pyroxenite or feldspathic pyroxenite within a gabbronorite or leuco-gabbronorite matrix. Below the TBM the gabbronorite is generally of a fine to medium grain size, with the exception of narrow pegmatoidal bands

From 586.82 metres to 716.42 metres consists of a number of thick fine grained intrusive, which are probably Bushveld sills and form part of the Marginal Zone of the complex. A narrow amygdaloidal unit can probably be correlated with footwall lavas from the Dullstroom Formation. Narrow zones of pink coloured gabbroic rock from 661.79 to 667.34 metres contain significant K feldspar and quartz indicating a probable contamination of the Bushveld magma after assimilation of country rock material.

Transvaal Supergroup sediments and volcanic rocks of the footwall sequence were encountered to the end of the hole at 733.39 metres. Laminated and hornfelsed volcaniclastic or pyroclastic rock of the Dullstroom Formation was intersected from 716.42 to 726.80 metres, and quartzite of the Steenkampsberg Formation to the end of the hole.

Sr-isotope analysis was carried out by Prof. Johan Kruger (University of the Witwatersrand) on selected samples taken from the drill core. Plagioclase samples were separated out to improve the accuracy. The Sr-concentration results, of between 320 and 560 ppm and clustered around 400 ppm, although not considered definitive, strongly suggest a Lower Main Zone stratigraphic position. The Sr-isotope data indicate initial ratios that are close to the Critical Zone (0.7065) and Main Zone (.7070-0.7090) boundary.

The south-eastern margin of the Bushveld Igneous Complex has an “onlapping” relationship with the Transvaal Supergroup lithologies that form the footwall. The Bushveld Main Zone is in contact with the footwall lithologies along the easternmost and southernmost contacts, but further north and west (i.e. deeper into the Bushveld Complex) Bushveld Critical Zone with its associated PGM bearing reefs can be expected in contact with the footwall.

It is proposed that a further diamond borehole is drilled between 1 and 2 kilometres NNW of this collar position (DP001) to intersect UG2 and possible Merensky Reefs at a depth shallower than 1000 metres.