Tectono-metallogenic units and metallogenic provinces of Africa

When the major mineral deposits of Africa are studied in relation to the structure of the continent, two tectono-metallogenic units emerge, as follows: (a) younger orogens consisting of zones which have suffered orogenesis from time to time during the past ca. 1200 m.y. - characterised by major deposits of Cu, Pb, Zn, Co. Sn, W, Be and Nb-Ta; and (b) older cratons, with a record of older orogenesis but which have remained stable throughout the younger periods of tectonism - characterised by important deposits of Au, Fe, Cr, asbestos and diamond. The more localised metallogenic provinces of ore con­centration within these major units are briefly discussed.

In the past sixty years, there have been a number of notable attempts to classify regions of mineral concentration. De Launay [1], for ex­ample, developed the concept of metallogenetic (or metallogenic) provinces for geographical re­gions characterised by certain types of ore min­eralisation. Somewhat later, Spurr [2] coined the terra metallographic provinces for regions char­acterised by certain types of mineralisation re­peated at different periods of geologic time.

In Africa, efforts have been made to delineate regions of similar metallogenic character [3,4] but these have, in a number of cases, been less than successful because they attempted to clas­sify mineral deposits in terms of time of forma­tion or emplacement, or geographical distribu­tion, rather than on structural environment. In recent years, however, the distribution of some major mineral deposits in southern Africa has been discussed in relation to the structural con­figuration of that part of the continent [5,6]; it is the purpose of this contribution to outline the ex­tension of these ideas to Africa as a whole.

In view of the wide extent of Precambrian rocks in Africa, structural analyses on a region­al scale must rely mainly on the results of ra-diometric dating studies (see, for example [7]). Prior to the use of these techniques, a number oforogenic events were recognised including: the Alpine orogeny (Atlas Mountains) [8]; and the Hercynian orogeny (northwestern Africa and the Cape fold belt) [9,10,11] (see fig. 1). Since the advent of radiometric dating techniques, a va­riety of Precambrian and early Paleozoic oro­genic belts have been dated. Of these, the more modern include: the late Precambrian-early Pa­leozoic (450-680 m.y.) belts of orogenesis ex­tensively developed throughout Africa [12-15]; and the Kibara belt (ca. 1100 ± 200 m.y.) of east and central Africa and its probable extension in the Orange River belt and in Natal in South Af­rica [14-16]. Together, these zones of younger Precambrian and Phanerozoic orogenesis repre-" sent a distinctive, though complex, regime of younger \orogens consisting of mobile zones which have suffered orogenic deformation from time to time during the past ca. 1200 m.y.; this more youthful structural regime is readily sub­divided from the older cratons which have re­mained stable over the past ca. 1500 m.y. and have not been disturbed by more modern (ca. 1200 m.y. to present) orogenesis. <...>