general introduction

4
Journal of African Earth Sciences, Vol. 16, No. 1/2,pp. 1-4, 1993. 0899-5362/93 $6.00+0.00 Printed in Great Britain Pergamon Press Ltd GENERAL INTRODUCTION P. G. ERIKSSON,S. A. DE WAAL, R. J. THOMAS*, S. McCOURT, E. B. FORTSCH and GRANTItAM Dept of Geology, University of Pretoria, Pretoria 0002, South Africa *Geological Survey of S. A., P. O. Box 900, Pietermaritzburg 3200, South Africa Southem Africa, that is Africa south of the Cubango and Zambezi Rivers, has enormous wealth and large human resources. Yet, due to its colonial past and the ravages of political instability in the last few decades, it has remained a poorly developed region. Through fortunate historical and geographical accidents, South Africa, with its long established mining industry, is the most developed country in the region. Consequently, by utilising its resources of infrastructure, electrical power grid, skilled work force, established transport system and free market economy, this country is certainly well placed to initiate the development of the entire region. As exploration activity within South Africa's borders decreases, the focus will probably shift increasingly to the countries to the north of it, and even into Central and West Africa. The geological, mining and extraction expertise within South Africa, which includes large numbers of people employed from the surrounding count- ries such as Lesotho, Swaziland, Moqambique, Malawi and Zimbabwe, should thus be utilised in such endeavours. This special issue of the Journal of African Earth Sciences aims to explore briefly the importance of the minerals industry to South Africa, and then to concentrate on the geology of three specific sequences which have contributed towards the a VALUE MINERALS ~OLD IN SOUTH AFRICA Z 40" o_ e~ Z 20- .< er f ! i i 1980 19v90 Fig. la. Value of minerals sold in South Africa favourable position of South Africa within the region, and which will continue to do so as the country becomes firmly entrenched within the family of southem African nations following the demise of apartheid. The Rand-value of minerals sold in South Africa continues to rise quite dramatically (Fig. la), but unlbrtunately this largely reflects inflation, one of Africa's endemic problems, as we move from being a supplier of minerals to a manufacturing region. The contribution of mining to the gross domestic product has dropped sharply in real terms within the last decade (Fig. lb), a trend largely due to the decline of gold mined in the Witwatersrand Super- group (Fig. 2). Although gold remains by far the most valuable commodity mined in South Africa (Fig. lc), its future must be limited by declining grades, increasing tonnages milled and most signi- ficantly by decresing profitability (Figs ld and e). Other maj or commodities, which unlike gold main- tained a constant contribution of about 5 % to the GDP of South Africa, are coal, platinum group metals, iron ore, copper, manganese, limestone and chrome (Figs. lb and c). In addition, very large mineral reserves of manganese, PGMs, chrome, vanadium and alumino-silicates (largely andalu- site) (Fig. 10 indicate a very promising future for non-gold mining in South Africa. This special issue brings together a collection of papers dealing with geological aspects of the for- b other mining 019,81. , , I , 1986 '19191 ' Fig. lb. Contribution of gold mining and other mining products to the gross domestic product of South Africa

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Journal of African Earth Sciences, Vol. 16, No. 1/2, pp. 1-4, 1993. 0899-5362/93 $6.00+0.00 Printed in Great Britain Pergamon Press Ltd

GENERAL INTRODUCTION

P. G. ERIKSSON, S. A. DE WAAL, R. J. THOMAS*, S. McCOURT, E. B. FORTSCH and GRANTItAM

Dept of Geology, University of Pretoria, Pretoria 0002, South Africa *Geological Survey of S. A., P. O. Box 900, Pietermaritzburg 3200, South Africa

S o u t h e m Africa, that is Africa south of the Cubango and Zambezi Rivers, has enormous wealth and large h u m a n resources. Yet, due to its colonial past and the ravages of political instability in the last few decades , it ha s r ema ined a poorly developed region. Through fortunate historical and geographical accidents, South Africa, with its long established mining industry, is the most developed country in the region. Consequently, by utilising its resources of infrastructure, electrical power grid, skilled work force, established t ransport system and free market economy, this country is certainly well placed to initiate the development of the entire region. As exploration activity within South Africa's borders decreases, the focus will probably shift increasingly to the countries to the north of it, and even into Central and West Africa. The geological, mining and extraction expertise within South Africa, which includes large numbers of people employed from the surrounding count- ries such as Lesotho, Swaziland, Moqambique, Malawi and Zimbabwe, should thus be utilised in such endeavours.

This special issue of the Journa l of African Earth Sciences aims to explore briefly the importance of the minerals industry to South Africa, and then to concen t ra te on the geology of three specific sequences which have contributed towards the

a

VALUE M I N E R A L S ~ O L D IN SOUTH AFRICA

Z 4 0 " o_

e~ Z 2 0 - .< er

f

! i i

1980 19v90

Fig. la. Value of minerals sold in South Africa

favourable position of South Africa within the region, and which will continue to do so as the country becomes firmly entrenched within the family of s o u t h e m African nations following the demise of apartheid.

The Rand-value of minerals sold in South Africa continues to rise quite dramatically (Fig. la), but unlbrtunately this largely reflects inflation, one of Africa's endemic problems, as we move from being a supplier of minerals to a manufac tur ing region. The contribution of mining to the gross domestic product has dropped sharply in real terms within the last decade (Fig. lb), a t rend largely due to the decline of gold mined in the Witwatersrand Super- group (Fig. 2). Although gold remains by far the most valuable commodity mined in South Africa (Fig. lc), its future mus t be limited by declining grades, increasing tonnages milled and most signi- ficantly by decresing profitability (Figs ld and e). Other maj or commodities, which unlike gold main- tained a constant contribution of about 5 % to the GDP of South Africa, are coal, plat inum group metals, iron ore, copper, manganese, limestone and chrome (Figs. lb and c). In addition, very large mineral reserves of manganese, PGMs, chrome, vanadium and alumino-silicates (largely andalu- site) (Fig. 10 indicate a very promising future for non-gold mining in South Africa.

This special issue brings together a collection of papers dealing with geological aspects of the for-

b

other mining

019 ,81 . , , I , 1986 '19191 '

Fig. lb. Contribution of gold mining and other mining products to the gross domestic product of South Africa

2 P.G. EmKSSON, S. A. DE WAAL, R. J. THOMAS, S. MCCOURT, E. B. FORTSCH and GRANTHAM

¢ TOP8

COMMODITIES Chrome

Limestone/dolomite Manganese o r e I

Copper (content) Iron ore

PGM's Coal Gold

I i

VALUE OF SALES, 1991, RANDS x106

d WORKING PROFIT, CHAMBER

OF MINES GOLD MINES

E 16 t o

0 I ' I i I 1987 1989 1991

f TOP6

COMMODITIES!

AI-silicstes Gold

Vanadium Chromium

PGM's Manganese

O TONS OF GOLD ORE MILLED & GRADE OF GOLD MINED

Tons (x million) milled

100"

50"

l ,

I

grade (gin/ton)

-10

-5

I I

10 2'0 30 4'0 5'0 (~0 70 80 9() 1()0 PERCENTAGE OF WORLD'S RESERVES

~ d l C L r ~ Minerals Bureau, Dept. of Mineral & Energy Affairs, Chamber of Mines Annual Report 1 9 9 1 & Newsle t te r 3 / 6 , 1 9 9 2

Fig. lc. The top 8 mineral commodities of South Africa in terms of sales. Fig. l d. Profitability of gold mining in South Africa. Fig. le. Grade and tonnages of gold ore mined in South Africa. Fig. lf. The top 6 mineral commodities of South Africa in terms of the world's total reserves.

m a t i o n s tha t in ou r view are essent ia l to the requi red indus t r ia l deve lopment of the s o u t h e r n African cont inent : the Transvaa l Sequence , the B u s h v e l d C o m p l e x a n d the Karoo S e q u e n c e (Fig. 2). The topics dealt with are not exhaus t ive and reference to the gold- and d iamond-bea r ing format ions is avoided on purpose . Al though gold and d i a m o n d s are indirect ly impor tan t a s ea rne r s

of foreign exchange and t h u s provide financial b a c k - u p to development , t hey have little direct appl icat ion in the s u p p o r t of:

I) a heavy i ndus t ry b a s e of i ron and steel plants ,

2) a reliable and relatively cheap supp ly of electricity,

3) adequa t e wa te r r e s o u r c e s for u r b a n , indus t -

General Introduction 3

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Fig. 2. Sketch map illustrating the locations of the three geological success ions discussed In this special issue: the Transvaal Sequence, Bushveld Complex and Karoo Sequence.

Also shown is the Witwatersrand Supergroup, the source of most of the gold mined in South Africa.

4 P. G. ERIKSSON, S. A. DE WAAL, R. J. TttOMAS, S. MCCOURT, E. B. FORTSCH and GRANTHAM

rial and agr icul tura l development , and 4) rapid and large scale urbaniza t ion . The first p a p e r in the collection b y T h o m a s e t aL

reviews the tectonic evolut ion of s o u t h e r n Africa and provides the n e c e s s a r y b a c k g r o u n d informa- t ion on the regional geological f r amework of the subcon t inen t .

E r iks son e t al. give an overview of the bas ic geologica l c h a r a c t e r i s t i c s of t he i n d u s t r i a l l y impor tan t Transvaa l Sequence , wh ich is also a large repos i tory of g roundwa te r , in the Malmani dolomite, and which also e n c o m p a s s e s the iron ore n e c e s s a r y for s teel p roduc t ion in the y o u n g e r Penge and corre la ted Gr iqua land Wes t iron forma- t ions. The water - r ich n a t u r e of the dolomites and thei r p r e sence in the s u b - t e r r a i n of m u c h of the indus t r ia l a rea of the coun t ry p resen t some in teres t ing env i ronmenta l chal lenges , as out l ined by Bu t t r i ck e t al. Hfilbich e t al. invest igate the geology, genes i s and exploi ta t ion of the Transvaa l and Gr iqua land-Wes t iron format ions , and com- pare the S i shen (Northern Cape) and Thabaz imbi (nor thern Transvaal) mining districts.

The review of the geology and geochemis t ry of the early Proterozoic Bushve ld Complex b y Eales et al. serves as a s ta te-of- the art descr ip t ion of th is extens ive layered in t rus ion and its impor t an t chromium, vanad ium, t i tan ium and p la t inum metal

deposi ts . The last of the th ree re levant geological format ions , the Karoo Sequence , is reviewed b y Smi th et a t , as a p re lude to the descr ip t ion b y S n y m a n and Botha of the n a t u r e and exploitat ion of S o u t h African coals. An overview of the Lesotho High lands Wate r s c h e m e b y Van Rooy and Van Scha lkwyk gives an insight into the engineering geological a spec t of th is impor tan t wa te r supp ly project.

The last two p a p e r s in the collection deal with envi ronmenta l geological i s s u e s in the Natal pro- vince of Sou th Africa. T h o m a s and Van Scha lkwyk look at geological haza rds a s soc ia t ed with flooding, w h e r e a s W a t k e y s et aL cons ider the envi ronmenta l geological con t ra in t s of the M a p u t a l a n d region,

Acknowledgements - The guest editors would like to express their gratitude to the following colleagues, who served as referees for the manuscripts submitted for publication: W. Altermann, G. C. Amstutz, T. G. Blenkinsop, G. A. Botha, J. H. Bredell, A. B. A. Brink, W. P. Colliston, R. N. Crockett, S. Hencher, D. H. Jones, F. J. Kruger, B. C. Lynn, G. R. Metzger, J. Reid, A. Smith, B. R. Turner, M. J. Viljoen, J. N. J. Visser, F. Walraven, M. K. Watkeys and M. Wolff.

The financial assis tance of the Foundation for Research and Development, South Africa, the University of Pretoria and the Geological Survey of South Africa are acknowledged gratefully.