24 Transactions of the Boyal Society of South Africa. 
Although therefore the complex is of norite aspect, its estimated 
composition indicates affinities with the picrites. 
The age of the intrusion is unknown, but it is post-Granite and prob- 
ably pre-Dolerite-Dyke, since several dykes of doleritic rocks having 
affinities with the Dolerite Dykes rather than with any other rock group 
in the Selukwe area have intruded into the Great Dyke. F. P. Mennell 
{A Manual of Petrology, Chapman and Hall, London, 1913) also states 
(p. 152) that the Great Dyke is pierced by dolerite dykes. B. Lightfoot 
{Bulletin No. 4, Geol. Survey S. Bhoclesia, 1914, pp. 13 and 14) describes 
a norite in the Wankie district of post-Archaean pre-Karroo age, which he 
parallels lithologically with the Great Dyke. He suggests the probability 
of the Great Dyke being of pre-Karroo age. Lithologically the Great 
Dyke bears a very strong resemblance to the basic portion of the remark- 
able Bushveld Igneous Complex of the Transvaal, which is regarded as 
having intruded between the Transvaal and Waterberg Systems at a 
period posterior to the deposition of the Lower Waterberg. It is not 
unlikely that the Great Dyke is of the same age, and the suggestion of 
Mr. Lightfoot above noted is in accordance with this conjecture. 
with the felspathic enstatitites. The felspar probably is about 15 per cent, of the volume 
of the rock. Not examined microscopically. 
No. 1022. — Taken 150 yards from Little Tebekwe, at Victoria road drift, Selukwe. A 
medium-grained felspar-rich norite, sp. gr. 2-88, consisting of about two-thirds by volume 
of labradorite-bytownite and one-third diopside and enstatite (together). A trace of 
pyrites, brown mica, bastite, and (?) zoisite. The diopside is more abundant than the 
enstatite. 
