Page 80 - Introduction to Mineral Exploration

4: RECONNAISSANCE EXPLORATION 63

●
Johannesburg
SOUTH
AFRICA Springbok
Flats
Cape Town
●
●
Johannesburg
●
Present limits of Karoo Basin in South Africa
Outcrop of Beaufort Group,
Molteno–Drakensberg volcanics
Uranium province in main Karoo basin
Palaeocurrents (Theron 1973)
● Qwa Qwa
● Ficksburg

● Edenburg

● Richmond
Fraserburg
●
● Graff Reinet
● Sutherland ● Beaufort West
Laingsburg

Cape Town
●

FIG. 4.7 The Karoo Basin in South Africa. (From Moon & Whateley 1989.)

An example of an exploration strategy can radiometric survey as its principal technique.
be seen in the search for sandstone-hosted, In this technique a scintillometer is carried in a
uranium deposits in the Karoo Basin of South vehicle and gamma radiation for the area sur-
Africa (Fig. 4.7) during the 1970s and early rounding the road is measured. Although a very
1980s. The initial reconnaissance was con- limited area around the road is measured it has
ducted by Union Carbide in the late 1960s. the advantages that the driver can note the
They became interested in the basin because of geology through which he is passing, can stop
the similarity of the Karoo sediments to those immediately if an anomaly is detected, and it is
of the Uravan area in Colorado, where the com- cheap. In this case a driver was chosen with
pany had uranium mines, and because of the experience in Uravan geology and he was able
discovery of uranium anomalies in Karoo sedi- to use that experience to compare the geology
ments in Botswana and Zimbabwe. As little of traversed with favorable rocks in the western
2
the basin, which is about 600,000 km , had USA. After a good deal of traversing a signific-
been mapped, the company chose a carborne ant anomaly (Fig. 4.8) within sandstones was